topic Re: Grillage Modelling in Robot Structural Analysis Forum

Grillage Modelling

Anonymous — Sat, 26 Nov 2016 16:12:05 GMT

Hi,

I am doing a grillage analysis for a precast concrete beam bridge with insitu concrete around the beams. When defining the transverse member (there is no transverse member in the actual bridge, but because the exist of insitu concrete, there is transverse effect), I want to define the transverse member as dummy member, define no strength to it, only allows it to transfer shear and bending moment. How can I define it using Robot? We have previously using another software Superstress, where there is a function allows to define dummy member, make it almost act like string. Can anyone solve the issue here for me please? Thanks along.

Re: Grillage Modelling

Artur.Kosakowski — Mon, 28 Nov 2016 08:31:41 GMT

I am doing a grillage analysis for a precast concrete beam bridge with insitu concrete around the beams. When defining the transverse member (there is no transverse member in the actual bridge, but because the exist of insitu concrete, there is transverse effect), I want to define the transverse member as dummy member, define no strength to it, only allows it to transfer shear and bending moment. How can I define it using Robot? We have previously using another software Superstress, where there is a function allows to define dummy member, make it almost act like string. Can anyone solve the issue here for me please? Thanks along.

Hi,

I'm not sure if I understand you correctly as first you wrote that you need a 'dummy member, define no strength to it, only allows it to transfer shear and bending moment' which I believe is what is known as a rigid link in Robot and then you wrote that it should behave as a string (so no bending and shear transfer) being more link tension only or cable element in Robot.

Re: Grillage Modelling

Anonymous — Mon, 28 Nov 2016 18:06:18 GMT

Thank you Arthur,

Sorry for the confusion here. All I want is that the dummy members to have no strength, but be able to transfer shear and bending moment between the longitudinal members it is connected to. And I believe that is what a grillage analysis does for. So, in this case, you are saying the rigid link is the way to go, but I am not sure how to use the rigid link, with all the master and salve nodes thing. How do I define transverse member using the rigid link you mentioned here? Many thanks.

Re: Grillage Modelling

Artur.Kosakowski — Tue, 29 Nov 2016 09:28:25 GMT

Imagine a rigid link being very rigid element connection two nodes. The connection in the master node is fully fixed whereas in the slave node you can release required degrees of freedom e.g. creating pinned connection. On the other hand if the transverse elements are to simulate the behavior of the deck then IMHO they should have 'resistance' and I assume the program you mentioned replaces the deck with the equivalent beam element (In RSA you would either model a deck as a panel or define properties to these bar elements manually). The same approach (grillage analysis) is used in Autodesk Structural Bridge Design program which is specifically designed for bridge analysis.

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Re: Grillage Modelling

Anonymous — Tue, 06 Jun 2017 12:40:20 GMT

Thank you Artur. Problem solved.

Re: Grillage Modelling

Artur.Kosakowski — Wed, 07 Jun 2017 04:30:26 GMT

Hi @Anonymous

I'm glad I manage to help