Energy Response Characteristics of Laterally Loaded Piles

Abstract

A bounding surface plasticity p − y model is used to examine the internal energy responses of a laterally loaded pile in static and dynamic simulations. The model response is first compared with those observed in physical centrifuge tests, including monotonic and cyclic loading, in a normally consolidated fine-grained soil. Then, the model is used to examine hypothetical static and dynamic situations. The monotonic load capacities determined by the model and an upper-bound limit analysis method are in agreement with that inferred from the physical test. The work done by external loads in static conditions is principally balanced by the plastic work in the p − y springs and the elastic strain energy in the structural pile elements, which are comparable in the cases examined. The numerical model is capable of reproducing accurately the observed test structural responses as well as the characteristics of plastic energy dissipation. In a dynamic free-vibration simulation, the pile is highly damped as a result of the significant plastic energy dissipation. The simple work-hardening elastic–plastic p − y model is theoretically sound, applicable to arbitrary loading histories, and requires the same level of effort to use as traditional p − y methods. An easy-to-use p − y model facilitates an efficient analysis of piles exposed to arbitrary lateral loadings. The implementation, use, and interpretation of results are familiar to engineers experienced in traditional p − y methods associated with piles founded in normally consolidated fine-grained soils. Energy balance equations demonstrate its theoretical soundness and provide insight into the accuracy of the numerical solution strategy. The calibration of the model parameters is accomplished with data available from standard site surveys and laboratory mechanical tests. Suggested typical model parameters are provided. The model is useful to those interested in computing the response of piles to loading conditions for which there are specific displacement service condition limitations. In the offshore oil production industry, typical applications would include the following: anchors to prevent pipeline walking as a result of thermal cycles, the design of conductors supporting wellhead control equipment, an evaluation of the dynamic response of riser bases exposed to dynamic environmental loads, and the design of foundation anchor piles for fixed or floating structures.