Moving Load Lanes

Question:

Hello

Please see the attached model.

When selecting moving load tracer function and then selecting element 182 for "My" load effects and then selecting "MVmax: MVL_1" loadcase. 

This show the moving load arrangement to obtain My effects on the element 182. The model has three moving load lanes. 

However, to produce the max My load effect on the element 182, one would expect to load the lane directly on top of the element 182 with max load which is 300kN axle weight as defined in Eurocode 1991-2 Table 4.2.

But the load arrangement produced by moving load tracer function suggest that the lane farthest away from the element 182 has been loaded with max axle weight and the lane above the member 182 has lowest axle weight.

Could you please explain this and let me know the correct way such that max My effect is obtained on member 182. 

Thanks

Answer:

Hello ,

The reason for this is the lane definition, and more specifically the Vehicular Load Distribution, which is not appropriate for the type of modelling you are using - grillage model. You need to use the Cross Beam distribution and assign all the crossbeams to a structural group which you specify in the lane definition. This will allow the load to be applied to the deck appropriately and you will obtain the results as expected:

The difference between the two types of Load Distribution is that:
 - Lane Element - the lane load is applied to the reference elements as a vertical load and torsion due to the lane eccentricity. This is used for large long-span bridges like pre-stressed box girder bridges, where we model the entire deck of the bridge as a single beam elements.
 - Cross Beam - the lane load is applied to the cross beams in the cross beam group specified in the lane definition, by detecting the points at which the lane crosses over the cross beams. The cross beams then distribute the load into the system. This is appropriate for grillage type models.

You can find more information on this in the Online Manual:

Kind regards,
Technical Support Team
MIDAS UK

Creation date: 12/1/2018 10:45 AM (MIDAS_UK_IM)      Updated: 12/1/2018 9:16 PM (MIDAS_UK_IM)
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CBW_CAT2_Stg03.mcb
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