Study On Vertical Stiffener Joint Of Concrete-filled Square Steel Tubular Column With H-shaped Steel Beam

In recent years, frame structures composed of concrete-filled square steel tubularcolumn and H-shaped steel beam have been one of the major representations in thedevelopment of steel structure of residential buildings. But at present, there are verylittle joint types for this kind of structure in the corresponding codes and regulations,which restricts its practice in the project.To coordinate the promotion of concrete-filled square steel tubular columnstructure and the implementation of new design code, this paper summarizes jointtypes of concrete-filled square steel tubular column with steel beam according tohinged joints, semi-rigid joints and rigid joints, and simply introduces the presentresearch of the rigid joints. On the basis of above analysis, one new type of rigidjoints—vertical stiffener joint is proposed and a theoretical and experimental study iscarried out to understand the mechanical property of this new-type rigid joint.Force transfer mechanism of the vertical stiffener joint model with only tensilebeam flange is firstly analyzed, and based on yield line theory, the formula forcalculating the bearing capacity of the joint is presented. Then ten specimens of thejoint model are studied by static tensile test to investigate the structure behavior of theconnection between concrete-filled square steel tubular column and steel beam flange.The failure process and feature of each specimen are described and the stress transfermechanism in the connection zone is analyzed. Then comparing analysis is executedon the measured value and the calculated value of bearing capacity of this joint.Research results suggest that vertical stiffener joint model has high capacity and goodductility and that the yield capacity and stiffness can be increased by the concretefilled in the tube. The formula which is deduced from theory analysis is very good topredict the yield capacity of joint model.In order to study the seismic performance of vertical stiffener joint, three full-scalecruciform specimens are studied under quasi-static test. The failure process andfeature of each specimen are described and the stress transfer mechanism in theconnection zone is analyzed. Based on the measured hysteresis loops, this papermakes a thorough comparing analysis on the index of seismic behavior such asload-carrying capacity of the joint, ductility, energy dissipation, strength degenerationand rigidity degeneration. The analysis results show that the construction details ofvertical stiffener joint are simple and reasonable and this new-type joint has a goodseismic behavior. Through comparison of the specimen not filled in concrete withthose filled, it indicates that concrete filled in the steel tube can enhance the seismicperformance of the joint.After experiments and analysis, this paper considers that the new-type joint hasthe advantage of transferring load reliably, construction details simply, thus it has awider foreground in application.