Are the Codes Safe for Wind Pressures?

Recent failures suggest a reexamination should be made of the codes for wind loading on buildings. The 1972 Building Code requirements for minimum design loads in buildings and other structures as published by the American National Standards Institute (ANSI) prescribe an average external pressure coefficient of 0.8 on windward walls, –0.6 on leeward walls, and –0.7 on side walls. Recent experimental work suggests that the average and local pressure coefficients prescribed by the code may be inadequate if the wind is turbulent and approaches the building at a small angle of attack. A series of pressure distribution measurements on rectangular rods in a cross flow was taken with the rods oriented at small angles with respect to the wind direction. The results reveal that the most critical pressures on the side walls occur with angles of attack between 6 and 10°. Furthermore, these measurements yield values of external pressure coefficients that are much more severe than indicated by the building code. These results suggest a weakness of the ANSI Building Code.