Comparisons among Earthquake Codes

This review paper compares ANSI, NEHRP, SEAOC, and UBC. A few essential differences among these documents are as follows: (a) The NEHRP document gives force levels corresponding to a strength‐based or limit states design, while the other three documents give force levels that correspond to working or service stress design; (b) the importance factor is used as a multiplier of base shear level in all documents except NEHRP, which treats building importance by a seismic hazard exposure group; (c) NEHRP and UBC‐1988 contain detailing requirements for all common construction materials and all seismic zones, while UBC‐1985 contains detailing requirements for zones of high seismicity but only limited requirements for zones of moderate seismicity; (d) P‐delta analysis is specified by NEHRP for all buildings that must be analyzed, by SEAOC for buildings that exceed drift limits, by UBC‐1988 for all buildings except those in Zones 3 and 4 meeting drift limits, and is not specified by ANSI.