Experimental Validation of Bracing Recommendations for Long-Span Concrete Girders.

摘要

During bridge construction, flexible support conditions provided by steel-reinforced neoprene bearing pads supporting precast, prestressed concrete girders may allow the girders to become unstable, rolling about an axis parallel to the span of the girders. Additionally, skew and/or slope angles significantly reduce bearing pads roll stiffness, which reduces girder buckling capacity under gravity and wind loading conditions. In this project, roll stiffnesses for bearing pads under skewed and sloped conditions were determined from experimental data gathered using a test device designed to measure such values. The test device reproduced the forces and deformations that act on a bearing pad in the field while simultaneously permitting axial load, skew angle, and slope angle to be controlled independently, so that the effect of each on bearing pad roll stiffness could be quantified. In total, 108 bearing pad tests were performed on three different standard types of bearing pad, with varying severities of imposed skew and slope angle. Full-scale girder buckling tests, designed and conducted to experimentally quantify the influence of bearing pad roll stiffness on girder buckling capacity, were also included in the project. The pad used to support each end of the test girder during the buckling tests were the same pads previously tested to determine roll stiffness. In total, nine girder buckling tests were conducted, with various skew and slope conditions imposed on the bearing pads. Following completion of the experimental tests, analytical (finite element) models of the experimental test conditions were developed and validated by comparing buckling capacities quantified from analytical simulations to experimental test results. Analytical buckling capacities were found to differ from experimental test results by no more than 15% over a range of ideal, skewed, and sloped bearing pad support conditions. Based on this favorable level of agreement, the analytical modeling and analysis techniques employed in this study were deemed suitable for use in developing bracing recommendations for long-span concrete girders supported on reinforced elastomeric bearing pads.