Thermal and seismic behavior of X-shaped energy dissipation brace featuring out-of-plane configuration: Experimental and numerical investigations

Energy dissipation exoskeletons present an effective intervention for enhancing seismic resilience of building structures, yet their operational safety was notably compromised by temperature variations due to their external arrangement. Addressing this issue, this study proposed an out-ofplane deformable X-shaped energy dissipation brace (OPD-XEDB), integrating an out-of-plane Xshaped brace with a shear-type metallic damper, designed to mitigate thermal stress through outof-plane deformation while preserving energy dissipation efficiency. To explore the out-of-plane deformation and hysteretic behavior of OPD-XEDB, thermal and quasi-static tests were conducted on three specimens with different damper web thickness, complemented by numerical analyses to evaluate the performance of OPD-XEDB compared to conventional X-shaped energy dissipation brace (XEDB) without out-of-plane configuration. The thermal tests and numerical analyses revealed that the out-of-plane configuration in OPD-XEDB enabled X-shaped braces to generate intended out-of-plane displacement by gusset plates bending. This behavior led to a significant reduction of 86.39-90.88 % in temperature-induced axial forces within the braces and their interconnected moment frames compared to the XEDB, validating the effectiveness of the out-ofplane configuration in thermal stress mitigation. Moreover, the quasi-static tests demonstrated that the damper web thickness significantly impacted the failure modes and hysteretic behavior, where appropriately strengthening could prevent tension factures and enhance energy dissipation, while excessive strengthening could trigger brace buckling, diminishing energy dissipation by 65.44-69.95 %. Furthermore, introducing an out-of-plane configuration with a specified angle, as employed in the OPD-XEDB for the prototype building, was proved to exhibit minimal impact on the hysteretic performance and energy dissipation mechanism of the bracing system, confirming the configuration's effectiveness in seismic applications.