Multisurface Plasticity for Concrete Subjected to Fire: A Spectral Decomposition–Based Approach

Abstract

The paper proposes a spectral decomposition–based approach for implementing a multisurface coupled damage–plasticity model for concrete subjected to fire. The multisurface approach enables distinct flow rules to be used for plastic flow in compression and tension. The spectral decomposition–based procedure enables, for general multiaxial loading, the Jacobian for the return mapping algorithm to be determined analytically without the need for finite difference approximations or additional nested iterations. The proposed approach, developed in the context of a general multisurface plasticity model subject to the small strain assumption, is specialized to the case of a combined Drucker-Prager and Rankine yield surface, and can account for situations where the eigenvalues of the stress tensor are degenerate. It is verified by solving finite element models for concrete structural components subjected to high temperature under a wide variety of mechanical loads. The simulation results, obtained using a sequentially coupled approach, are found to closely match established experimental results.