Study on seismic performance of the RC beam-column edge joint strengthened with PVA-ECC

The reinforced concrete frame beam-column joint is often severely damaged under strong earthquake action, which reduces the seismic performance of the structure. In order to solve this problem, the polyvinyl alcohol fiber toughened cement-based (PVA-ECC) with excellent mechanical properties and damage tolerance is used to strengthen the beam-column joint. The working mechanism of the beam-column joint strengthened with PVA-ECC is investigated by the cyclic loading test on three beam-column edge joints, including the traditional beam-column joint, the beam-column joint added with the U-shaped connecting steel bars, and the beam-column joint strengthened with PVA-ECC. Furthermore, the enhancement effect of the beam-column joint is evaluated by comparing the bearing capacity, ductility, stiffness degradation, and energy dissipation. The results indicate that the PVA-ECC has good bonding performance and cooperative deformation capacity, which is not only beneficial to restrain the development of cracks in the joint zone and improve the failure mode of the joint, but also significantly improves the seismic performance of the joint. Compared with the traditional beam-column joint and the beam-column joint added with the U-shaped connecting steel bars, the yield displacement of the beam-column joint strengthened with PVA-ECC is increased by 11.20% and 6.09%, the peak displacement is increased by 17.73% and 16.65%, and the ultimate displacement is increased by 14.80% and 8.79%, respectively. The deformation capacity of the beam-column joint strengthened with PVA-ECC is enhanced. Through the finite element analysis of the joint, it is found that increasing the pouring length of the PVA-ECC will reduce the bearing capacity of the joint, but it can improve the ductility and energy dissipation. Increasing the PVA-ECC strength can enhance the bearing capacity and ultimate displacement of the joint, which shows that the use of PVA-ECC in the joint area can effectively improve the seismic performance of the joint and is beneficial to improving the deformation capacity of the beam-column joint unit. Based on the current code, the calculation formula of the bending capacity of the beam-column joint is revised by the test data. The theoretical value is in good agreement with the test value, which provides a reference for the same type of beam-column joint design.