Lidar-Based Methodology to Evaluate Fragility Models for Tornado-Induced Roof Damage

Structural fragility models have been developed to provide probabilistic estimates of building component damage states caused by exposure to differing wind speeds. Limitations in taking accurate measurements and gathering quantitative loss information in the aftermath of tornadoes has not allowed for comparing fragility-based information with actual building-loss data. This paper presents a methodology for extracting damaged building geometry and roof sheathing loss information from three-dimensional (3D) point cloud data collected with laser scanning technology. The observed building component damage states are then compared to fragility model predictions to validate the models. The methodology was tested on 3D data collected after the 2013 Moore, Oklahoma tornado. From this initial study, which was performed on 5 houses having 27 damaged roof surfaces, it was shown that fragility models underestimated the loss in the center of roof planes (Zone 1) and overestimated the loss in the corners of roof planes (Zone 3). The differences between the predicted and observed roof sheathing loss are attributed to the simplifying assumptions used in current fragility models. Implementing the proposed methodology with a larger number of damaged buildings will provide more insight into the reliability of the fragility models.