Verification of Texas superheavy load criteria for bridges.

This report evaluates Texas Department of Transportation (TxDOT) criteria for the superheavy loads that trigger bridge analyses to determine whether the criteria adequately protects Texas bridges. Researchers used solid modeling calibrated with a bridge test of a 3-span continuous steel girder unit of SH 159. The bridge testing measured girder end rotations with tilt loggers and load position using a sub-foot accuracy Global Positioning System (GPS). Solid modeling was done with ANSYS 12. The calibrated model was used to conduct a parametric study. Axle distribution factors of 0.28 and 0.45 were experimentally determined for interior and exterior girders respectively. Results of the parametric study showed that the Texas superheavy load criteria are valid for this bridge type. A study of service life extension showed that operational stress level loads applied as little as 5 percent of time to a particular structure will have a significant effect on the lifetime of the structure, and that the number of fatigue load-cycles per truck cannot be assumed to be one. A graphical version of the bridge review trigger (load-length curve with existing allowances and restrictions) might serve TxDOT and heavy-haul carriers better than does the gross vehicle weight triggers. Data collected long term of load frequency and load level from a relevant bridge would help TxDOT determine what effects stress level variations have on the life of Texas bridges.