Investigation of L'Ambiance Plaza Building Collapse

The writers' firm, Thornton‐Tomasetti Engineers (T‐T), was retained by the city of Bridgeport within hours of the collapse of L'Ambiance Plaza to investigate its cause. As the city's consultant, T‐T had unrestricted access to project documentation, to witness statements, to the collapse site, and to the collapse debris. T‐T personnel were present around the clock at the collapse site during the rescue operation documenting and preserving perishable evidence. This paper is a summary of a detailed report. The paper includes background information, field observations, the results of laboratory tests and computational analyses, and findings concerning the most probable cause of the collapse. Recommendations for reducing the risk of a similar lift‐slab failure in the future are also provided. New physical evidence is presented that may affect the findings of previous investigations. The most probable cause of the collapse was found to be instability of the steel wedges at a particular column. This caused a loss of support to the slabs at that column, which triggered the progressive collapse. This mechanism has not been identified by previously published investigations.