Abstract:
Calculating the seismic shear capacity of reinforced concrete (RC) beam-column joints is a key measure to ensure the seismic performance of the joints. The calculation formula in the
Code for Design of Concrete Structures (GB 50010−2010) temporarily adopts an expedient method when considering the influence of axial force, which is related to the fact that the influence of axial force is complex and the existing research results have not clarified the effect of axial force. On the OpenSees platform, the applicability of the Beam Column Joint Element (BCJE1) model, the BCJE2 model considering the bidirectional stress dispersion effect of diagonal compression member, and the MBCJE model which discretizes the joint area into diagonal concrete compression members, horizontal and vertical steel bar springs, have been calibrated in this paper. The appropriate prototype of beam-column sub-assemblage specimens were selected, and the BCJE2 and MBCJE models with better simulation results were used to perform the parametric analysis of RC joints and beam-column sub-assemblage through a series of changes in axial load. The results show that when the shear-compression ratio of joint \nu is higher (\nu \geqslant 0.3), the joint damage is serious; increasing the axial load will reduce the ductility of the sub-assemblage, and the beneficial influence of the axial load on the peak shear stress of the joint will be significantly reduced when the axial compression load is large or small. The formula for calculating the seismic shear capacity of the joint in GB 50010−2010 does not fully consider this relationship, and there is a potential problem. When \nu is medium (0.2 \leqslant \nu < 0.3), it is generally feasible to consider the beneficial effect of axial force according to the calculation method of GB 50010−2010, but the stirrup of joint should be appropriately increased when the axial compression ratio is small. When \nu is low (\nu < 0.2), the stirrup of joints can be determined according to the calculation method for the shear capacity of joint in GB 50010−2010.