Moment resistance of bolted timber connections with perpendicular to grain reinforcements
This paper reports the results of an experimental study to evaluate the contribution of self-tapping screws as perpendicular to grain reinforcements for bolted glulam connections with slotted in steel plates. Test results of beam-to-column connection specimens subjected to monotonic and reverse cyclic loading show that the connections reinforced with self-tapping screws have an increased capacity by a factor of 2 and 1.7 when compared to un-reinforced connections under monotonic and reverse cyclic loading, respectively. Retesting retrofitted failed un-reinforced connections with selftapping screw reinforcements also show increase in the capacity by 1.87 and 1.53 times compared to the un-reinforced case connections under monotonic and reverse cyclic loading, respectively. An extremely ductile failure mode was also observed with the reinforced connection.
It is well known that bolted timber connections with slotted in steel plates have poor ductility and low moment resisting capacity. Due to their simplicity and elegance, designers commonly use these connections to transfer shear forces and ignore the contribution of their moment carrying resistance. When subject to loading such as seismic forces, the connection may experience bending moments not intended in the design, and the connection could fail prematurely because it may not be able to provide the needed moment resistance as they are governed by the tension perpendicular to grain and longitudinal shear strengths of timber: the two weakest strength properties of wood.