Winkler model for pile seismic analysis considering end constraints effects

Beam on nonlinear Winkler foundation (BNWF) analysis of pile foundation subjected to vertically propagating earthquake ground motions is presented in this paper. The BNWF is considered a simplified approach that is capable to model nonlinear soil-pile-structure interaction. Soil nonlinearity is simulated by p-y curves according to American Petroleum Institute (API) procedure. The analyses are carried out using the open source finite element platform OpenSees. Results are verified against centrifuge experiments and numerical finite element simulations published in the literature. In this paper pile tip and head constraints effects on bending moments and displacement responses are investigated. Three types of pile tip constraints are applied: floating, end bearing, and fixed supports. Pile top constraint is modeled as either free or fixed head. Three different earthquake ground motions are applied in the model. Effect of superstructure mass is investigated for the three considered earthquake records and the different assumed pile end and head constraints. The results indicate significant influence of pile tip and head constraints on pile bending moment and displacement responses. A significant effect of superstructure mass on the analyses results is also observed. The analyses show that earthquake record characteristics remarkably influence pile response behavior. Different earthquake records scaled to the same peak ground acceleration give different pile seismic responses.