Wind-Borne Debris Resistance of Façades: Identification of Alternative Impact Test Requirements
Doctor of Philosophy
Civil and Environmental Engineering
Kopp, Gregory A.
Iuav University of Venice, Italy
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.
Summary for Lay Audience
The effects of climate change are causing an increase of windstorms worldwide that are reported on at least a weekly basis by major news organizations. The extreme winds are known as tornadoes, hurricanes, tropical cyclones, typhoons, depending both on the wind characteristics and on the location of the disaster event in the Globe. During these events, one of the major risks is related to wind-borne debris that could lift from its position and subsequently fly, impacting building envelopes and urban objects such as cars, houses, and anything in its path. Wind-borne debris impact could, therefore, cause window and façade breakage and, consequently, damage the entire building structure, all the mechanical and electrical systems, and its contents. For essential facilities such as hospitals, if these problems occur, it means that primary services cannot be guaranteed in emergency circumstances such as the immediate aftermath of an event. To mitigate the negative consequences of wind on the building envelopes, and to avoid breakage of windows, doors, and façade solutions in general, there are testing procedures to verify if these building components can withstand wind-borne debris impacts. These procedures have been developed in the last fifty years through damage observation, without considering the aerodynamic behavior of free-to-fly objects in specific urban environments. This thesis proposes an alternative design framework for window and façade design, to make these building envelope technologies resistant to the impacts of local debris that is seen in specific contexts. The results are especially addressed to essential facilities, to avoid in the future dramatic outcomes such as the May 22nd, 2011, Joplin tornado that killed 161 people, of which 14 were receiving treatments at the St. John’s Regional Medical Center. The hospital’s structure was not affected by any damage, but almost all the windows were broken by wind-borne debris. When the windows were not protecting the interior of the building anymore, the patients turned to be victims, and the facility did not help the Joplin population to recover from the event.
Mejorin, Angela, "Wind-Borne Debris Resistance of Façades: Identification of Alternative Impact Test Requirements" (2022). Electronic Thesis and Dissertation Repository. 9037.