Monday, September 28, 2015

Coming soon to Vancouver: Ginormous girders longer than five football fields!

By Tamara Greenwell

UPDATE: The girder installation began Tuesday, Sept. 29. Watch this video to see the work in action.

It's hard not to notice the cranes, drills, trucks and machinery along Interstate 205 between State Route 500 and Mill Plain Boulevard in southwest Washington. East Vancouver is getting a new interchange, which reaches a HUGE milestone this week.

Ginormous steel girders will make their way to the work zone as part of the new Northeast 18th Street on-ramp to southbound I-205 that will help relieve congestion for drivers.

Girders are like giant Legos; they connect the support columns to the bridge deck. Like building with Legos, several steps must be completed in order for a structure to stand tall. Support columns are formed with two separate 120 feet by 8 feet steel bridge cages that are dug deep into the ground and filled with concrete. After the concrete cures, columns and support structures are constructed. Once those are set it's time for the girders to be placed on top.

Bridge foundation cage ready for installation.

Looking down into the bridge foundation cage after installation.

The girders are so big they are broken down into sections to be trucked to the work zone. It takes five sections to make up one girder. For this project we need three girders, so there are 15 different sections.

Placing girders this size is no easy task. To keep traffic moving, contractor crews will transport the girders to the construction area and set them into place overnight. A single lane of southbound I-205 will close each night, from 8 p.m. to 6 a.m., Sept. 28 to Oct. 3.

Next steps
  • A temporary bridge deck mold is built on top of the girders.
  • Rebar is installed inside the temporary mold.
  • Concrete is poured into the mold, which is removed when the concrete cures and is able to support itself.
  • The first section of concrete deck is scheduled to be poured in early 2016.
Column structures on southbound I-205 south of Northeast 18th Street.

Fun facts
  • Fifteen girder sections have a combined length of 1,680 feet. That's more than five football fields in length!
  • The single longest girder section is 114 feet. That's longer than a blue whale, the largest animal on the planet.
  • Once constructed, the heaviest girder, made up of five sections, will weigh approximately 293,600 pounds, the weight of more than 11 standard school buses.
Project benefits
  • Reduce congestion on northbound I-205 between SR 14 and SR 500
  • Improve safety and reduce congestion for southbound I-205 between SR 500 and Mill Plain Boulevard
  • Improve freeway access for east Vancouver drivers
Final configuration of on- and off-ramps when the interchange project is complete.

This interchange is the last Transportation Partnership Program (TPA) project to be built in Clark County.