A nonlinear finite element model for shear deficient heat-damaged concrete beams repaired using NSM CFRP strips

Abstract

The mechanical performance of heat-damaged and shear-deficient beams, retrofitted using near surface mounted (NSM) CFRP strips, was investigated using nonlinear finite element (NLFE) modeling. This was carried out using the software ABAQUS with the cohesive element and the virtual crack closure technique (VCCT) implemented to model bond interface between concrete and NSM CFRP strips and concrete cover separation, respectively. The NLFE model was validated using experimental data from tests on shear-deficient and heat-damaged beams before predictions expanded to consider wide spectrum of exposure temperatures in the range of 23–700 °C and varying spacing between vertical NSM CFRP strips (75–200 mm). NLFE predictions of mechanical response and cracking and failure modes for intact, heat-damaged, retrofitted and strengthened beams were in an excellent agreement with experimentally obtained results. The study revealed that the retrofitting efficiency hence benefit was higher for beams, exposed to temperatures below 600 °C and repaired using NSM CFRP strips at spacing greater than 75 mm. In general, concrete beams, exposed to 400 °C and greater then repaired for shear, tended to fail by concrete cover separation; especially when NSM CFRP strips were inserted at spacing values of 100 mm and less; others experienced dominant typical shear failure. Finally, the present NLFE model explained failure mechanism of NSM CFRP shear-strengthened beams through concrete cover separation.