Timber Roof Structure - Problem with Deformations

[swieciakpawel]

Hello,

I was trying to calculate the structure as shown on att. , and for some reason Random rafters are just flying away when i check results...

- Tried changing the sections, didn't work

- Tried correcting the connections with proper hinges, didn't work

- Tried trial and error method for calculation options aswell, including the DSC Algorithm, didn't work

Basic info :

- Model was made in Robot (not imported or sth)

- When only Dead loads were applied, nothing was wrong

- I checked the loads for any sign of mistakes without success

File Snap9.jpg shows my issue. I'm also sending you the ROBOT file. Currently I'm out of ideas...

ps. Hidden cladding was made for wind

Thanks for replying,

Paweł

[Anonymous]

w narożnikach rzutu więżby masz podparte tylko jednostronnie krokwie (wahadał), podczas obliczeń wyskakuje ci komunikat o niestabilnościach na kierunku uz z podaniem nr wezłów, po numerach wezłów znajdziesz miejsca do poprawy...rozwiązaniem może być wprowadzenie belek okapowych

[swieciakpawel]

Dzięki macjar,

- Po zastosowaniu belek okapowych problem nadal nie znika.

- Próbowałem analizować te wyskakujące niestabilności węzeł po węźle bez skutku i poprawy.

English:

Thanks macjar,

- After using eaves beams the problem still occurs.

- I tried analysing node after node that Robot warns me during calculations without any help.

[Artur.Kosakowski]

Rafters are defined as simply supported beams with supports at one side only. E.g. for the instability reported in node 269 for bar 163 you should replace release defined in node 269 with corresponding support that represents a wall which most likely exists in this place. For the definition as it is the bar 163 can rotate about the node 46.

The above applies to all similar bars in the model.

Aby belki okapowe pomogly nie wystarczy tylko sama ich definicja - musza one byc rowniez w jakis sposob podparte, co jak przypuszczam nie zostalo zrobione.

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

[swieciakpawel]

I've repaired my model, the way i wanted it to be, thanks to your suggestions , the eaves + connection control gave some results... but could you please explain such situation as on picture attached?

 
Take into consideration that rafters next to this one have :

- Same section

- Same force

- Indentical statical scheme?

My suggestion are the boring beetles inside the section, cause i have no idea what else

[Rafal.Gaweda]

Before you you start looking at results you have to correct model firts -> get rid of instabilities.

I think in case of your model you have to look at defined releases.

http://docs.autodesk.com/RSA/2012/ENU/filesROBOT/GUID-52C292E1-5C73-4FB1-B4E0-E5E8107777D-615.htm

http://forums.autodesk.com/t5/Autodesk-Robot-Structural/Instabiliyty-of-type-3/m-p/3179932/highlight...

[Pawel.Pulak]

Instabilities resulting for instance from rotation of many members about their longitudinal axis like on the screen capture below:

Member composed of bars 188 and 68 has xxxfff releases on both ends - so it is rotating about longitudinal axis (node 79 too). One of these releases should be replaced by xxxxff to fix this rotation. Such situation observed in many members of your model - for instance composed from bars 189 and 190 on the same screen capture

Regards,

[Rafal.Gaweda · Accepted solution]

Some corrections made:

- removed some releases

- corrected position of node 590 -> 997 and claddings

- applied releases Utwierdzenie-Przegub1

Please check model - correct it looking at deformation results and torsion diagrams.

[swieciakpawel]

Thank you both Pawel Pulak and Rafal Gaweda,

I found every and last of the instabilities in my structure looking at torsion + deformation schemes,

stiffened it properly and made it work like it should.

I appreciate your work and time you spend to help me.

Best regards,

Pawel Swieciak

[Rafal.Gaweda]

Powodzenia!