Calculation of wind borne debris impact in tornado event

Abstract

In strong wind events like tornado and hurricane, significant destruction is caused to buildings due to wind-borne debris, which are usually damaged structural members and components with insufficient attachment. This debris, also referred to as missiles, can penetrate building walls and roofs and jeopardize human life. Because of this, there are standard impact criteria provided by Federal Emergency Management Agency (FEMA-P-320, 2014; FEMA-P-361, 2015) and International Code Council (ICC-500, 2014) that need to be met when designing safe rooms or storm shelters. The national wind institute at Texas Tech University has done extensive impact testing on different types of structural and non-structural components, which are the basis for current design guidelines. This thesis focuses on investigating previously developed methods for evaluating the perforation of concrete and steel targets and selecting the most relevant formulas that can be applied for the design of tornado safe rooms. For cast-in-place(CIP) concrete, precast concrete and concrete masonry units (CMU), the best method to estimate perforation limit is the Central Research Institute of the Electric Power Industry (CRIEPI) Formula. For Steel target, both the Ballistic Research Laboratory (BRL) Formula and the Stanford Research Institute (SRI) give useful estimate for perforation limit. These selected concrete and steel target perforation limit formulas can be used for preliminary design of buildings, to withstand the required impact criteria, giving engineers the flexibility to design structures without depending only on using structural components that have been tested to meet the FEMA criteria.