Combining Snow and Earthquake Loads for Limit States Design

Abstract

ASCE Standard 7, “Minimum Design Loads for Buildings and Other Structures,” and the “NEHRP/BSSC Recommended Provisions for Seismic Regulations for Buildings” both contain load requirements for earthquake-resistant structural design. Many of the NEHRP provisions are being implemented in building codes and are the basis for the seismic load provisions in Chapter 9 of ASCE 7. However, the treatment of combinations of earthquake and snow loads differs in the ASCE 7 and NEHRP documents. Concerns regarding these differences were raised during the balloting of both the ASCE 7-93 and ASCE 7-95 provisions. To address these concerns, the load combination requirements involving dead, snow and earthquake load in these two resource documents were examined using modern probabilistic load models and load combination techniques. It is found that approximately 20% of the nominal snow load should be considered in combining snow and earthquake loads.