DAMAGE BASED CONSTITUTIVE MODEL FOR PREDICTING THE PERFORMANCE DEGRADATION OF CONCRETE

Abstract

AN ANISOTROPIC ELASTIC-DAMAGE COUPLED CONSTITUTIVE MODEL FOR PLAIN CONCRETE IS DEVELOPED, WHICH DESCRIBES THE CONCRETE PERFORMANCE DEGRADATION. THE DAMAGE VARIABLE, RELATED TO THE SURFACE DENSITY OF MICRO-CRACKS AND MICRO-VOIDS, AND REPRESENTED BY A SECOND ORDER TENSOR, IS GOVERNED BY THE PRINCIPAL TENSION STRAIN COMPONENTS. FOR ADEQUATELY DESCRIBING THE PARTIAL CRACK OPENING/CLOSURE EFFECT UNDER TENSION AND COMPRESSION FOR CONCRETE, A NEW SUITABLE THERMODYNAMIC POTENTIAL IS PROPOSED TO EXPRESS THE STATE EQUATIONS FOR MODELING THE MECHANICAL BEHAVIORS. WITHIN THE FRAMEWORK OF THERMODYNAMIC POTENTIAL, CONCRETE STRAIN MECHANISMS ARE IDENTIFIED IN THE PROPOSED ANISOTROPIC DAMAGE MODEL WHILE EACH STATE VARIABLE IS PHYSICALLY EXPLAINED AND JUSTIFIED. THE STRAIN EQUIVALENCE HYPOTHESIS IS USED FOR DERIVING THE CONSTITUTIVE EQUATIONS, WHICH LEADS TO THE DEVELOPMENT OF A DECOUPLED ALGORITHM FOR EFFECTIVE STRESS COMPUTATION AND DAMAGE EVOLUTION. ADDITIONALLY, A DETAILED NUMERICAL ALGORITHM IS DESCRIBED AND THE SIMULATIONS ARE SHOWN FOR UNI-AXIAL COMPRESSION, TENSION AND MULTI-AXIAL LOADINGS. FOR VERIFYING THE NUMERICAL RESULTS, A SERIES OF EXPERIMENTS ON CONCRETE WERE CARRIED OUT. REASONABLY GOOD AGREEMENT BETWEEN EXPERIMENTAL RESULTS AND THE PREDICTED VALUES WAS OBSERVED. THE PROPOSED CONSTITUTIVE MODEL CAN BE USED TO ACCURATELY MODEL THE CONCRETE BEHAVIORS UNDER UNI-AXIAL COMPRESSION, TENSION AND MULTI-AXIAL LOADINGS. ADDITIONALLY, THE PRESENTED WORK IS EXPECTED TO BE VERY USEFUL IN THE NONLINEAR FINITE ELEMENT ANALYSIS OF LARGE-SCALE CONCRETE STRUCTURES.