Seismic behavior analysis of RCS composite joints with embedded profile steel

Abstract

To ensure that the internal forces can be effectively and reasonably transmitted to the joint area, a new type of reinforced concrete column-steel beam(RCS)composite joint with profile steel is proposed. A series of quasi-static experiments are conducted to examine the different extension lengths of profile steel on the failure mode of the joint. The experiments results indicate that the extension length has a significant impact on the failure mode of the joint. As the extension length increases, the failure mode shifts from the concrete failure in the profile steel cutoff to the concrete failure in the joint area. The hysteresis curves exhibit certain pinching phenomena, among them the curves of the joints with concrete failure in the joint area are more plump and it has a high flexural capacity. This is because the internal forces can be effectively transmitted from the beam to the column through profile steel. To further investigate the relationship between the reasonable extension length Lsr and limit length L0 of the profile steel, as well as the influence of other design parameters on the failure mode and seismic performance of the joint. It is necessary to use finite element software ABAQUS for modeling and analysis. Therefore, the finite element models of 18 RCS composite joints are established, the variables include different extension lengths, different steel ratios, and different concrete strengths. By comparing the energy dissipation capacity, deformation capacity, flexural capacity, stiffness degradation, and strength degradation, it can be concluded that the joints with concrete failure in the joint area has good seismic performance and flexural capacity. To satisfy that the concrete failure occurs in the joint area, the reasonable extension length Lsr needs to exceed 1.24 times longer than the limit length L0. With the increase of the steel ratio and concrete strength, the flexural capacity continues to rise. However, when the steel ratio and concrete strength exceeds a certain value, the increase rate is gradually slowing down. It is recommended that the reasonable steel ratio and concrete strength is around 6% and C40 respectively. Moreover, a general form of design methed is presented for computing the reasonable extension length and the flexural capacity of the RCS composite joints.