Phenomenological Hysteretic Model for Steel Braces Including Inelastic Postbuckling and Low-Cycle Fatigue Prediction

Abstract

This study presents a simple yet efficient phenomenological hysteretic model for hollow circular steel (HCS) braces without a middle connection in concentrically braced frames (CBFs). The model is calibrated on the basis of the available experimental results and on a series of numerical simulations by finite-element (FE) models, which are validated by existing experiments. The Miner linear cumulative damage theory based on the Coffin-Manson expression is used to represent the low-cycle fatigue deterioration of a brace subjected to cyclic loading. Furthermore, the cumulative yielding strength degradation is considered by a simplified formulation, which is defined as the cumulative fatigue damage. Comparisons of the hysteretic responses obtained by the proposed model with the results of the FE models show that this model can capture several failure modes of a brace during inelastic cyclic behaviors, such as yielding, inelastic postbuckling, strength degradation, and fracture due to low-cycle fatigue, as well as the fracture point. The cumulative dissipated energy of a brace is well-predicted by the model. In addition, this model takes much less computing time than the FE model and is therefore suitable for structural analyses. The model should be further examined to more precisely consider the effect of the local buckling of a brace with different cross-sectional geometries.