Comparison of the Directional and Envelope Wind Load Provisions of ASCE 7

ASCE 7-10 allows design of the Main Wind Force Resisting System (MWFRS) of buildings with a mean roof height of less than 60 ft using either the Directional Procedure of Chapter 27 or the Envelope Procedure of Chapter 28 (sometimes referred to as the all-heights and low-rise procedures, respectively). These two procedures were developed based on research that used very different methodologies to develop “enveloped” wind loads. As a result, the two methods may predict very different wind loads and subsequent structural behavior. This paper presents motivation for the research, a comparison of the structural demands calculated using the two procedures, identifies some situations for which the low-rise procedures may give unconservative MWFRS member loads, proposes changes to the provisions, and identifies avenues for future research.

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