Nemetschek Engineering User Contest 2009 • Category 3: CAE Civil Works 147 3 Road bridge over the Váh river, Trenčín (SK) • The temporary supports will be removed after the hardening and activation of the concrete and the subsequent construction works will be executed on the cable stayed structure of the final static scheme. Firstly, several plane member models in Scia Engineer were analysed for the preliminary design. For instance, the following models were created: a model of the steel structure during the casting and hardening of the concrete, a model of the final cable-stayed structural system, a model where cables were substituted by dummy supports… During the analyses of those plane models, data were designed and optimised using Scia Engineer modules and custom-made programmes: e.g. the depth of the deck, the thickness of the steel plates for steel cross sections, parameters of the reinforced concrete slab, height, shape and inclination of the pylon, cross sections of the pylon, cable-type and number of strands in cables, initial prestressing, etc. Optimised geometry, stiffness redistribution, cable prestressing, load cases and critical cross-sections were implemented into the three dimensional model and checked. For the final FEM analysis, the spatial model combining both plane and beam finite elements was also created in Scia Engineer. The main attention was paid to accurate geometry modelling and approximation of stiffness redistribution of structural members. Programme modules for atypical cross-sections, variance of plate elements thickness and for member haunches were used as well. Nonlinear behaviour of prestressed cables was simulated by the module for rope members including the influence of self weight on the strain in the rope. Interaction of bridge supports with the ground was finally not implemented into the model, because the described nonlinear analysis including this effect was time consuming. However, quasi-constrained behaviour of the pylon was verified using the Soilin module in software NEXIS 3.60.17. Consequently, values of settlement were considered in relevant combinations of load cases in a 3D model. More than a thousand linear combinations of load cases and almost two hundred nonlinear ones had to be considered. Initial prestressing, nonlinear behaviour of cables and second order effects were taken into account during the nonlinear analyses. Because of the block slab casting, the rheology effects of concrete could be solved using a simplified methodology in which the distributed relative deformations are approximated by the imposed loads in two time phases during the lifetime of the bridge. Finally, the dynamic calculation was done. Only natural frequencies and modes of vibration were determined at this stage of the project.
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