The Two Towers:
Expansion Team
Previous essays on the new Tacoma Narrows Bridge construction:
- Introduction
- History of the Narrows Bridges
- The Caissons
- The Bridge Anchors
- The Tour Begins
- The Tower Struts
- To the Top
- The Cable Catwalks
- Starting the Cables
- Spinning the Cables
- Compacting the Cables
- Banding the Cables
- Two Towers: Life on the Bridge
- The Deck Cranes
- Lifting the Deck Sections
- Inserting the Deck Sections
- The Last Deck Sections
The deck itself, whose sections are now joined as a single unit, is still unattached to the anchors. Two giant expansion joints must be placed at either end, to accommodate length changes from changes in temperature, as well as horizontal motion from both traffic, load, and potential earthquake.
These huge joints, manufactured in Minnesota, provided a bit of local drama. The first joint was shipped across 5 states on a monstrous flatbed trailer, happily sailing along until it reached the Washington border where it ground to a halt, courtesy of the State Patrol.
States have laws governing the maximum vehicle weight allowed on their roads, but vary in how this is determined. Washington determines weight allowances on a per-axle basis: if your load is too heavy, you may transport it legally by increasing the number of axles on the trailer bearing the weight. For huge loads such as this, reconfiguring the axles is no small feat; the original shipping company had to turn the project over to another company, who ultimately delivered the joints safely:
The money quote of this fiasco came from the original trucker: “What I’ve told them is, ‘We’ll do this anyway we can. If it’s impossible, then it’s real easy: Y’all can build the bridge in Idaho.'”
I love a can-do attitude!
Here’s a video of the expanion joints being transported along the I-5 freeway:
Now that all the deck sections and expansion joints are in place, they need to be joined as a single unit. This involves heavy steel plates bolted to the steel girders, and welding:
The deck has been completed, secured with bolted plates, and welded together. The welding must be adjusted to exacting tolerances with the precision of a piano tuner. Or better, a guitar:
The similarity between tuning a guitar and welding is not something just anybody would pick up on.
But to Bill Madron the connection is obvious.
Madron, who’s an accomplished country and blues musician in addition to being a welding supervisor on the new Tacoma Narrows bridge, says laying down a righteous weld is like making music.
“If you’re tuning the E string against the A string, you know it’s right when you hear it,” he said recently. “A guitar is either in tune or it ain’t. Welding is the same way. It’s either on the money or it ain’t…” “Welding is part science, part art,” he said. “It’s not entirely one or the other …”
Normally, it takes young welders at least three years to bring their welding skills to a point high enough to qualify for an exacting industrial job like the bridge, but Madron said career development depends heavily on natural aptitude.
“You either are a welder or you aren’t,” he said…
And thus, the structural part of the bridge is completed. All that remains is wrapping the cables,laying the roadway, painting, and final touches.
Next: Wrapping the Cables
Next: Wrapping the Cables
