Mechanical Behavior of Rigid Joint Between PEC Column and Beam in Weak Axis Direction——Test and Calculation

A PEC(Partially Encased Composite) member is the composite component with concrete filling between the flanges of I-beam or H-shaped steel, and reinforcement or flange connecting bars in the concrete. The structure using PEC members is called PEC structure, whose load bearing capacity, ductility and stiffness are better than pure steel and reinforced concrete structures, and has good fire resistance. A special technical specification CECS 719-2020 has already been developed for PEC structures by our national researchers, but the experimental research on the mechanical performance of rigid connection between PEC columns and beams in the weak axis direction is still insufficient. So in this paper, three sub-structural joint specimens between PEC columns and beams in the weak axis direction were designed, which were numbered JM, JH, BH. The monotonic static loading and hysteresis loading tests were carried out to investigate the mechanical performance and the failure modes. The joints were connected by the endplate and bolt. To meet the requirements of prefabrication and assembly in engineering projects, the divided plate and flat steel were used in the specimen design. Based on the technical specifications in Europe, Canada and China, many factors such as loading mode, failure mode, loading path, steel strength and concrete strength were taken into account for the design of the test apparatus, loading regime and testing scheme. And then, by using antisymmetric loading at the beam ends, one monotonic static loading test and two hysteresis loading tests were carried out. Among the 3 specimens, the column flange and plane zone of JM and JH specimens were weakened, JM specimen was loaded by static monotonic loading and JH specimen was loaded by hysteresis loading; both of them showed column failure mode, and the ultimate loading capacity of JH specimen was lower than that of JM specimen; the beam flange and web of BH specimen were weakened and loaded by hysteresis loading, and finally the beam failure mode appeared. The results show that: 1)The tested joint between PEC beam and column in its weak axis direction can meet the requirements of rigid joints. 2) By using the calculation method of bearing capacity of beam, column and weak axis connection joints specified in CECS specification, the failure mode of specimens can be predicted correctly, which guiding significance for the projects. 3) Due to the lateral restraint from the concrete in the beam member, the concrete portion of the PEC weak-axis joint can effectively increase the shear loading capacity of the joint. 4) The accumulation of damage to the concrete under hysteresis loading will cause a reduction in the ultimate loading capacity of the PEC specimens.