Questions on load transfer for one way slab

[Anonymous]

Hello,

I would like to know how exactly analytical load transfer differs from one way load transfer in robot when it goes to the case of calculating one way slab. 

I have rather simple case with a bridge deck slab supported on steel frame. The slab should work in one direction which is the transverse direction of the bridge so I have been considering of using the one way load transfer. However Robot seems not to distribute the load correctly as I get 0 reaction for the uniform loads on the slab. If I change the load transfer type to be analytical, then it works fine. 

This then makes me wonder what robot is really doing with one way load transfer. I have understood it this way reading robot's description: all loads on the slab and the slab's own weight are distributed considering as if the slab's y direction has no stiffness, so in my case almost as if the slab is 2d (except for those enforced displacement). In my case, the Mxx moment should be flatter compared to the case using analytical for DL. However I only get error messages and robot seems not to understand loads applied on the slab. What did I understand wrong?

Attached is my model. I would very much appreciate if you could explain me this through!

Thanks in advance,

Fei

[Rafacascudo]

In the help file ,cladding topic , it should transfer loads to supports with advanced properties assigned which is your case. I know your panel is not a cladding but the method for transfering loads is the same.

But I tested also on a pure cladding and couldn´t make it work either . Maybe @Artur.Kosakowski  , @Rafal.Gaweda  or @Pawel.Pulak  can clarify this issue .

Anyway , you can make it work as it should creating a fake bar along the support lines.

   But I see no point on doing that as when you set the calculation model to distribute the nodes through the simplified method , you will get fake or no results at all for you slab ,which I think is your main goal with this model , isn´t it ? See below for a test case

    Other than that , you must take care with when using simplified method of load distribution when the load is not distributed on the whole area of the panel , which is the case for contour loads. The method is based on tributary areas which can lead to huge mistakes for concentrated , line and contour loads as you can see below for a concentrated load just 1cm off the midspan.

[Anonymous]

Hello Rafacascudo,

Thanks for the quick answer.

If I understood right, the one way load transfer should be mostly used when the structural elements of interest are those supporting the slab. If the subject of interest is the slab itself, then analytical method should be used. What one way slab differs from the cladding is only that one way slab has stiffness and self weight. This then explaines why it failed to work for my case.

Please let me know if I understood it right or not?

Thanks in advance,

Fei

[Rafacascudo · Accepted solution]

Exactly!!