| The problem related to lateral flange bending of steel plate skewed girders during the non composite phase of construction can be simply stated as a consequence of the significant support skew, typical staggered crossframes along the span in between adjacent girders, differential deflections commonly present on skewed bridges, out of plumb condition associated with girder camber and imperfections, and the force transfer mechanism due to the overhang falsework.;Two different simple span steel I-girder skewed bridges were monitored during the non composite phase of the construction process in order to study the effect of Lateral Flange Bending (LFB) on both displacements and stresses. Using ANSYS V 11.0 as the Finite Element software, numerical models of the bridges were developed in an effort to identify the key components that allow characterization of torsional rotation displacements and the lateral displacements as well as the LFB stress profile. A parametric analysis was performed to single out the most sensitive parameters and to establish a possible mitigation strategy for both the stresses and displacements. The study identified that increasing the polar moment of inertia of the girders by slightly increasing the thickness of either the flanges or the web produces more beneficial effects than the traditional idea of increasing the number of crossframes or diaphragms along the span. The crossframe layout was also found to be crucial on the rotational response of the bridge and the X-type crossframes proved to be more efficient in controlling transverse rotations. On the other hand, it was determined that the worst case scenario produced a maximum LFB locked-in stress of 18% of the yield stress. |
