EFFECTS OF CYCLIC LATERAL LOADS ON PILES IN SAND

The effect of repetitive lateral loads on deflections of two drilled piers in Tampa Bay were significantly greater than predicted by a p-y procedure commonly used in practice. Reasons for the discrepancy between predicted and measured deflections are discussed. Two methods for predicting the effect of repetitive lateral loads are developed using results of 34 cyclic lateral load tests to quantify model parameters important to the behavior of piles subjected to repetitive lateral loading. The two methods model cyclic lateral load behavior of a pile by degrading soil resistance as a function of number of cycles of load, method of pile installation, soil density, and character of cyclic load. The two methods differ in the computational effort required to make the prediction. The first method is most suitable for hand calculation and rule-of-thumb estimation and is based upon a beam-on-an-elastic foundation model with a soil reaction modulus, K-h, increasing propertionally with depth. The second method modifies nonlinear static p-y curves to derive a cyclic p-y curve. The two methods provide a simple means for estimating effects of cyclic lateral load.