As you know, HSS refers to hollow structural sections – round, square and rectangular.  A new HSS specification, ASTM A1085, was announced at the North American Steel Construction Conference (NASCC) in St. Louis on April . . . → Read More: Curving a New Grade of Tubing: A1085]]> Curved tubing is becoming increasingly popular in building design, and the introduction of a new grade of tubing may increase its usefulness.

As you know, HSS refers to hollow structural sections – round, square and rectangular.  A new HSS specification, ASTM A1085, was announced at the North American Steel Construction Conference (NASCC) in St. Louis on April 16, 2013.

The new grade will have a more consistent wall thickness:  previous specifications allowed 10% variation; the new standard is 5%.  The corner radii will be larger.  (Engineers joked that the developers of the new standards were trying to make the square and rectangular tubes round.)  The new material has a defined upper and lower yield stress which will make it better-suited for seismic applications.  Finally, having standard requirements for Charpy notch toughness will make it more suitable for dynamic loading as in bridge applications.

In summary, the new spec should make HSS more economical and more efficient.  Read more on this new steel specification.

From the viewpoint of a bender/roller who will be curving this new material, greater consistence in the raw material should lead to greater consistency in the curved members.  To a greater degree than previously, each straight piece should roll more similarly than the last.  And that contributes to productivity and reduced costs.

Some tube mills plan on producing this product.  It will be interesting to see which other mills follow and which service centers stock it.

Designed by Theodore P. Zoli, the first structural engineer to win a MacArthur “Genius” Award, this truss bridge eliminates the gusset plates typically used to connect beams and girders to columns . . . → Read More: The First Gussetless Truss Bridge in the World]]> And the first to incorporate cold bending of steel, and the first vertical-lift bridge to tuck its machine rooms under the bridge.  A triply innovative play!

Designed by Theodore P. Zoli, the first structural engineer to win a MacArthur “Genius” Award, this truss bridge eliminates the gusset plates typically used to connect beams and girders to columns and truss members.  Gusset-plate connections have been problematic in truss design:  they tend to collect debris, to corrode and deteriorate, to be difficult to inspect, and to be impossible to remove and replace without shoring from below.  In the picture below, you can see the gusset plates on the Memorial Bridge connecting Portsmouth, N.H. and Kittery, ME.  Their deterioration contributed to the demise of the 1923, historic structure which required its replacement.

Gusset Plates Connecting Vertical, Horizontal and Diagonal Members*

Zoli’s genius was to replace the gussets with splice plates in a design for the new Memorial Bridge that is cleaner and easier to inspect while allowing for partial splice replacement under load.  Additionally, the gussetless design required significantly less bolting which in turn resulted in faster construction and less costly maintenance long-term.

Splice Plates on the Horizontal and Diagonal Members Eliminated Gussets*

The top and the bottom chords were efficiently fabricated as plate girders with pieces that fit together like a puzzle.  Chicago Metal Rolled Products curved 24in wide 1in thick steel plate as well as 30in wide both with eased edges to the specified radii and the specified straight tangent lengths.  The inside radii were either 20in or a tight 10in.  The customer supplied lengths ranging from 8ft to a very long 34ft 7in.  (This last required a considerable under-hook height to fabricate in the shop.)

These bent plates looked like the letter “V” with a rounded bottom or like giant sleds or toboggans.  Assembled, the curved plate sections formed triangular shapes inserted horizontally (like a sleeve) into the flame-cut plate girders.

24in x 1in Plate Curved with Straight Tangents

Another innovation was locating the machinery to operate the vertical-lift bridge underneath and at both ends of the bridge.  Typically, this machinery would be located in a room built above the roadway at mid-span of the lift truss.  The benefits of the new design include increased protection of the machinery, reduced tower height and truss depth, installation of the equipment before bridge construction, and an open view of all three bridge spans.  The bridge is scheduled to open this summer.

Architectural Rendering of the Memorial Bridge Opening Later this Year

*All photographic images courtesy of Denise Goldberg

Steel fabricators provide part of . . . → Read More: Of Floods, Droughts and Floodgates]]> The Midwest (and beyond) has been plagued by months of drought followed by severe floods causing evacuations, limiting barge traffic on its rivers, and disrupting farmers’ planting schedules.  And it may not be over yet:  additional rain may cause rivers to remain high into May.  Both cities and rural areas have suffered.

Steel fabricators provide part of the solution to the challenges of Mother Nature – whether drought or floods – when they manufacture flood gates.  For example, flood gates are now being installed at the Olmsted Locks and Dam Project, the largest project of its kind in the history of the U.S. Inland Marine Transportation System.  Located on the Ohio River where Illinois and Kentucky share a border, this project is “essential to the regional and national economy” according to the Army Corps of Engineers.  Indeed, this is the busiest stretch of river in America’s inland waterways:  it’s a hub where it all comes together – the Mississippi, the Ohio, the Tennessee and the Cumberland rivers.

Olmsted Lock and Dam Project

But until the project is complete, river traffic will depend on two 80-year-old locks and weak wooden wickets.  (Wickets are large planks that are manually raised to a steep angle or lowered flat to control the river flow.)  Should they fail, barges that haul some 90 million tons of rock, coal and other goods could not travel because the river’s height fluctuates as much as 50ft in the course of a year.

Two popular types of floodgates are Tainter gates and sector gates.  Both served to control the flow of water in dams and canal locks.  The Upper Mississippi River Basin alone has 321 Tainter gates.

A Tainter gate (named after the Wisconsin structural engineer, Burnham Tainter) has the shape of a piece of pie set on its side.  The round section faces the source or upper pool of water; the pointed end faces the destination or lower pool.  At the point is a trunion on which the gate pivots as it is raised or lowered by an assembly of chains and a gearbox above.

Tainter Gate Diagram

The virtue of the Tainter gate is its design for efficiency.  Closed, the water pressure is on the convex side of the gate.  When the gate is rotated, the water passing under the gate helps it open or close more easily than a flat gate.  Sector gates look like Tainter gates turned vertical.  They, too, incorporate a radial arm.

The component parts of the steel fabrication in either type of gate include plate rolling of the curved face or skin plate of the gate as well as section bending of stiffeners on the back side of the plate.

Tainter Gate with Rolled Plate and Plate Stiffeners

For the Olmsted project, Chicago Metal Rolled Products split 245 ea W24 x 55# wide flange beams into 490ea WT 12 x 27.5 tees.  The company subsequently curved the tees stem-out to a 59ft 3/16in radius measured to the tip of the stem.  Holding that outside dimension guaranteed a close fit-up to the concave side of the plate.  Since the usual measurement process of drawing a chord and measuring the mid-ordinate rise would not work, a special plate template was rolled to check the radius.  A tolerance of +/- 1/8in was held for both the splitting and the curving.

Close Tolerance Tees Rolled Stem Out as Stiffeners for Tainter Gates

These Tainter gates will replace older ones, the last before the Ohio spills into the Mississippi.  Especially during periods of drought, the gates help pool the water when low to improve its navigability.  Five each 110ft-long Tainter gates function with some 500ft of wicker gates to span the Ohio which is very wide there.  Chicago Metal Rolled Products has rolled beams as large as W40 x 297 for companies specializing in flow control.

Hauling freight on this river is more environmentally friendly than moving it by truck or railroad.  “One barge can tow the equivalent of about 890 trucks on the roadway,” says Bill Gilmour, the Corps resident engineer for the project.  The locks and dam should be finished by 2016.

Essentially, you should calculate the centerline arc:

(Outside Diameter – Thickness) x 3.1416 = Length of Plate Required

(Inside Diameter + Thickness) x 3.1416 = Length of Plate Required

Note:  Additional plate may be required depending on the material thickness and the machinery . . . → Read More: How to Develop the Blank Flat Length for a Cylinder]]> To develop the blank flat length for a cylinder rolled from sheet or plate is quite simple:

Essentially, you should calculate the centerline arc:

(Outside Diameter – Thickness) x 3.1416 = Length of Plate Required

(Inside Diameter + Thickness) x 3.1416 = Length of Plate Required

Note:  Additional plate may be required depending on the material thickness and the machinery used.

Centerline Arc of a Cylinder

Aluminum 20in Schedule 100 Pipe

Given that Bender/Rollers will supply many parts to OEMs, what measures or metrics should . . . → Read More: Rolled Steel Shapes Supplied to Equipment Manufacturers – What Should be Measured?]]> Bender/Rollers, those companies that specialize in curving structural steel, steel sheet and steel plate, often supply rolled steel and metal shapes to equipment manufacturers as component parts.  These original equipment manufacturers (OEMs) turn to Bender/Rollers precisely because their make-or-buy analysis indicates they should buy these parts.

Given that Bender/Rollers will supply many parts to OEMs, what measures or metrics should the Bender/Roller put in place regarding this type of work?  Best practice indicates that they should align their performance measures with what customers want.  And what the customer wants is almost always quality, service, on-time delivery, and value.

Many OEMs provide suppliers with something like a “Supplier Report Card” or a “Vendor Performance Report.”  These, of course, are a direct expression of what an individual customer wants.  One such report card measures “Spend” (the cost of the parts ordered), “Line Rejects/Returns,” “Delivery Score,” “Quality Factor,” and “Total Score.”  Another measures the number of “On-Time Receipts” and its percentage, the number of late receipts and its percentage, the number of early receipts and its percentage, and the number of orders within tolerance and its percentage.  It allocates 45 points for delivery, 10 points for quantity, and 45 points for quality.  Ratings of 100-95 are “Exceptional;” from 94-85 “Preferred;” 84-70 “Qualified;” and 69-0 “Probational.”

Most OEMs, however, do not provide suppliers with a report card.  Consequently, it is important for Bender/Rollers to maintain their own internal report cards.  Again best practice is to measure what the customers want.  On-time delivery and quality are metrics that the best companies should be able to track.  Service and value may be more difficult to quantify.  Service could include requirements such as special packaging, aid in sourcing raw material, and even invoicing correctly.  Value is measured in part by the willingness of customers to continue to order parts at a given price year after year.

Manufacturers, of course, measure many other things including machine utilization, sales volume, profitabilility, and the cost of labor and material for a given item.  As important and critical as each one of these metrics is, a truly customer-focused organization puts the highest priority on measuring and meeting customer needs and strives to continually improve in the eyes of those customers.

Performance Report

There is a large range of sizes of curved steel:  from eight-inch diameter angle flanges to W44 x 290# wide flange beams 100ft long.  The former can be shipped by . . . → Read More: Ways to Reduce the Cost of Shipping Curved Steel Sections]]> There are several solutions to the challenges of shipping curved steel sections.  The challenges include safe loading of the trucks, ensuring timely delivery, and keeping costs low.

There is a large range of sizes of curved steel:  from eight-inch diameter angle flanges to W44 x 290# wide flange beams 100ft long.  The former can be shipped by UPS; the latter can be shipped by a specially designed, flatbed truck.  Some trucks incorporate steerable back wheels.  Some trucks carry an extra set of wheels which are attached to one end of a curved beam.  The curved beam is attached to the cab at the other end.  The beam becomes–in effect–the “body” of the truck.  An experienced shipping clerk can choose the most efficient and least costly method of transportation.

Directly related to the means of transporation is the method of loading bent steel on a truck.  Particularly with large steel sections, a shipper tries to maximize the loads while constructing them in the safest manner possible.  For example, if all the pieces of steel are loaded on the truck curved in the same direction, the load might not be balanced on the flatbed.  Instead, half the steel sections might be loaded on the truck curved the opposite way to balance the load.  At times, special framing is attached to the truck bed and the curved steel to create a balanced load within the allowable height and width limits.

Shipping decisions also affect the timely delivery of finished goods.  Curved steel sections are often required within a very tight time frame.  The costs to the customer resulting from late delivery can far exceed the cost of both the shipping and the product.

Curved steel sections are shipped all over the United States.  Especially when the shipping distance is great, freight costs should be minimized.  Savings can be achieved by maximizing the loads, by seeking competitive pricing from reliable shippers, and by combining loads being carried to the same areas of the country.

One type of customer orders a “one-off,” that . . . → Read More: Rolling Steel Sections as a Job Shop and as a Contract Manufacturer]]> By definition, a job shop produces specialized products in relatively small batches, and this is true of companies who specialize in rolling steel sections.  Such companies often develop a variety of customers who turn to these bender/rollers for their expertise in bending structural steel, steel plate and steel sheet.

One type of customer orders a “one-off,” that is, a unique product like curved steel for a sculpture.  On a larger scale, architects may design a wavy roof made of curved steel beams whose design will never be duplicated.  The structural steel fabricator may order this curved steel once and then never have another project like this again.

Another type of customer makes the shop operate more like a contract manufacturer fulfilling the same parts on a repetitive basis.  Curved steel tubes that form the arms of a front-end loader or tractor are a product that a Bender/Roller could supply as a contract manufacturer.  Curved plate for gutters on “big box” stores also represents this type of repetitive business.

The type of work a Bender/Roller handles has implications for its place in the supply chain.  The flow of the incoming raw material when the company is functioning as a job shop requires suppliers who inventory a wide variety of steel sections since the demand is unpredictable.  On the other hand, when the Bender/Roller is functioning as a contract manufacturer, the inventory a supplier maintains is more limited and more precisely matched to the predictable requirements.

The type of customer also has implications for the layout of a metal fabrication firm.  Job shops are often organized by grouping similar equipment together.  Roller/Benders, for example, might group the section benders together, the welding equipment together and the hole punching equipment together.  Contract manufacturers, however, tend to create work cells combining several different types of equipment which are dedicated to manufacturing just a few similar parts.

Many companies operate as both a job shop and a contract manufacturer.  Prototypes produced in the job shop mode often become repetitive orders produced in the contract mode.  Nimble companies are able to adapt to the ever-changing demands of the marketplace.

Sometimes we don’t pay enough attention to how we receive steel in our plant.  We might be focusing too much . . . → Read More: Best Practices in Shipping and Receiving Structural Steel]]> Those of us who work with steel should always strive to eliminate waste in our operations.  Some call this approach “lean manufacturing” or “just in time manufacturing.”  Whatever you call it, it can contribute to your productivity.

Sometimes we don’t pay enough attention to how we receive steel in our plant.  We might be focusing too much on the fabrication processes themselves.  But there is much to be gained by looking closely at our receiving operations.

When steel is delivered to our shops–either material we bought or material our customers have sent in–it is, of course, critical to maintain its identity for traceability reasons.  Our customers must know that the right material was used for their parts.  Many will require mill “certs” which identify  the heat as well as the chemical and physical properties of the steel.  Those employees charged with that responsibility must match up the paperwork and the steel to ensure traceability.

Once the material is properly identified, ideally it would be stored at the point of use, i.e. next to the machine(s) that will process the material.  If this is possible, then such storage could elminate handling the material a second time in order to move it to the machine(s).

If the material needs to be stored elsewhere, then it is important to record the location so it can be easily found when needed.  Identifying zones with a grid system can help in this regard.  Also, if the material cannot be stored next to the machinery, then it is desirable to store it as close to the processing area as feasible.  This will result in a reductin of both flow time and flow distance–goals of any lean manufacturing initiative.

Lastly, good housekeeping can also contribute to the effective receiving of material.  Excess material must be disposed of quickly so there is no chance of mixing it with new material.

Any improvement, however small, in the effective receiving of material will pay dividends far beyond the cost involved.

Strakes can be attached to towers in multiple ways.  Sometimes they are . . . → Read More: Clips to Attach Helical Strakes]]> We have rolled and twisted the hard-way, helical flat bars known as strakes for use in preventing wind vortex shedding on towers, stacks and other tall round structures.  The wind vortex shedding can cause damaging vibration in structures which the helical strakes dampen or eliminate.

Strakes can be attached to towers in multiple ways.  Sometimes they are welded directly to the columns.  At other times they need to be attached to a clip which is then welded to the column, as is the case in the stainless steel clip on the left side of the picture below.

Clips to Attach Helical Strakes to a Steel Tower

One customer needed to allow for expansion of metal due to large fluctuations in temperature in his application.  The solution was to design a clip which is two angles welded together.  The strake was to be welded onto one angle while the other would be welded directly to the stack.

As part of these projects, we have occasionally formed the angles ourselves such as in the example on the right side of the photo.  A small bent plate out of Corten was required with a hole punched to plug weld the strake to the stack.  The tolerances were fairly tight, so the most cost effective route was determined to have blanks laser-cut from plate that we then formed into angles.

In a more recent design, we used our AngleMaster to cut over 190,000 clips from 2 x 2 x 1/4″ angle for our customer and package them per their needs.

Clips Cut from Structural Steel Angles on an AngleMaster Machine

Helical Strakes on a Mock-Up of a Tower

Rolling two pieces of steel to . . . → Read More: Rolling Channels into an “S” Curve with Straight Tangents]]> In many cases, a company that specializes in bending structural steel to a specified radius is able to roll steel channels to create an “S” curve.  The “S” shape can be formed either by curving two pieces of steel and then welding them together or by rolling one piece with reverse curves.

Rolling two pieces of steel to create an “S” is easier to do because any deformation where the rolling starts can be trimmed off.  Not so with the single piece construction.  Care must be taken so that there is no deformation at the points where the curve reverses (or meets a straight tangent).  Depending on the steel section, the radius and the orientation of the part (e.g. for channels, flanges in, flanges out, or the hard way), rollers may or may not have the ability to form reverse curves.

There are several benefits to one-piece construction.  It can eliminate costly, full-penetration welds saving perhaps $1,500 per weld on a medium -sized structural steel member.  It can have superior  aesthetic value especially in AESS (architechtually exposed structural steel) applications.  And it can result in a reduction in raw material required.

Sometime the requirement is for a straight section followed by a curved section and so on.  In this case the cost of cutting and welding all the straight and curved sections together could be prohibitive.  Single piece construction could be less expensive.

"S" Curve Incorporating Three Straight Sections

Drawing of the "S" Curve

There may be some disadvantages to one-piece construction of an “S” shape.  It may be too large to ship on a truck or require special permits for shipping.  It may require closer tolerances to fit up in a fabrication shop because with multiple-piece construction, the welders can cut and trim to a greater degree.

Matching Leg-In and Leg-Out Channels for a Monorail Curved into an "S" Shape

A rolling shop should be able to respond to your inquiries regarding a reverse curve with information on 1. Can it be done in one piece?  Or will multiple pieces be required?  2.  Can it fulfill any AESS requirements?  3.  Can the part(s) fit on a standard flatbed or will permits be required?

The . . . → Read More: Packaging Helical Strakes for Shipment]]> We recently had a unique job with unique packaging requirements.  A customer was in need of helical strakes to wrap around a tower.  Strakes are helical flat bars that are curved the “hard way,” i.e. against the strong axis.  This is the same type of bending process that is used for ribbon mixers or ribbon flights.

The job called for strakes to cover a tapered column.  The radius of the tube gradually changed, and thus the strake pieces were all going to be different.  However, there was a large number of similar tubes, and for cost purposes, all the same pieces needed to be made at once.

The customer needed to receive them clearly labeled, sorted and separated per tower as they were being dropped in the field.  This led to logistical challenges between production and packaging.

Helical Strakes Being Bundled

A rubber stamping system was developed to clearly mark each piece.  The pieces were then bundled together with 250lb tensile strength zip ties in the quantity required per structure. 

Clear Marking of Each Bar

Temporary workers were hired for the additional work load to build crates and pick each set of strakes.  The clips that are being used to attach the strakes to the structures were counted and packaged inside the crates so everything was ready to be dropped at each work site.  Working with the customer, Chicago Metal was able to package and ship per their needs in a cost-effective manner that greatly reduced their labor and saved valuable time in their production schedule.

Helical Strakes Kitted to be Delivered Directly to the Jobsite

AISC sets the standards for steel construction in the United States. Its handbooks specify everything from the tolerances for fabricated structural steel to the criteria for certifying the practices of . . . → Read More: The American Institute of Steel Construction]]> The American Institute of Steel Construction (AISC) has the motto “There’s Always a Solution in Steel.”  Within the universe of steel, AISC serves several very important functions.

AISC sets the standards for steel construction in the United States. Its handbooks specify everything from the tolerances for fabricated structural steel to the criteria for certifying the practices of a structural steel fabricator. The organization publishes professional journals (such as Engineering Journal) as well as glossy magazines (such as Modern Steel Construction). It offers seminars, webinars, and conventions such as the North American Steel Construction Conference (NASCC).

AISC’s website not only provides expert information on steel construction, it also provides steel tools useful to those in the industry.

Membership in AISC includes a wide range of groups: architects, engineers, general contractors, structural steel fabricators, detailers, specialty subcontractors, steel service centers, and producers of steel. Another segment of the membership provides equipment for the fabrication of steel that cut, pierce and form the material. Lastly, there are suppliers that supply the literal nuts and bolts for the steel connections in buildings.

AISC also promotes sustainability in construction through its “green initiatives” and through helping to sets the applicable standards for the industry.

Finally, AISC reaches out to the community beyond steel construction by, for example, its annual steel day. Throughout the nation, various steel producers, fabricators, and others open their facilities to the general public to help educate them about the virtues of using steel in construction.