Technical University of Denmark ♦ DTU Ballerup Campus Exam project 2015/2016 ♦ Answer Book & Case Study Motorway Bridge over Savstrup Stream in Jutland Denmark Terrain - Geometry - Analysis 1 , 2 , 3
Analysis model (2 of 3)
Deformations & natural mode shapes
First at all in a FEM analysis is to check deformation figure of the bridge at deadload. Then animation of natural mode shapes for the first 7 modes (and more if needed). Deformation figure and the natural mode shapes will confirm the correctness of the static system. Especially animation of the natural mode shapes will reveal often the forgot lateral fixation of the bridge deck through bearings. Deformations and the natural mode shapes performed in LUSAS Analysis 1 have
only deadload and prestressing. I.e. you will get the results within a few seconds for a normal PC/Laptop.
Once the deformation and vibrations are as expecting, you can continue to run Analysis
2 with thousands of variable load cases and load combinations for further verifications. In this context, LUSAS allow you to run a selected particular load case(s) at any Analysis when you want to check the results for that case(s) only. Note that in railway bridge the natural frequencies can lead to the need of changes in dimensions and thicknesses of the deck. Thus, do not start the Analysis 2 to save the time, if you later found out the changes already needed at Analysis 1.
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