An Approximate Damage Model for Concrete Under Finite Deformation

Abstract

As the computing power of computers is constantly increasing, more accurate finite element analysis and detailed modelling of structures are sought. The critical issue of concern at hand is the characterization of complex material constitutive behaviour using numerical techniques. Finite element analysis of reinforced concrete structures under severe and reversible loadings requires a proper representation of concrete material behaviour. Abnormal loads such as impact, blast and seismic are generally reversible and cause structures to vibrate. To arrive at a reasonable approximation of damage in reinforced concrete structures under abnormal loading, the cracking of the concrete and its direction must be addressed. The inclusion of a mechanism that accounts for crack closure should be considered to include the compression strength of the cracked concrete if the load direction is reversed and the crack is closed. Thus, development of an improved material model for concrete and its implementation in a non-linear finite element code that is well suited to this class of problem is undertaken. In the work described in this paper, the methodology used in the development of this new material model for concrete is discussed. A sample case is analysed and the results of these FE analyses are discussed. The new concrete material model predicts the location and the direction of the cracks accurately and also allows for the inclusion of the compression strength of the cracked material in directions parallel to crack plane. In addition the closure of the crack and reactivation of the compression strength of the concrete orthogonal to the crack plane when the crack is closed is achieved.