CONTRACTOR SKANSKA'S Swedish sister company, Skanska Teknik, is using Lusas Civil & Structural to analyse and design a complex 128m long section of the Gota Tunnel, under construction in Gothenburg.
The twin reinforced concrete box tunnel - complete with integral access ramp structure, ventilation shaft and 30m high chimney - will carry two lanes of traffic in each direction and is also subject to vehicle loading from above.
Almost 22,000 elements were used to model the tunnel structure to the required level of detail. Thick shell elements modelled the concrete so that out-of-plane shears could be identified with joint elements models for the end bearing and frictional piled supports.
The software enabled engineers to calculate maximum and minimum load combinations for any selected design code, and customised scripts were developed to automate results processing. Skanska Teknik's own in-house software was then used to transform data into graphs, screen plots and spreadsheets.
Sections could also be taken between selected points on the model for further analysis.
'Since the geometry was so complicated it would have been difficult to model the tunnel in 2D and a far more conservative approach would have had to be taken, ' says Skanska Teknik structural engineer Mathias Uhlßn. 'Using a 3D Lusas model we could slice sections through and easily plot the results at chosen locations. The main benefit was being able to get all of the results from the one model.'
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