Transitioning from FEMA 350 to the ANSI/AISC 341-05 and 358-05 Standards

摘要

Until recently, steel special moment resisting frame (SMRF) design standards were based on AISC Seismic Provisions (ANSI/AISC 341) and FEMA 350 - Recommended Seismic-Design Criteria for New Steel Moment-Frame Buildings. The FEMA document describes prequalified connections that were based on tests of these connections. FEMA 350 was intended to be an interim document in response to the 1994 Northridge earthquake, and over the years the AISC Seismic Provisions adopted many of the FEMA 350 design recommendations. FEMA 350 continued to fill a need, however, because it was the most commonly used design document that described specific details and design procedures that could be used for moment frame connection design. AISC recently published a document ANSI/AISC 358-05, Prequalified Connections for Special and Intermediate Steel Moment Frames for Seismic Applications. This document is closely integrated with the 2005 AISC Seismic Provisions and lists the criteria for design of special moment resisting frame connections. The 2007 California Building Code, which is based on the 2006 International Building Code, will reference both AISC 341 and AISC 358. The Connection Prequalification Standard (ANSI 358) contains design requirements and design provisions for two prequalified connection types. In addition, there are provisions that describe built-up sections that can be used as beams or columns and also contain simplified quality control and quality assurance requirements. This paper will compare and contrast FEMA 350 and the new Seismic Provisions and Connection Prequalification Standard, specifically as it relates to the reduced beam section (RBS) type connection. A case study to illustrate application of the new AISC standards will be presented using built-up rectangular and I-shaped sections as columns and shallow wide flange sections as beams to achieve the desired architectural design intent.