Seismic behavior and design of repairable precast RC beam–concrete-filled square steel tube column joints with energy-dissipating bolts

Abstract

The dry jointed precast frame structure has the potential in less reliance on wet concrete, low cost and repairability after earthquake. The seismic behavior of the novel precast dry connections with different beam end arrangements was studied in this work. For the precast specimens, the concrete-filled square steel tube (CFSST) column and RC beam were prefabricated, and field assembly was carried out by energy-dissipating (ED) bolts and unbonded prestressed tendons. Design equations were formulated according to the strong-column–weak-beam concept and the capacity design philosophy. The viability of the repair method of the precast internal beam–column connections after earthquake was explored. The joints were repaired by replacing the ED bolts and loaded again. The seismic indicators, such as ductility and energy dissipation capacity, were determined and compared. The results showed that the excellent structural characteristics and practical design method could ensure low damage to the joints except for the ED bolt yield. The new-type precast beam–column joints exhibited good hysteretic performance with high ductility factors greater than 5. After repair, the failure mode of the joints was controlled by the plastic hinge on the beam. The repaired joints had good strength stability, and the ultimate bearing capacity was the same as before repair. The ductility of the repaired joints was 13.29%–32.14% higher than before. The energy dissipation capacity could reach more than 1.2 times that of the cast-in-place concrete joints, which proved the feasibility of the repair method.