STAAD Pro - Member releases

[csd72]

Any STAAD pro wizards out there.

I have a small structure where I need to release a member to have pinned connections each end.

I have used the command

MEMBER RELEASE
2 START MX
2 END MX

but the analysis results still show a point of contraflexure at each end.

Can anyone give me any advice on how to rectify this.

csd

 

[ctcray]

I havent used STAAD in while, but isn't MX torsion?

 

[dgkhan]

Make sure you are releasing the correct moment.

 

[csd72]

Thanks, I was releasing the wrong one. It still doesnt account properly for axial shortening though.

I hate this program I find it the least user friendly of the dozen or so that I have used, including a few dos based programs.

csd

 

[SteveGregory]

Should you be releasing MZ? This would be appropriate for a structure in the XY (global) plane.

 

[civilperson]

Releases are element specific, the direction is related to the member and not the global axis.

 

[csd72]

Yes,

Thanks for that, I figured that out after I made the posting.

The program doesnt seem to take axial shortening into account though, which is the whole reason why I modeled it in the first place.

Thanks all, I have given up using this horrible program.

csd

 

[COEngineeer]

What are you designing where axial deformation is very important?

http://www.swijetty.com

Sea Water Intake and Jetty Construction

 

[Bagman2524]

x is the longitudinal axis in local coordinates in STAAD. z is the major axis and y the minor axis.

 

[csd72]

It is just a banner sign with two poles fixed to a wall and an aluminum plate supporting the banner between them. There are 50 of them in a sports stadium.

The problem is that:

If I design the banner as a pure catenary, the vertical reaction is very large due to the high stiffness of the plate.

If I design it in bending the plate stresses work but the deflection is 14".

In reality it is somewhere in between so I thought I would throw it in the analysis program and see what it ends up at.

I really dont want to do this thing by hand but it looks like I will have to.

csd

 

[dgkhan]

I understand your frustration. Though I really prefer Staad over bunch of others in market, in my pc and I know very well to use them too.
If you explain little more , I can model it for you. Staad can model cable elements too. I have designed cable suspended bridges , so really know what catenary is but could not figure out how a banner will behave like it. It is a thin rectangular sheet (L > > Width) but it will tend to web buckle rather fall uniformly under it's own weight(as per defn of catenary). It will be designed for wind load I guess. I will encourage you to keep using staad as eventually it will do (actually you will know how to) and than in future you will save time. I am not very old but been in industry for enouh time that have seen 40 engineers structural company now working with four engineers and 40 s/w. So follow the trend my friend.

 

[csd72]

dgkhan,

Thanks for the offer but I really dont want to model it as a cable as I can do it by hand for that quite easily.

The catenary is not under dead load but under wind load.

I really dont think that it does what I want it to do.

csd

 

[graybeach]

csd,
Sounds like you need to run non-linear analysis because the deflected geometry affects the member forces.