FEATURE VALLEY PRESTRESS On day three, when the designed release
strength of 6300 psi is determined, the product is ready to strip. After the bed is de-tensioned, the product with core and headers is moved longitudinally to the staging area. The core is collapsed and re- moved on a roller assembly. Next, the head- ers and excess strand are removed from the product ends. The product is then moved to a curing area and covered with wet burlap for a four-day wet cure. That same day, the set-up procedure be-
gins again using a second set of voids and headers, provided so that the next casting cycle can begin without having to wait for the voids and headers to be removed from the last cast piles.
Piles were shipped by truck to the job site, about 160 miles from the precast plant, taking about four hours. Because of the size of the product, transportation had to take place in daylight hours using a route with less traffic. At the bridge, cranes belonging to the contractor were used to remove the piles from trucks and install.
36 | SEPTEMBER 2012
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