Pile Group Under Transient Impact Loading

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Abstract Award: CMS 97-13951 P. K. Banerjee et al., SUNY Buffalo "Pile Group Under Transient-Impact Loading" This research focuses on the principal force experiences in transportation and waterfront structures during impact which is transient horizontal loading. Such loads are often transmitted to the structure's foundation supported on groups of piles and/or drilled shafts. State-of-practice design for lateral loading of pile and drilled shaft foundations used beam-on-elastic-foundation analysis to model this dynamic loading. In this analysis, load shedding from a pile to the soil is represented by "p-y" springs in which the soil response (p-y or force versus deflection curves) is modeled as a series of discrete nonlinear springs. Although p-y curves have been empirically modified to take into account many of the observed phenomena such as non-linearity, slow cyclic response, shadow zones and group interaction factors, etc., the propagation of dynamic disturbance from pile-to-pile in a group has never been considered. Therefore, the use of these springs for dynamic loading has ! to be significantly improved and soundly validated by combined experimental and analytical research. The objective of this research is to develop and validate an improved method of analysis for the design of pile groups (including drilled shafts) subjected to transient lateral impact loads. The research tasks encompass: a) a critical study of the transient impact behavior of pile groups founded in layered media, both analytically and experimentally, b) development of improved methods of analysis; c) testing and validation of the proposed new methods; and d) implementation of the improved methods in a numerical code. Experimental research will involve analysis of existing load test data as well as creation of new test data for testing and validation of the improved analytical method. The work will have national applicability as well as an immediate impact. From the re sults of this study, revisions can be recommended to AASHTO for inclusion in rationally applicable design specifications for the design of new structures subjected to vessel impact loading. ****