Collapse of a Steel Space Truss Roof due to Rainwater and Ponding Effects

Inadequate drainage systems and ponding effects pose risks in long-span roof structures. This study investigates the collapse of a double-layer grid system roof of a terminal building after heavy rainfall due to rainwater accumulation and ponding effects. The terminal roof, supported by reinforced concrete columns, had long spans and cantilevered sections. To investigate the cause of the collapse, this paper presents a comprehensive collapse analysis by performing linear and nonlinear finite-element analyses and ponding analyses considering geometric nonlinearity. The recently developed program, TrussImp3D, was enhanced in this study to capture geometric and ponding nonlinearities, has been validated through comparisons with previously published analytical results. These comparisons demonstrate that the analysis model is both efficient and accurate in representing the behavior of roofs under ponding conditions leading to collapse. The results show that the rainwater load accumulated at the cantilever end due to an inadequate drainage system, and the ponding effect played a critical role in the collapse.