Seismic Performance of Concrete-Encased CFST Piers: Analysis

Abstract

The analytical behavior of concrete-encased concrete-filled steel tubular (CFST) piers under cyclic lateral loading is reported in this paper. A finite-element analysis (FEA) model is developed to investigate the cyclic behavior of such composite piers. Comparisons are made between measured and predicted results on failure modes and load versus displacement relationships. It is found that the proposed FEA model can reproduce the experimental results with reasonable accuracy. Full-range load-displacement relationships, contact stresses between the steel tube and concrete, contact stresses between the restricted region and the outer concrete, and comparisons on different members are analyzed using the verified FEA model. Parametric analysis is conducted to investigate the influence of various parameters on load-displacement (P-Δ) envelope curves. The parameters include the material strength, the steel ratio of inner CFST, the wall thickness to sectional width ratio, the longitudinal reinforcement ratio, and the axial load level. Finally, a simplified hysteretic model for the P-Δ relationship of a concrete-encased CFST pier is proposed.