The purpose of the testing procedure was to determine the stress at the top of a prestressed concrete pile to determine the bending moment at the section where the pile was embedded into an abutment at the end of a bridge with integral abutment piles. The abutment was modelled with a concrete mass attached one foot above ground level, leaving only a small space to mount the strain gage components. In previous tests on steel piles, the gages were welded to the pile, a procedure that obviously could not be followed, with the prestressed pile. The gage length needed to be about 100 mm. long to eliminate the effects of the large aggregates in the concrete pile. It was not possible to mount the gages on the pile prior to driving the pile 10.7 meters into the clay soil. A series of laboratory tests was used to verify the methods of attaching gages to the concrete. A 150 mm. by 150 mm. prismatic concrete member 610mm. long was used as the test specimen to be tested in compression. The specimen is shown in Figure 1 with the attached gages.
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