MONITORING STEEL GIRDER STABILITY GOR SAFER BRIDGE ERECTION

[mowafi3m]

MONITORING STEEL GIRDER STABILITY GOR SAFER BRIDGE ERECTION

SUMMARY
The stability of steel plate girders during erection should be given special attention because the lateral support on the compression flange might temporarily not be present. Rules of thumb have been adopted by contractors to check the stability of cantilever or simply supported girders under erection using the maximum L (unbraced length) over b (compression flange width) ratio, beyond which lateral torsional buckling failure would occur under the girder’s self-weight. In order to check the rules of thumb, closed-form equations for the maximum L/b ratios of cantilevers and simply supported girders were developed following the current AASHTO LRFD code, and parametric studies were conducted for various girder sections. Finite element analyses (FEA) were conducted on a girder section for both the cantilever and the simply supported case to further understand the lateral-torsional buckling behavior of the girder under self-weight and identify the maximum L/b ratio through a trail-and-error approach, as well as verify that bracing the top tension flange at the cantilever free end would be more effective to prevent lateral torsional buckling than bracing the bottom compression flange.

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