Staad finite element analysis 1

[1161]

Greetings

How accurate is Staad finite element analysis.In case of water
tank resting on soil, can we give springs only KFY value, not
releasing MX, MZ.e.g.
supports
1 to 200 KFY 24000
We get very less moments in bottom slab.
Please respond.

Regards.

 

[wmccain]

I feel compelled to respond to the
irresponsible remarkes by QSHAKE. The
"baseline" used to measure the accuracy
of the STAAD solution is stated in my
original post. The type of element used
is explained in the STAAD manuals. ERRORS
in a numerical analysis are dependent upon
boundary conditions and assumptions in
the analysis itself, as well as on
the numerical method. I see in this forum
numerous examples of faulty boundary conditions
associated with the use of the STAAD elements
in foundation mats or tank bottoms. The post
I responded to as well as previous and following posts
are prime examples of this.


For 1161(visitor)
For example: A moment's thought will enlighten one
to the fact that to make joints in a soil supported
tank bottom pinned in X and Z would be an error. Also,
as suggested in another post, to fix moments in Z, X,
and Y, would be in error.
These conditions would produce nonsensical results.
To evaluate a structural force associated with a
degree of freedom, one must release that degree
of freedom.

The Example 10, which is in the STAADPro 2001 Online
Documentation, is, as far as I am concerned, in error.
I will not work a problem such as this in the manner
suggested by STAAD. I refer you to the post I placed
earlier, using springs, and limited lateral restraints for
solution stability.

Happy howling,

 

I have evaluted STAAD verificacion manula. It seems good. I have question in Problema 11, what method used to got mode shapes?

 

In STAAD 2001, they report the method used in eigenvalue extraction. Check the output files. The STAAD engine will say Subspace Iteration method used. The STARDYNE engine has the HQR and LANCZOS methods.

 

[JAE]

I guess I don't see how remarks in this forum, especially the ones above by Qshake are "irresponsible". He simply made a point about STAAD relative to his assurance level of the program's accuracy and use.

My single point was that STAAD is marketed aggressively as the best structural program out there and yet over and over again I hear engineers complain about it, seem confused about its application, and doubt its results.

I haven't used the program for some years but when I did, weird results would appear and not correspond to the results from an exact replica model built in STRUDL. This was about 12 years ago and Eng-Tips forums still have posts appearing with STAAD issues.

When someone offers me a program to use and then says "Its a great piece of software as long as you keep to standard designs"...would you feel confident in using it? Not me.

 

Thank you carl! I am new user to STAAD in Brasil and I think product is so good. Me company have used Sap 90 in past days. Its is to confusing. Mr. JAE, please don not be mad at me for using the STAAD. I still like to hear your good advise to me. A work friend used the STAAD in US and liked it so much. So we buyed it here. Also our cheif used STAAD 3 in Europe and also liked it much. I look at Exmples Mr. Born2build write and they look good. What are problemas I should look for? Thank you.