topic Re: Tension only bars in compression under static wind pressure in Robot Structural Analysis Forum

Tension only bars in compression under static wind pressure

Anonymous — Fri, 20 Jan 2017 17:38:17 GMT

Good afternoon,

I'm currently working on a steel frame and tried to design my bracing element under wind loads.

I've modelized them as truss tensions bars and performed non-linear analysis but the results show me bars in compression only and/or inactive.

I've defined my wind loads as static load cases.

I do not understand where is the problem?

Thanks for your help.

Re: Tension only bars in compression under static wind pressure

Artur.Kosakowski — Fri, 20 Jan 2017 17:49:41 GMT

Has the analysis converged with no instability errors reported?

Re: Tension only bars in compression under static wind pressure

Anonymous — Fri, 20 Jan 2017 18:14:28 GMT

Yes, I have couple of type 3 instabilities throughout the structure. But they so not seem to me as the roots of the problem. (see clip attached)

The separate structure is explained by the fact that I have a movement joints splitting the building in 3 parts.

Re: Tension only bars in compression under static wind pressure

Artur.Kosakowski — Fri, 20 Jan 2017 18:19:50 GMT

You may want to calculate each of the parts separately (in a separate file) for easier investigation of the cause of this situation. I wouldn't rule out the instabilities as the reason without checking this first. Is it the same if you delete releases from the model?

Re: Tension only bars in compression under static wind pressure

Anonymous — Fri, 20 Jan 2017 18:39:19 GMT

I've removed all the releases and the results are the same.

I will try to slip the model on Monday and come back to you if necessary.

Thanks for your help and have a nice weekend.

Re: Tension only bars in compression under static wind pressure

Anonymous — Mon, 23 Jan 2017 10:56:45 GMT

Good morning,

I've tried again this morning but this time I've selected the default setup (in compression only) and it works perfectly.

Is that a bug?Indeed, when you open the selection window

Indeed, when you open the selection window "Compressions bars" is selected by default but the sketch suggests tension. If you clic on tension or compression the sketch changes and displays an adequate picture.

Re: Tension only bars in compression under static wind pressure

Artur.Kosakowski — Mon, 23 Jan 2017 11:06:05 GMT

I'm sorry but I'm not sure if I understand what you mean.

Re: Tension only bars in compression under static wind pressure

Rafacascudo — Mon, 23 Jan 2017 15:44:43 GMT

Sorry to ask , but did you select all the bars you want to be "tension only" and then clicked to apply?