Wind-Borne Debris Resistance of Façades: Identification of Alternative Impact Test Requirements

Climate change effects are causing a steady increase of previous records both in terms of monetary losses and in fatality occurrence due to severe storms. The frequency and intensity of disaster events are increasing worldwide and areas that were excluded from these extreme weather scenarios in the past, are now looking for solutions to increase the urban resilience. Among others, extreme winds are endangering the built environment, often leading to the breakage of the primary barrier to protect people and property: the building envelope. On May 22nd, 2011, the Joplin tornado killed 161 people, and 14 of those were receiving treatments at the St. John’s Regional Medical Center. At the hospital, most of the windows were broken by the impact of wind-borne debris. The structure of the hospital has remained intact and only one section of the building was not affected by façade breakage: the Behavioral Health Unit, a result that was ensured by breakage-resistant windows. To avoid façade breakage, in areas hit almost every year by tropical cyclones and hurricanes, code and standard requirements have been developed in the last five decades, to provide wind-borne debris impact resistance to the building envelope. This thesis develops a performance-based design framework to identify alternative impact test criteria, to verify the resilience of façades to wind-borne debris, in specific contexts. The design framework is, therefore, set for case-specific wind-borne debris types, to explore the design possibility given by the code and standard best practices. The analysis considers building aerodynamics, and the trajectory and velocity of specific debris elements to implement performance-based façade technologies. The reference target buildings of the thesis are essential facilities, to avoid disruption of essential services, especially in the post-event scenario. If new buildings and façade retrofit projects can improve their resilience to wind-borne debris impacts, there can be a notable mitigation of the overall consequences of extreme wind events. The current widely adopted testing equipment to conduct wind-borne debris impact testing is presented in its implementation to work out alternative impact tests. Adopting performance-based design impact tests, building envelope solutions can sustainably address local needs to improve urban resilience.