Curved Trusses And Roof Modification, Finite Element Methods

[Anonymous]

Hi everyone and good morning,
I am trying to mimic a stadium in Robot,but i am unable to make the calculations. the reason for this is improper nodes. Anyone who can guide me how to model this roof in a correct way. I am attaching my model. 

[Krzysztof_Wasik]

Hi @Anonymous 

In that case curved roof can be defined using curved contour consisting of bars and arcs (I suggest arc discretization to control number of elements along arc)

See attached video with roof geometry definition

Curved roof

If I managed to answer your question(s) press the Accept as Solution button please. This will help other users to find solution(s) much faster. Thank you.

[Anonymous]

Hi @Krzysztof_Wasik  Thank you so much for your timely reply. It thoroughly solved my problem. But there is one more😂.
1.I have modeled both steel and concrete roofs . But the displacements(bar deformations) in steel structure(light weight roof under DL1) are more as compared to concrete roof. I was wondering if there is some building code that can justify this. 
2.Moreover, what should be the appropriate system of local axis for determining MXX and MYY?
3.How can I use the values of Moments to calculate the steel reinforcement in concrete roof?
4. I want to model the trusses so where should I use pinned-pinned releases(it results in instability issues) or use truss elements?
Pictures are attached.
I am really hopeful that I didn't bother you asking such simple questions.😊

[Krzysztof_Wasik · Accepted solution]

Hi @Anonymous 

ad1 I think that in each steel design and concrete design codes are limits for maximal members deflection or displacements. In all codes I have used up to now there is section about displacements (SLS conditions) Please refer to your local steel design and concrete design codes.

ad2. In case of each roof segments i would define direction according to vector determined by middle arc points

 

Ad 3 You can use required reinforcement design procedure for shells. Please refer to Required reinforcement procedure

There are many tutorial for shell required reinforcement design on Youtube as well Autodesk Tutorials refer to webinair 5

Ad4

I would define pinned pinned connections for diagonals and chord ends. To reduce possibility of instability I would define releases for rotation around axis perpendicular to truss plane (If members are not rotated around its axis it should be RY-RY release. In 3D structure it is difficult to define stable structure using truss members so I would not recommend using them.

[Rafacascudo · Accepted solution]

  As it is a circular geometry ,for "Maps..." you can choose direction as " Polar" , define the center node or point and it will work for all curved roof pieces at once