SIMULATION FOR BRIDGES

Starting with a Dassault Systemes’ CATIA® model, one can use physics apps on the 3DEXPERIENCE platform to create simulation models and perform analyses for events such as the movement of trains on bridge decks. One such example is shown below in Figure 1. Two balanced cantilever spans of a representative box-girder bridge are meshed, and finite element analysis is performed. A standard TGV train is considered to pass over the spans, and appropriate axle loads are taken into account at the wheel locations. The wheels are considered to be point masses, and vertical loads are generated at the point mass locations due to the action of gravity. Contact conditions are specified between the point masses and the bridge deck, and the set of point masses is then translated longitudinally over the bridge deck in order to simulate the passing of the train.

Figure 1 shows the contours of the component of tensile stress along the bridge’s longitudinal direction as generated by the train’s live load. One can see high tensile stresses along the deck top surface in the neighborhood of the pier as the train’s weight is borne by the cantilever portion of the bridge deck. Although just elastic properties have been used for the bridge deck in this analysis, other material models appropriate for concrete will need to be used along with reinforcements and pre-stressing cables to get more realistic results. The latter will be essential when responses of the
bridge to scenarios such as seismic and extreme loading need to be predicted.

Figure 1. Bridge showing contours of tensile stress along the axis. The tensile stress gets generated due to live load from the train.

Figure 2 shows a picture of the 8-lane, 1,907 feet long steel truss arch bridge over the Mississippi River on I-35 in Minneapolis, Minnesota USA that collapsed on August 1, 2007. National Transportation Safety Board and other agencies thoroughly investigated this collapse, and detailed finite element analyses were performed.

Figure 2. Picture of the truss-arch bridge over the Mississippi river that collapsed in 2007. Image courtesy: National Transportation Safety Board.

Figure 3 shows a close-up view of a section of the bridge where the collapse initiated. Detailed analysis of the gusset plates and the connections was performed using Abaqus simulation software. The analysis led to the conclusion that the collapse occurred due to the gusset plate having insufficient thickness to bear increased loads. The increased loads were due to modifications to the bridge in combination with enhanced concentrated loads due to
construction activities on the bridge on the day of the collapse. The contours in the picture show Von Mises stress values.

Figure 4. A close-up view of the bridge section where collapse initiated. Contours show Von Mises stress values. Image courtesy: National Transportation Safety Board [Ref. 1].

Tags: BIM, construction, Simulation

Categories: AEC, Dassault Systèmes, Structure Design

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