Hysteretic performance of frictional glulam beam-to-column connections

By introducing shape memory alloy (SMA) strips and frictional connection into heavy glulam timber structures, the frictional glulam beam-to-column connections were proposed and their hysteretic performance was investigated. With steel and timber as frictional pad materials, a total of three half-scale specimens were designed and fabricated. Low cyclic reserved loading tests were conducted to obtain typical damage and failure modes and hysteretic curves. The elastic rotational stiffness, peak moments, energy dissipation capacities and residual deformations of the specimens were compared. Based on the working mechanism of the proposed connections, a hysteretic model was proposed. The results show that SMA strips undergo tensile failure while the timber in connection zone mainly remains intact. Compared to those of conventional bolted connections with slotted-in steel plates, the elastic rotational stiffness of frictional connections does not significantly change, the peak moments decrease by 2% to 17%, but the energy dissipation under each loading cycle increases by 64%-278%. The equivalent viscous damping ratios for most loading cycles are more than 0.2, and the residual deformation decreases. Frictional connection with steel pads has relative smaller residual deformation, and frictional connection with timber pads has greater equivalent viscous damping ratios. The proposed hysteretic model captures the experimental curves well, indicating that the model could be further utilized in engineering structural analysis.