CCEER-13-05: Seismic Modeling and Analysis of Curved Steel Plate Girder Bridges

Abstract

This report presents the analytical investigations into the seismic response of curved steel plate girder bridges. Three levels of modeling techniques – spine beam, grillage (traditional grillage and plate-and-beam), and 3D finite element – of curved steel plate girder bridges were discussed. Guidelines for the development of these models were presented. Spine beam model is where the superstructure is modeled as a 3D singe beam with equivalent section properties. Traditional grillage model is where the superstructure is modeled as a grid of longitudinal and transverse beam in one plane. Plate-and-beam model is where the deck is modeled using shell elements while the girders are modeled as beam elements. 3D finite element is where the deck and girders are modeled using shell elements. Guidelines for modeling the bearings and substructure components were also presented.

The effects of the different modeling techniques on the seismic response were investigated and limitations on their application were identified. The spine beam model was able to capture the global seismic response of the bridge and give reasonable estimates of the column forces. However, this model was unable to capture the response of local components such as bearings and cross-frames. The response of the plate-and-beam model was comparable to the 3D finite element model. This model may be used to design local components such as bearings and cross-frames.

In addition, 3D finite element models of the curved steel plate girder bridge were developed to determine the influence of the stiffness of the cross-frames, girders, shear connectors, and reinforced concrete deck on the distribution of seismic forces between the girders and the cross-frames. It was found that the cross-frames were most effective in transferring the seismic forces to the bearings when the cross-frame-to-girder stiffness ratio was about 3.0. The shear connector stiffness had negligible effect on the framing action between the deck and girders. The number and spacing of shear connectors required for service loads, according to AASHTO Specifications, is sufficient to achieve this framing action.