Analysis model

[atee001]

I have an analysis model composed of bracings,beams and columns.

When I have verical loads only applied to my structure, I find the axial forces in bracing (in some of them) greater than the columns connected to it.

What could be the reason?

 

[kslee1000]

atee001:

Without numbering system on the graph, there is no way to interpretate the numerical results. However, I did notice there are excessive localized movements in direction of "X", and, albiet small, plane rotations about "Z" axis. Without attribute to irregularities in structural arrangement, I am puzzled as well. If there is no rotation (fiz) without the braces, try to rearrange the braces to a symmetrical manner, and see what results.

Or, have you tried to offset the braces from the common joint with columns?

 

[atee001]

Thanks a lot all.

however, I find that even on removing ALL the braces lateral drift exists.

Is this indicative of problem in defining the restraints?

 

[kslee1000]

How about "fiz"?

 

[atee001]

hi,

Thanks again.Yes,fiz is also present.

What do you suggest now?Does this indicate probllem in restraint definition?

Attached is the list of displacements without braces

 

[atee001]

As well as attached a pic showing the node numbers

 

[kslee1000]

atee001:

I will print both out and have a look on Monday. Wish your project deadline last longer than that.

 

[RonRoberts]

Can you try a little experiment? Can you remove all loads from the model then try applying a vertical load to the top node of each column and then check the reactions at the supports? If the support reactions aren't all equal it might point us in the direction of a modelling error.

What is the angle that the brace makes with the horizontal plane? I'd like to see if the 7.89 KN, 3.5 KN and 8.5KN reactions make any sense. The 3.5 + 8.5 cos (theta) should equal 7.89.

 

[steve1]

atee001

If the load is horizontal at the top of your brace column loacation then the brace is much stiffer since it is being loaded axially while the column is beng loaded in bending.

 

[atee001]

Thanks Steve--working on what you said (making braces symmetric)

Ronroberts- the summation 3.5 + 8.5 cos (theta) is not equal 7.89.

Am attaching a line model again

 

[RonRoberts]

I'm not familiar with the software you are using. Why are the support "icons" not showing up at all the column bases and why do the members have different releases at some of the column bases?

 

[kslee1000]

atee001:

Your 2nd attachment turns out a blank page.
From the latest attachement, either the printing tool of the program was not accurate, or your support system is a mess. There are footings missing, also, the footing rows seem do not line up right.

Please have some one in your office check your model.