Reliability of Timber Beams Subjected to Ponding

Abstract

A common cause of structural failure in flat roof systems is attributable to rainwater accumulating on the roofs as a result of the ponding phenomenon. This study investigates the structural reliability of timber roof beams that are subjected to ponding loads. An approximate ponding amplification factor is derived, and a simple design equation is proposed in the context of reliabilitybased design, which is suitable for implementation in a limit‐states design code. The reliability assessment of the bending strength limit state of sawn lumber and glued‐laminated roof beams is carred out using standard first‐order reliability methods. By adjusting the performance factor, which modifies the characteristic modulus of elasticity, the proposed design equation is calibrated for both types of timber beams. The objective of the calibration procedure is to ensure that a prescribed level of reliability is achieved with the proposed design equation.