Defining Structural Collapse

Evaluating whether a structural system has collapsed may not be as obvious as it sounds. Most people consider collapse to be a condition where the structure or a portion thereof has fallen down. However, in the context of insurance coverage, evaluating whether “collapse” has occurred may be far more nuanced—especially when collapse is not explicitly defined in the policy. State courts have generally adopted one or more of three interpretations for the term collapse, broadly described as: (1) actual collapse, (2) imminent collapse, or (3) substantial impairment of structural integrity (SISI). Even with these interpretations, there are widely varying opinions regarding the level of structural impairment that qualifies as collapse. This is especially true for SISI. Although some state courts have attempted to define collapse using commonly understood terms, there are no industry standards that define these conditions in customary engineering terms (demand, capacity, factor of safety, etc.). This ambiguity leaves individual engineers to form their own opinions, which predictably, vary widely between engineers. This paper draws from available literature and prior legal findings to propose a rational method for engineering professionals to evaluate collapse based on design loads, strength of materials, and system effects, with a particular focus on SISI.