Flexural behavior of RC beams strengthened by steel plate with bolt anchors and random bond defects

Abstract

The application of bolt anchoring method has been found effective for enhancing the flexural performance of steel plate-strengthened reinforced concrete (RC) beams. However, bond defects that may develop at the steel-concrete interface and the loss of bolts due to corrosion can compromise the strengthening effectiveness. Thus, this study conducted four-point bending tests to examine the impact of bond defects and the loss of bolts on the flexural behavior of RC beams strengthened with steel plates. The results exhibited that an 11% bond defect area and the loss of 20% number of bolts led to premature debonding due to stress concentrations around the defects and the loss of mechanical anchorages that can reduce the peeling stress, resulting in a 32.8% reduction in the debonding load. Nevertheless, the remaining bolt anchorages effectively impeded the debonding development, allowing the steel plates to sustain the load and achieve an ultimate load comparable to beams without bond defects. Finite element (FE) simulations were performed and verified against experimental test data, demonstrating good agreement with an R² value of 0.98. The verified model was extended for parametric analysis, revealing that the increase in ultimate load of the beams diminished with a larger bond defect area and fewer bolts. Finally, an analytical model was proposed to predict the ultimate load of the strengthened beams, considering the influence of carrying bond defect area and bolt quantity.