Response of toe-nailed, roof-to-wall connections to extreme wind loads in a full-scale, timber-framed, hip roof

A full-scale, timber-framed, truss, hip roof was subjected to simulated wind loads. Spatially and temporally varying pressures were applied using an array of 58 Pressure Loading Actuators, together with air-boxes covering all roof surfaces. Load cells were incorporated at the top of the wall frame, just below the top plate, to measure the reactions at the toe-nailed roof-to-wall connections. Changes in influence functions and load sharing between adjacent trusses were observed to occur during withdrawal (slip) of the toe-nail connections caused by large magnitude, short duration peak pressures. Even for relatively small displacements, it was observed that the effective tributary area is substantially increased by the incremental withdrawals. This acts to increase the resilience of the roof by allowing more limber and/or more highly loaded connections to transfer loads to stiffer and/or less highly loaded connections. Influence functions, measured both prior to and following damage, were able to predict this behaviour.