Hysteretic Performance of Self-Centering Glulam Beam-to-Column Connections

This paper investigates the hysteretic performance of self-centering beam-to-column connections for glulam structures. Such connections incorporate a posttensioned high-strength steel strand to provide recentering capability, and an energy dissipation device (a special steel cap or a pair of steel angles) was installed to increase shear resistance and provide energy dissipation. Moreover, disc springs were installed at the anchor of the steel strand to reduce the loss of pretension force. Seven full-scale specimens with different connection layouts were designed for a series of cyclic loading tests. The observed failure modes are reported, and the hysteretic moment-rotation responses of the specimens are evaluated. It was noted that due to the installation of the energy dissipation device, both the moment-resisting capacity and rotational stiffness of the specimen increased, but larger residual deformation was observed because plastic deformation in the steel components was more difficult to fully recover. The variation in pretension force in the steel strand was monitored. The monitoring data indicated that disc springs were capable of eliminating pretension force loss in the steel strand under the normal service condition (i.e., indoor environment with varied humidity/temperature). However, during the cycling loading tests, the specimens with disc springs showed very similar pretension force loss behavior to the specimens without disc springs, indicating that disc springs failed to prevent pretension force loss in the steel strand caused by plastic wood embedding under large rotational deformation. Furthermore, a nonlinear numerical model was developed for the self-centering connections, and numerical results showed that the model was capable of providing good predictions in terms of moment-resisting capacity under various levels of rotational deformation. The presented experimental and numerical research aims to assess the hysteretic behavior of glulam self-centering connections, which supports the development of innovative timber connections with enhanced seismic performance.