Load Transfer in Deep Foundations Under Repeated Axial Loading

An analysis is presented of changes in axial load transfer for deep foundations under repeated loading, compared with static uplift and compression loading. Existing load test data demonstrate that, for repeated axial loading, the amount of load transferred along the sides decreases relative to tip resistance, when compared to static compression. The observed change is more pronounced for increasing magnitude of repeated loading, number of loading cycles, and downward displacement. Results of an experimental program are presented in which measurements were made of axial load transfer versus depth in model drilled shafts in sand under static uplift and repeated uplift/compression loading.