Washington bridge collapse

Yesterday a deck truss in Washington state near Mount Vernon collapsed while carrying four-lane Interstate traffic over the Skagit River.

The new mentions a truck present at the time of the collapse and may have struck an overhead member. Typically you would not think of sway bracing or other lateral members when you think of fracture critical bridges like a truss. This collapse has me thinking of a ways that might improve future designs, ratings and inspections of bridges (trusses).

Could the force of a collision cause a gusset plate to fail at a diagonal or vertical member of a truss?

Should gusset plate ratings incorporate checks for these addition collision loads?

Should we design our lateral members to shear at a desired force to not cause a collapse?

As always for inspections we need to check the vertical clearance at the portals and any lateral members over the roadway and verify that signs are in place in advance and at the bridge.

I look forward to hearing more about this collapse (that sounds bad) so that we can improve future designs, inspections and ratings.

A few weeks ago I did some rigging for the first time out in western Mass. The inspection was for a pony truss with severe section loss to the steel stringers. At first it was a little hairy walking on the 2 foot wide platform but by the end of the day it felt normal. 

The inspection took about 5 hours and the drive was 3 hours each way.

Mississippi Truss Rating

Starting to help our Mississippi office with some truss ratings.

Several of the trusses do not have plans and measurements of all the members and deficiencies had to be taken.

On Friday I started a Truss in Hinds-Warren County which spans over Big Black River and carries Old Highway 80. The bridge consists of ten approach spans to the west and one east. The main truss spans 170 feet and has 8 panels.Currently I'm just checking the net area for the measured members for section properties and dead load calculations.

Trapazoidal Steel Box Girders

Still working on the Central Artery Inspection contract, we have switched from concrete segmental boxes to steel box girders.

Now just north of Boston near Cambridge and Somerville, we are inspecting ramps for Interstate 93 which consist of steel box girders.

Currently I'm working on a bridge which has two steel box girders there for making it a fracture critical bridge as well. The bridge is six span continuous with a cast in place concrete deck. The bridge carries Interstate 93 Ramps NS and SN over Boston Sand and Gravel.

For the exterior of the box we used a manlift to inspect and gain access to the interior of the box. The interior of the box is a permit required confined space so we needed air meters and rescue inhalers.

Two Week Bridge Inspection Course

The past weeks I was taking the NHI Safety Inspection of In-Service Bridges course.

Since I've been doing bridge design, ratings and inspections for a few years now I already had a good grasp on a lot of the topics but it gave me a more in depth knowledge into the appraisal and condition ratings of bridge elements and items.

I'd recommend anyone working in the bridge engineering, construction or maintenance to take a look at the course. It also gives you 60 hours towards your professional development.

Western Kentucky Bridge Collapse

Apparently two spans of the Kentucky Bridge Collapsed Thursday after being hit by a 312 foot long cargo ship. Luckily no one was injured.

This collapse will expedite the plans of replacing the bridge which carries 2,800 vehicles a daily. I'm hoping this makes the state realize the benefits of having pier protection in the channel, making sure navigation lights are working and checking the freeboard on vessels better. Here's a story about how it caused the internet to go out at local schools, oh yeah side note it also made a bridge collapse.

P.T. Segmental Concrete Box Girder Inspection

This past week I started inspecting the Central Artery ramps in South Boston. The ramps we are inspecting consist of concrete Type IV precast box girders and span over 150 feet. The ramps carry I-93 Northbound and Southbound as well as the Southbound HOV lanes.

The past two weeks we have inspected seven ramps, which has made me very familiar with South Boston (one of the few areas I wasn't familiar with before).

To gain access to the interiors we used a 40' bucket truck and on the last day we used a 70' elliot with a HUGE basket. 

Each span has access hatches but one near the ground level was locked. After calling MassDOT to unlock it we found out that the lock was not theirs. Once inside we discovered the typical debris left by the homeless. All the other boxes were fairly clean in comparison though.

The previous inspections had sketches with deficiencies which made the inspections move a efficiently with the majority of the efficiencies still in the same condition as it was two years ago.

What a concrete box girder motel looks like.

RI Route 4 Culvert

Currently working on an inspection report of a two barrel concrete box culvert I inspected a couple weeks ago. The culvert carries RI Route 4 over the Frenchtown Brook.

The inspection started off a little hairy with our inspection van getting stuck in mud and soggy grass next to the highway. We attempted to get it out but after a lot of effort we were able to get it more stuck. Next we called a tow truck to help us get out.

While waiting for the truck we started the inspection. The previous inspection noted only 12" of water but when we arrived at the channel we noticed that recent rain had elevated to water depth and was nearly 4 feet deep. So instead of wearing hip waders we opted out for full waders.

With flashlights in hand we started down the 250 foot long barrel. At the end we noticed downed trees partially blocking the inlet. The second barrel was completely clogged and we had to back track down the first barrel to gain access to the second.

The second barrel was much deeper and had a faster flow with white water at the clogged end.

We also started a new thing of taking pictures of dead animals we find at the bridges