Indian Civil Engineer

Features of 2D CAD Drawings – Real Figures

2014-05-27T01:02:00.000+05:30

Inasmuch as we discuss about drawings in orthographic projections or 2D drawings, the single most important feature of a CAD Drawing is the plane of the drawing. For an object of Euclidean or non-Euclidean geometry being represented by a drawing, the plane of drawing may cut across the object (Section Drawing) or view the object from outside (View Drawing).

All drawings (sections and views) consist of sets of lines (polylines, multi-lines, arcs, curves) that form closed/open figures at section/view. These figures may be detailed by renderings such as hatches and annotations such as dimensions and texts. A set of figures along with necessary rendering and annotation, used as an interchangeable unit constitute a block.

The figures on drawings/blocks can be distinguished into real and reference figures. Real figures such as walls, furniture, doors and windows represent objects that do exist or are created in reality. The set of lines that form the real figure represent the edges of the real object in the plane of the drawing. Reference figures such as grid lines, centrelines, axes, dimensions, tables serve as references to real figures and do not exist in reality. We shall make few observations about real figures here.

For a real figure as it represents a real object, any point on the drawing represents a point either inside or outside of the real object, in the plane of drawing. Hence, we shall postulate that all real figures are indeed closed figures (closed polylines or curves) as all real objects are bounded. Exceptionally, a real object may be represented by an open figure on a drawing if and only if one of the dimensions of the object is negligible by the scale of the drawing.
An important corollary of this observation is that, when two real objects or figures interfere, there has to be an even number of points of intersections. As interference of two objects is a Boolean operation, this observation is equally valid for Boolean subtraction. Any cut-outs or openings thereof should also have even intersections with the real figure.
Another significant observation about real objects is that, two objects cannot occupy the same space on a drawing, as it is in reality. This means that when two real figures meet, one of the figures needs to be trimmed to accommodate the other and the edges of the figures coexist at the interface.
The plane of drawing is a fixed coordinate along the normal to the plane, hence in a way the edges of the real object represent the edges at that coordinate or elevation. Therefore, a real object can have only one set of closed edges, on a given plane of observation. Multiple closed or open edges represent themselves as duplicating/overlapping collinear lines, which does not have a corresponding mapping in reality.
Foregoing discussion shows that two collinear lines can co-exist if and only if they represent edges of two different objects. This introduces an important imperative on drawing standardization – that different or discontinuous objects should be represented differently on the drawing. CAD drawings enable the differential representation by layers, line-types, colours and line-weights.
A drawing may represent lines that are not necessarily on the plane of drawing (beneath or above the plane of drawing). Out-of-plane lines are of two types: hidden lines on view drawings and section drawings represent real edges that are invisible in the plane of drawing, and view lines on section drawings, also representing real edges that are visible from the plane of drawing. Although most draftsmen place hidden line on separate representation, they keep view lines in same layer/line-type/colour/line-weight as real figures.
For same object, the layout of hidden and view lines depend on the plane of drawing. Consider the difference between architectural key plans, drawn just below of just above window sill levels. For plans drawn below sill levels, the sill lines are part of real figure, there are no view lines and lines on either side of the windows are hidden lines. For plans drawn above sill levels, the window side lines are part of real figure, sill lines are view lines and there are no hidden lines.
For out-of-plane lines, hidden and view lines together constitute the closed figure. A view line may be closed by a hidden line and vice-versa. However, when the configuration of a view line or hidden line falls exactly on the real figure (that is the edge surface overlays on a different plane), it is conventional to leave the view/hidden line unclosed.

To summarize, following types of lines (polylines and curves including) may be seen on a 2D drawing.

Reference lines
Closed real figure lines
Open real figure lines
Coexistent collinear edge lines of interfering objects
Closed hidden lines
Closed view lines
Closed view-hidden lines
Open hidden lines
Open view lines

Alternate for River Sand for Concrete Aggregate

2010-02-24T20:50:00.000+05:30

Ordinary river sand is becoming extremely scarce due to the environmental impact of river bed dredging in the country. In some parts of the country, cost of sand is about Rs. 90 per cft whereas cost of cement may be about Rs. 180 per cft. Very ironically the inert inexpensive aggregate of concrete is now more costlier than cement in a nominal 1:1.5:3 concrete. Its cost share is much more high in cement mortar plasters, whose ratios may be nominal 1:5.

Replacement has been sought by manufacture of sand by crushing stones to sieve sizes of sand. Although appearing to be a less expensive solution, this has its own share of problems to the environment. There has also been apprehension about quality of grading and lack of quartzite composition of stone crushed fine aggregates.

One more alternative needs to be explored considering the gravitry of the problem, namely use of sea bed sand for fine aggregate in concrete. Over 15% of the sand and gravel currently used in England and Wales is won from the sea-bed and has been used in a wide range of reinforced concrete structures, according to a 1987 publication of Building Research Establishment UK [Gutt, W. and Collins, R. J.].According to the paper, the main difference between the majority of land-based aggregates and marine aggregate lies in the presence in the latter of sea salts, which usually have to be washed out to meet British Standard maximum limits for chloride and latest guidelines for limited alkali content to prevent alkali silica reaction (ASR). Many island countries such as New Zealand are now exploring the possibilities.

Sea bed sand are not devoid of their own share of environmental problems. A summary of problems is presented at http://www.seafriends.org.nz/oceano/seasand.htm. The environmental and quality related apprehensions if addressed appropriately might lead to a significant solution to the construction industry in general.

Incremental Milestone Works in Earned Value Analysis

2010-02-15T15:00:00.002+05:30

Works with earned values associated with distinct points of time have cost functions of the form

V = Vz at tz less than t less than tz+1

are called Incremental works. The TCM Framework of AACE calls this type of measurement as Incremental Milestone. Definition of incremental works is not amenable to PDCA analysis because resources do not appear on cost function. Cost function is identical to measurement function and hence the advantage of measuring work from two directions viz. deliverables as well as performable is lost.

For PDCA analysis, incremental works need to be homogenized by defining distinct homogeneous work packages with constant cost functions and extremely short fixed durations at instances of increment. The interval between increments is covered by trivial works that cannot be measured or paid.

An example of increment work previously discussed was installation of an equipment. Work was defined with values as –

• Delivery of materials (7th day, 20% value)

• Assembly (14th day, 60% value)

• Installation (17th day, 15%)

• Testing (20th day, 5%)

The cost (or value) function in this instance is

V = 0% at 0 less than t less than 7, 20% at 7 less than t less than 14, 80% at 14 less than t less than 17, 95% at 17 less than t less than 20, 100% at t greater than 20.

In the above example, supply of materials is a work of duration one day and value 20%, scheduled on 7th day. Similarly, assembly is a work of duration 1 day, value 60% and zero cost. This work is scheduled on 14th day. A work called assembly-in-progress may be defined as a trivial work with zero value but non-zero cost function scheduled from 7th to 14th day. If the trivial work is homogeneous, percentage work completed on each day can be tracked and rectification applied whenever necessary. Since, trivial works have zero values; it cannot be measured and paid. From the contractors’ perspective, trivial works have non-zero cost function, to keep track of resources needed to complete work and control over cost of such resources. Sum of the work package at increment and trivial work in between equates the cost and value functions without altering the mode and method of measurement.

Fabrication and erection of steel buildings usually falls under incremental milestone works. Fabrication of a girder beam from a rolled section may involve:

• Receipt of rolled section at yard

• Straightening of section

• Cutting to length

• Grinding edges

• Jointing to length

• Drilling holes to catch mating members

• Placement of end plates and reinforcement plates

• Positioning of intermediate stiffeners

• Positioning of cleats

• Continuous welding,

• Providing priming coat

• Pre-erection painting.

Each of these tasks is in-turn distinct activity consuming different resources at different proportions and associated with different costs. However, value is attached generally only at the beginning and end, say 40% at receipt of materials and 25% upon completion of fabrication.

If a managerial interference is extended on the scheduled day of completion of the fabrication, it is likely that project delays and cost over run might remain unnoticed for corrective action. Hence, a suitable reporting system is needed to track the progress of this fabrication.

In order to homogenize the fabrication work, trivial works are defined for straightening, jointing, drilling, welding, painting etc in WBS. During detailed planning, each of these trivial works also should be scheduled assigning resources. The number of beams completing each stage can be reported as tracking parameter every day. Thus, completion of works can be compared against performance of resources in PDCA analysis and corrective measures can be taken whenever these are warranted.

Trivial works are not associated with physical measures of completion. For example, there is no percent value complete associated with fixing of end plates on the girder. That is, trivial works accrue cost but do not accrue value. During physical measurement and payment, trivial works shall not be measured or paid, unless all the trivial works leading to the incremental work is completed.

Incremental works also justify the necessity of separating planned value curves from planned cost curves. Although, value is accrued at completion of work, cost is continuously accrued during the work. Comparison of earned value against planned value is of least administrative significance in this case, since it does not enlighten about delay or cost increase during the work. On the other hand, comparison of actual cost against planned cost provides insight about these deviations.

Definition of incremental works is common in software development projects, design projects and film industry because intermediate deliverables do not possess stand-alone value. In software industry and in design projects, person-hours are the most significant resources. Planned value and cost is defined in terms of the person-hours. Earned value is defined by the completion of work on hand. It is hence necessary to define intermediate deliverables to be tracked albeit without value, so that corrective actions may be taken when such deliverables do not meet targets. After final delivery, the work is valued by physical measurement and earned value curve is updated.

If the accrual of value is associated only with financial transactions such as billing to client or payment to vendors, trivial works can be associated with earned value and flagged off for payment at later stages of work.

Staggering of financial transactions can be seen in many incremental works. For instance, in the steel building example, client is unlikely to be billed or contractor to be paid for completion of fabrication of every girder. Such transactions may occur for instance after completion of say fabrication of columns, braces, purlins, runners, base plates etc that is after entire lot of fabrication is completed. In such cases, it needs to be specified that transactions are staggered until another incremental work is completed.

ASSESSMENT OF DESILTING QUANTITIES

2010-02-13T13:19:00.000+05:30

Work methodology adopted for desilting of stormwater drains in an industrial estate:

Drain Geometry

To ascertain the invert levels of drains in dry areas, leveling was adopted using dumpy levels at two or three locations on each drain. The locations were cleaned using manual labour to make invert visible for leveling. For wet locations and locations with sludge, sounding was adopted using sounding rods after removal of silt/sludge manually at two or three locations per drain.

The drain cross sections were measured using tape. Bottom width is measured at typical locations were invert levels are measured after removal of silt.

Drain linings have been classified by visual inspection into five categories:

A: Good Lining

B: Mild Damage, needs replastering

C: Moderate Damage, needs refurbishment

D: Completely Damage, needs reconstruction

E: No Drain

Drain length covered by cover slabs, culverts and entrances of industrial units have been individually measured.

In some areas it has been noted that existing drains have been destroyed by previous desilting excavation using excavators. In these cases, it is difficult to locate the invert levels of the drains. In such cases, invert levels are assumed to be the hardest levels that have been achieved by sounding. This approach may be subject to errors if the sediments have consolidated considerably. In these areas, execution of contract should be based on cost-plus-fee basis rather than lumpsum basis.

Similarly some areas are such that grades have been blocked by on going development. Flow gradient has also been reversed due to deposition of construction debris at many locations.

Sediment Geometry

The profile of silt deposited in the drains is assessed by leveling at approximately 10m intervals in dry areas. In wet locations and sludge locations, profile of silt is assessed by sounding rods at 10m intervals. The height of deposit is calculated from the depth of invert levels measured previously.

Type of sludge has been classified as follows:

D: Dry

W: Wet

S: Sludge

E: Effluent

In most areas it is found that quantity of silt is about 0.8m3 per running meter of drain. Silt in areas already destroyed by excavators is nominal.

Desilting Quantities

Based on the drain width and silt height, the quantity of silt is calculated for every 10m length of drain and summarized

Technical Specifications for Desilting

1. The contractor shall visit the site and assess the adequacy of the data regarding drains and silt quantities provided.

2. All unit holders shall be notified to take necessary precautions to prevent damage to services or utilities during the desilting work.

3. All unit holders shall be notified to remove cover slabs over drains wherever necessary.

4. Not more than 10m of drain shall be continuously covered during desilting.

5. Vegetation on the drains if any shall be removed by the contractors using his own equipment and labour.

6. If found necessary traffic on road shall be diverted during desilting. This may be necessary on narrow roads.

7. The contractor shall not pump water from drains onto roads. Care shall be taken to prevent flooding of roads with water during desilting.

8. While working from upstream side of drain care should be taken to ensure that water flow is not blocked down stream.

9. While working from downstream, care should be taken that silt is not washed again into already cleaned areas of downstream from upstream.

10. Silt deposits on the existing drains are classified into following types: Dry earth, Wet earth and Earth mixed with sludge/solid waste.

11. The material may include earth, debris of construction materials, vegetation, dead vegetation, organic matter, effluent, sludge and non-decomposable solid wastes.

12. Equipments such as excavators with maximum bucket size 300mm shall be permitted only on drains wider and deeper than 1m. Even on these drains only mass excavation shall be permitted mechanically. Thickness of silt about 15-20cm in contact with the lining shall be removed by manual excavation only.

13. Material that does not require dewatering arrangements or water stop arrangements for removal is considered dry earth.

14. Material that require dewatering arrangements using ordinary dewatering pumps for removal shall be classified as wet earth.

15. It may be necessary to make arrangements to stop flow of water into the area by bunds and to employ dewatering pumps to remove water. After removal of water, the residual material may be treated similar to removal of dry earth.

16. Material that require sewage/sludge pumping arrangements for removal shall be classified as sludge/sewage mixed earth.

17. Sullage may be removed using sewage/sludge pumps or sewage loading trucks. Residual material may be removed by ordinary excavation. In this case compulsory precaution shall be taken for labourers working in sewers.

18. If necessary the contractor may be permitted to deposit material from within drain to the banks for drying for one or two days. Later the material can be loaded into trucks for disposal.

19. Contractor should notify wherever debris is left for drying on roads, so that dispute regarding transportation may not arise.

20. Site for deposition of excavated silt shall be arranged.

21. The material removed from drain shall be removed as immediately as possible without creating hindrance to road traffic and construction work in progress.

22. Arrangement shall be made to deposit the transported material uniformly at the deposit sites. If any agency deposits heaps of materials at entrance of spoil areas, subsequent deposition becomes difficult.

Relative Economy of Pre-Engineered Buildings

2010-02-08T11:17:00.001+05:30

Over past two decades, popularity of so-called Pre-Engineered Buildings have increased over conventional truss structures in industrial and warehouse construction. Technically, Pre-Engineered Buildings are portal frames with moment transferring connections and are not new. In fact, portal frames had been less popular alterrnative to truss buildings from economy considerations.

The current popularity of portal frames is due to the following reasons:

Introduction of High Grade High Carbon Steel at prices comparable to that of Mild Steel. Use of Grade 350MPa Steel in place of conventional Grade 250MPa results in slender structures achieving greates economy.
Advent of Submersion Arc Welding that imparts built-up sections homogenity and strengths comparable to that of Hot Rolled Standard Sections. However, SAW is not still feasible on all joints of built-up sections.
Popularity of Cold Rolled Light Guage Sections such as Zed and Lipped Channnels for Purlins. Cost of these sections have now come down and their lower thickness is more friendly to self-tapping screws of Galvalume sheet roofing.
Galvalume sheet roofing has itself served as a viable allternative replacing disdvantages of conventional forms of roofing.
Flatter slopes are possible with Portal frames, (as less as 1 in 10) since slopes are not required from structural considerations. Flatter roofs reduces sheeting areas and make appearance more aesthetic.
Aggressive marketing efforts of PEB manufacturing companies.

It is generally seen that use of high grade steel is more economical in PEB construction than using conventional MS sections. The cost saving in using 350MPa Grade Steel reduces weight of structture by around 20% whereas cost differences are about 10%. It is advisable to check supply of MS grade structures whereas designs are made for higher grades.

However, slender structures are vulnerable to higher defflections than conventional structures. In most cases, PEB structures cannot meet the requirements of deflection control as per IS:800. Bracing using rods also fails to satisfy the slenderness ratio criterion of IS Codes. In practice, performance of rod braces are subject to the extent of prestressing achieved by tightening the same. These are specifications that have to be decided between the client and the vendor.

It is generally seen that strength per unit weigt (in terms of moment carrying capacity) of built up sections are sensitive to section parameters in decreasing order as follows: Width of flange, Thickness of Flange, Depth of Section, Thickness of Web. Stiffness per unit weight (in terms of MI on major axis) are sensitive respectively as Depth of section, Flange Dimensions, Thickness of Web.

A Checklist for Inspection of Buildings with Damages or Cracks or Distress

2010-02-06T17:11:00.000+05:30

History of Building

Details of Building Design

1. Project Definition:

a. Construction Period:

b. Architect:

c. Owner:

d. End Users:

e. Contractor:

f. Construction Manager:

g. Site Engineer:

2. Drawings

a. Approval Drawings:

b. Architectural Drawings:

c. Structural Drawings:

d. If no drawing sketch of column positions and sizes:

3. Building Details:

a. Type of building – RC Framed, Steel, LBM, LBM with Madras Terrace

b. Type of foundation: Footings, Spread, Combined, Raft, Pile

c. No. of floors in building:

d. Type of building for each floor: Residential/Commercial/Industrial/Assembly

e. Any Floating columns/Eccentric footings/Concealed beams

f. Any well/sump near footings

g. Any Expansion, control, construction joints

4. Soil Investigation:

a. Soil test result enclosed: Yes/No

b. Soil Testing Consultant:

c. Soil test not conducted because:

Distress Audit

1. Structural Distress

a. Major structural cracks wider than 2mm

b. Narrow structural cracks

c. Pattern cracks

d. Noticeable deflections/sway

e. Vibrations or other alarm

f. Noticeable support settlements

g. Noticeable walls out of plumb

h. Floor heaving or cracking

i. Cracks on Compound walls

2. Non-Structural Distress

a. Cracks at joints of frame and infill walls

b. Cracks due to corrosion

c. Cracks related to construction

d. Plastering cracks on walls

e. Joinery sill/lintel cracks

f. Cracks on floors

g. Movements related to dimensional instability due to temperature, shrinkage, relaxation or creep

h. Cracks or movement of parapet walls

i. Cracks on weathering course

3. Maintenance Damages

a. Penetration dampness

b. Rising water dampness

c. Spalling finishes

d. Biological degradation – Rodents

e. Biological degradation – Insects

f. Biological degradation – Fungi/algae

g. Chemical/environmental degradation

h. Overall Maintenance condition

4. Terotechnical Diagnosis

a. Detrimental distress/damages requiring immediate repair or rehabilitation

b. Detrimental distress/damages requiring further investigation

c. Detrimental distress/damages requiring periodic observation

d. Non-detrimental distress requiring regular maintenance

Ready-Made-Steel in India

2010-01-29T21:31:00.000+05:30

Recently ready made steel has been making strides in the construction industry, waiting to take it by storm as RMC did a few years back.

Ready made steel is reinforcement bars cut and bent to required size and shape so that it is only necessary to tie them in place before concrete.

The product is useful on the following grounds:
• Practically, however carefully you order steel from a vendor, the exact number or weight of steel bars do not match to your requirement. So conventional steel purchase always tend to be in excess of exact requirement. This leads to balance after usage.
• When steel is purchased and handed over to craftsmen, there is a tendency to cut the required lengths at random on an as required basis. This leads to un-optimized cutting schedules and results in wastage.
• There is always a lot of wastage or scrap of steel generated at site. Much of these get buried in construction debris and some of them are lost in theft/vandalism. And whatever scrap you recover after fabrication, is worth 25% of its original price.
• The space of steel yard is saved by using RMS and site looks clean of unwanted steel material.

Since RMS providers use top brands of steel and add the service charges for fabrication, RMS appears costlier than steel bent at site. The steel is transported to site with tags showing the bar marks. Note that in most cases, bending radius is specified on the outer dimensions. Sharp bends are not possible for stirrups.

Generally, RMS suppliers provide 8, 10 and 12mm bars cut to shape from coils. This ensures zero percent wastage on these bars. Coils are costlier than straight bars by about 5-10%. Bars more than 12mm in dia or bars cut from bent lengths generate scrap. The RMS suppliers generally use some optimizing routines to find the best cutting schedules. Despite this some scrap is generated – longer pieces are reusable elsewhere, shorter ones are not. Scrap that is not reusable by the company has to be purchased by the client.

Supply is generally of lengths less than 6m, although upto 12m can also be transported on trailers. Straight lengths less than 16mm can be bent to fit 6m length – this cannot be done on already bent bars.
By far the most important limitation of RMS is the necessity of a detailed bar bending schedule to be provided to the vendor. In most construction such schedules are not prepared as part of design. However, irrespective of using RMS or not, it is always advisable to prepare bar banding schedules (BBS) for all steel cutting works.

The position of lapping of steel reinforcement is the most difficult specification of a pre-determined BBS. The lapping requirement results in BBS such that total length of cut pieces is always greater than the total length required by the total length of number of lap splices. There is now an upcoming tendency to replace lap splices with butt splices using couplers.

Threaded couplers require ends of lapped bars too be threaded to accommodate the coupling sleeve. There are also couplers which can be crimped to bar profile at site, or inject filling of space between sleeve and rod. Bars can also be spliced with flanged butt connections. These types have not appeared in the Indian construction market yet. Threading has now appeared as a common splicing method in many major projects.

Even using coupler connections, it is necessary to foresee the staggering of laps at BBS preparation stages itself. Hopefully, RMS manufacturers may come up with automated solutions for preparing comprehensive BBS to tap the large market of middle level construction in the country.

Non-homogeneous Works in WBS for Earned Value Tracking in Projects

2010-01-26T13:42:00.002+05:30

Assuming homogeneity of work, introduces many (over-)simplifications in definition of work, as follows.

Contribution vector c (t) = c is constant during the duration of work; productivity of resources in a prescribed geographical and technological condition is fixed. This means that work is well learnt and resources are sufficiently skilled. Hence, homogeneity may not be applicable to works that follow non-linear learning curves.
Cost of resources r(t) = r is constant during the duration of work. In reality, cost of resources varies considerably on long range and fluctuates marginally on short range. These cost variations are at best statistical and non-analytic. Hence, it is customary to consider the most probable value of costs as constant in time during the project subject to revision in long range. Similarly, cost reductions for hiring equipments on long term, depreciation of materials over time etc fall outside the applicability of homogeneity.
Value of work done in a control period Dt is the linear sum of cost of resource contributions to the work. Cost of resource r(c, t) = r is not influenced by the quantity of the resource used and/or another resource. That is cost of resources are mutually exclusive. However, this simple conception is not applicable in over-time and night shifts. Rate per unit weight of steel is dependant on bar diameters and rate per unit area of flooring tiles is dependant on tile size.
Value of work in a control period is assumed linear with respect to time. However, there are works whose values are not linear functions of time. For example, cleaning the site throughout the duration of the project when defined as a single work, it would be a repetitive cyclic work with several peaks and troughs during the entire project period. Thus, in order to scale the resources, different scales may have to be used at different stages of the project.
Homogeneous cost function is continuous. Hence, works with earned values associated with distinct points of time are not homogeneous. For instance, work defined with values at delivery of materials (7th day, 20% value), assembly (14th day, 60% value), installation (17th day, 15%) and testing (20th day, 5%) is a work with discontinuous valuation. The cost (or value) function in this instance is V = 0% in t[0,7), 20% in t [7,14), 80% in t[14,17), 95% in t[17,20), 100% in t>20. These cases called incremental works may be associated with same or distinct sets of resources at points of measurement and resources do not appear on cost function. Definition of work for measurement of earned value in this manner is conventionally called incremental method of measurement.
Since cost function is linear, rate of change of work value per unit time is constant. Homogeneity is not applicable in stepwise-linear works, with different rates in different intervals so that value may be defined as DV = cz.rz Dt where tz less than t less than tz+1. Consider that one set of resources may work during say 30% of work duration to create 60% value. Another set of resources may contribute in a particular proportion for 40% of duration to achieve 30% value and at different proportion for 30% of time to create 10% value. In many cases, the durations in which different resources work may also overlap. Stepwise-linear works are conventionally measured by combined system of measurement, where unit value measurement with respective coefficients is used between each incremental stage.
When a work is expressed as a combination of two or more cost functions that occurs simultaneously or in close succession, the combined cost function is not scalable. On a control period Dt € U (Dtz for z = 1 to Z segments of time), if cost function is defined as DV = S cz.rz Dtz for z = 1 to Z, the work itself becomes a mini-project. For example, column concrete involves fixing of reinforcement, marking column shoes, shuttering of column sides and concreting of columns. Each activity requires different set of resources and are measured in different units. Some of these activities may overlap in execution whereas others may follow in close succession. These works shall be called composite works.
Limitations of work front availability may constrain scaling of resources in an erstwhile homogeneous work. For example, 250 piles cannot be cast in one day using 250 pile rig sets and corresponding labour due to operational space of each rig. Mathematically, cost function DVz is bound by Vbz less than Vb for z=1 to Z groups of spatial fronts. This makes mathematical calculations on cost functions difficult until works are split based on front availability. Such works may be called split works.
Some resources contributing to work may itself be result of other works, say for instance in assembled products such as trusses, gates, steel fabrication, doors and windows. These works require a matrix definition of resource cost as Dr = c’.r’ Dt. The resource work and real work are both separately homogeneous, but are not homogeneous when combined. When the set of intervals in which resource work is performed overlaps with set of intervals in which real work is performed, the cost function may also become non-linear because, resource cost itself is a function of time.

In all aforesaid non-homogeneous functions, one can visualize typical deviations of cost function from the format DV = c.r Dt. In incremental works, c.r is directly defined as a Lebesgue measure, whereas in stepwise linear works, c.r is variable over intervals of time. In composite works, there are numerous functions of the linear c.r form for different components in the summation. In split works, application of resource scales are discontinuous on cost functions and in assembled works, cost functions are functions of other cost functions.

In this context, it is necessary to define a procedure that consumes prescribed quantities of a prescribed set of materials, equipments and labour uniformly and continuously in a prescribed time-period. Such procedure shall be called an activity such that activities always have a simplified cost function DV = c.r Dt. Works are linear/non-linear, continuous/discontinuous, simultaneous/overlapping/disjoint, uniform/non-uniform arithmetic/functional combinations of activities.

The major conceptual difference between activity and work is such that physically works are the entities that are managerially reported, although activities are the entities with homogeneous cost functions. Managerial reports of work values in PDCA-EVM analysis are of five types – Scheduling, Execution, Tracking, Measurement and Payment.

We shall now see how this concept can be applied to simplify analysis of each of the exceptional cases of work, so that they remain amenable to PDCA analysis by earned value tracking.

Tracking Function for Earned Value in Construction

2010-01-23T18:16:00.004+05:30

PDCA analysis is extremely simplified for homogeneous works, if measurement of work can be simplified in generic instances of time. It has been shown that for homogeneous works, measurement of work during ith segment of time Vi = ti Vb {for ti<1}. This can also be extended to show the validity of superposition in work measurement as : Vi+j = ti Vb + tj Vb = Vi + Vj. Hence, measurement functions are linear and due to the absence of intercept, should also be scalable.

This is possible if and only if measurement function Vb = g (x1, x2, x3,… xm) is homogeneous in at least one variable x1, so that g (zj x1, x2, x3,…xm) = zj g (x1, x2, x3,…xm). Thus, the measurement function can be rewritten as Vb = x1. x2…xq j (xq+1,…xm) and is homogeneous in the product function x1. x2…xq. This product function can serve as a quick measure of work at generic instants of time, since it does not involve measurement of all Lebesgue integrals. We shall call this function as a tracking function, q = x1. x2…xq. Therefore, measurement function is Vb = q j (xq+1,…xm) such that zj Vb = zj q j (xq+1,…xm).

For instance, a common measurement function is Vb = NLBDR (N=numbers, L=length, B=breadth, D=depth and R=cost of unit volume). For homogeneous works, there always exist tracking functions in the set of functions {N, NL, NLB, NLBD} which can be used as a quick measure for work during generic intervals of time. Thus for footing concrete, no. of footings may be a tracking function. Similarly, total length of road may be used as tracking function for pavement carpet, total area for plastering and percentage of total volume itself in mass concrete works.

There is a tendency to assume the measurement function itself or percentage thereof as the tracking function. Although, there is no technical error in this assumption, it warrants complete measurement of works in all short intervals of time. It is necessary to keep the tracking function simple in measure albeit under the expense of a complex definition of work package. For instance, conventional measurement of brick masonry in walls by short wall-long wall survey minus deductions is not viable to simple tracking. Length of wall can be used as a tracking function instead of total volume, if wall masonry is defined at instances – below-sill, sill-lintel and above-lintel units with respective deductions applied. The difference is basically that all site quantities are pre-measured and correlated to a unique tracking measure.

Not all measurement functions fall in the category of NLBD measurement. For volume of truncated pyramids in footings, the measurement function is not a product function, which is why the non-tracking component is generalized above as j.

Trivially, the measurement function may also be defined as Vb = S qj j (xq+1,…xm), such that measurement during ith segment of time is the sum of measurements in j works of similar nature. The measurement function here is indeed a summation function. Similarity of works is such that other functional components except tracking function remains constant for all terms of summation. When a work is defined as Vb = q j (xq,…xm), we call the work as a simple work. When the work is a summation of simple works Vb = S qj j (xq,…xm) we call it compound work. In NLBD measurement function for brick masonry in walls, the function may be (N1L1BD + N2L2BD + N3L3BD) for instance, in which case this will be a compound work.

Homogeneous Works in WBS for PDCA/EVM Analysis

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Proper definition of work packages in WBS with appropriate analytic cost functions is itself the most formidable assignment in PDCA management of construction projects. The simplest form of WBS definition is characteristic to (linear and) homogeneous works. Homogeneous works are such that resources are scalable during the control period to achieve a proportionate scaling of work value in that period. That is kDV = f (kc,r,t).Dt.

Homogeneous works are linear without an intercept. The cost function can be expressed as a linear function DV = c.rDt + m; but m=0. The intercept m is a fixed value of work associated with start of work. Homogeneous cost functions are integrable, scalable, invertible and monotonously increasing. At the end of work, measurement function Vb = Sum of c.r [Tfj - Tsj] {for j = 1 to p} if there are (p-1) breaks in execution of work. [Note that p=1 for fixed duration works.] Work executed in ith segment of time can be expressed as a fraction of total measurement function as follows:
Vi = c.r [Tfi - Tsi] = [Tfi - Tsi]/ Sum of {[Tfj - Tsj] for j = 1 to p} Vb = ti Vb {for ti less than 1}

Noting that if Vb is a Lebesgue integral, ti Vb {for ti less than 1} is also a Lebesgue integral, earned value of a homogeneous work during any given segment of time is a simple Lebesgue measure. Hence homogeneous works can be directly measured by Lebesgue units completed. This type of measurement is conventionally called Unit Value measurement.

Scaling of resources implies that Vb = Sum of kj c.r [Tfkj - Tskj] for j = 1 to q for q segments such that for fixed quantum works, duration of each segment is reduced to [Tfkj - Tskj] = [Tfj - Tsj]/kj.
The scale factor k and no. of segments q are always 1 for fixed duration works. Fixed duration cannot be speeded up, broken or delayed. If resources are increased in fixed duration works, actual cost increases proportionately.
For fixed effort works, resources operate even in intervals between discontinuous segments of work. Total cost is hence defined for resources over period [Tfq - Ts1] that is start of first segment to end of last segment. Hence, during a break or delay in such works, no incremental value is achieved although cost increases at the same rate as k.

Homogeneous works are amenable to PDCA analysis provided each work package in the WBS are mutually exclusive – that is one work is independent of another in terms of cost, productivity, scale and time. In such cases, PDCA analysis can be carried out as follows:

All works are defined as mutually exclusive homogeneous works. The logical relationship between activities is established using conventional Gantt chart and CPM analysis.
Dividing the project duration into fixed periods, the planned value curve can be established as cumulative summation of cost functions on Gantt chart over each fixed period. Floats and statistics on CPM analysis may be incorporated in planned values to obtain statistical region of planned value.
At any time during the project, a desired planned value of work is scheduled for a control duration. The resources required for this objective may be calculated and sub-optimised by inverting the cost function to find a suitable scale factor k. (Sub-optimization procedure is to be elaborated eventually.)
Project managers advise contractors and vendors to supply material, equipment and labour in accordance with the sub-optimized value of k during the control duration.
The earned value of work during a period may be different due to actual variations from planned works. The earned value shall be measured at generic instances of time using the Lebesgue measurement function or tracking function. Definition of a simple tracking function is necessary to operate this stage of management. This shall be discussed eventually. The actual resources employed in the duration can also be tracked in terms of material receipts, equipment time cards and muster roll registers.
Deviation between generic earned value and planned value designates the difference between slope of the cumulative planned and earned value curves. Whereas, cumulative planned and earned value curves are plotted continuously to present the conventional earned value diagram, the necessary adjustment of generic slope of earned value curve can be applied on the next cycle of management control. If the rectification slopes are within the planned value ranges, attempt can be made for rectification. Otherwise, baselines are to be revised rationally for irrecoverable damages done.

The foregoing analysis is possible only for homogeneous works because the all mathematical calculations viz. integration, differentiation and inversion are simplified on such works. We shall henceforth discuss

Integration procedure for summation of cost functions into planned value diagrams
Differentiation procedure for generic measurement of earned value using tracking functions
Inversion procedure for sub-optimization of scale factor k for desired planned value in scheduled durations
Statistical definitions for mathematical expectation of planned value in CPM analysis
Identification of works that are not inherently homogeneous and methods of homogenizing such works

Real Estate Finance

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Finance for construction in most cases, cannot be completely arranged from builders own funds. It is necessary to raise funds from other sources, such as banks or private parties.

Types of Borrowers

Property developers require finance to construct residential or commercial developments. Developers sell apartments, shops & office space to individual buyers. The finance has to be fully repaid upon sale of property
Individuals & firms require funds to purchase an undeveloped land and construct residential, commercial or industrial development, purchase a finished development, renovate/redevelop an existing development. Owners either occupy the property or let/lease it to a tenant. Finance is repaid in installments over long term.
Government require finance for developments. Public developments such as roads and bridges are usually owned by the government, and sometimes tolls are collected from users. Residential, commercial, industrial developments of government are either held by public sector organizations or sold to individual buyers.
Owners of existing developed property require finance for other purposes. This can be raised against the property by mortgage or lease, in which borrower may or may not occupy the property. Interest has to be paid regularly and capital is repaid at the end of mortgage or lease term

Borrower Behaviour

Profitability over and above interest on loans. Developers can achieve profit only if they earn a margin in sale more than outstanding interest payment with the bank. Developers are keen to keep the construction, interest and holding cost before sale as low as possible. For this reason, developers tend to consider one or more of following options: - Reduce amount of high interest loans and maximize use of low interest funds - Raise finance by direct equity funding i.e. on profit sharing basis such as joint ventures - Construct using own funds and mortgage the property to banks during the holding period before sales - Seek longer term finance from financial institutions allowing some equity partnerships.
Limited funding by banks. Limitation of bank funds to 60-80% of total project cost makes it difficult to small entrepreneurs, who would be advised to limit to smaller projects. They can take up ambitious projects only after establishing sufficient credentials.Larger firms on the other hand can offer collateral security with other properties and collective returns from various assets can repay the borrowed loans. A loan that calls upon other assets of the developer than the current project is called a recourse loan.
Selling and holding property as investments. Since short term finance is expensive, a developer starts construction as soon as the site is acquired and get the building completed quickly. Thereafter, he starts selling the development or holding it as an investment.Property trading companies realizes profits as soon as construction completion by selling. Ideally, the company would sell during construction period.However, successful developers retain some better developments or a share in them as investment. This offers returns on the development, serves as a hedge against inflation and also helps to provide collateral security to further developments

Development Finance

Property developers require finance to construct residential or commercial developments. Developers sell apartments, shops & office space to individual buyers. Finance for this purpose is arranged by following methods:

Short term loans from private parties or banks that can be repaid after sale of the property.
Raising equity from company share holders
Raising equity loans from institutions by assuring minimum priority returns
Entering into joint venture with individuals such as land owners or other firms for a share in the return.

Short-term Loans

Short term finance is like working capital of industries, to cover the production period until finished good is sold. The sale of the finished construction or developed property is the sole means of repayment of such loans. In order to control risks on lending, banks take risk factors into consideration whereas developer trying to maximize the benefit of the loan and minimize costs, take particular measures in this regard.

Loans can be either overdraft loans or term loans. Overdraft loans allow an account holder of the bank to draw a specific percentage of funds more than available balance. Overdrafts are usually cheaper than term loans. Term loans are predetermined funds advanced for predetermined term. Term loans give more security to the developer because, it can be fixed for the whole period of the loan enabling developing costs to be forecast accurately.

As most occupiers purchase completed property with long term funding from financial institutions, in one way, institutions are the ultimate purchasers as far as the lending banks are concerned. While institutions base security on the completed and occupied property, banks rely on the project assessment and knowledge of the developer. Banks account for this high risk by considering following factors.

Liquidity of the property. If there is a fall in the property market, money of the bank gets locked.
Successful project and marketing management of the developer. Project should manage to be saleable. Hence, history of the developer is an important consideration.Besides, funds are released by the bank only in stages of construction, to give the borrower sufficient flexibility and exercise a measure of control over the project.Banks also monitor the time of completion of the project. A loan for an industrial godown would be for a shorter period period than for an office block as latter takes longer time to complete.Banks also limit loans to about 60-80% of the project cost as determined by its own valuer for same security reasons.
Increase in short term interests given by banks to small investors.If there is an increase in short term interest rates offered by the bank to small investors in response to government or bank policies.

Equity
Equity capital consists of funds that are to be given a share of the profit after sale of the construction.
As against loans, it is not a liability and interest payments may not be made.
Equity capital is obtained by ploughing back profits, selling shares or by joint ventures. Normally, except for well established companies, profits are not large enough to purchase capital property. Raising equity shares is open only to public companies, with minimum raising limitations.

Equity financing has two main disadvantages: First, the cost of equity finance depends on popularity of the company at the Stock Exchange. Second, issue of shares could mean the control of the company passes out of the hands of the original owners.

Besides, the property companies are more suited to loan finance than equity finance because, income is based on regular rents and capital gains by appreciation. Hence, payment of fixed interest offers less botheration than dividends. Moreover, the property itself can be provided as security for the loan.

In real estate, certain types of financial arrangements which combine the advantages of equity and loans are useful. Equity loans are based on paying returns on priority basis to lender. Equity can also be ploughed in by two or more firms to construct joint venture.

Equity Loans

Since short term financing is difficult for major developments such as shopping complexes or office blocks, many developers seek long-term finance during development stage itself. This mode of borrowing is based on equity participation by the lender i.e. lender directly seeks returns from the project rather than interest. Many financial institutions may be interested in this arrangement as security in prime property developments allows participation in returns from the land as well as in appreciation. Sometimes private investors may also be involved. Such finance may be arranged in various manners enumerated in increasing order of equity participation as:

Priority Returns Basis: Long term finance institution agrees a minimum return with the developer. Thus, developer can keep the costs minimum, let the project complete as quickly as possible and seek profits.
Sale and Leaseback Arrangement: The property is sold to a financial institution which then advances the development costs at a fixed rate of interest. If the development is not let out within a fixed period after project completion, developer receives the balancing payment or can enter into fresh leaseback or rental agreement. The agreement is terminated when letting to an occupational tenant is achieved.
Profit Erosion Basis: This is a special type of lease back arrangement in which the base rent is adjusted against the balancing payment if the property is not let out. If the balancing payment gets exhausted, developer ceases to have interest in the property and institution takes over full letting out responsibility.
Institution Occupation: With developers having successful record, institutions advance entire development costs at a fixed rate of interest and after completion occupies the premises at a rent agreed with the developer.
Joint Venture: The development and usually a private investor such as land owner undertakes the project as a joint venture, wherein the profits are shared according to agreed proportions. However as dividends and shares cannot be deduced from assessing corporate tax, this scheme represents a tax disadvantage to the joint company.
Direct Development by Institution: Institution develops the entire project, by employing the developer as a project management consultant at an agreed fee structure fixed as a percentage of construction cost.

Economics of Finance

Following factors may affect any arrangement of development finance:

Usually, finance industry consists of a few monopoly lenders such as banks or financial institutions with more or less same conditions for loan. Advantage of competitive lenders may not be present.
When banks are required to limit their lending by government policy, property developers turn to small merchant banks, foreign banks and even hire purchase finance companies.
When there is more than one owner for a shared property, arrangement of finance may reflect relative bargaining strength of each principal in bilateral negotiations.
Exemptions from income tax offer advantages in lease-holds and security-mortgages whereas capital gain tax and corporation tax schemes discourage leasehold and mortgage arrangements and prefer sharing of returns.
Sources of capital also alter as the requirement of lenders change. Insurance companies seek equity shares when they introduce profitable policies to its policy holders or as an inflation hedge

These factors underline that a developer should organize facilities with three or four alternative sources.

On the Eternal Client-Contractor Conflict

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Client: No, Mr. Contractor. I cannot pay the outstanding balance amount to you. The Fire Security Department had clearly stated that the clear passage on the fire escape staircase flight shall be 2 feet 6 inches. What you have provided is only 2 feet 2.5 inches. Now since, this fire stair that you built would not be approved by the department; I do not have any utility for your construction. Why then should I pay you?

Contractor: Sir, the fire stair case that I have constructed for you is exactly in accordance with the drawings that you have given me. The architectural drawings clearly state that the overall external dimension of the stair structure should be 5 feet 4 inches for two dog-legged flights. The fabrication drawings were submitted to you. Your maintenance engineer was there at site during construction and he could have very well instructed the need of additional width of flight, if that was necessary. I would have placed a fresh quote with you in that case. You are deliberately making it an issue at this stage when final bill is raised, just because you do not have the intention to pay.

Architect: The architectural drawings do indicate an outer-to-outer dimension of 5 feet 4 inches for the staircase structure. Two balustrades on either side of the flight that also accommodate the handrails are 2.5 inches wide. Hence clear width is reduced. The fabrication drawings have never been submitted for my approval. Neither am I paid for preparing any working drawings or checking them. Even if, I had educated you about the necessity of checking working drawings before execution, you would dismiss me as an extra cost.

Bureaucrat: I can help you to approve a 2 feet 3 inches wide stair by showing that this construction is according to the old rules. Of course, at a price – all government matters, you know.

Formulation of PDCA Cycle in Construction

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We shall tentatively define a mathematical formulation for value of a work package with complementary resource contributions and permitting necessary calculations as follows. Value DV of a work package in a control period Dt is mathematically expressible as a cost function (Read D as delta):

DV = f (c,r,t).Dt

Where c is the contribution (vector) of resource efforts in unit time to achieve unit quantum of work, r is the cost (vector) of resources and f is a function of productivity, cost and time. Resource contribution and cost are defined as vectors because they apply to set of relevant resources. The cost function has following characteristics:

The cost function can be integrated or summed up over duration of work. The sum of cost function over duration of work is the budgeted cost of work or total planned value of the work.

The cost function DV need not be a continuous function in time. Integration or summation over durations is possible even on discontinuous functions. However, sum or integral V of cost function over duration T should necessarily be continuous, such that rate of change of work value in real time and real cost may be calculated. As an extension, summation of integrated values of different works during a given interval of time need also be continuous.

The cost function DV can be scaled for resources, costs or time by a scalar as f (k1c, k2r, k3t)Dt to scale the value of work in the control period Dt. Scale cannot not be a vector, because different resources cannot be scaled differently to achieve a scaled value of work due to the complementarities of resources.

The cost function DV should be invertible because during planning, it is necessary to determine scaled contribution k1c for given quantum of work in given control period.

Cost functions DV are monotonously increasing functions (straight upward lines, exponential curves, S-curves etc) because work cannot reduce with increasing effort or increasing time. This means that cost function does not have a zero intercept value at any time except if necessary at start of work.

Cost functions DV are always positive. That is no resource is consumed negatively and no resource is with negative cost.

The cost function DV is a bounded function that is not defined in - ∞ to + ∞ or being positive function in 0 to + ∞. Value of work executed in control period is finite and sum of cost functions are limited to total planned value of work. The bound of cost function may be applied in three forms:

Fixed quantum work is such that duration of work may be reduced by uniform scaling of resource such that the work value remains constant. Most works in construction projects fall in this category. A delay of work reflects as a flattening of slope of earned value curve. Delay of work does not necessarily cause a cost increase. Slope of cost curves follow the value curves unless cost or wastages cause escalation. The bound of cost function is fixed and scale of resources and work duration are variable for given work value according to the inverse of the cost function.

Fixed duration work is such that duration of work cannot be altered by scaling resources, such as in curing of concrete. Fixed duration works cannot be delayed and earned value curve always follow planned value curve. Scaling of resources in fixed duration works directly results in cost over-run, that is cost curves are steeper if resources are wasted on fixed duration works. Bound of cost function, duration of work and scale of resoources are all fixed in this work, and cost function is a continuous function of time, that is there cannot be a break in execution of work.

Fixed effort work is such that a limited effort of resources contributes into the work. Plant-in-site, technical supervision and timbering of excavation is examples of fixed effort works. Delay of fixed effort work is always caused by delay in other (fixed-quantum) works. When physical time of resources in fixed effort works is not utilized any delay invariably causes cost-over-run. Delays present themselves as flat earned value curves and actual costs become steeper at all delay. The bound of cost function and resource efforts are fixed in these works. The cost function may not be continuous in time, so that net duration of work may be longer than the duration according to inverse of cost function.

In the PDCA cycle, the cost function enables to define planned values as a function of resources employed, their anticipated costs and the duration in which they are employed. Each work package on the WBS defines or quantifies a certain bound Vb for work value based on fixed quantum, duration or effort criterion. Summation of the values of works on scheduled period provides the planned value curve.

The binding value of the work package is determined by measurement of deliverable that necessitates a separate method of measuring completed work. For this purpose, we will define a measurement function:

Vb = g (x1, x2, x3,………….. xm)

Where x1, x2, x3,………….. xm are vectors of Lebesgue measures such as lengths, areas, volumes, weights and counts of deliverables in the work package. Generally, on all projects measurement of deliverable as a Lebesgue integral is possible after completion of work. However, for application of EVM-PDCA cycle, it is necessary to define a Lebesgue measure such that deliverables can be measured during execution and before completion of work. We shall call such a measure as a tracking function.

The resource efforts required during a control period to achieve a certain value of tracking function can be calculated since cost functions are invertible. For all Lebesgue measurement of works, albeit after completion by measurement function or during execution by tracking function, the earned value of project can be calculated at generic time. The work performance can be controlled during a control period by scaling the resources, so that slope of earned value curves may be varied at will.

Thus, the cost function and measurement or tracking function is useful for control during PDCA cycle, since it enables separate measurement of all quantities DV, k, c, r, Dt and deviation of any measurement from plan can be immediately acted upon for managerial control.

Earned Value Method from Management Control Perspective

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Construction Management Part IV

From a management control perspective, an analytical model of a system should also be capable of offering solutions to problems. Hence, it is necessary that PDCA analysis using Earned Value Method, provide insight on the corrective action for variances during assessment phase. Thus, it is necessary to address the following aspects of earned value representations:

Permanence of project delays or cost over-run: (semi-)objective indications are needed to assess how far of a deviation is an irrecoverable damage. Attempting to recover a permanent delay or expenditure is meaningless or sometimes harmful.
Causes of over-expenditure: Extent to which planning errors, price escalations, sub-optimal resource allocation, wastage of resources or idling of resources during delays contribute to cost over-run.
Causes of delay: Extent to which planning errors, low productivity, insufficiency of resources and uncoordinated resources contribute to schedule delays

Heuristically, in addition to measures of variances in the project as a whole, additional measures of control are necessary to address control-related issues as contained above. Control is essentially an attempt to change the slope of earned value and actual cost curves at will, hence these measures need to be based on the slope or derivative of the PV,EV and AC curves at generic instants of time and generic stages of value of the project.

To elaborate, consider that a smeared PV region is created probabilistically based on optimism of planning. The region would also accommodate deterministic early start (ASAP) or late start (ALAP) PV curves. For different cash-flow conditions, smeared planned cost PC region may also be created with deterministic ASAP/ALAP planned cost curves. (PC curves may become probabilistic themselves, if resource costs are probabilistic). When earned values and actual costs are recorded in this system, it may also be possible to plot the costs as required to earn the value by ASAP/ALAP schedules – we may call this as earned cost EC region. (It is not emphasized that planned costs and earned cost would be identical to planned value and earned value respectively if Just-in-time inventory control is applied).

This approach can provide impressive conclusions, such as; slope of optimistic PV at generic value may be upper bound of expediting project by resource enhancement. Slope of ASAP/ALAP PC may indicate upper bound of cash flow requirements. In a well-controlled project during a delay, EV follows PV at least pessimistically, slope of EV tends towards optimistic PV and AC is comparable to EC.

Projection of cost over-run and delay also fares well when slopes are accommodated in the forecast, because deliberate control attempts to compensate delays by resource adjustments and cost increase by resource performance. As a result, during control the slope of EV curves change towards slopes of optimistic and early-start PV curves. Thus, affine translation of suitable PV curve and suitable affine rotation for recovery is a realistic transformation than simple affine scaling for forecasting. In this analysis, rotations are limited by the slope of optimistic PV curves, so that any delays that cannot be rectified by following optimistic PV curves remain irrecoverable. Delays that are within the difference between ASAP and ALAP may be recovered without cost-over-run.

For a given EV curve and corresponding EC curve, deviation of actual cost from absolute maximum earned cost may represent an irrecoverable expenditure. Deviations between ASAP and ALAP earned costs may be recoverable by better control.

[All foregoing discussions are strictly only mathematical hypothesis and do not amount to inference. Actual behaviour of earned value curves in reality are subject to multitude of parameters. Inference is sought to be developed after actual implementation of earned values on different projects.]

Testing of aforesaid methods, leave alone their practical application, is formidable due to the extensive data capturing and mathematical computations involved. A suitable methodology needs to be devised for this purpose in order to derive fruitful results. Notwithstanding this difficulty, it stands that the slopes in EVM are as significant as the values and indices both from control perspective and forecast analysis, where recovery curves are used at generic instances.

Analysis by Earned Value Method

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(Construction Management Part III)

Quantity of work planned or completed in specified duration should be measured with a reliable variable. The measure should be applicable with same units for all kinds of work and should be relatable to the quantity of resource-effort and duration of work.

Budgeted cost of work BCW is a reliable measure in planning (BCWP) and tracking (BCWC). This measure can be made dimensionless by considering the ratio over budgeted cost of the project. For purposes of analysis, fraction of budgeted cost of project in works (or parts thereof) planned during a control period is called the Planned Value in the control period. Fraction of budgeted cost of project in works (or parts thereof) completed during a control period is called the Earned Value in the control period. Tracking projects by earned value is called Earned Value method and is amenable to PDCA analysis.

A PDCA analysis following above approach attempts to quantify problems in the project as deviations in planned value, earned value and actual cost over project duration elapsed. Such measures of deviation that require corrective action can be identified as:

Resource variance RV when Actual cost to date is greater than Planned Value to date.
Schedule variance SV when Earned value to date is less than Planned value to date.
Cost variance CV when Actual cost to date is greater than Earned value to date.
Time variance TV when Planned duration for current earned value is less than duration elapsed.

These definitions of variances measure non-concurrence of projects to plan. Many of these variance measures may appear redundant and much literature has examined the efficiency of these measures under various situations. A conceptual description of earned value method may be presented here without emphasizing the measures of variances.

Earned value analysis identifies two major contingencies in a project – delay and cost over-run. Delays are usually caused by insufficient or inefficient resources; cost over-runs are caused by purchase price escalations and wastages. Delays might themselves cause cost escalation during idling of resources. Moreover, delays and cost rise might be planning errors, as well. On the EVM curve, a downward deviation of earned value (EV) curve from planned value (PV) indicates a project delay. An upward deviation of actual cost (AC) from planned value indicates a cost over-run.

For a delay, an affine transformation of PV curve may be used to estimate the projected project completion time. It is conventional to scale the PV curve to arrive at a proportionate delay at project closure. The scale factor may be ratio of PV/EV at generic time or Actual Time (AT)/ Scheduled Time (ST) at generic EV. Similarly, an affine transformation by scaling PV curve is used to estimate the cost at completion, the scale being the ratio AC/EV at generic time.

These estimates do not deterministically predict actual delay or cost over-run because the PV curve is itself not deterministic. Indeterminacy of PV curves may be due to various reasons:

Probabilistic nature of planning: Optimistic PV curves are steeper, accommodates minimum float and does not allow for schedule compression. Pessimistic PV curves are flatter and allows for expedition during execution.
Adjustment of float in non-critical tasks: Early start PV curves are steeper during initial stages and flatter at later stages. Late start PV curves are flatter at initial stages and steeper at later stages.
Inventory management method: By definition, PV curves are plotted with JIT inventory management basis. When materials are purchased in bulk and stored in central stores, planned costs (PC) are likely to be greater than planned values during initial stages of the project. In such cases, it may be necessary to plot PC as a separate curve in the time domain.

Although, PV curves are in reality smeared over the time domain by probabilistic nature, adjustment of float and cash flow parameters, it is customary in EVM analysis to regard PV curve as a deterministic curve. Thus, estimates of project delays or expenditure over budget at completion turn indicative and non-deterministic.

Summary of PDCA Analysis by Earned Value Method

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(Construction Project Management - Part V)

The essence of PDCA analysis using EVM method in project management may be summarized in following procedures:

Probabilistic planning and scheduling; delineation of planned value region
Calculation and depiction of early start and late start schedules
If inventory is not Just-in-Time, probabilistic or deterministic inventory flow analysis to calculate planned costs
Continuous measurement of earned value and actual cost, such that curves are differentiable and slopes can be calculated
Superposition of inventory flow on earned value to identify earned costs
Comparison of earned values to planned values; (for no deviations thereof,) actual cost to planned cost; (and for deviations thereof,) actual cost to earned cost
Formulation of delay or cost recovery curves by proposing suitable recovery slopes
Analysis of proposed recovery curves for inequalities defined by smeared planned value region, float adjustment and cash flow constraints
Forecast of projected delay and cost over-run based on approved recovery curves

Intensive application of EVM analysis requires mathematical formulation of work values and costs that are amenable to calculations at all stages of analysis. Value is associated with the numerous works in the project and cost is associated with the numerous resources that contribute to various works. Accordingly, each work package in the WBS should allow following mathematical operations:

Scheduling for a planned value of work in a given duration; calculation of effort of each resource required for this planned value.
Execution of certain earned value of work over a control period mutually exclusive of other work packages in proportion to the actual effort of resources employed during the control period.
Measurement of actual resource efforts in the control period and earned value of executed work.
Assessment of deviation between planned value and earned value over the control period and attribution of the deviation to deviation in resource effort.

The resources that contribute to a work package in foregoing formulations are always complementary. No resource can independently affect quantum of work. Resources jointly act in functional combinations to produce a quantum of work. Hence, value of a work in unit time depends on the cost of the set of relevant resources and effort of each resource contributing to produce unit work in unit time. When resource supply is enhanced during a work with an intention to expedite a work, such enhancements has to be uniform on all resources in accordance with the functional combination of resources in the work. Increasing one resource without proportionately increasing others would not result in meaningful transactions vis-à-vis increase of work performed and/or reduction of work duration.

In economic terms, two or more resources are said to be complementary if they are used together during consumption. In construction, most resources are complementary in specific contribution ratios in activities. Three types of complementary resources can be identified in economics (of construction):

Perfect Complements: Bolts-nuts and Machines-operators are complementary resources in all instances with fixed mutual contributions. For many practical purposes, two or more perfect complements may be consolidated as a single composited resource. However, during definition perfect complements may have distinct units and distinct values.
Imperfect Complements: Majority of construction resources fall into this category, because complements combine in different non-fixed ratios in different consumption events. Relative proportions of resources may vary in reality and consumption occurs with non-fixed contributions.
Non-mutual Complements: This type of complementarities occur when consumption of one resource requires a complementary contribution of another, but consumption of second resource does not require a contribution of first. For instance, when a process consumes a labour day, tool-days are also simultaneously consumed. A labourer may use different tools on different days; hence, consumption of a particular tool-day does not necessarily indicate a labour day.

Project Management - A suitable system?

2009-12-12T21:17:00.002+05:30

The issues in foregoing post can be offset by replacing the conventional linear incremental system by cyclical systems such as Deming-Shewhart cycles. Deming-Shewhart cycle of Plan-Do-Check-Assess described in 1930s is conducive to project management. It is also referred to in PMBOK of Project Management Institute and TCM framework of Institute of Cost Engineers.

The cycle attempts to plan projects in measureable parts, execute them, measure them and take corrective action. Frequency of planning, execution, measurement and correction vary among projects. Thus, the PDCA cycle creates a short-lived system and closes itself at predetermined intervals. Linear incremental systems on the other hand are enduring and intermittently improved at unforeseen contingencies.

Breakdown of project into measureable packages of work is imperative to project management because PDCA management is equivalent to measurement. An enumeration of works on a project is called a Work Breakdown Structure WBS. Works may be measured in three methods:

Quantity of work executed and quantity of resource-effort in fixed duration of time.
Quantity of work executed and duration consumed for fixed efforts of resources.
Duration consumed and quantity of resources at fixed stages of work.

The second model of measurement is generally used in pareto-optimization and operations research. It makes the domain of analysis extremely multi-variate. Resource-efforts seldom remain constant or cyclic in practical projects; hence, this model is not amenable to cyclic system. Controls based on this model constitute Go/No-Go Decisions or Binary Control techniques, wherein trial runs about a method can be used to decide about application of the method to an ensemble.

The third model of measurement is suitable in Post-Control or Retrospective Control techniques. It is by far the most accurate model of measurement and hence followed for commercial operation of projects – to receive and make payments. However, since works are not repetitive, this method is not suitable for implementation of cyclic systems.

By far, the most suitable method is to analyse work done and resources employed in fixed spans of time because time domain is uni-dimensional. All variables can be related to time and cycle frequency can be easily defined in time. Monitoring work on limited periods offers possibility of imposing Steering Control. This has been used in defintion of Meredith-Mantel Cybernetics (2006).

To conclude, it is necessary to measure work for fixed effort before the project (or part thereof), for fixed duration during the project (or part thereof) and for fixed work after the project (or part thereof).

Project Management - Difficulties

2009-12-09T20:35:00.002+05:30

An organization is a set of resources ordered by a mission driven towards a set of predefined objectives through a set of operations. Management is the profession of directing resources towards objectives through pragmatic decision-making.

Management seeks to impose uniformity of decisions and collective binding on the decisions across the organization, because output of organization is collective effort of different individuals. The most accepted method of management in this regard is the systems approach of management. This approach attempts to formulate a systematic procedure for a majority of routine works in the organization. Contingencies are situations that are not covered by the system, and discretion during contingency updates the existing system.

Operations are of various types. It may be continuous as in line production, intermittent but repetitive in batch production. An operation that has a distinct life span is called a project. A project that transforms the quality of geographical space is called a construction project.

The basic distinction of Project management is that mission, objectives, organization and operations of a project are transient. This throws many challenges on project management:

Definition of projects and their objectives are one-time events. Hence, they tend to be incomplete (causes scope-creep), optimistic (causes over-run), non-comprehensive (causing conflict in various operations within the project) and ineffectively communicated (causing conflict among team). When projects are technical, as in construction, they also tend to be complex and procrastinated for detailed technical designs.
Processes in a project are short lived; documentation & data-capture are non-routine. Identification of suitable system, training project personnel on the system, real-time implementation and adaptation for contingencies – all may be individually or collectively longer than process duration. Hence, project personnel tend to work without a proper management system; projects (or processes thereof) close with unsatisfactory completion or gross failure. In construction projects, projects are subdivided into activities that are even more short-lived than the project and each activity may need a technical system for proper control.
Project organizations are ad-hoc. They are assembled specifically for the project and are hence subject to considerable inertia. Introduction of a project is itself a perturbation on existing system. In construction projects, project organization involves different firms with different objectives. Ad-hoc assembly of different organizations are governed by documented contracts. Limitations in project definition and system usually make contract documents non-transparent and ambiguous. Technical assessment and/or value engineering by contractors at pre-tendering stages is skipped.

Simulation Analysis in Architecture

2008-07-12T11:51:00.003+05:30

Model making has always been a significant tool for architects in decision making supplementing bare imagination and experience. Modelling itself has evolved through a long way. Schematic presentations such as perspective drawings and physical models have been used for a long time. Techniques for proportioning such as the modular man and golden section rules were developed with advent of modern architecture. Virtual and animated models using software such as 3DStudio are recent variants, enabling analysis of prototype with more attention to details.

A new family of modeling applications called Monte Carlo models is emerging to make possible analysis of dynamic movement of men and materials within the built environment.

Monte Carlo Simulation Models
Schematic and physical models, serve in analysis of static aspects of the building such as its form, scale and proportions. Seldom do they lend useful information on the more so dynamic parameters of design of the built environment such as the circulation of occupants and actual functions of the building. Proportions of parking lots, elevators and escalators cannot be analyzed based on the actual utility and function in hand using these techniques.

Consider for instance the task of fixing the number, capacity, operation and layout of elevators in commercial complexes. Golden rules for proportioning elevators are indeed available for simple buildings with limited and uniform traffic on centrally located elevator systems. However, there are larger projects with lifts located at different positions in the building, such that some of them operate at express speeds and some are larger in capacity than others are. Normally architects rely on experience to select a suitable mix of elevator capacity and speed. Severe drawbacks in this approach are evident from real experience of users waiting long for elevator service in some buildings and lifts that remain idle for long durations in some.

Monte Carlo family of modelling applications is now becoming increasingly applicable to such analysis. This consists of virtually modelling the proposed circulation system on a computer and allowing a randomly generated oncoming traffic to flow through the system. This model is statistically analyzed for the average waiting time of the traffic and the idle time of the system. The system is then, continually modified to strike a balance between the two.

Software for Monte Carlo Simulation
Monte Carlo modelling has been used for some time in industrial and manufacturing engineering fields. A score of general simulation software such as GPSS (General Purpose Simulation Software), SimCad, FlexSim, Arena, Promodel, Simfactory, Siman and Simula have thence been developed for the purpose. As architectural applications are relatively new to this field, virtual modeling software used in architecture, are yet to include modules that permit movement simulation within ordinary animated models. An active drive may be necessary to facilitate the same within commonplace software.

However, most general-purpose simulation packages can currently be customized and programmed for the architectural application in hand. For example, the GPSS-World software contains an example application for car parking lot at a supermarket, in its manual. Information and free download of student version of the software is available on http://www.minutemansoftware.com/. The airport lobby model is detailed in FlexSim enterprise simulation software; more details about this software are available on http://www.taylorii.com/. SimCad from Create-a-Soft Company works on combining CAD with simulation (Refer http://www.simulationsoftware.com/). More information regarding simulation works and engineering applications are available on http://www.tcdc.com/.

Technology is indeed taking us places: we are driving nearer to designs that proportion the form closely following the functions.

Application to Lift System
Carrying the foregoing involvement slightly further, an examination of the difficulties in making rational decisions concerning the lift system example reveals the following:

People arrive from outside the complex and wait for lifts to upper floors and people within the building wait to come to lower floors in different manners.

The arrival rate vary from time to time with peak values during particular timings

People using the lift may come in groups and may prefer to move in such groups

The building may comprise of different segments, say a few floors for shopping, few for office spaces and few for residential occupation. Of the customers who arrive some may have to go to shopping floors, some to offices or residences

Lifts may be located at various places in the building so that a person may select a lift based on his proximity to the lift when he wants to travel upwards/downwards

The lifts may be of various speeds, some of them not stopping at certain floors so that the traffic is split among the lifts; not all passengers wait for the same lift

The situation is indeed complicated that it is apparently senseless to pursue to find a rational solution to the problem. Randomn simulation comes to help in such conditions.

In order to make an analysis, the modeler proposes a suitable elevator system comprising of certain number of lifts, some of them with a particular capacity/speed located at various places in the building. The number, capacity, speed and layout of the lifts become the parameters of the problem. The arrival of the passengers (outgoing and incoming), the passengers selection of lift location and speed, and the destination floor are simulated by randomn number generation. (A randomn number is a number generated by a wild guess; for any number guessed, it could have been some other number as well. Then, a wild guess between 0 and 10, for example, can be used to decide which floor a particular passenger is heading to, in a ten-story building. Guesses can also be made educated using actual statistics; if it is known that around thirty percent of traffic moves to first floor only, randomn number can be so generated such that thirty percent of all the randomn number is 1). Thus as passengers arrive, if the lifts are busy, they wait and the waiting time of each passenger is recorded, while passengers keep further coming according to randomn number generation. On the other hand, if no passenger is using the lifts for some time and the idle time of each lift is also recorded. Any discrepancy in the guesses evens out as the process is carried out for a full-simulated day.

At the end of this experiment, the modeler is informed about the limitations (average waiting time of the passengers and idle time of lifts) of the initially proposed system. Based on the results of this analysis, the modeler can make changes in the initial propositions, such as changing the position, number, capacity and speed of the lifts. The parameters of the problem are hence varied and the experiment is carried out again for a fresh simulated traffic. By repetition of this routine, the lift system can be optimized. The wild guesses can be made more educated if actual statistics of arrival time of passengers, service time of lifts and time spent by customers in the building are known, to yield more accurate and realistic results.

A similar analysis can also be made for car parking lots in commercial complexes for number of parking spaces such that space is neither wasted nor insufficient. It is also useful for deciding on circulation spaces such as airport lobbies and taxiways, production and storage space in laying out factories with line/batch production and so on.

Expansive Soils

2008-07-02T14:22:00.005+05:30

The problem of expansive soils was not recognized until late 1930s. Then, cracks on brick wall structures of light buildings were then attributed to bad workmanship or foundation settlements. The first recorded observation about soil heaving was made by USBR in 1938 associated with foundation for a steel siphon on Owyhee Project in Oregon.

For purposes of definition, expansive soils are (clayey) soils capable of undergoing considerable volumetric deformation usually along with variation of moisture content. While a rational analysis is sought about such soils, it is necessary to address two issues. One, why soil heaving takes place or what geological/chemical processes are responsible for swelling of some clayey soils. Other, how can the process of swelling be physically measured and quantified so that it may be useful for engineering decision making.

Nature of Expansive Soils

Expansive soils originate by two types of geologic process:

Basalts of Indian Deccan Plateau, dolerite sills and dukes in Central South Africa have underwent considerable chemical residual weathering, so that feldspar and pyroxene minerals have decomposed to montmorillonite.
Expansive soil deposits in North America and Israel are mainly due to physical weathering of secondary sedimentary rocks containing montmorillonite minerals.

In the above context, the term montmorillonite minerals is used to refer to all clay minerals with an expanding lattice (except vermiculite), because montmorillonite is the clay mineral that presents most of the expansive soil problems. Normally clay minerals: montmorillonite, illite and kaolinite are formed through a complicated process of weathering or halmyrolysis of parent materials, especially, feldspar, mica and limestone. The process usually includes disintegration, oxidation, hydration and leaching. Formation of montmorillonite occurs under extreme disintegration, strong hydration and restricted leaching so that magnesium, calcium, sodium and iron cations may accumulate in the system. Thus an alkaline environment, presence of magnesium ions and lack of leaching aids formation of montmorillonite minerals. So semi-arid regions with relatively low rainfall or highly seasonal moderate rainfall, particularly where evaporation exceeds precipitation contains such deposits. Under these conditions, enough water is available for hydration but accumulated cations will not be removed by flush rain.

In the light of research works conducted during 1960s, swelling mechanism is attributed to the osmotic pressures developed between fresh rainwater and montmorillonite minerals with cation base on surface. Since montmorillonite minerals are smallest and permit maximum base cation exchange reactivity, it is capable of attracting water into interstitial spaces as adsorbed water. As osmotic pressure is the only internal pressure acting between particles, if the soil is subject to external pressure, the distance between particles decrease, water is squeezed out. As a result, cation concentration between particles increases and osmotic pressure in turn increases. Equilibrium is finally reached when osmotic pressure equals the external pressure. Subsequently if there is a reduction in external pressure, suction of water by osmotic pressure occurs between the particles to dilute the concentration of ions, causes increase in volume and reduction in the osmotic pressure. This process continues until a new equilibrium is established.

Mechanics of Swelling

If the environment of the expansive soil has not been changed vis-à-vis - Release of pressure due to excavation, Desiccation caused by increase of temperature, And/or introduction of moisture - Swelling does not take place.
Moisture introduction into an expansive soil deposit can be expected if there is a potential gradient for migration of water and a continuous passage for transfer of water.

The gradient is usually gravity and/or capillary rise of ground water. The possibility of transport by vapour, formed on hotter surface to cooler surface, say under pavements, and can initiate swelling. The review panel of engineering concepts of Moisture Equilibria and Moisture Changes in Soil beneath Covered Areas, states that the major change induced in soil by a surface cover is the detraction in the rates and quantities of water able to enter and leave the soil at surface.

Kraynski (1973) explained the moisture content variation with depth in a homogeneous soil under covered and uncovered conditions. In a covered area, moisture content of soil reduced with the depth and there is no moisture exchange with the atmosphere. On an uncovered area too, moisture content reduces with depth below an intermediate zone, so that above this, surface evaporation is critical as well. At some depth called the depth of desiccation below the ground level the water content under uncovered area could be equal to that if area were covered, hence this depends on climatic condition and type of soil. The depth of desiccation represents the total thickness of material which has a potential to expand because of water deficiency. It is impossible to determine this depth, while it is at the maximum equal to depth of ground water table. During time of precipitation, moisture content of near surface increases and again reduces during evaporation. However, the seasonal variations are limited generally, over what is called a depth of seasonal moisture content fluctuation, which may extend from about 1-3.5 m depending on the alternation of drying and wetting climate. Influence of other factors such as watering of lawns, trees and shrubs and domestic drainage on the variation of this depth cannot also be neglected. In case of covered areas moisture transport by gravity, capillarity and vapour migration occurs very slowly and causes swelling over several years after construction. For such span of time, the depth of seasonal moisture content fluctuation is equivalent to depth of desiccation.

Among various factors that influence the expansion are:

Initial moisture content and dry density: Expansive soils do not swell or shrink unless there is an increase in moisture content. Dry soils expand the most and the slope of e-log p curve of swelling decreases as initial moisture content increases. It is also established that prolonged wetting well result in more swelling than short duration wetting. Also complete saturation is not required to result in large heaves; thus removing free water by drainage does not arrest foundation movement.
Superimposed loads: Without superimposed loads, swelling cannot be controlled even with a minimum amount of moisture change. For lightly loaded structures, including slabs on grade, a short duration wetting can cause equally heavy damage as long duration wetting.

Since the characteristics of swelling were dependent on numerous parameters, it has been difficult to standardize a unique measure of swelling capacity. Nevertheless, the most common measure is the swelling pressure defined as pressure required to maintain zero volume change in undisturbed or maximum Procter density in remoulded samples. The swelling potential is measured using a consolidation test apparatus either by adjusting superimposed pressure such that volume is maintained constant or by allowing the soil to expand freely under a surcharge and measuring the pressure to regain original volume. The advantage is that the swelling pressure is not affected by initial moisture content, degree of saturation, stratum thickness or extent of shrinkage. It is affected only by the initial dry density as swelling potential increases exponentially with the dry density, in-situ. Thus for undisturbed samples, the swelling pressure at in-situ dry density can be used directly to describe the swelling characteristics. For remolded soils, swelling pressure varies with the degree of compaction and maximum Proctor density (at optimum moisture content) is taken as guide.

Foundation & Soil Engineering on Expansive Soils

A number of projects in this country, are constructed on expansive soils. There are two approaches in engineering developments on such soils. One, the structural components such as foundations and slabs on grade that are directly in contact with such soils should be designed for possible upheaval and swelling pressure. The other way is to control moisture and stabilise soil with an intention to bring down the swelling potential of the soil. It cannot be over emphasized that, both these approaches or a mixture of these would not be possible, without a complete understanding of the nature and mechanics of swelling soils.

It is known that buildings can be constructed on swelling soils using straight shaft/underreamed piles; however, the utility of undereamed piles is questionable in many circumstances and there is a general tendency to misuse these. Besides, it is rarely appreciated that footings and rafts can also be conditionally used for buildings on expansive soils.

Installation of moisture diaphragms and barriers are sometimes effective in control of swelling. soil stabilization can also be undertaken by ponding or chemical treatment.

Foundations in Expansive Soils

Straight shaft or underreamed piles have been used on expansive soils for quite some time. The piles may be friction or end bearing or both and requires the bulb to be placed below the depth of seasonal ground water fluctuation. There should also be no direct contact between the soil and structure excepting the piers. For piles with straight shafts, the uplift pressure proportional to the swelling pressure of soil acts on the wetted surface of the piles and is withheld by the dead load pressure on the pile and skin friction along unwedded portion of the pile. Underreamed piles on the other hand offers two additional components withholding the uplift viz.; weight of soil in shaft described by the bulb and shearing resistance along a circular plane of failure caused by the bulb. Thus, whereas a straight pile shaft may be affected by loss of friction if the soil gets wet, undreamed piles provide a marked advantage.

Footings can be successfully used on expansive soil if sufficient dead load pressure is exerted on the foundation, the structure is rigid enough to withstand differential heaving without cracking and/or swelling potential of soil can be eliminated. Narrow continuous spread footings under masonry walls have been found to be effective in soils with low degree of expansion (with less than 1% swelling potential). Such spread footings are preferably to be constructed with RC walls or the entire structure can be converted into an RC box. Individual RC column footings may be used in cases where underreamed piles are not economical, soil cannot mobilize skin friction, swelling potential is moderate and bearing capacity of soil is high. It is however important to strike balance between allowable bearing capacity and the swelling pressure, It must also be noted that, swelling can be prevented only in localized zones beneath the footings where the stress induced by the foundation are concentrated.

Raft foundations on expansive soils are likewise to be designed for both the bearing pressure and the swelling pressure. The stiffness of the raft makes it advisable for simple lightly loaded buildings on moderately swelling soils. The design of the raft requires the value of a support index that depends on soil sensitivity and climatic rating. Hence, usually adoption of raft requires tests to be undertaken on undisturbed samples.

Slabs on Expansive Soils

By far, the most important problem in design of structures on expansive soils is that of slabs of grade. Slabs placed directly on grade with or without high reinforcement, crack heavily due to rise in water table. It is disputed about the use of gravelly layer beneath such concrete floors, but a major advantage of sub-floor drainage and even distribution of loads could be achieved. Use of structural slabs on grade and raised structural slabs with crawlspace or honeycombs separating from the soil are also clear but expensive solutions. Sometimes it is possible to insert slip joints between floor slabs and grade beams such that the slab is capable of independent movement. Such slabs are called floating slabs, and prevents transfer of uplift pressure to column foundations. The slip joints are provided using asphalt felt expansion sometimes oiled with tempered masonite and silicone lubricant. It must however be noted that heaving of floor slab also result in cracking of partition walls directly supported on ground and requires separate slip joints. Further, the doorframes are required to be hung from the top rather than supported on floor.

Stabilization Methods

Moisture Control:

It is possible to control swelling by maintaining moisture content of soil constant although the procedure is very difficult. Horizontal moisture barriers, such as polythene membranes buried near surface, concrete aprons around building and asphalt membranes can limit direct percolation of water and rise in water table. Vertical moisture barriers such as sheet piles, concrete diaphragm walls or polythene membranes are required to arrest moisture and vapor transport from surrounding area into the foundations. It is noted that, compacted backfill can usually serve the purpose of a vertical diaphragm at cheaper cost.

Subsurface drainage is installed for three purposes:
1. To intercept gravity flow of free water into the site using intercepting drains
2. To protect against formation of perched water tables
3. To arrest capillary and vapor movement of water by installation of peripheral drains around the building.

It is advisable to avoid lawn sprinkling, vegetative landscaping and faulty internal plumbing. More so, roof downspouts should be directed away from the ground.

Soil Stabilization:

Soil stabilization methods for expansive clay ponding and chemical stabilization.

The oldest is to flood the soil by ponding, so that swelling is achieved prior to construction. Pre-wetting takes a considerably long period of ponding (1-2months) for complete swelling due to impermeability of clay. Footings cannot be placed on pre-wetted soil that has low bearing capacity and pre-wetting can cause detrimental long-term effects as moisture travels to dry lower strata in course of time. These shortcomings may be removed by compacting the soil to low densities and high moisture contents, so that swelling pressure (of loose soil) is reduced. Replacement of soil unto that level where surcharge would compensate swelling is also a plausible but usually expensive solution.

For highway and airway pavements, lime stabilization by direct mixing or pressure injection has been successful. Lime can lower base-exchange capacity of soil, increase particle sizes by flocculation and hence reduce the plasticity of soil. Chemical stabilization may be done using cement, fly ash and organic or inorganic chemicals.

Fire Hazaards in Buildings

2008-06-30T12:01:00.004+05:30

Damages caused by fire in buildings

Fire can cause damages to buildings in various ways:

Actual burning during fire

Heat generated during fire

Smoke from fire

Problems during extinguishing of fire

A brief account of damages possible is discussed below:

Actual burning during fire:
Effects of actual burning during fire are confined to combustible materials including wood and wood products, paints, asphaltic types of roofing and sliding electrical insulation etc. Masonry, plaster, steel and other materials do not support combustion

Heat from fire:
Extent of damage to building materials from the heat that is generated by the combustible parts of the building depends on temperature reached and time of exposure.
- Brick, stone works, steel and other metals expand in presence of heat.
- Lateral expansion of steel girders during a fire may push out exterior masonry walls.
- Light exposed steel structural members soften and lose their strength causing collapse even in moderate fires.
- Long exposure of masonry to fire or alternate heating then cooling by water may cause spalling of masonry.
- Glass cracks at relatively low temperatures and softens at about 1600°F.
- Plaster tolerates fairly high temperature before flaking and chalking on the surface, with a change in its chemical composition.
- Wood shrinks slightly as they lose moisture especially boards of timbers wider dimension.

Smoke from fire:
Two kinds of smoke can occur during a fire. One is a hot smoke; the other is a cold smoke. Hot smoke is closer to the fire and carries the heat of the fire. While cold smoke is away from the fire and has cooled and condensed, sometimes in the form of soot.
Hot smoke can penetrate porous surfaces and leave heavy stains on building decorations such as wallpaper and ceramic tiles. These stains are generally impossible to remove. Hot smoke damage in stonework, brickwork and cement surfaces and are difficult to remove. Hot smoke also causes smoke odour in the building.
Cold smoke does not cause smoke odour and stains can usually be removed by vacuum cleaning or washing.

Operations undertaken during fire:
Operations undertaken during fire to extinguish it may also cause damages to the building.
Water used to let out fire may cause following:
- Wetting of electrical cables and conduit
- Kiln dried or well-seasoned wood absorbs moisture to swell. Swelling occurs until fibre saturation point (about 25%).
- Plaster and adhesives softens in presence of water.
- Water behind enamel paints forms small blisters ruining appearance.
- Use of salt water causes corrosion of metals.
Freezing of water in winter during or shortly after a fire cause damage by expanding in plaster, water pipes, toilet bowls, taps and hot water systems.
Use of calcium chloride, foamete, carbon tetrachloride etc as fire extinguishers may stain or discolour surfaces. However, carbon dioxide does not cause any harm.
Operation of firemen such as breaking open of doors or windows for getting in or ventilating the premises may cause permanent damages. Debris from upper floors and cupboards that fall on to floors, may cause damages by impact.

Fire Proof Construction
A fire proof construction is a typical construction that has facilities to prevent origin and spread of fire and has necessary fire exits and extinguishing systems.
A fire originates in the event of development of ignition temperature over a combustible material in the presence of air or other fuels. It is almost impossible to prevent the development of ignition temperature. Torch effect resulting from intensive heat radiation across façades such as glass is next to inevitable.
A better idea is to prevent use of combustable materials in the structure and emphasize better fire control over building materials.

Fire resisting characteristics of common building materials are detailed below:

Stones: Although stones are bad conductors of heat, event of fire may cause disintegration of stones into small fragments as it is heated and suddenly cooled.

Bricks: Brick is a fire resistant material being both a bad conductor and having an ignition temperature over 1200 deg C, when combined with good mortar and workmanship.

Timber: Timber ignites rapidly and gets destroyed in fire and may also intensify any accident, however deep sections of wood takes time to ignite and proper fire protection can be imparted to timber.

Glass: Glass responds to alternate heating and cooling with formation of cracks. Reinforced or fibreglass is more fire resistant than ordinary ones, however.

Cast Iron: Cast iron flies into pieces when heated and suddenly cooled. In structural works, it is covered either by one brick thick brickwork or by concrete.

Steel: Steel gets heated up in case of fire and its tensile yield stress at 600 deg C is reduced to about one third. Thus, fire is often accompanied by structural collapse. Steel also assists in spread of fire. However, plates of steel are effective in resisting the passage of the flame.

Concrete: Concrete is an effective fire resisting material. the actual behaviour however depends on the quality of cement and type of aggregates forming the concrete. In reinforced concrete, the position of steel is an important requisite. Expansion of cement although partly balanced by shrinkage due to loss of water, may cause cracks however there is practically no decrease in strength until 250 deg C. A small loss of strength occurs thereafter, and the rate of loss decreases gradually with temperature. At about 1000 deg C, the strength of concrete is only 20% of its original strength.

Fire Protection of Buildings
It is practically impossible to eliminate the possibilities of fire in a building. However, much can be done by proper selection is to limit the fire size and duration, and the hazards during fire.

From this footing, modern buildings require:

Means of exit of occupants during fire

Provision of fire extinguishing and fighting devices

Access for the brigade extinguishing fire

First aid facilities for victims

Services to prevent the spread of fire

While the aforementioned services are necessary for public if not all buildings in general, the construction should be made fire resistant to the extent possible in those buildings, where there is an impending or potential danger of fire.

Fire Protection of Concrete Buildings

Fire in concrete structures may be prevented by increasing the cross section, using low-density concrete having lower coefficient of thermal conductivity and use of highly fire resistant concretes.
The reinforcement bars must be prevented by clear cover. On this consideration, low alloy steel is better than high strength cold drawn reinforcement or hot rolled bars.
RC ceilings with hollow tiles are better than ordinary open ribbed structures because fire resistance can be increased by limiting the heating of lower boundaries during a fire.

Fire Protection of Timber Buildings
While the ignition temperature of timber is 330-470 deg C, a temparature over 430 deg C may be harmful due to formation of pyrophorous charcoal. Woods of higher density ignites with difficulty because of its high conductivity that requires more heat per unit volume to ignite. The surface to volume ratio also has marked effect on flammability. Besides all these, timber is unfortunately not very effective in spreading a local fire.
Fire retardants and salt melts such as monammonium phosphate, boric acid, borax or diammonium phosphate may be applied to decrease fire susceptibility by
1. Preventing direct contact with oxygen
2. Liberation of gases that extinguishes fire during decomposition and
3. Evaporation of the salt at lower temperatures.
An application of solution of sodium silicate and kaolin in water is also very effective in fire protection. Generally, two coats are applied. Facing materials and plastering on timber retard rise in temperature of wooden structures. The facing materials and plastics must have low thermal conductivity. Asbestos cement sheets, gypsum plates may be used for this purpose.
Avoiding cavities in the whole construction can effectively prevent the spread of fire wooden buildings may be divided into fire areas by fire barriers to prevent spread of fire and advantage in extinguishing fire.

Fire Protection of Steel Buildings
Steel structures undergo structural collapse in the event of fire. The fire resistance is only about 15 minutes and connections may be substantially affected. Presence of combustible materials makes systems worst.
Fire resistance of steel may be increased by plastering or facing. Concrete, bricks, hollow ceramic tiles, plaster gypsum, porous clay slabs, asbestos cement etc prevent fire damage to steel structures. The integrity of facing and plaster must be assured under normal working conditions as well as during fire.
Special design provisions and factors of safety can be applied to steel design.

Long Term & Housing Finance in Construction

2008-06-24T11:34:00.005+05:30

Finance to construct, purchase or renovate a development repayable over long term -
The borrower is usually a person intending either to occupy the development or let/lease it to a tenant. Loan is issued based on the income of the borrower, and developed property is mortgaged to lender. Borrower cannot sell the property until the loan is settled.

As, these loans are repaid in installments over very long span of time say, 10-20 years and they are called long-term loans. For example ordinary housing finance is a long term loan. Long-term loans are usually given by financial institutions which can hold the loan for long term. This includes insurance companies, provident fund or specialized housing finance institutions. Large banks which can hold funds for long term may also provide long-term finance.

Difference between long term finance, short term finance and mortgage loans
The difference between long-term and short-term finance is that former are secured on completed buildings whereas the latter are issued before construction. Hence capital is much safer, although not liquid. Profit to occupant is contained by the difference in interest payable and the rental income.
The difference between long-term and mortgage hold is that former are repaid in installments consisting of interest payments plus capital repayments on a regular basis. In mortgage hold, borrower is required to pay only the interest until the end of loan period and pay back the capital at the end. Other modes of repayment also exist for long term loans.
Types of long term finance are based on the kind of development that is involved. Accordingly, long term finance takes form of housing loans, industrial loans and commercial loans.

Long term finance includes:

Finance to purchase undeveloped land and construct property. Both land and proposed property is security in mortgage. Loan is issued in stages of construction and repayment starts after the construction period, agreed upon between the lender and borrower.

Finance to purchase a finished property. Depreciation at the time of purchase may be an important factor in the quantum of loan. Repayment starts immediately after occupation.

Finance to renovate a property. Usually existing construction is security in this case. Loan is issued in stages of renovation work and repayment starts after the development period,that is agreed upon by the lender and borrower.

Housing Finance
Housing finance is a long term loan where land use is residential. Being a long term loan, housing loans are issued by banks or private lenders who support long term lending or more predominantly by financial institutions. The general term housing finance includes and encompasses following types of loans.

Purchase of land

Construction of house

Expansion or renovation of house

Purchase of house or apartment

Refinance of completed loans by mortgage

Features of Housing Loans
Housing finance industry predominantly consists of two types of service providers.
First and more common, the financial institutions such as HDFC, LIC etc. They procure money from small investors by insurance schemes, provident funds, family welfare schemes, gratuity funds etc. These funds are not reimbursed to the small investors in principal or interest until a maturity period. Hence, institutions have the benefit of long term holding of funds. So they are capable of investing on long term assets such as real property and securities, whence they are called Institutional Investors (FII).
Second types of players in the housing finance industry are banks, mutual/benefit funds and private lenders. In most cases, these lenders are unable to hold loans for long periods. However, some companies supported by long standing fixed deposit and savings schemes from small investors do provide long term loan facilities.

Common features of housing loans are enumerated as follows.

All housing loans are mortgage loans i.e. the banks remain in possession of the title deeds of the property and execute a first mortgage agreement with the owner entitling the banks to sell the property to recover the loan in case of default.

Housing loans are repaid by the borrower from his personal income such as salary or profit of business. Hence, lenders of housing loans require evidences of income of the borrower in addition to security. In most cases, it is possible to include the collective income of spouse or other joint applicants of loan.

Occasionally, banks may also require additional security such as guarantor and/or life insurance policies. Sometimes additional or collateral security may also be asked for. Government promissory notes, securities and fixed deposits are also accepted by few banks

Usually most lenders issue housing loans up to 85% of cost of the house. The other 15% (called seed money) needs to be provided by the borrower himself. The loans are disbursed in stages: upon identification of property, execution of legal documents and/or various stages of construction.

Normal rates of interest on housing loans vary from 5-15%. Interest rates may vary according to rules and sops introduced by the government and special offers given by companies towards marketing finance. Many banks offer fixed rate of interest that do not change with fluctuations in the market, whereas others offer floating rates of interest that changes with market conditions.

The repayment period may be varied at convenience between 5-20 years. The term usually does not extend beyond retirement age or 65 years age of the borrower whichever is earlier.

Housing loans are repaid by the borrower in monthly installments along with principal and interest. There are different types of installment schemes. Most banks offer Equal Monthly Installment (EMI) mode of repayment. Housing finance companies are entitled to collect post dated cheques towards EMIs over the repayment period.

The EMI comprises of both principal and interest and its value for a particular amount of loan over particular repayment period at a given interest rate depends on the period of interest calculation. Interests may be calculated on annually, monthly or daily basis. When there is a delay between commencement of EMI and disbursement of loans, the borrower may be required to pay the interest alone on the outstanding balance as pre-EMI interest.

Both principal as well as interest paid on housing loans involve tax benefits to the borrower. Tax deduction amounts to 15-20% of principal and interest payments can accommodated as outgoings before tax.

Most institutions charge a processing and/or documentation fees while processing and sanctioning the application apart from the interest. Processing fees are usually a fixed sum or sometimes a percentage of the loan amount.

Most institutions charge a penalty of 1-2% of outstanding due for closing a loan by paying back the principal before completion of the repayment period. This is called pre-payment penalty. Some institutions also charge a commitment fees for non-utilization of a sanctioned loan within a specified period.

For legal requirements, issue of housing loans require in addition to documents pertaining to the property, documents concerning identity, age and address of the borrower, credentials with bank accounts and documents relating to income and tax standing of borrower.

Selection of Housing Finance Parameters
Following observations are useful in determination of housing loan parameters on EMI basis.

For given loan amount, repayment period and rate of interest, EMI is lower for monthly balance schemes than annual balance schemes and is even lower for daily balance schemes. This is unless the savings in interest is offset by increased processing fees or other service charges.

For a given loan amount at a given rate of interest and calculation period, EMI reduces with increase in repayment period. The reduction is drastic from 5 to 15 years of repayment. Beyond this period, the reduction is slow.

For a given loan amount at a given rate of interest and calculation period, total amount repaid increases with increase in repayment period. The increase is gradual from 5 to 15 years, thereafter there may be drastic increase.

It is advantageous for the borrower to avail floating rate of interests when there is possibility of reduction of retail prime lending rates (PLR) in future. But when interest rates are likely to go up, fixed rate of interests are more beneficial to the borrower.

When a fixed rate of interest has been availed by a borrower in uncertainty of future market lending rates, it is advisable to avail a balance transfer facility with another bank offering an interest lower than the current rate, prepayment penalty and new processing charges put together.

Selection of Bank
Housing finance is an active sector in the finance industry even in the worst of times. With the entry of (subsidiaries of) multinational financial institutions and the growth of Indian institutions to international standards have contributed in various ways to the housing finance segment.
In general, while choosing financial institutions for procuring housing loans, borrowers look for following aspects.

Criterion of eligibility: Enhanced value of housing loans can be claimed from lending institutions by considering age, qualifications, spouses income, number of dependants, assets and liabilities, savings history and credit repayment as eligibility criterion in addition to income.

Processing time: Formalities of processing, paperwork involved etc. have come down considerably with improved systems of automation. In ideal cases, processing time should be less than 15 days. Most banks can sanction loan in matter of hours with proper documents. Many banks may also offer sanction the loan even before identification of the property.

Rates of interest: The lending rate war among companies are constantly bringing down the rates until, they may reach the minimum stipulations specified by the central bank of the country. It is advantageous to avail floating rate of interests in which interest rate responds dynamically to the sops introduced by government and market competition. But when retail prime lending rates (PLR) are likely to go up, fixed rate of interests are more beneficial to the borrower. When bank interest rates do not change while market rates changes, it is possible to arrange balance transfer facility with another bank. By balance transfer, the outstanding dues to bank charging higher interest are transferred to another bank that charges lower interest.

Reducing Principal: Almost all banks offer equal monthly installment based repayment, where the equated installment pays back both principal and interest steadily. While calculating reducing balance it is advantageous for the borrower to keep the calculating period to be lesser. Daily reducing schemes are more preferable than monthly reducing schemes, which are in turn better than annual reducing schemes.

Accessibility features: Availability of ATM, phone and net banking facilities make services of lenders more attractive

Benefits and incentives: Additional benefits such as free accident and property insurance to the extent of loan outstanding, discounts of interest and waiver of processing fees, prepayment penalty, commitment fees etc. are decisive factors in selection of institution.

Flexibility of schemes: Finance schemes should offer flexibility of schemes in terms of interest rates and repayment period. Many banks allow payment of outstanding dues ahead of repayment period with an intention to save interest. The facility to close account before repayment period and amount of prepayment penalty are decisive factors in selection of banks. Daily balance schemes make repayment more flexible, as an occasionally large deposit can be adjusted against outstanding balance to reduce interest costs.

Eligibility Criterion
Housing loans are repaid by the borrower from his personal income such as salary or profit of business. Hence, lenders of housing loans calculate eligible loans based on the income certificates. However, banks can be negotiated for higher values based on following considerations.

Age and qualification of the borrower: Younger the age and higher the qualifications, future earning prospects are brighter. As a result, higher estimates of eligible loans can be permissible.

Income of spouse or other family members: Income of spouse or other family members may be cited to enhance loan amounts, provided the joint applicants permit such arrangement.

No. of dependants: Lesser number of dependants may be used to advantage in calculating possible repayment of EMI.

Assets and Liabilities: Existing assets such as cars, stocks, shares and consumer durables increase confidence of lender on the applicant

Savings history: If applicant has remarkable savings history, this can be reliable evidence for credit worthiness. Many banks have innovative schemes where savings deposited in bank is considered against principal outstanding, so that interest may reduce. These savings deposits can also be withdrawn on requirement, so that interest is recalculated again on outstanding principal.

Credit repayment history: Banks where borrowers have a previous history of successful credit repayment, such as by credit cards, vehicle loans or personal loans support initiatives of the borrowers better.

Installment Schemes
Usually, during initial stages after development, projects fetch lesser revenue and revenue increases later either through increased demand or through inflation. Hence, the occupant pays installments more than incoming cash flow during the initial stages, whereas returns become more than outgoing installments at a later stage.
The arrangement of installments vary from institution to institution. Two extremes can be identified.

In Diminishing Monthly Installments, borrower pays constant installments of capital repayment every month, so that the interest on outstanding capital diminishes continuously. According to this scheme, borrower has to pay larger amounts during initial stages when the revenue from development is not fully matured.

In Equal Monthly Installments, borrower pays constant installments every month so that interest payments are larger initially and capital payments are larger towards the end. The EMI scheme appears convenient because it delays large payments until returns from development can be fully realized.

Rehabilitation of Corrosion Damages in Columns by Jacketing

2008-06-13T15:07:00.007+05:30

(This article is intended to present the technology and materials of construction, as practiced for a G+4 building in Chennai. This is not intended to be of diagnostic or design significance.)

Minor Damages

Jacketing with micro-concrete was adopted for columns in initial stage of corrosion with minor damages such as narrow cracks and discolouration, without appreciable damage to existing steel. The brief specifications and methodology for the same are as follows:

Existing structure shall be propped to ensure support during rehabilitation work
Plaster/concrete on distress areas shall be removed and steel exposed. The entire surface is cleaned preferably with sandblasting.
Zinc based epoxy primer shall be applied on exposed surface of reinforcement in one or two coats to ensure complete protection.
Packaged cement-based micro-concrete shall be provided to sufficient thickness all round existing columns. It is only needed to add water to packaged micro-concrete.
If after cleaning, fresh concrete area is larger than 100mm, concrete shall be provided with larger aggregate instead of micro-concrete. In this case, graded aggregates are to be mixed with packaged micro-concrete.
Before concrete, the column surface shall be soaked in water for few hours. Concrete surface may be provided with slow setting epoxy adhesive primer film to ensure composite action of old and fresh concrete.
Curing shall be done for 7 days.
A polyurethane outer coating may also be provided, if necessary
All chemical application shall be done by skilled contractors and shall be in accordance with manufacturers specifications.

Moderate Damages

Jacketing with carbon-fibre-composite micro-concrete was adopted on columns with later stage of corrosion and moderate damages such as cracks, spalling and some damage to existing steel.

The brief specifications and methodology for the same are as follows:

Existing structure shall be propped to ensure support during rehabilitation work
Plaster on distress areas shall be removed and steel exposed. The entire surface is cleaned preferably with sandblasting.
Zinc based epoxy primer shall be applied on exposed surface of reinforcement in one or two coats to ensure complete protection.
Depressions on surface may be filled with epoxy putty and/or cement-based micro-concrete. Large depressions shall be filled using micro-concrete with graded aggregates.
One or more layer of carbon fibre fabric shall be applied onto the surface sandwiched between two layers of suitable saturant polymers.
Before concrete, the column surface shall be soaked in water for few hours. Concrete surface may be provided with slow setting epoxy adhesive primer film to ensure composite action of old and fresh concrete 24 hours prior to application of jacketing.
Curing shall be done for 7 days
A polyurethane outer coating may also be provided, if necessary
All chemical application shall be done by skilled contractors and shall be in accordance with manufacturers’ specifications.

Severe Damages
Where columns are badly spalled and column steel is considerably eaten away, structural repair was done with RC Jacketing. The brief specifications and methodology for the same are as follows:

Existing structure shall be propped to ensure support during rehabilitation work
Excavation shall be done to expose footing top below.
Plaster on distress areas shall be removed and steel exposed. The entire surface is cleaned preferably with sandblasting.
Zinc based epoxy primer shall be applied on exposed surface of reinforcement in one or two coats to ensure complete protection.
Depressions on surface may be filled with epoxy putty and/or cement-based micro-concrete. Large depressions shall be filled using micro-concrete with graded aggregates.
The column size is proposed to be increased all round using M20 micro-concrete with graded aggregates. New main steel and lateral steel are to be provided. Steel shall be HYSD TMT bars. Clear cover of 50mm may be provided. Steel for use shall be clean and free from dust, rust or oily material.
Holes shall be drilled into overhead soffit and footing beneath. The depth of hole should accommodate load transfer. Rotary percussive drills may be used with air or water flushing. Diamond drilling is not considered suitable.
Pumpable grade polyester resin grout (paste/capsule) shall be used for filling overhead and vertical drill holes.
The bars are now pushed into the drill holes and positioned. Butt welding of bars may be permitted in case of lap splices. After the respective curing period of the grout, steel ties shall be tied round the steel and formwork for concrete may be made ready.
Before concrete, the column surface shall be soaked in water for few hours. Concrete surface may be provided with slow setting epoxy adhesive primer film to ensure composite action of old and fresh concrete 24 hours prior to application of jacketing.
M20 cement based micro-concrete shall be applied in the formwork to jacket the column
Curing shall be done for 7 days
A polyurethane outer coating may also be provided, if necessary
All chemical application shall be done by skilled contractors and shall be in accordance with manufacturers’ specifications.

Summary of Chemicals for Rehabilitation

Chemical	Forsoc	Pidilite	Sika
Zinc based epoxy primer (for corrosion protection of steel)	Nitozinc Primer	Dr. Fixit Epoxy Zinc Primer	--
Cement-based Micro-concrete (with/without graded aggregates)	Renderoc RG	Dr. Fixit Micro-concrete	SikaRep Microcrete
Epoxy putty	Nitocote VF	--	--
Carbon fibre fabric with saturant	Nitowrap EP	--	SikaWrap
Pumpable grade polyester resin grout (paste/capsule)	Conbextra capsule & Lokfix	--	AnchorFix
Slow setting epoxy adhesive primer (for bond between new & old concrete)	Nitobond EP	Dr. Fixit Epoxy Bonding Agent	SikaDur - 32
Aliphatic polyurethane coating (optional over finished surface)	Nitocote UR512	--	Sikalastic
Wax based Concrete curing compound	Concure	--	Antisol

Some Observations on Project Scheduling

2008-06-09T12:14:00.005+05:30

Many progressive engineers have attempted to plan and schedule moderate construction projects mostly unsuccessfully. This is despite the most advanced academic theory, sophisticated computational equipments and rigorous automated procedures of modern times. Successful project management never emerges despite earnest efforts: is this due to differences between theory and practice, inefficiency of modern technology or mismanagement of scheduling engineers?

Whatever be the reasons, scheduling has remained a mystery that demoralizes engineering community. Engineers with unsuccessful experience in project planning have given up the idea of rigorous scheduling as unpractical and have adopted management by day-to-day control of activities without a pre-engineered baseline. If a schedule is not useful in practice, the effort used in preparing it is an unnecessary overhead – cost can be saved by not scheduling, rather. Many other engineers still prepare schedules, for documentation purposes alone with little managerial applications. Few construction managers make contractors prepare weekly or monthly schedules and track project progress based on the submitted schedules, without attempting to revise or refine the plan holistically. Control is applied on what is, but thought is not applied on what could have been. Many construction companies also feel that conventional and run-of-the-mill projects such as construction of apartments, does not derive any advantage by scheduling, even if scheduling as a method were successful.

However, it cannot escape our attention that most projects around us (including conventional and run-of-the-mill types) have not been completed on time. Given the competitive economy of the day, builders are required to give consumers more utility at lesser costs. The importance of cost reduction on intangible components such as time cannot be over-emphasized, but to date there is no effective mechanism to make at least 80% control on construction projects possible.

Certain observations can be made about current practices of scheduling

Rigorous Schedules

Engineers tend to plan and schedule the project at initial stages rigorously and submit baselines for on-site control. This requires larger initial effort and more important, rigorous schedules require equally rigorous implementation and monitoring leading to failure at implementation stages.

Rigorous schedules cannot necessarily accommodate potential contingencies and unforeseen problems. There is no simple technique such as allowing contingencies in project cost estimates when it comes to project scheduling.

In most cases, information required for rigorous schedule such as extent of working capital available, interest cost of borrowed capital and extent of availability of materials, equipments and labour on credit is uncertain. Managers with sufficiently long experience to quantify the above parameters are seldom well versed with technology of scheduling. The cost of collecting information on a most-probable-basis by surveys is usually very high.

Shortest-path Schedules and Working Capital Management

Planning engineers usually concentrate on minimizing the time period of construction while scheduling. However, shortest period of construction need not be necessarily be the objective of the company for most moderate constructions. Expedient construction is important for contracting organizations executing time-bound projects; for other companies faster construction may involve escalation of costs, in terms of working capital requirements. This makes shortest-time-schedules to fail due to apparent working capital mismanagement.

Working capital on projects may comprise of borrowed and relatively free funds, such as own investments, retained earnings, capital released by sale of previous projects or capital generated by sale of developments in advance of construction.

Consider a stage of project where company needs to borrow capital in order to operate the project on schedule. If the company expects realization of a free fund in few days, it may attempt to deliberately delay schedule rather than increase liability. Under these circumstances, it is necessary for scheduling engineer to evaluate the cost of delay of project at every stage of construction. If the cost of delay is greater than the cost of borrowed capital, the company needs to borrow and maintain the schedule whereas if it is not company should delay the project.

The cost of delay includes interest cost of already borrowed capital during the delay period, cost of hired equipments and daily labour in the middle of work, overhead cost such as site office rents and site engineer salary during the delay period, loss of credit advantage on already purchased materials and hidden cost due to staggering of turn-over. Unfortunately, most minimum-time-schedules evaluate projects for a given time-frame but do not analyze possible cost-overruns due to prescribed delays at every stage of construction. It is necessary to make the schedule an information system for managerial decision making rather than as a document of tracking a hard-and-fast criterion.
The objectives of scheduling may be different for different organizations. Scheduling objective may be to

Reduce time period of construction irrespective of any actual or hidden cost escalation

Minimization of actual cost which may or may not require reduction of duration of construction

Minimization of hidden costs which may or may not require elongation of duration of construction

Managerial Coordination

Construction assignments are seldom undertaken single-handedly by one person or organization. There are a number of small players involved – architect, engineers, material suppliers, sub-contractors, labour contractors, casual labourers, equipment suppliers. It is important that information regarding the project schedule should reach each concerned organization or person by coordination.

If one of the organizations fails to make a commitment there is necessarily a schedule delay usually accompanied by a cost over-run. Procurement schedule of goods or services from different people is seldom created from a project schedule. Consequences of delay in procurement need to be highlighted and suitable alternate arrangements needs to be planned.

Sometimes schedules itself affect project organization. Consider for example a linear running meter process such as laying drainage channel. The process is characterized by a continuous fast process say excavation, followed continuous slow process say concreting the channel, then by a fast process say plastering of channel walls. Suppose there is also an imposed restriction that open excavation should be closed with cover slabs after a limited number of days. The direct approach of scheduling may be to consider the project as four continuous events: excavation starting from the first day, concreting starting from the second day, plastering starting after curing period say seven days followed by placement of cover slabs from tenth day. This schedule may not be successful because excavation and plastering being relatively faster jobs are out of phase with concreting. This may either result in idle labour/equipment for excavation and plastering or employment of plastering and excavation labour/equipment intermittently. Else it may be necessary to perform double work of placing the cover slab after excavation/concreting, removing them for concreting/plastering and replacing them again. The schedule needs to assist the project administrators in deciding which method of scheduling is best.

Schedules should also make parametric study on procurement of labour and equipments. For instance on a job of raising n number of RC columns what is the least cost schedule using m column boxes out of which k boxes are owned and (m-k) are hired? The schedule in this case should consider the number of days of job for different values of m, and calculate labour and other costs during that period to select that value of m that gives least cost. Academic routines are available today to treat such types of problems but these are not practiced and time tested.

Project plans should also assist the site engineers on day-to-day decision making for tracking purposes. For instance, consider a continuous concreting job with tight schedule of prescribed quantity of concrete per day. Suppose due to some unforeseen reason such as failure of equipment, only 75% of the prescribed quantity could be completed on a day. Is it advisable to carry over the remaining 25% to next days work or to complete the work on the same day by staying over-time? For this purpose, schedules need to specify the opportunity cost of cost components with respect to the work activity and project stages.

Many times top management of companies is not capable of appreciating schedule information in paper. Planning engineers may not possess vested powers for implementation of the schedule. Under such conditions, engineers may have to simulate different possible schedules in order to objectively make advantages of adhering to the schedule evident.

Some Guidelines

Based on the above observations, some guidelines can be arrived to make practicable work schedules.

Schedules should be on multiple tier architecture in following levels and characteristics.

Each activity such as concreting involving shuttering, bar-bending, placing of reinforcement, concreting and curing should be worked out for different parameters at one level to form a database of different work organization such as item rate, daily labour, lump sum, RMC, hired/owned equipments & labour contract for activities. Opportunity cost of parameters such as delay, credit, cost of capital etc need to be quantified for each activity. This database then becomes reusable again and again on projects.

The second level of schedule may consist of phases of the project such as foundation, floor concreting, painting etc. To begin with, the minimum time schedule may be applied on these project phases. The procurement and cash flow schedules may be derived from this shortest-time schedule. At this level on a generic day, various activities take place. Opportunity cost of parameters such as delay, credit, cost of capital, overhead expenses etc at every stage may be quantified by adding those for all activities at that stage.

The third level of schedule comprises of different project schedules incorporating parametric differences at second level. With broad outlines specified on this schedule it may be possible to exercise appropriate control over the schedules prepared by sub-contractors on periodic basis.

This multiple-tier scheduling may be academically similar to superimposition of optimization by dynamic programming with optimization by network programming.

The schedules prepared in the above format may be operated in the following manner

For every project only the third level project planning needs to be done because database of first level and arithmetic logic of second level scheduling may be available or may be developed based upon actual requirements. Thus, schedule becomes an information system for managerial decision making.

Let working schedules be prepared by subcontractors on periodic basis. The working schedules may be studied and modified against fair schedules that represent the requirement of the projects.

Monitor the schedules for project objectives and wherever there is a deviation, its impact needs to be quickly analyzed and corrective measures may be taken. If the deviations are due to unpredicted practical conditions the logic of schedule needs to be revised.

It may be better to employ singular person within the organization or external agency to be in charge of entire project, including interaction with auditors and financiers.

Unlike a building plan or structural detail, project schedule is not a document to be followed at a project. It is a language to interact. Schedules are similar to schemes prepared by architects. Schemes change many times during discussions between architects and clients; the changes diminish as design and construction are progressing. Schedules need to change during construction; all associated features need to be reanalyzed.

The aforesaid methodology is nevertheless, not ruthlessly practiced or time tested in the knowledge of the author. Suitable modifications or grossly different methodologies to confront the problems may also be possible. The objective of this document is to create awareness among construction companies that academic research on schedules is better sponsored and carried out by the industry with association from academia and software development companies