Hi,
I am modelling a 3 faced tower which has horizontal and diagonal bracing members welded to the tower legs. When I run the non-linear analysis there are ineffective or buckled members. I checked the member forces for the brace members which are circular bars and they have no forces. I suspect the brace members have not been accounted for in the analysis leading to ineffective members during the analysis.
Help on this will be much appreciated.
I have tried to attach the MSTower model but get errors.
Thanks.
It does sound like those bars have buckled and are no longer in the stiffness matrix. For a bit more info see the program help topic on Non Linear Analysis (and the subtopic "Troubleshooting Non-Linear Analysis")
To attach a file, save it as a .zip file first then attach using the insert button. You can also use the secure file upload link process below.
Hi Seth,
Thank you for the reply. I have uploaded the file using the secure upload method.
I changed the bars to stronger members and reduced the loads to check if buckling was the problem, but I still get the same error. I think it may have something to do with the connection with the main legs. Could you please have a look at the model.
Cheers.
In the file you sent, the rod bracing is 16Rod below, 12Rod above. They are up to about 2m long in typical X configurations with the CR type connection and all defined as tension-only members so any compression causes "buckling". There are 114 diagonals total. In the non-linear analysis (with min. displacement control and 0.0005 tolerance), many of the braces buckle, or fall out of the stiffness matrix, but this is to be expected I think. The DL only case basically throws all the braces into compression, but for the other load combinations 76 or fewer braces buckle. The structure is still stable.
Reviewing brace forces I see brace axial forces for some combos, 0.0 for others as expected. Looking at displacements I see reasonable displacements like 0.0128 in x for combo 4120.