Tuesday, April 22, 2014

Boston Cable Stay Bridge Fire

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

Wednesday, April 16, 2014

Cable Stay Bridge Inspection

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.

Friday, April 11, 2014

Milton Madison Bridge

Last month I was down in Kentucky and was part of the team which inspected the bridge after the bearing dislodged. The bridge has now been repaired and slid into its final location.

Here are some videos of the bridges construction and moves:

Bridge phase animation

Ramp demo

Center span demo

Bridge lifted into place

Approach span slide

Bridge slide

Thursday, April 10, 2014

Bird Problems

I know most bridges I have worked on have problems with pigeons or even a falcon but this one is new to me. Caltrans is having trouble demolishing the old bay bridge since cormorants are nesting at the eastern end.

Full article here

Monday, April 7, 2014

Overhead Tunnel Inspection

A few weeks ago we started the inspection of Tip O'Neill Tunnel in Boston. All of the work is conducted at night when the state is able to close down portions or all of the lanes in the tunnel.

The work from the bucket truck is pretty easy and clean. Mainly we have just had to worry about dressing warm since a few nights have dropped to 10°F (-12°C). 

The dirty work is having to inspect the exhaust plenums which are considered to be permit required confined space. Much like their name suggests they are full of exhaust and caked with soot.

Tuesday, April 1, 2014

Ohio River Bridge Inspection

This was my second trip to Kentucky to help inspect one of the Ohio River bridge crossings. I have now been part of four of the river crossings and look forwards to being part of many more.

For this inspection we were doing a detailed inspection of the floor system so the state would have a very detailed report of the current condition. They plan to use this report to justify their reasons for the new deck replacement and whether or not to keep the stringers, which currently control the rating for the bridge.

One detail which we noticed were the diaphragms over the floorbeams had cracks propagating from the toe of the weld. A few locations had  propagated into the web of the stingers.

We even got one day off which gave us time to check out the bourbon trail. We stopped by the Maker's Mark Distillery and the Jim Beam  Distillery.

Tuesday, March 25, 2014

Emergency Bridge Inspection

Had to perform an emergency bridge inspection last week for the first time in my career. I was already down in Louisville, KY for the inspection of the Kennedy Bridge which crosses the Ohio to Indiana. Soon after hearing that a bridge further upstream had been closed, we received a phone call from the state asking for our assistance. We assembled relatively quickly even with the hour long drive to the bridge site.

Early in the morning, while construction workers were preparing the bridge for it's future move to it's permanent concrete piers, a bearing at the southwest corner dislodged and injured a construction worker. After the bearing had dislodged, the upstream truss fell about 12" until it made contact with the temporary pier. Although there were signs of movement throughout the southern span the bridge remained in good condition.

Sunday, March 9, 2014

Collapsed bridges in Central America (Guatemala and Honduras)

On a recent trip to Central America I ran into many collapsed bridges or failed bridge members. I was only able to grab a few picture of a couple that we drove by and was able to find another near San Pedro Sula, Honduras victim of the May 28 2009 earthquake, which we drove past on our way the airport.

I haven't started to look into their infrastructure ratings or if they have any bridge design, load rating and inspection standards yet due to work and graduate school classes. Hopefully soon I'll be able to take a look into this. In the meantime be careful of both the bridges and the drivers in Central America (makes Boston drives seem sane).

And here are some non bridge related pictures from the trip

Wednesday, February 19, 2014

Snow day for a Load Rating Verification

Went out yesterday to do two load rating verifications and as soon as we started the first one it started to snow and it didn't stop until we were finished. Winter in New England is always trying to mess up your photos for reports.

Monday, December 30, 2013

Pony Truss Special Member Inspection

A few weeks ago I was down in Burrillville RI inspecting a pony truss. The special member inspection consisted of the superstructure and deck since the bridge is load posted for 10 tons.

Two girders were added in 2008 to support the floorbeam and deck system with threaded hangers, the remaining pony truss is ornamental but is still inspected. In addition to the girders the state also added stop signs at each end to help reduce the impact on the structure.

The structure carries RI 98 over the Nipmuc River spanning 74.1 feet and has a width out-to-out of 24.6 feet.

We inspected the majority of the underside with a boat and just used paddles since there was little to no flow present. The west truss  diagonals, verticals and top chord were easily and safely inspected since there is a sidewalk running along the full length. The east truss was inspected by free climbing (100% tied off even though its only 5 feet over the water).

While inspecting we noticed numerous overweight trucks passing over the structure, I usually try to take a photo of the truck and write down the trucks plate number and any other information.