Fragility analysis of the roof structure of low-rise buildings subjected to tornado vortices

Abstract

The fragility curves of roof failures for wood-frame low-rise building were developed in this study with the focus on the roof sheathing panels and roof-to-wall connections. Two different nail spacings for roof sheathing panels and three types of roof-to-wall connections were considered. This study focused on the first failure of roof sheathing panels without considering the sequential loss of the sheathing panels, and the unit failure of effective wind zones containing different numbers of roof-to-wall connections. The tornado simulator-based dataset was used for determination of the statistics of wind loads, without considering the translational motion effects of tornado vortices. The results show that the failure probability of roof is dependent on the proximity of a tornado to a building and the opening azimuth on walls. Additionally, the combined effects of pressure drop and aerodynamic interactions dominate the failure modes of roof system. The obtained fragility curves in this study can be used to estimate the maximum tangential wind speed of the tornado vortices and the local oncoming tangential wind speed at roof height. The estimation of tornado intensity using the present results is likely to approach the lower-bound of wind speed estimation in WSEC (2006) report.