Cyclic hardening and softening behavior of the low yield point steel: Implementation and validation: Fid-Bau Portal

Cyclic hardening and softening behavior of the low yield point steel: Implementation and validation

Wang, Chen / Fan, Jian-sheng / Xu, Li-yan / Nie, Xin

Highlights • An advanced constitutive model is developed on ABAQUS UMAT for application. • A modified radial return algorithm for J2 plasticity with A-F hardening law is proposed. • The consistent tangent moduli of the stress update algorithm is derived stepwise. • The newly-developed model is validated by a vast number of experiments.

Abstract The low-yield-point (LYP) steel exhibits complicated cyclic hardening and softening response under reversed loading condition when applied in the seismic control and isolation system, thereby the evaluation of its hysteretic behavior demanding a sophisticated constitutive model with robust multi-dimensional implementation for reasonable finite element analysis. In this paper, the implementation and validation of an advanced constitutive model for LYP steel developed in a previous study is illustrated, which formulates the cyclic hardening and softening features by decomposed A-F hardening laws with strain memory effect and a novel concept of “transformation zone” with multi-stage evolution rule, respectively. To convert the theoretical model into numerical utilization, a modified radial return algorithm is proposed for the fully-implicit stress integration, and the corresponding consistent tangent moduli are derived. Moreover, the constitutive model is incorporated into a general finite-element software package based on the ABAQUS UMAT platform to facilitate its universal application. A number of experimental results, including the material coupons, the shear panels/links, and a frame-shear wall system made of LYP steel, are collected to validate the model ranging from material level to structural level. The close fit between simulations and experimental results indicates that the developed model is capable of accurately describing the nonlinear cyclic hardening and softening properties with memory effect for LYP steel, which proves the model suitable for the structural seismic simulation and analysis.