Buckling analysis of a long-span roof structure collapsed during construction

Numerical simulation of damage and collapse mechanisms suffered by engineering structures can be an effective tool for a quantitative assessment of their causes. Large displacement inelastic analysis may be required in the case of highly flexible structures, such as steel roofs, which frequently experience large failures or even collapse because of buckling. This paper discusses the collapse of a long-span steel roof structure, which fell down suddenly during construction as a result of an out-of-plane buckling phenomenon induced by a gust of wind. Forensic investigations were carried out on behalf of the judicial authority to identify the causes of the accident. Based on detailed information gathered from site surveys and project documents, a three-dimensional numerical model of the as-built structure was created, and buckling analyses were performed to assess the safety level at the moment of the collapse. The as-built structure was braced through some purlins and steel cables fixed at the ground level. Structural stability was also investigated under further modeling assumptions to compare the effectiveness of several bracing systems in preventing the collapse. Analysis results showed that the as-built structure was in an unstable equilibrium condition when the wind breeze occurred. Temporary bracing elements installed on the structure instead of concentric roof braces were not sufficient to ensure the overall stability.