Theoretical study on the nonlinear contact mechanism of reinforced self-centering bridge pier system based on the Winkler model

Self-centering (SC) bridge piers generally set one or several gaps to avoid the occurrence of plastic hinges and mitigate both damage and residual drifts during major earthquakes. However, the gap opening mechanism also produces new problems in theoretical analyses, such as the strong nonlinear contact motion behavior between adjacent segments. An accurate contact mechanism is therefore significant to describe the gap-opening process and evaluate the mechanical properties of rocking systems. Firstly, for the low-damage SC bridge pier system especially with different reinforcement measures in contact segment, this study investigated the nonlinear contact mechanism by decoupling the linear and nonlinear motions of the SC bridge pier system, which were elastic-body rotation and contact segment bending-to-yielding, respectively. Secondly, the entire gap opening process was divided into three stages, and force analysis of the contact segment in each stage was conducted. Subsequently, the differential equations and rotation equation of the contact segment were established and derived based on the Winkler model. The corresponding contact parameters in the equations were obtained. The proposed equation was verified using published experimental data. In addition, finite element analysis (FEA) results showed that the rotation equation can accurately describe the contact state at each moment during the entire nonlinear contact process. Finally, the key parameters describing the contact state is investigated including the contact width, rotation posture, rotation angle, and contact stress. The results show that proposed theory can accurately predict the improvement effect of hysteretic performance for different reinforced measures on the rocking interface, which will be helpful and efficient for the optimal design of reinforced SC bridge pier system.