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Wednesday, March 18, 2015

Check it out: Loop 101/90th Street bridge time lapse



Loop 101 is being widened from Shea Boulevard to Loop 202, and within that span, there are several bridges that get additional lanes. However, one of those bridges – the one at 90th Street – required a little more work than the others.

For one thing, it’s curved. That means precast girders, ones that are prebuilt offsite, weren’t an available option for the lane additions. So, crews had to build the components at the project location, which required falsework (we’ve blogged about falsework before, but if you need a refresher: falsework gives temporary support to a structure until it can carry its own weight).

That falsework, which is what crews constructed the additional Loop 101 lane on top of, hangs lower than the final height of the bridge and had to be built high enough to give adequate clearance to the traffic traveling below on 90th Street.

Still with us?

To recap, the necessary falsework meant that crews had to build the new lane a few feet above its eventual resting spot and, as you can see in the video above, when the lane construction was finished, they had to lower it into place.

That covers why the lane was lowered, now let’s look at how it all got done.

ADOT Transportation Engineering Specialist David Locher explains that lowering the new lane was accomplished with the help of four jacks – each rated at 250 tons.

“We use very strong jacks,” he said. “We just lifted the lane ever so slightly so that we could remove some of the timbers (part of the falsework) at a time.”

Locher said that the road was lowered in three-inch increments until it was in place about 13 hours later.

In the coming months, crews will pour concrete to connect the new lanes to the existing bridge. After that, they’ll build the roadway deck on top.

One more thing…

ADOT is expanding Loop 101 on both the southbound and northbound sides, but you might notice in the video above that only the northbound side of the freeway had to be lowered.

Wondering why?

Locher explains that the southbound side was actually high enough to clear traffic because it is built on a banked curve. The slight incline gave crews the space they needed to build the additional southbound lane without having to elevate the falsework.

For more on this project, visit our website, or check out these previous posts. You’ll also find project photos on ADOT’s Flickr site.
Posted by Angela DeWelles   |  Labels:  Construction, Loop-101, Video


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