The Partihall Link
TDV was approached by Consulting Engineers Johs. Holt A.S.to assist in this project.
The project Partihall link in Gothenburg, Sweden, had already been calculated using a BEAM model in RM2006. The client asked TDV to model and calculate part of the bridge using Finite Element Method (FEM) representing the structure by shell elements. RMV8i version of the software was used. The rest of the model was left unchanged, so the final model is a hybrid between FEM and BEAM. The purpose of this work was to compare FEM against BEAM analysis and to provide lateral integration of results for the reinforcement design.
Figure 1: Structure overview
TDV was part of the Consultant team and was responsible for the construction stage analysis, the full FEM modelling, the structural analysis as well as the member design of this structure with complicated layout.
The bridge concept of the Partihall link consists of post-tensioned concrete and span by span erection method. The 11 spans of the main girder have lengths ranging from 42 m to 50 m adding up to a total of 503 m. There are in addition two ramps, one with one span of 31 m and another with three spans ranging from 33 m to 49.5 m adding up to a total of 120.5 m. The typical cross-section has 14 m width and 2.4 m height.
The main difficulty was the transition between a double cell box cross-section in one part of the bridge and a two separate box cross-section in the other part of the bridge.
Figure 2: Cross-section transition
The bridge is divided in two parts, with a 0.6 m gap between them. The FEM analysis was carried out in one part, while the other part was subjected to beam analysis. The bridge deck on the FEM side comprises two, curved shaped, concrete edge beams on either sides. These edge beams were modelled using beam elements.
RM Bridge V8i software allows the modelling of the structure using beam elements and/or shell and volume finite elements. The solution called “hybrid FEM model” allows modelling of the bridge by shell and volume elements but extracting the integral results in a similar way to beam elements.
In the more detailed FEM analysis the assumptions of the beam theory are no longer valid, namely the assumption that the cross-sections remain plane and non-deformed. The hybrid FEM model combines the advantage of a classical beam analysis (well defined final integral results) with better accuracy of more detailed FEM analyses using shell and volume elements.
The results of FEM analysis were then integrated both longitudinally and laterally. The lateral integration was made along cuts in the cross-section defined by the client.