Effect of moment gradient and load height with respect to centroid on the reliability of wide flange steel beams subject to elastic lateral torsional buckling

• Published in: Engineering structures Vol. 150; pp. 656 - 664
• Main Authors: Eamon, Christopher D., Lamb, Alexander W., Patki, Kapil
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.11.2017; Elsevier BV
• Subjects: Bending; Buckling; Buildings; Curvature; Dead loads; Differential equations; Load resistance; Random variables; Reliability; Reliability aspects; Stability; Static loads; Steel; Steel beams; Steel structures; Structural steels; Reliability; Steel structures; Stability
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2017.07.087

•The reliability of steel beams subjected to elastic lateral torsional buckling was investigated.•Beams were designed according to AISC Specifications.•The effects of moment gradient and load height were investigated.•Significant discrepancies between code-expected and calculated safety levels were observed.•Greater consistency in reliability can be achieved by adjusting the current design procedure. The reliability of doubly-symmetric wide flange steel beams designed to the AISC Specification for Structural Steel Buildings subjected to elastic lateral torsional buckling was evaluated when considering variation in moment gradient and load height. The analysis considers continuous loads on spans subjected to various end moments with supports that are torsionally fixed and laterally supported, without additional intermediate restraints. Dead load, occupancy live load, and beam resistance random variables were considered. Beam lateral torsional buckling resistance was evaluated from numerical solution of a fundamental differential equation that accounts for the effect of moment gradient and load height. In some cases, it was found that use of the AISC design procedure results in significant inaccuracies for estimation of elastic lateral torsional buckling resistance, where underestimations occur in regions of reverse curvature bending and when loads are placed below the beam shear center, while large overestimations can occur when loads are placed above the beam shear center. These discrepancies result in significant variation in beam reliability. However, the use of accurate equivalent uniform moment factors can restore uniformity in notional reliability level.