Numeral modeling of fracture failure of recycled aggregate concrete beams under high loading rates

Abstract

Fracture tests of recycled aggregate concrete (RAC) beams of different sizes were conducted under high loading rates. In order to characterize the effect of high loading rate on the behavior of RAC beams, two new material models were used together with the commercial finite element software \(\hbox {ABAQUS}^{\mathrm{R}}\). One model is a viscoelastic model that can predict the increase of stiffness (modulus of elasticity) of RAC with increasing loading rate, and the other model is a multiphase composite model that can determine the effective stiffness of RAC taking into account the special internal structure of recycled aggregate. Two different cases were considered in the numerical simulation. Case 1 is for fixed beam size under different loading rates, and Case 2 is for fixed loading rate with different beam sizes. For Case 1, the simulation results of the maximum loads under three different strain rates agreed with test data quite well. The Force-CMOD curves of the numerical simulation and test data showed similar trends. The higher the strain rates, the wider the high stresses spread in the crack propagation zone. The good agreements with the test data indicated that the two new material models can characterize the effect of high loading rate on RAC beams very well. For Case 2, three beam sizes and one loading rate was studied. The post-peak Force versus CMOD curves from the simulation follow the same trend of the test data. The stress distributions in the beams of different sizes are similar. On the other hand, the maximum loads predicted by the numerical model did not agree very well with test data. This is due to the fact that the maximum forces of RAC notched beams exhibited size effect, which was not considered in the fracture criteria adopted in \(\hbox {ABAQUS}^{\mathrm{R}}\) and not in the two new material models. This will be a topic for future research.