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

Abstract

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. This study examines the structural behavior of long-span steel roofs under ponding effects caused by inadequate drainage systems. Using the TrussImp3D program, the research simulates rainwater accumulation and its impact on roof stability, providing a practical tool for analyzing structural failures due to ponding loads. Under ponding conditions, insufficient stiffness or inadequate strength in the roof system can result in instability and eventual collapse. This highlights the importance of designing structures that can withstand such effects and implementing adequate drainage systems to manage water accumulation effectively. The findings are relevant for engineers, architects, and facility managers designing and maintaining large-span structures. Incorporating secondary drainage systems and accounting for ponding effects in designs can significantly reduce the risk of failure during heavy rainfall. This study’s practical implications extend to updating design standards and codes and encouraging professionals to adopt better practices for evaluating water loads on roofs.