Caltrans began full-scale testing Friday of some of the anchor rod bolts removed from the new eastern span of the Bay Bridge.
Though only a few bolts on the span have broken, Caltrans is now verifying that they will last for 150 years or more as designed or, if necessary, be replaced decades down the road.
The huge outdoor lab is located a short distance from the Bay Bridge toll plaza.
Rod bolt bars removed from the new span will be tested at the lab under extreme stresses in a bath of highly corrosive salt water.
In a very real sense, the lab will serve as a time machine that will age these bolts decades in literally just a few weeks to help determine when the bolts might need to be replaced or if they need to be replaced at all.
"As you load it, you're going to find what tension it's going to want to break, if it ever wants to break," said Caltrans new span engineer Bill Casey. "And that gives you a lot of information to make a lot of decisions of what you want to do in the future."
The test begins with 200,000 pounds of stretching pressure. Then every other day for the next three weeks, the pressure is intermittently stepped up to more than 700,000 pounds. That is the equivalent of ten fully loaded semi-trailer trucks.
If cracks develop, the corrosive salt water can weaken the metal and shorten the life of bolts.
"If a bar were to have a problem somewhere in here, that's decades out," explained Casey. "These bars may have no problems and they'll be just fine. So that's why we're trying to qualify, so we can start making decisions of the long term in what we do."
All of the testing will be done under a temperature-controlled tenting system.
"Where if the test rig were to heat up but the rod does not heat up, that would put a load into the rod. That is not what we want in this precise test," said Caltrans bolt engineer Bob Brignano.
Many additional less critical bolts will also be tested over the next few months.
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