Almost all types of dynamic analysis can be carried out, including calculation of frequencies and modes, transient analysis (implicit and explicit), and analysis using mode superposition or modal participation factors. Harmonic and random loads can be applied, and seismic analysis with a response spectrum or prescribed ground motions can also be carried out. A few typical examples of dynamic analyses are shown below.

Natural Frequency/Mode Shape Analysis of Cable Stayed

Bridge

This model is a natural frequency analysis of a medium span cable stayed bridge. Estimated sizes and thicknesses are used for the steel box girders, concrete slab and towers. The first/second bending modes, and first torsion mode are shown below and in this animation.

Analysis of High Speed Moving Load on Truss Bridge

The above model is of a truss bridge with a high speed moving load, as might typically be found in a railway bridge. This animation shows a continuous display of displacements and accelerations. The ability to continuously plot variables together with the moving load appears to give a useful insight into structural behaviour.

Analysis of Harmonic Moving load on Arch Footbridge

The following model for a preliminary design of a “Calatrava” type pedestrian footbridge was initially used to carry out a nonlinear analysis, to check on buckling and displacements. It was then modified to carry out a dynamic analysis using the moving harmonic (sinusoidal) load from BD37/01.  An animation of the dynamic behaviour is available here. Other types of harmonic or random loading could readily be applied. Because of the ability to change section sizes/thicknesses and rerun the preliminary model in a few minutes, initial dimensions and sizes were obtained using the FE model. This enabled a rapid assessment of the torsion member size to be obtained. Please contact us with any comments or queries. Based in the UK with convenient access to Avon, Bath, Birmingham, Bristol, Cardiff, Gloucester, Gwent, London, Newport, Oxford, Reading, South Wales, Swansea, Swindon.
Chris Booth Associates
Copyright © Chris Booth Associates Ltd  2014
FEA - Dynamic
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