Cyclic behavior of alkali-silica reaction-damaged reinforced concrete beam-column joints strengthened with FRP composites

The research investigates the effect of using external fiber-reinforced polymer (FRP) –composites to strengthen the alkali-silica reaction (ASR)-damaged reinforced concrete (RC) beam-column joints. The nonlinear finite element analysis (NLFEA) method has been used to achieve the aims of this paper. Before experimenting, the B-C beam model has been verified following accredited previous experimental. Afterward, the experiment was extended to include the impact of the column’s axial load level and the ASR damage stage. For these purposes, the levels of the axial load were set at 0%, 25%, 50%, and 75%, while the stages of the ASR damage were: stage 0 (un-damaged), stage 1 (45 days), stage 2 (80 days), and stage 3 (120 days). Some of the models were strengthened with FRP, while the others were not. The evaluation of the models' structural performance was conducted by monitoring: the failure mode, distribution of stresses, degradation of stiffness, dissipation of energy, displacement ductility, pulling-pushing ultimate load capacity, and correspondent displacements, in addition to the horizontal load-displacement hysteretic loops and envelopes. The achieved results from this work indicated that the strengthened-with-FRP of ASR damaged RC B-C joint models showed an enhancement in their cyclic performance, as they showed: higher load capacity, more significant horizontal displacement, more displacement ductility, more dissipation of energy, and less secant stiffness degradation. It was also noticed that the higher the stage of the ASR damage, the better the efficiency of FRP composites. Further, strengthening the joint models with FRP transformed their failure mode from brittle mode to ductile, by forming a plastic hinge in the beam side at a column axial load exceeding 25%. On the other side, applying a column axial load below 25% only improved the ultimate deflection and corresponding axial load capacity.