Wind load statistics for probability-based structural design

ASCE Standard 7, "Minimum Design Loads for Buildings and Other Structures," has contained provisions for load combinations and load factors suitable f or load and resistance factor design since its 1982 edition. Research in wi nd engineering in the intervening years has raised questions regarding the wind load factor 1.3 and load combinations in which the wind load appears i n ASCE 7-95. This paper presents revised statistical models of wind load pa rameters based on more recent research and a Delphi, and reassesses the win d load combinations in ASCE Standard 7 probabilistically. The current appro ach to specifying wind loads in ASCE 7 does not lead to uniform reliability in inland and hurricane-prone regions of the country. It is recommended th at the factor accounting for wind directionality effects should be separate d from the load factor and presented in a separate table in the wind load s ection, that the wind load factor should be increased from 1.3 to approxima tely 1.5 or 1.6 to achieve reliability consistent with designs governed by gravity load combinations, and that the exposure classification procedure i n ASCE Standard 7 should be revised to reduce the current high error rate i n assigning exposures.