The building code allows engineers and contractors to load test a structure that calculates to an overstressed condition. This is important to owners as it may save significant money otherwise spent to strengthen a structure that has been performing for many years. It is also important to engineers and building officials as it allows an apparently overstressed structure to be deemed safe for use.
Recently Restruction Corporation participated in load testing a 62 foot long, 8 foot wide double tee stem containing three ½” diameter 7 wire pre-stressing strands per stem. Seven inches of soil and turf with waterproofing membrane had been placed over the 2” thick un-topped tee flanges. A string line was run and negative deflection in static state was measured at approximately 1.5-inches.
The load test consisted of installing shoring, cutting double tee flange connections, marking existing cracks and the initial deflection, placing water barrels and filling in one quarter increments to a total of approximately 40,000 pounds live load, (5000 gallons of water). Loaded deflections were measured, new tension cracks measured and marked and 24-hour time period elapsed prior to unloading the tee. The deflection “rebound” response was measured and compared to acceptance criteria in the code.
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