topic Re: LM2 Wheel Axle Load model error? in Structural Bridge Design Forum

LM2 Wheel Axle Load model error?

andrus.kolossov — Wed, 16 Jun 2021 09:57:38 GMT

Hi,

When applying vehicle loads (Eurocode & UK Annexes) to my bridge model one of the structure loads (LM2 Axle Load) comprises a double wheel axle load of 400kN and when selecting from the Type drop down to "wheel" the charact. axle load is still 400kN. See below. I have never seen this axle load type applied before, is this correct?

Thanks

Re: LM2 Wheel Axle Load model error?

dave_geeves — Wed, 16 Jun 2021 11:37:18 GMT

Hi,

The characteristic value of 400kN is just the default value for the LM2 axle load, which relates to the full axle load but can be changed if required. EN1991-2 4.3.3(1) also specifies that "when relevant, only one wheel of 200bQ(kN) may be taken into account." In this case, the value of 400 will need to be changed manually to 200 for it to be applied correctly, when manually applying the loads. The vehicle load optimisation feature should do this automatically when optimising for load model 2, if there is a case that the single wheel load will give a more onerous effect than the full axle load.

I hope this helps and if this has answered your query then please mark my reply as a solution so that others may benefit. Thanks

Kind regards

Dave Geeves

Re: LM2 Wheel Axle Load model error?

andrus.kolossov — Mon, 21 Jun 2021 08:59:31 GMT

Hi Dave,

Thanks for the explanation. Could you further explain why the analysis chooses 2No. 200kN wheel loads and not a single 400kN load. Is this an error?

Re: LM2 Wheel Axle Load model error?

dave_geeves — Wed, 23 Jun 2021 15:18:46 GMT

Hi,

I assume that when you say "The program chooses....." you are referring to the load optimisation, as if you are doing this manually then it is you, the engineer, that is choosing whether to define a 400kN axle load or a 200kN wheel load to define the worst case scenario (the latter would only be the worst case if one wheel was adverse and the the other relieving). I don't believe there is a requirement to have a single 400kN wheel load as you have suggested, but if I'm wrong then please tell me which clauses you are referring to.

The load optimisation will check both the 400kN axle load(2 x 200kN wheels) and the single 200kN wheel load and decide on which provides the worst case before creating the live load compilation.

I hope this helps.

Kind regards

Dave Geeves