Direct FEM Analysis of Concrete Fracture Specimens

Abstract

A direct numerical procedure that extracts the fracture parameters and also predicts fracture responses of concrete fracture specimens is developed. This procedure involves a finite element analysis of the fracture specimen together with an optimization program for incorporating the overdeterministic boundary conditions. The input data for this procedure are the measured crack opening displacements, the applied load, and any additional experimentally obtained displacement data. The fracture process zone (FPZ) model assumes a unique smooth relationship between the crack closure stress and the crack opening displacement (COD) and is obtained by superposing Green's functions of the crack closure stress versus unit COD relation for the finite element model of the fracture specimen. The Newton‐Raphson nonlinear equation solver coupled with a Householder transformation least square routine are used to obtain the distribution of crack closure stress in the FPZ. The FPZ model is then used to predict the fracture responses in crack‐line, wedge‐loaded double cantilever beam, concrete specimens, where good agreement between the predicted and numerically determined results are noted.