Experimental studies on foundations of compliant structures-II. Under cyclic loading

The foundations of compliant structures are subjected to a large magnitude of tension and a superimposed cyclic load. The cyclic load is due to the rocking and bobbing motion of the superstructure caused by the motion of the wind and waves past it. In this paper, the behavior of piles (both single and group) under a cyclic load is studied by conducting tests on model steel pipe piles in a soft marine clay. The cyclic loading is applied with the help of a pneumatic loading system. The tests are conducted at different cyclic load levels ranging from 30 to 75%. From the tests results, it is found that when the cyclic loading level is low, the movements get stabilized within the first few hundred cycles of loading. If these movements are less than the movements at ultimate load in static tests, there is no reduction in the capacity. However, at higher loading levels, piles failed within the first 100 cycles. The movement of pile during cyclic loading is found to be a very important parameter controlling the post-cyclic static pull-out capacities. The validity of the stability threshold concept that is being used for clayey soils under cyclic loading is extended and examined for anchors under cyclic loading in clayey soils. © 1994.