Steel base plate with 4 nodes from truss: Options for modelling and non-convergence (RSA 2022)

[mikelt6CWRJ]

Hi all,

I have a truss which I am thinking to weld to a base plate. I have 4 nodes with supports and I am thinking about use one steel plate for those nodes as the truss sides are 50 cm. My question is how to model this situation properly. I have two ideas. I would like to know how you see these approaches.

 Here the possibilities:

• Most simplified one.  Create a center node between the four I have where I can locate an auxiliary compound profile of 500x500 and connect that node with my four nodes with rigids links. This could be quite close to reality if I select properly the compound profile and If I don’t assign great length to the auxiliary profile just to avoid additional displacements and efforts. Then the profile of 500x500 will serve me as a typical example to calculate a base plate with bolts if the program have that situation.

• More realistic (and complicated to model). Using auxiliary polyline I can create a contour of a steel base plate with those four nodes included. I even can create the bolt holes in the steel plate to check the approach.

But I am getting a non-covergence in combined cases. The holes have a support with UY, UZ and UX- as fixed directions. The steel plate has only fixed direction for UX+. Whay am I doing wrong in this case? Could be a lot of things.

• The next step to the previous option would be to model a short line of the profiles to be welded to the steel plate to analyze how it performs. We all know that in reality node connection is not exactly as that, we have volumes. IMO as I have L profiles I can assume that the node connection is pretty close to the reality.

Find attached the initial model and the two options (the second one as I explained dont work properly).

Thanks in advance.

[Simau · Accepted solution]

@mikelt6CWRJ 

You option 2 model is convergent.

Just:

Tick "matrix update after each iteration" for all cases/comb

Uplift is UX+ for Support bolt and UX- for Wallbearing

Model attached

[mikelt6CWRJ]

Thank you very much @Simau , I undestood the uplift option the other way around.