Fire-induced response-based collapse monitoring of burning buildings

Fire induces low-level, measurable, structural vibrations in burning buildings. These vibrations can be detected with sensitive accelerometers, and monitored to track changing structural conditions and possibly collapse mechanisms. Full-scale field tests have been performed on wood frame and steel frame structures. Based on response magnitude, response statistics, and system identification, three types of "collapse indices" have been developed, which show discernable trends leading to structural collapse. The first two collapse indices quantify the visual character of the building response. The system identification approach extracts the product of natural frequency and damping. These indices are being developed to provide firefighters with information about the changing structural integrity of a burning building.