The Performance of Low-Rise Open Span Heavy Steel Structures in Extreme Winds.

Abstract

This report is an engineering study of the field performance of open span lowrise steel frame structures that have been subjected to extreme wind events such as hurricanes and tornadoes. The wind velocities in these events either approached or slightly exceeded the normal design values specified in ASCE 7-95. This report focuses specifically on the performance of heavy steel structures and does not include pre-engineered metal buildings. All types of building failures are observed and analyzed in this report, including roofing and secondary cladding component failures as well as main structural failures. In each case study, the probable cause of failure is determined and through an analysis of the different case studies, patterns of failure are identified. Through an analysis of the patterns of failure, recommendations for general design improvements are made and areas requiring further study are identified. The study found that the main structural systems of heavy steel structures performed very well in these extreme winds. Virtually no damage was observed to any of the components of the main structural systems of the buildings, even when the wind velocities exceeded design values by as much as 30 percent. However, the components and cladding did not perform as well. In almost every instance of failure, at least some portion of the roof decking was removed. In most cases the damaged area was restricted to the windward edge of the roof/wall intersection. Another weak component was the overhead doors. In over half of the instances of damage, the overhead door was the first point of failure. The failure of the overhead door(s) then caused the failure of other building components.