Experimental study and theoretical analysis on mechanical properties of prestressed bolted glulam connections under cyclic loading

Abstract

Due to the development of assembled buildings and public environmental awareness, glulam structures have been widely concerned nowadays which have the advantages in terms of energy efficiency and environmental protection, compared with concrete and steel. However, the beam-to-column connections connected by bolts with slotted-in plates in glulam frame structures generally have some disadvantages, such as the low load-bearing capacity, low stiffness, low ductility, and poor energy dissipation capacity. To improve the mechanical performances of conventional glulam beam-to-column connections against seismic effect, a prestressed bolted glulam connection was proposed in this paper. Twelve connection specimens from four groups were tested and numerically studied under cyclic loading. The results show that the application of prestressing force can improve the brittle failure of connections. Compared with the traditional glulam bolted connections, the application of prestressing force can improve the load-bearing capacity, energy dissipation capacity, ductility and initial stiffness of the connection, and slow down the stiffness and strength degradation. However, excessive prestressing may cause an early failure of the connection. The numerical analysis shows that the bolt diameter and the number of steel bars have significant positive influence on the load-bearing capacity of the connection. Even though increasing bolt diameter would be more efficient for the mechanical behavior of the connection, the transverse splitting failure of glulam would be more likely to occur. A calculation formula for the load-bearing capacity and a theoretical model for the moment-rotation relationship of the prestressed bolted glulam beam-column connections are proposed respectively for practical design. The rotation behavior evaluation of the prestressed bolted glulam beam-column connections indicates that the proposed connections are classified as semi-rigid connections, which can be used for ductility design.