ABSTRACT:

According to test data on model pile in clay subject"~ fl to variety of static and cyclic loading combinations, two kinds or characteristic values or cyclic shaft capacity are evaluated by using different displacement conditions, t he relationship between these two characteristic values and the variation of them with the ratio of cyclic load amplitude to static load arc studied in the paper.

INTRODUCTION

With the development of pile-supported jacked platforms, tensile leg structures, and buoyant and guyed towers in deepwater ova areas, the proportion of cyclic load to total load on the pile (or on the anchor pile) increases significantly, In this case, the pile behavior in shaft capacity (skin friction) will change essentially in comparison with that under static loading, A series of model pile tests in remolded clay have been conducted in Tongji University to simulate the behavior of a tension pile element under cyclic axial loading. The model pile tests were carried out in steel tank 1. 6m in diameter and 1. 4m in height. An aluminum tube 3.0cm In diameter and 1. 15m in length was used as model pile. The properties of remolded clay obtained from Shanghai are; water content w=29. 3%, plasticity index Ip=13. 3 and undrained shear strength Cu= 47kPa. Cyclic tension load applied to model pile in the tent is load-controlled mode, and actuated with pneumatic piston controlled by electro pneumatic valves. A relatively low frequency of cyclic loading at 0.1Hz is used for simulating wave loading. The displacement of pile top subjected to a combination of static and cyclic loads consists of three components (Fig.II: Initial displacement ρo caused by static load, cyclic displacement amplitude pc. and cumulative displacement ô ae during cycling.

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