Lateral-Torsional Buckling Research Needs and Validation of an Experimental Setup in the Elastic Range

The AISC Specification Chapter F I-section member flexural resistance equations are a central part of structural steel design in the United States. The provisions of Sections F4 and F5 address general singly and doubly symmetric I-section members. Analytical studies and experimental tests subsequent to the implementation of these provisions within the 2005 AISC Specification suggest that the corresponding inelastic lateral-torsional buckling (LTB) and tension flange yielding (TFY) resistance equations can be improved, resulting in significantly larger predicted strengths in certain cases and somewhat smaller predicted strengths in other cases. Additional large-scale experimental tests, specifically pushing into the inelastic LTB range, need to be conducted to further investigate these predictions. The broad objective of the additional tests is to achieve a target reliability index of b = 2.6 for building design at a live-to-dead load ratio of 3.0 throughout the design space involving all types of statically determinate I-section flexural members. This paper discusses the need for these tests, specifically focusing on the details of how the test fixtures and bracing systems were configured to minimize incidental restraint, which is a critical consideration when conducting flexural experimental testing. The paper discusses the validation of the testing system by comparison of elastic buckling experimental results to analytical and numerical solutions.