Probabilistic Analysis of Tornado Wind Risks

Abstract

A methodology for the prediction of tornado wind probabilities has been developed for site- and structure-specific wind loading risk assessments. The inputs to the model include local tornado occurrence data and the structure plan, orientation, height, and design life. The wind-risk calculations are based on a Monte Carlo procedure that uses a stochastic model of tornado occurrence, a probabilistic tornado windfield model, and distributions of tornado parameters developed from an analysis of 19,085 storms. Example calculations for different building sizes and lifeline geometries are given for four broad regions in the United States. One of the findings of the study is that tornado wind risk dominates the combined wind loading function for lifelines with lengths greater than about 10 miles (16 km). The estimated uncertainty intervals in the risk predictions range from a factor of 10 for 75 mph (36 mps) winds to several orders of magnitude for 200 mph (89 mps) winds.