Always Civil

ASCE 7-16 launches early 2017

2016-10-07T20:35:00.002-04:00

ASCE 7-16 will be online in early 2017 and it looks like it will be a smooth transition with 7-10 and 7-16 available online with side by side provisions and commentary as well as redlining changes from 7-10.

Watch the video which seems to be geared towards the next generation of younger engineers
ASCE 7-16 video here

as well as this video with a preview of changes

Arcitc Module Design

2016-08-31T17:31:00.000-04:00

Currently working on the structural design of a module which will be transported by truck to the North Slope of Alaska. The design was carried out with the clients specifications which require the use of ASCE 7 for design loads. In addition to ASCE 7 the client specified frost jacking and adfreeze strength from permafrost for the vertical support members. Additional considerations into snow drift loadings were carried out as well as windward and leeward wind forces on the structure. Point loads were added for valve and piping dead loads.

Kennedy Fracture Critical Inspection

2016-08-25T17:45:00.002-04:00

Last week I made the trip down to Louisville KY to assist with the Kennedy Bridge Fracture Critical Inspection. The trip got off to a rocky start with multiple flights being delayed and I spent about 14 hours stuck in the Denver Airport.

After getting to Louisville we were able to get started on the inspection despite a couple days of iffy weather that consisted of fog and scattered rain showers. On days that did not rain we were able to inspect the upper chord and diagonals. The lower chord, floorbeams and general photos were left for rainy days.

We were able to efficiently move throughout the structure only being delayed by locations that required NDT. We worked in groups of two or three, each group carried mag particle (MT) with them as to reduce the load on each climber while still being able to confirm deficiencies.

Loading Dock Seismic Analysis

2016-08-08T21:26:00.003-04:00

Currently working on the seismic analysis of a loading dock in Alaska. Using RISA 3D I have been able to construct a 3D model using existing plans from the 1960s. The model is very detailed to capture the necessary dynamic properties with lump masses to represent dead loads not captured.

I'll update this as I have time to include more information

Passed the PE

2016-06-06T15:14:00.002-04:00

After hundreds of hours of studying spread across four months and an 8 hour exam, I found that I have passed the PE exam. Now I am officially a Professional Engineer in Alaska.

Sherman Minton Bridge Inspection

2015-10-20T22:01:00.000-04:00

Copied Info from Wiki until I have time to update this post about our inspection

The Sherman Minton Bridge is a double-deck through arch bridge spanning the Ohio River, carrying I-64 and US 150 over the river between Kentucky and Indiana. The bridge connects the west side of Louisville, Kentucky to downtown New Albany, Indiana.

History[edit]
In 1952 the "Second Street Bridge" was reaching peak traffic, and the K&I Bridge faring similarly. Arthur W. Grafton commissioned two studies in 1952 and 1953, with their results being a need for two bridges in Louisville; one crossing to Jeffersonville, Indiana, and the other to New Albany. Hoosiers as far as Scottsburg, Indiana (30 miles (48 km) away) were vastly against making any bridges toll, and many residents of Louisville were against toll bridges as well.[1] When the Interstate Highway System was announced by President Dwight D. Eisenhower, the solution became clear. The Federal government would finance 90% of both bridges, with Indiana paying 10% of the New Albany bridge, and Kentucky paying 10% of the Jeffersonville bridge.[1]
The New Albany bridge was given to Hazelet & Erdal, of Louisville to design in 1956. Construction began in June 1959, and was completed in August 1962. It was built at a cost of $14.8 million. In December 1962 Indiana governor Matthew E. Welsh announced it would be named for the former United States Senator and Supreme Court justice Sherman Minton, who was a native of New Albany.[2] The American Institute of Steel Construction in 1961 named it the most beautiful long-span bridge of the year.[1]

View of the bridge from the Main Street in New Albany
On February 5, 2009, a fifteen container coal barge lost power and was pushed downstream by the current and struck the bridge's central pier. The Indiana Department of Transportation (INDOT) closed the bridge for several hours while it was inspected for damage. When no damage was found, the bridge was reopened later the same day.[3]
Closure of 2011-2012[edit]
On September 9, 2011, Indiana Governor Mitch Daniels ordered the bridge closed. This was done after construction crews found cracks in the main load-bearing structural element. Experts from INDOT, the Kentucky Transportation Cabinet (KYTC), the Federal Highway Administration (FHWA), and private engineering firms and academic institutions participated in determining the severity of this crack and others found on the bridge, and determine whether the bridge could be saved.[4][5][6]

It was initially feared the bridge would remain closed from several months to up to 3 years, and that the entire span would have to be either completely replaced or extensively renovated before the Sherman Minton Bridge could reopen to traffic. However, engineers determined the crack that initiated the bridge closure dated back to the bridge's original construction in the 1960s, but had not been discovered until the summer of 2011 because another structural component was covering it. On September 23, 2011, Kentucky Governor Steve Beshear and US Secretary of Transportation Ray LaHood announced the 2.5-inch crack has been repaired, but the bridge would remain closed until crews completed an inspection of the remainder of the bridge.[7] Five to seven additional cracks were discovered during the following inspection in welded areas in a load-bearing steel beam. "The fissures were discovered in a type of steel frequently used in the 1950s and 1960s that is now known to be susceptible to cracking. ...". This necessitated the bridge being closed for an extended period of time for repairs. Repairs cost $20 million and ultimately took four months to complete.[8]
In a news release from the Indiana Department of Transportation, dated October 18, 2011, Governor Mitch Daniels announced that Louisville based Hall Contracting of Kentucky had been awarded the repairs contract in the amount of $13.9 million. A time frame of 135 work days was announce with an incentive of $100,000 per day to finish early. Likewise, a penalty of $100,000 would be deducted from the contract payments for each day over. Repair cost were covered by the Federal Highway Administration, who announced on September 30, 2011 that it would contribute 25% of the cost, with the remaining 75% being equally split between Indiana and Kentucky.
The contract attached 2,400,000 pounds (1,100,000 kg) of reinforcing steel plating along both sides of the bridge ties spanning 1,600 feet (490 m). The repairs along with regular maintenance increased the bridge's safety and reliability and extend its useful life by at least 20 years.[9]
Repairs were completed and the Sherman Minton Bridge reopened at 11:50 pm on February 17, 2012.[10]

Construction[edit]
The bridge is a double-deck configuration—westbound traffic from Kentucky to Indiana travels on the upper deck of the bridge, while eastbound traffic from Indiana into Kentucky travels on the lower deck of the bridge. It is of similar construction to the Hernando de Soto Bridge in Memphis, Tennessee (but the de Soto Bridge is single-deck).
The steel used was T1 steel, which in the early 1960s was "innovative material" but is much weaker than modern steel. Classification of the bridge is "fracture critical" because if one part of the bridge should fail, the entire bridge could be at risk.[11]

References[edit]
Wikimedia Commons has media related to Category:Sherman Minton Bridge.
1.^ Jump up to: a b c Kleber p.123
2.Jump up ^ Kleber pp.123,418
3.Jump up ^ Mike Dever (2009-02-05). "Sherman Minton Bridge Reopens". WAVE 3 News. Retrieved 2011-09-12.
4.Jump up ^ "Sherman Minton bridge shut down; crack found in bridge". Louisville, Kentucky: WDRB. September 9, 2011. Retrieved September 9, 2011.
5.Jump up ^ "Sherman Minton Bridge closed indefinitely due to structural cracks". Louisville, KY: The Courier-Journal. September 9, 2011. Retrieved September 11, 2011.
6.Jump up ^ Barrouquere, Brett; Cappiello, Janet (September 12, 2011). "Traffic nightmare over closed Ohio River bridge". Associated Press. Archived from the original on August 20, 2014. Retrieved September 12, 2011.
7.Jump up ^ LAHOOD: One Sherman Minton Bridge crack repaired; no timetable for re-opening WDRB-TV, Sept 23, 2011
8.Jump up ^ "Sherman Minton Bridge repairs to take six months, cost $20M". The Courier-Journal. October 1, 2011. Retrieved October 1, 2011.
9.Jump up ^ "Sherman Minton Bridge Repair to Require 135 Work Days" (PDF). Indiana Department of Transportation. Retrieved 27 October 2011.
10.Jump up ^ http://www.corydondemocrat.com/Articles-i-2012-02-21-224052.114125-Motorists-celebrate-bridge-reopening.html
11.Jump up ^ "Agency: Sherman Minton Bridge's Steel More Brittle". Associated Press. 12 September 2011. Retrieved 12 September 2011.
Kleber, John E., ed. (2001). The Encyclopedia of Louisville. University Press of Kentucky. ISBN 0-8131-2100-0.

Wrapping up my Masters Degree

2015-06-29T23:15:00.000-04:00

Its been a busy 18 months but I'm finally wrapping up my Masters of Civil Engineering with a Structural concentration. Just need to finish my Capstone Project, which will be a three hinged glulam tied arch that will carry the Appalachian Trail over the Kennebec River in Caratunk Maine.

Sneak peak of the design so far:

Hydraulic using HEC-RAS

Preliminary Structural Analysis using Visual Analysis (will hopefully be able to use MidasCivil for a refined analysis)

Tunnel Overhead Inspections

2015-06-15T12:30:00.000-04:00

Since the Tunnels in Boston are congested during most hours of the day inspections which require lane closures need to be done between 10pm and 5am. The typical closures we have been working in go out at 11pm and we need to be out of the closure by 4am.

This doesn’t leave us a lot of time to finish out inspections so we are usually very organized and prepared to inspect before we enter the closure. Most notes are refined down to a check list and previous tables of deficiencies are used to keep track of changes. Since our inspections for this assignment are just overhead inspections we spend a great deal of time looking at the lighting supports, panels and hangers. We look at all the overhead items but these tend to be the elements which have the most notable deficiencies. We also need to inspect the hangers which are located in the exhaust plenum. The exhaust plenums are often very dirty and cover us in soot, which is why we wear tyvek suits to protect our fancy field clothes.

Kennedy Bridge Pin Testing

2015-06-12T15:00:00.000-04:00

After our In-depth inspection of the Kennedy earlier in the year, we had to test the pins. Using non-destructive testing (NDT), to be more accurate ultrasonic testing (UT) we were able to verify that our visual inspection was correct and there were no deficiencies. Using rope access we were able to access the pins without the need of traffic control or heavy access equipment.

Corrugated Steel Low Profile Arch Load Rating

2015-06-08T12:30:00.000-04:00

Recently I finished a load rating for a corrugated steel low profile arch which carries a rural road over a small brook. Unlike the recent masonry and concrete load ratings I have worked on, this load ratings was not as cumbersome. The rating criteria is much more straight forward with the codes that are currently in place. Much like the arches this structure can be analyzed using a column earth load and a live load which is distributed through the depth of the earth fill. We were able to model the live load action thru the earth fill using STAAD and creating influence lines.

The field verification inspection was very straight forward and now issues were found. The details from the plans were verified and no changes were needed. Issues that could have arose would be a flat or reverse curvature in the corrugated section which would show that the structure is either under designed, it has seen a load which was much greater than it was designed for or that the earth fill could be eroded leading to the live load not being distributed. To inspect the structure and give myself a little more practice I decided to use rope access instead of carrying down ladders through the 4 feet of snow still surrounding the bridge.

Hernando de Soto Bridge Inspection

2015-06-03T14:52:00.002-04:00

Back in March I was part of the Hernando de Soto Bridge inspection, where we were able to inspect the entire structure without using lift equipment. We climbed and used rope access to inspect the bridge, minimizing traffic control and saving the state lots of money.

The Hernando de Soto Bridge is a through arch bridge carrying Interstate 40 across the Mississippi River between West Memphis, Arkansas and Memphis, Tennessee. Memphians also call the bridge the "New Bridge",[1] as it is newer than the Memphis & Arkansas Bridge (carrying Interstate 55) downstream, and the "M Bridge", due to its distinctive shape. It is of similar construction to the Sherman Minton Bridge between Louisville, Kentucky and New Albany, Indiana.

At night, the bridge is illuminated by 200 sodium vapor lights along its "M" shape structure. The bridge was first lit on September 5, 1986, after $373,000 of private funds had been raised to fund the cost and installation of the lights. Due to some river traffic having issues with the lights at night reflecting on the water, the city installed a remote switch to toggle the lights on and off briefly while the vessel passes under the bridge.[3] During the 2011 Mississippi River floods, the bridge became dark for about 2 months because the transformers that supply the electricity for the lights were removed to prevent damage to them by flood waters. The bridge was re-lit in a ceremony which occurred on June 21, 2011.

For our inspection we had to turn the lights off each day and turn them back on after we were finished.

The weather varied from 80F sunny to 34F with sleet. With varying weather we had to pay close attention to the radar and incorporate it into our rescue plan.

One of the days the Memphis Fire Departement came out to see how we can access the bridge by rope access. We were able to answer questions they had and they were able to talk to us about their rescue capabilities.

Infrastructure - John Oliver - Last Week Tonight

2015-03-03T12:13:00.001-05:00

This entire show is great but their HBO clip is awesome

How to tie a Bowline Knot

2015-02-19T12:18:00.001-05:00

Thought I'd start to post some of my rope access techniques/skills, I'm sure some other engineers might be interested in learning some rope access techniques/skills for when access is limited.

Here I'll quickly discuss the Bowline knot, which I use often for rope access, hiking and kayaking. CMC Rescue posted a great video on how to tie the bowline knot and you can watch it below. Usually seeing a knot being tied is much easier than reading how to do it.

The Bowline (ABOK # 1010, p 186) makes a reasonably secure loop in the end of a piece of rope. It has many uses, e.g., to fasten a mooring line to a ring or a post. Under load, it does not slip or bind. With no load it can be untied easily. Two bowlines can be linked together to join two ropes. Its principal shortcoming is that it cannot be tied, or untied, when there is a load on the standing end. It should therefore be avoided when, for example, a mooring line may have to be released under load.

There are a few variations of the bowling knot:

With a Safety Knot either in the Loop or Line
Yosemite Tie-off
Eskimo Bowline
Left Handed Bowline

Rope Access Level II

2014-12-29T12:21:00.003-05:00

A few weeks ago I attended a Society of Professional Rope Access Technicians (SPRAT) training course in Bristol RI at Axcess Rescue for my SPRAT Level II certificate. This means that the past year and half I have accomplished:

SPRAT LEVEL II (LEAD TECHNICIAN)

Minimum of 6 months and 500 logged rope hours as a SPRAT level 1 (verification of SPRAT log book should be acceptable).
Complete a four-day rope access training course from a qualified trainer (recommended, not required).
Complete a level 2 written test
Level II Field evaluation by an independent SPRAT Evaluator on day 5.

At the training I was able to learn the follow:

Management and communication awareness
Job Safety Analysis proficiency
Principles of mechanical advantage systems
Load sharing anchor mastery
Pull-through anchors
Rope systems analysis
Cross hauling – (platform and pitch head)
Rescue hauling – (platform and pitch head)
Aid climbing
Pick-off rescue with victim in ascent

The rope access course reviews all level I skills such as:

Equipment use and inspection
Job Safety Analysis awareness
Level 1 Knots
Back-up device use and handling
Use of ascending system for ascent and short descents
Use of a descender for descent and short ascents
Use of work seat/Bosun’s chair
Passing Knots in ascent and descent
Rope-to-rope transfers
Negotiating a rope deviation (redirect)
Short rebelay
Long rebelay
Negotiate an edge
Installing and Passing Rope Protection
Configurations and Strengths of Simple Structural Anchors
Awareness of load-sharing anchors and force magnification charts
Climbing with shock-absorbing Lanyards
Belaying – Methods and communication
Lowering a load with a two rope system
Pick-off rescue with victim in descent
Theoretical rope concepts such as fall factors, safety factors, min. breaking strengths, and safe working loads

A great part about the training was being able to see Level IIIs train next to me. Hopefully in a few years I will be in their shoes going for my Level III. The second part the was useful about the training was the Axcess Rescues instructor has been a big part of the SPRAT organization and has help mold and shape it into the organization it is today.

A great way to stay fresh or learn new rope access techniques are the great videos that are posted on youtube. They walk you through the techniques as if you were in the course.

Road trip

2014-12-20T19:24:00.000-05:00

On my way home to Mass driving though New Hampshire got to see a few covered bridges. Still haven't had the opportunity to work on yet but hopefully I will in the future.

Fictional Bridges on Euro Currency Transformed into Reality

2014-12-17T13:47:00.003-05:00

The fictional bridges depicted on Euro banknotes have been been transformed into reality at a new housing development near Rotterdam. Link to article

"The European Bank didn't want to use real bridges so I thought it would be funny to claim the bridges and make them real," Stam told Dezeen.

"I wanted to give the bridges an exaggerated theatrical appearance – like a stage set," adds Stam, who poured dyed concrete into custom-made wooden moulds to make them.

Taylor Southgate Fracture Critical Inspection

2014-12-03T12:07:00.000-05:00

Last month I was down in Cincinnati, OH for the Fracture Critical Inspection of the Taylor Southgate Bridge. From Wiki:

The Taylor–Southgate Bridge is a continuous truss bridge that was built in 1995. It has a main span of 850 feet (260 m), and a total span of 1,850 feet (560 m). The bridge carries U.S. Route 27 across the Ohio River, connecting Newport, Kentucky and Cincinnati, Ohio.

Some regard this bridge, which was a replacement for the Cincinnati-Newport Bridge built by Samuel Bigstaff [1], as a little too plain in its design for a major urban bridge, especially considering many cities today are opting for a more elegant design, such as a cable stayed bridge.[2]

The bridge is named for the families of James Taylor, Jr. and Richard Southgate, two important early settlers of Newport. Richard was the father of William Wright Southgate, a pre Civil War Congressman from northern Kentucky.

Like other inspections, I tried to get the inspectors POV by wearing my GoPro. Only ended up wearing it one day since it does get in the way when you stick your head into built up members.

Much like the other inspections I've been part of in Kentucky, this truss was primarily inspected through rope access techniques. The first three days were spent on the upper chord and doing drops to see the underside of the chord and connection to the diagonal tension members. This bridge was easily climbed due to its designers incorporating details for inspectors to use such as extra angles for stepping around gusset plates.

On the weekend a man-lift was used to inspect the area between the lower and upper chord where it was not efficient to use climbers.

The Cincinnati area is home to many other Ohio River Bridge crossings

Kennedy Bridge In-Depth Inspection

2014-11-24T11:31:00.001-05:00

A couple months ago I was down in Louisville KY to help inspect the Kennedy Bridge which carries I-65 over the Ohio River. Earlier in the year I was out at the Kennedy Bridge to inspect the floor system for Kentuckey's Transportation Cabinet (KYTC) since they wanted a detailed inspection before they decided to rehab or replace the deck and stringers. Previous Post about Kennedy Bridge floor system.

See that post for photos and details about the bridge. This inspection, much like the previous floor system inspection was done almost completely by rope access climbers. Two days were used for snooper and man-lift work on the weekend when traffic was not an issue.

Railroad Routine Bridge Inspection

2014-09-02T13:27:00.000-04:00

The past few weeks I've been busy working long nights for bridge and tunnel inspections. Our inspections were located in Revere, South Boston and Brookline and each had its own unique access requirements.

The Revere bridge spans over the Blue Line and was inspected using ladders since it was a short span consisting of prestressed concrete butted box beams in good condition. Using ladders allowed us more time for inspection since we did not have to wait for a hi-rail lift truck to be put on and driven to the bridge. We were able to get on track around 1am and finished just before they needed power back.

The South Boston bridge spans over the Red Line and MBCR commuter rail tracks and was inspected with ladders even though it was a larger span consisting of prestressed concrete butted box beams in good condition. We decided to use ladders since we could inspect the commuter rail portion starting at 10pm and finish before the MBTA would allow us access to the Red Line around 2am. There was also a small portion over a dirt road with no traffic at 1am. Working in all three sections could not be accomplished using a hi-rail lift since the truck would require traveling further south to be able to get onto the tracks.

The Brookline bridge spans over the Green Line near the Beaconsfield Station and was inspected with a 40 foot hi-lift since the bridge was wide and consisted of 57 rolled steel beams. We were able to get on right near the bridge just after 1am and finished the wide bridge just before power was needed back.

2014 ASCE Concrete Canoe Winner

2014-07-10T13:23:00.001-04:00

Brings me back to the days when my team qualified with our canoe Cherry π

2014 ASCE Concrete Canoe Winner

Here are a few photos from back at school when we were placing the concrete.

Owensboro KY Routine and Fracture Critical Inspection

2014-06-17T22:47:00.000-04:00

Yesterday I arrived in the balmy city of Owensboro KY to inspected the Glover H. Cary Bridge. The carries Indiana 161 and Kentucky 2262 over the Ohio River. Today we began our inspection of the truss starting at node 0. By the end of Day 1 we reached node 20 on the upper chord with two teams and node 24 on the downstream lower chord. With a high temperature of 93 degrees we were spent and my right hand had begun to cramp up. The truss makes great use of solar panels for powering the lighting, which were not on during inspection hours for safety. All of our climbers are now SPRAT certified and we are looking forward to many more climbing projects coming up at the end of the summer.

Here is a taste of the climbing that I caught with my GoPro

Here is the bridges information from Wikipedia:

The Glover H. Cary Bridge is a continuous truss bridge that spans the Ohio River between Owensboro, Kentucky and Spencer County, Indiana. It was named for the late U.S. Congressman Glover H. Cary (1885–1936), and opened to traffic in September 1940. It was originally a toll bridge, but tolls were discontinued in 1954.

The bridge was funded through a $1.03 million federal grant, part of President Franklin D. Roosevelt's New Deal program, and public fundraising efforts. At first, the bridge connected Kentucky Highway 75 to Indiana Highway 75; in 1954, Kentucky 75 was redesignated U.S. Highway 431 and Indiana 75 became U.S. Highway 231.

The bridge was closed temporarily for a day and a half the weekend of March 13, 2011, due to the need for emergency repairs to the bridge deck with traffic temporarily detoured over the William H. Natcher Bridge. Following that emergency repair, transportation officials pressed ahead with planning and design on a full-depth deck rehab that was already scheduled for bidding in April 2011.

Structural condition:

Following the collapse of the I-35W bridge in Minneapolis, Minnesota in August 2007, Kentucky officials (including Governor Ernie Fletcher) sought to reassure motorists that Kentucky's bridges are safe by conducting a special safety review of all long-span bridges at that time. The Cary Bridge was subject to a detailed biennial inspection in August 2008. Kentucky and Indiana highway officials conducted a joint walk-through inspection of the structure on September 22, 2008.

On July 5, 2011, the Kentucky Transportation Cabinet closed the bridge to all traffic for a $3 million partial rehab of the bridge deck after a large hole developed in the concrete driving surface. Hall Contracting of Louisville was the prime contractor on the 3-month project. The project, which saw 40% of the bridge's deck replaced, was completed and the bridge reopened to traffic on September 30, 2011—three days prior to the October 3 deadline imposed by KYTC on the contra

Prior to its reopening, the bridge was opened to pedestrians and bicyclists for "Bridge Day" on Sept. 30; thousands of visitors crossed the 72-year-old span between the hours of 8:00 AM and 6:00 PM, when crews began preparing to reopen the bridge to auto traffic, which occurred at 6:30 PM.

Cape Cod Bridge Inspection

2014-04-28T12:00:00.000-04:00

A couple months ago we were down on the Cape inspecting the Dennis Yarmouth Bridge. The cast-in-place reinforced concrete slab has 33 spans which carry Route 28 over the Bass River.

This was a Special Member inspection of the deck and substructure and was very helpful since we were also currently rating the structure. The Bass River flows tidally North and South.

Spans 1, 2, 32 and 33 were accessed from manholes and inspected with ladders. The lower portion of the concrete piles were inspected by boat (and went much faster after we purchased a new motor). The underside of the deck, pile cap and upper portion of the piles were inspected with a 50 foot Snooper (Under Bridge Inspection Unit from McClain). With the help of local police and traffic control, we were able to shift traffic over while we worked in the break down lane safely.

Night Work Problems

2014-04-25T11:16:00.000-04:00

Last week our inspection of the I-93 tunnel were brought to a halt after the bucket truck began to stall out. We couldn't risk driving the truck out of our pattern and causing an accident if it were to stall again. We had to have the state police help us with a heavy duty tow to the DOTs lot near by. The tow truck was so large that it could not bring the bucket truck to the back where visitors can park, so we ended up having to push it into a spot.

Boston Cable Stay Bridge Fire

2014-04-22T12:39:00.001-04:00

An 18-wheeler collided with a taxi on the Zakim northbound shortly after 5:30 a.m..

The crash and fire led police to shut both sides of the bridge; the northbound side remained completely shut until 9 a.m., when one lane was reopened.

Josh Wardell says based on the debris strewn across the bridge, the truck was carrying apples

The accident was close to the pier tower leg and in some photos you can see the soot on the concrete. Fortunately the fire was not close to the cables which could have meant the bridge needing to be closed for inspections and repairs.

Here is an article about a fire on a cable stay bridge in Mexico where cables were damaged and repairs were made.

Mezcala Bridge Fire Damage Event

The multispan stayed or cable bridge suffered damages to one of the stay cables with a minor damage to an adjoining cable during a fire that was created due to an accident on March 17, 2007 between two school buses and a truck at the middle span of the bridge. The truck was carrying coconuts, which was the reason for the fire. After closing the bridge for vehicular traffic temporarily, the cable was replaced; though traffic was partially restored when the cable replacement started. Analysis of the cause of the fire by the American Society of Civil Engineers and the China Communications and Transportation Association indicated that the High-density polyethylene (HDPE) sheathing, which has hydrocarbon composition, was not ideally fire resistant as it caught fire and created the additional fire load which resulted in snapping of one cable line. A moot question that was posed in the analysis was "would this bridge have survived the loss of two or three adjacent cables?" Analysis also showed that multiple cables could be included in a fire caused by a lightning strike.

Bridge designers have examined the lacunae in design of major long span bridges of various types in the world, keeping in view the failures that have occurred in many bridges including the limited failure of the cable of the Mezcala Bridge due to a single point loading event that occurred due to a fire. This study was done with the objective "to enhance the reliability and safety of these major structures in the built environment." The approach now under consideration for cable stayed bridge is "a more rational approach from assigning factors of safety to key elements such as suspenders and stay cables, to setting depth and stiffness requirements

Cable Stay Bridge Inspection

2014-04-16T12:00:00.000-04:00

Last October I was part of a cable stay bridge inspection in Boston, MA. While I was away in Kentucky inspecting, the rest of my office was busy inspecting the underside and beginning the lower section of the piers and cables.

After I arrived home I had a day off and I began my part of inspecting the upper portion of the pier towers and cables which reached heights of 270 feet over the roadway. Since equipment could not efficiently inspect that high we used SPRAT climbers (myself and other guy from PA). We started by carrying over 1,000 feet of rope to the top of the north tower and rigging up our lines and rescue lines. That night we began to inspect the northern cables. With limited hours (11pm to 3am) we had little time to inspect since we were not allowed to enter the towers until lane closures were out. The first few nights were mainly learning what was the most efficient way to climb. The limiting factor for this bridge was our need for night work and thus lane closures. Luckily for us weather was good and winds were calm (less than 10 mph most nights).

As far as how we climbed, for the concrete pier towers we were able to climb out of the top at the aviation beacon and descend to the portion that was inspected by man-lifts and then ascend back up to the beacon. The first few nights we tried different ways such as ascending from a man-lift about 110 feet above the roadway (figured out that we can climb faster than a man-lift). Next we tried rope to rope transfers from the access vent located about 130 feet over the roadway. This was fast but each night we had to tie off the ropes which led to us ending almost an hour early for this.

For inspecting the cables we started off just like we did before from the aviation beacon but we carried a pair for rollers which were used to hold us ear the cables. This allowed us to stay within an arms reach of the cable we were rolling on and allowed us to see the cable below us. When we were low enough we exited the cable onto a man-lift which was waiting for us. Most nights we inspected 6 cables, we originally thought we could inspect more each night but due to less time each night we weren't able to inspect the 9 we thought we would be able to.