Wind load fluctuations on roof batten to rafter/truss connections

Abstract

Batten to rafter connections in light framed housing can be vulnerable to progressive or cascading failures where a localised failure can cause the loss of a large section of the roof envelope. The synchrony of loads at neighbouring connections may affect the initiation of such failures. A 1/50 length scale wind tunnel model study was performed on a gable roof house to record spatial and temporal pressure fluctuations on the roof surface and data were studied to determine the flow separation mechanisms causing different loading patterns on batten to rafter connections. The cross correlation between load time histories was used to give a measure of synchrony between loads experienced at neighbouring connections and indicate the direction that fluctuations move across the roof. Orthogonal wind directions result in 2-dimensional flow separation that produce more synchronous loads at batten to rafter connections than cornering wind directions, where conical vortices produce high uplift forces on connections. The patterns of loading and their correlations give a means of identifying which parts of the roof and which approach wind directions may result in the initiation of a progressive failure of batten to rafter connections.