Collapse fragility assessment of steel roof framings with force limiting devices under transient wind loading

Steel structural frame is a popular structural form to cover large-span roof space and under high winds.Either part of the roof enclosure or the entire roof structure can be lifted off a building,particularly for low sloped roofs subject to wind-induced suction force.Collapse of roof could cause severe economic loss and poses safety risk to residents in the building.The buckling of members in a steel roof frame structure,which may lead to progressive collapse,may be dynamic in nature.This paper presents a fragility analysis of the collapse of steel roof frame structures under combined static and transient wind loading.Uncertainties associated with wind load change rate and member imperfections are taken into account in this study.A numerical example based on a Steel Joist Institute(SJI)K series joist was used to demonstrate the use of force limiting devices for collapse risk mitigation.For the presented fragility assessment of steel roof collapse,a Monte Carlo method combined with response surface approach was adopted,which greatly reduces the computation time and makes the Monte Carlo simulation feasible for probabilistic collapse analysis of steel roof frame structures.