Windborne debris impacts on metal wall panels and their implications

Windborne missile-impact criteria for glazed systems have been adopted in the USA. Buildings clad with metal panels also have potential for perforation by windborne missiles. Objectives of this study were to determine the threshold perforation velocity of various timber missiles and to measure the change in internal pressure caused by the wall openings. A wall section 4.6 m high by 5.5 m long was constructed to represent a typical Metal Building System. Perforated wall panel sections were installed in a window of the Wind Engineering Field Research Lab building. Wind speed and internal pressure were recorded in fifteen-minute data runs for each missile-produced opening. Internal pressure varied with opening size up to about one percent of the wall area and remained essentially constant for larger opening areas. The change in internal pressure from a missile perforation is negligible.