Simulation of Highly Ductile Fiber - Reinforced Cement - Based Composite Components Under Cyclic Loading

Ductile fiber-reinforced cement-based composites (DFRCCs) are being investigated for new design as well as retrofitting of structures in seismic regions. DFRCC is highly ductile and is characterized by strain-hardening in tension to strains over 3% and by unique cyclic loading behavior. To accurately predict the structural performance of DFRCC components under cyclic and seismic loading, a robust constitutive model is needed for structural-scale simulations. In this paper, a constitutive model based on total strain is proposed and applied to simulate structural component tests. The model in particular captures DFRCC's unique reversed cyclic loading behavior. The simulation results show that the implemented model is robust and reasonably accurate in simulating DFRCC structural components reinforced with steel and fiber-reinforced polymer bars. INTRODUCTION Ductile fiber-reinforced cement-based composites (DFRCC) are types of high-performance material that exhibit multiple, fine cracks upon loading in tension as a result of steady-state cracking Leung 1992). DFRCC materials are composed of portland cement, water, silica fume or fly ash, fine sand, and roughly 2% by volume of high-modulus, high-aspect-ratio polymeric fibers. DFRCC displays a much higher tensile ductility, tensile (strain) hardening behavior, and energy dissipation than traditional concrete and many fiber-reinforced concrete materials (summary in Li [1998]). Other fiber-reinforced composite materials exhibiting a similar strain hardening phenomenon include those studied by Majumdar and slurry-infiltrated fiber-reinforced concrete (SIFCON) (refer to, for example, Balaguru and Shah [1992]). Because the ductility of DFRCC materials is significantly larger than that of conventional concrete, applications of DFRCC materials to structures under severe loading conditions are being investigated. Most of the research to date on DFRCC has focused on experimental investigations of the material and structural components. A simulation framework that can verify, validate, or predict the performance of the structural members using DFRCC material has been explored by very few researchers for cyclic analysis of structural members. The primary objective of the research presented herein is to develop a constitutive model that can be used to simulate structural components with DFRCC under cyclic and seismic loading. In particular, the constitutive model must be efficient and robust for large-scale simulations. This paper focuses on models for cyclic loading. Different modeling approaches of concrete cracking are well summarized in de Borst (1997). Approaches based on the thermodynamic potential and damage-mechanics-based