Effects of bolted connections on behaviour of timber frames under combined vertical and lateral loads

Abstract In this paper, a new bolted beam-column connection comprising of top-and-seat steel angles and bolts was used in timber frames and its influence on structural behaviour was determined through comparisons with connections with slotted-in steel-plates. In the experimental programme, three full-scale timber frames were tested to failure under combined vertical and lateral loads and their load capacity and lateral stiffness were obtained. Different failure modes of frames were also observed at beam-column connections and column bases. Strains at selected sections of beams and columns were measured by using strain gauges and rotations of beam-column connections and column bases were also captured by using displacement transducers. Bending moments at beam and column ends were calculated based on plane-section assumption and moment-rotation relationships of beam-column connections and column bases were established. Test results showed that timber frame with top-and-seat-steel-angle connections could develop 44% higher lateral stiffness and 20% greater load capacity than the frame with slotted-in steel-plate connections. The increases in stiffness and load capacity mainly resulted from the 3.0 times higher rotational stiffness of top-and-seat-steel-angle connections than that of slotted-in steel-plate connections. By decreasing the cross-section of beams and columns in the frame with top-and-seat-steel-angle connections, the rotational stiffness of connections was slightly reduced, but the connection could still sustain significant bending moments under lateral loads.