A novel steel–timber buckling restrained brace (STBRB) system for seismic applications

This study provides details of the steps taken to advance the development of steel-timber buckling restrained brace (STBRB) as a lightweight alternative to conventional concrete-filled BRBs. The STBRB comprises of a steel core, a steel tube (casing) and a timber infill. Fourteen STBRB specimens, in two groups (up to 2.1 m in length) were fabricated and tested following the AISC 341 cyclic loading protocol. To investigate the influence of different parameters on the failure modes of STBRBs, a range of timber species and grades, i.e., Radiata Pine (MGP10), Douglas fir (F5), Blackbutt (F27), and laminated veneer lumber (LVL), were used with steel cores and casings of varying geometries. Experimental results demonstrated that STBRBs with steel collars achieved the highest cumulative inelastic deformation (CID) and showed no significant failure mechanisms, even under high cyclic demands. STBRBs with thin steel casings (<3 mm) and low-grade timber infill exhibited local buckling and timber crushing. High mode buckling was observed in some specimens, with minor kinks in hysteresis curves for STBRB with low-grade timber infill. The study concluded that STBRBs with thicker steel casings (3–4 mm) or steel collars display stable hysteresis behaviour and exceeded AISC 341’s energy dissipation requirements. The test results confirm that the proposed STBRBs offer promising seismic performance. Future work should explore the cyclic/seismic performance of the full-scale frames with STBRBs.