| Research Abstract |
A cyclic horizontal load test was performed on a real size test specimen of pile head joint. A PHC pile with 50cm in diameter, welded 8 stud bars to end face and burned 5 cm into foundation slab, was used as test specimen. Stud bars are bound up by lead. The foundation slab is fixed to the floor, and cyclic horizontal load is applied to pile, under the axial load of 98OkN, at 1.75m up from the surface of foundation slab. The reason why the stud bars are bound up by lead is to expect damper effect of lead that the stud bars are moving in lead under the rocking motion of pile head by cyclic horizontal load.
As a test result, the following is obtained. Load-displacement relation keeps linear state up to the load level corresponding to the short-term allowable bending moment of pile, but exceeding that level, changes to S-shaped wide hysteresis roop until the ultimate state, i.e., damper effect of lead is displayed clearly. Cracks are observed on the surface of foundation slab at the step of displacement of pile head 28mm. By progressing these cracks, producing other cracks and connecting mutually, the final state becomes the surface concrete surrounding the pile comes off totally.
A shaking table test was also performed for 2 box-type superstructures supported by laminar piles in shearing soil-box, the first one of which is fixed condition at pile head joint and the second one is damper condition by using visco-elastic material. The main test results are as follows ; Natural frequency and response amplification are also lower in the case of damper model than the fixed model showing the damper effect clearly. The peak of sweep test appears also in the case of random wave input and earthquake input motion. As the revel of input motion is larger, effects of non-linearity of model ground appears still more.
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