ABSTRACT
This paper focuses on the response of horizontally curved steel I-girder bridges to changing thermal conditions. Bridge curvature complicates the structure’s response to thermal loading as the bearing configuration must be able to handle expansion and contraction in the transverse, or radial, direction. Failure to properly design bridge bearings to accommodate thermal loads will lead to unaccounted for deformations and stresses in the superstructure. This paper presents a case study of the Buffalo Creek bridge structure subjected to changing thermal conditions prior to any in-service loading. Two detailed 3D finite element models of the bridge were created, one modeling the piers as rigid members and one modeling the piers as flexible members, and both were subjected to uniform temperature increase and decrease. Results indicate that uniform thermal loading leads to lateral displacement along the I-girder web centerlines, lateral distortional buckling in the web cross section, and thermal stresses in the I-girder webs. Although pier flexibility is shown to reduce the magnitude of thermally induced local and lateral distortional buckling and thermal stresses, I-girders experience larger lateral displacements when the piers are flexible. Additionally, even the introduction of pier flexibility does not relieve all thermal stresses in the I-girder webs. At some locations, when the piers are rigid, the I-girder stresses exceed the AASHTO web bendbuckling capacity as well as the overall stress capacity of the section. In both the cases of flexible or rigid piers, this study shows that uniform thermal loading will lead to increase out-of-plane web deformations and increased web stress levels, which will both combine to decrease the load carrying capacity of the bridge when subject to subsequent live-loading conditions.
