warning instability at joint (STAAD)

[repsol]

Hi guys ..i found this site very informative..I model a structure USING STAAD software but this warning keep on appearing in out put file..any help to solve this problem will greatly appreciated..thanks in advance.hope for your reply

[engr1900]

Hy
can u post the staad file, error may be due to support condition
chek it again whether fixed, hinge or roller
bye

[jaks]

Hi,

The particular error may be due to the type of the model you are working with(Space/Plane). Suppose if you are working in a single plane and the model is Space, then this instability will be there.

And suppose if you are working in a Space model and there are certain horizontal forces applied, you need to see that the loads are transferred to the bases. If your base supports are say pinned then you may need bracings/moment connections, likewise...

I hope this might answer some of your problem if not all.

Regards,

# Upload your model/file if you are facing problem other than the above.

[repsol]

engr1900,sent to your email the STAAD INPUT FILE of the said project...HOPE you can help me.A lot of thanks in advance

---

hi jaks,thanks also for your reply....

[engr1900]

Hy
u can check there shud not be any multiple structures
go to tools, check multiple structures, coz almost all softwares checks stiffness between elements
try to change the column section coz beam has to transfer the load to columns, beam section must be equal or less
second thing is as follows
There are 2 important checks that should be carried out if instability messages are present.

a) A static equilibrium check. This check will tell us whether all the applied loading flowed through the model into the supports. A satisfactory result would require that the applied loading be in equilibrium with the support reactions.

b) The joint displacement check. This check will tell us whether the displacements in the model are within reasonable limits. If a load passes through a corresponding unstable degree of freedom, the structure will undergo excessive deflections at that degree of freedom.

One may use the PRINT STATICS CHECK option in conjunction with the PERFORM ANALYSIS command to obtain a report of both the results mentioned in the above checks. The STAAD output file will contain a report similar to the following, for every primary load case that has been solved for :

hope it will help u to sortout problem

byee

[dynamics]

Instability warning will usually occur when some of the members degree of freedom are released and forces in the structure are flowing in all axis i.e. by declaring the member as truss, compression or tension only but there other members connecting to that member in orthogonal direction thus transfer of loads from the orthogonal direction is not restrained by any other member because of the member specification of the other. There are several ways to address this issue depending on the type of structure declared in the analysis i.e space, plane or truss.

Kindly attach your file so that I can check it and try to resolve your issue.

[engr1900]

instability in joints in staadpro

info:
Hy
u can havae more details reg your problem here




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[repsol]

hy guys,

i just resolve the problem and now no instability messages occured.I also noticed
that equilibrium exist base from the report of STATIC check.Big thanks for those email and advise.....more power to this site