Unified Flexural Resistance Equations for Stability Design of Steel I-Section Members: Moment Gradient Tests

摘要

The 2004 AASHTO and 2005 AISC provisions for flexural design of steel I-section members have been revised in their entirety relative to previous specifications to simplify their logic, organization, and application, simultaneously improving their accuracy and generality. This paper evaluates the lateral-torsional and flange local buckling (LTB and FLB) resistance predictions from these specifications versus the results from moment gradient experimental tests. Two types of moment gradient tests are considered: (1) "end-loaded" tests in which the moment varies linearly within the critical unbraced length and (2) "internally loaded" tests in which the member is subjected to concentrated transverse load, resulting in a multilinear moment diagram within the critical unbraced length. A total of 27 welded and 10 rolled I-section end-loaded FLB tests, 73 rolled and 93 welded end-loaded LTB tests, and 129 rolled and 111 welded internally loaded LTB tests are considered. Reliability indices are estimated for load and resistance factor design of buildings based on the statistics from these tests combined with established statistics for material and fabrication bias factors and the ASCE 7 load model.