Mechanical performance of space sandwich joints under bidirectional cyclic loading

Abstract

In high-rise buildings with high-strength concrete column and normal-strength concrete floor, the beams and slabs are usually cast in a continuous fashion through the beam–column joint to simplify construction, and this results in the lower strength concrete at the beam–column joint core (sandwich joint). It will influence the capacity of the joint. In this article, three groups of three-dimensional specimens consisting of sandwich joint specimens and corresponding traditional joint specimens were tested under bidirectional reversed cyclic loads to investigate seismic performance, including the failure mode, ductility, energy dissipation, and deformation. The test results show that the beam–column joint core can be cast with normal-strength concrete when the column concrete strength is less than 1.5 times that of the beam. However, when the ratio exceeds 1.5, the failure mode of the joint may change from beams flexural failure to joint shear failure and additional strengthening measures should be taken. Finally, the formula for calculating shear capacity of the three-dimensional sandwich joints is presented, and the predictions are compared to the experimental results.