CHOKEPOINTS

A deep dive on the final stages of repair to the West Seattle Bridge

Aug 30, 2022, 8:20 AM | Updated: 8:29 am
bridge...
(KIRO 7)
(KIRO 7)

Load testing is one of the final steps to perform before the West Seattle Bridge can reopen to traffic. We’ve talked about it a little bit before, but it’s time for a deep dive.

It’s one thing to say engineers are going to put dump trucks full of rocks at key points on the bridge to test its strength. I wanted to hear from an actual engineer on the subject.

Residents celebrate West Seattle Bridge reopening, but still much to do

Greg Banks is the top engineer for this repair project. I met with him on the West Seattle Bridge during my tour inside the box girders Thursday. Banks said there will be static and dynamic testing, with those trucks being stationary and moving.

“We have six different load cases, and we’re positioning them at various locations,” he said. “Up to twelve trucks will be on the bridge at a time, but each of those trucks will weigh 80,000 pounds.  They’re strategically placed to create worst-case stress conditions.”

So what will Banks be looking for in these tests? He will be watching all the sensors which have been embedded in the bridge to make sure the numbers he sees are what he expects. Banks will be looking for an expansion of the concrete cracks under the load, and he’s looking for movement in the fractions of millimeters. That’s how small and precise this testing is.

What if the numbers don’t line up?

“If it doesn’t, then we go and look at the analytical prediction to make sure we didn’t mess something up with data input,” Banks said. “We’re going to make sure a sensor hasn’t popped or anything like that and is giving us faulty readings. We are going to ground-truth it first before we think it’s not behaving as expected.”

Heather Marx is the project director for the Seattle Department of Transportation. She expects this load testing to go as planned. Her confidence comes from the last two and a half years of the repair work, and the bridge has been responding as expected.

“When it was cold and we had a huge weight of snow on the bridge, it behaved as we expected it to,” she said.  “During the heat dome, the bridge behaved as we expected it to.  We have no expectation that any of those tests are going to come back anything other than exactly as anticipated.”

But if they do, Marx will not hesitate in delaying the reopening, which is now scheduled for September 18.

“We need to make sure,” she said.  “We are not going to open a bridge that isn’t safe for ordinary travel.”

You might find it interesting that live traffic doesn’t add that much weight to the bridge. Most of the weight stresses come from the weight of the bridge itself. Only about 20% of the weight comes from the vehicles using it.

Check out more of Chris’ Chokepoints.

Chokepoints

520 bridge construction...
Chris Sullivan

Here’s your warning: Seattle’s SR 520 will be fully closed all weekend

We've been warning you all week because we don't want a repeat of last weekend: 520 is going to be closed this weekend.
1 day ago
I-90...
Chris Sullivan

Major traffic shift coming to I-90 east of Snoqualmie Pass

A big change is about to happen on I-90 east of Snoqualmie Pass. WSDOT is widening six more miles of I-90 starting next week.
3 days ago
I-90...
Chris Sullivan

Avoid I-90 for the Seahawks game officials say, with westbound closed at Mercer Island this weekend

Good luck getting to the Seahawks game from the east side this weekend. Westbound I-90 is going to be closed at the west end of Mercer Island.
7 days ago
lane splitter...
Chris Sullivan

Sullivan: My experience with a lane splitter and why it is still illegal

A question for all motorcyclists today. Do you want to make it home alive? Then don't be a lane splitter.
8 days ago
I-405...
Chris Sullivan

WSDOT closes parts of I-405 this weekend to repair ’15-foot-deep sinkhole’

You will not want to be using Interstate 405 this Saturday, because construction is going to close the freeway south of Bellevue.
17 days ago
Rose petals in the shape of a heart are left on the sidewalk near the spot where four international...
Chris Sullivan

WA looks for answers as bike, pedestrian deaths hit 20-year high

The numbers are in, and we are not doing a good job behind the wheel when it comes to sharing the road with bikes and pedestrians.
22 days ago

Sponsored Articles

Anacortes Christmas Tree...

Come one, come all! Food, Drink, and Coastal Christmas – Anacortes has it all!

Come celebrate Anacortes’ 11th annual Bier on the Pier! Bier on the Pier takes place on October 7th and 8th and features local ciders, food trucks and live music - not to mention the beautiful views of the Guemes Channel and backdrop of downtown Anacortes.
Swedish Cyberknife Treatment...

The revolutionary treatment of Swedish CyberKnife provides better quality of life for majority of patients

There are a wide variety of treatments options available for men with prostate cancer. One of the most technologically advanced treatment options in the Pacific Northwest is Stereotactic Body Radiation Therapy using the CyberKnife platform at Swedish Medical Center.
Work at Zum Services...

Seattle Public Schools announces three-year contract with Zum

Seattle Public Schools just announced a three-year contract with a brand-new company to the Pacific Northwest to assist with their student transportation: Zum.
Swedish Cyberknife 900x506...

June is Men’s Health Month: Here’s Why It’s Important To Speak About Your Health

According to the Centers for Disease Control and Prevention, men in the United States, on average, die five years earlier than women.
...

Anacortes – A Must Visit Summertime Destination

While Anacortes is certainly on the way to the San Juan Islands (SJI), it is not just a destination to get to the ferry… Anacortes is a destination in and of itself!
...

Ready for your 2022 Alaskan Adventure with Celebrity Cruises?

Celebrity Cruises SPONSORED — A round-trip Alaska cruise from Seattle is an amazing treat for you and a loved one. Not only are you able to see and explore some of the most incredible and visually appealing natural sights on the planet, but you’re also able to relax and re-energize while aboard a luxury cruise […]
A deep dive on the final stages of repair to the West Seattle Bridge