instability of type 3

[Anonymous]

hi there , 

I’m having the same problem but , having the instability of type 3 in Ux direction , these is what i tried so far after reading the possible solutions in forum 

1) First, I used the bars as truss having as result a lot of instability of all kind every node, so i decided to make the releases manually 

2) After that everything worked out but resulting to have in instability of type 3 , sometimes in different nodes after changing the calculation method . 

Checking the result of calculation, i see a big difference in the min and max of matrix, but can’t now how this happen, to me it seems ok ,,, 

A little help would be welcome. 

Regards. 

[Rafal.Gaweda]

Releases wrongly defined - structure is unstable ; lots of mechamisms in trussses

Screen shot from test load results:

[Anonymous]

HELLO , MAN YOURE VERY KIND TO ANSWER SO QUICKLY , THANX 

FIRST , I THINK MY MISTAKE WAS THAT I DINDT TAKE INTO ACCOUNT THAT RELEASES ARE DEFINED BY THE LOCAL AXES OF BARS , SO I DELETED ALL AND CORRECTED , 

1) I APPLIED PINNED-PINEED RELEASE TO THE BRACING AND  POST OF THE TRUSS, GETTING ONLY AXIAL FORCE , BUT WHEN APLLYING THE PINNED-PINNED CONECTION TO CHORD I GET AGAIN THE INSTABILITY , SO I TRIED WITH FIXED-PINNED , AND PINNED-FIXED , AND AGAIN. 

IM SORRY WITH ALL THIS QUESTIONS , BUT IM KIND OF LEARNING THE STEEL DESIGN FEATURE OF THE PROGRAM. 

I DEFINED SPECTRAL CASES ALSO . 

PLEASE IF YOU CAN ADVISE ME , HOW TO DEFINE CORRECTLY THE RELEASES ON CHORDS , OR IF THERE IS AN EASIEST WAY THAT IM NOT FAMILIAR WITH WHEN DEFINING THE RELEASES OF THE 3D TRUSS, OR IF THE TRUSS MEMBER OPTION COULD BE APPLIED TO BARS ONN 3D TRUSS WITHOUT GETTING ANY ONSTABILITIES. 

REGARDS. 

[Anonymous]

I THINK THAT ASUMING CONTINUOS CHORD , AND PINNING BRACING AND POST , IS A GOOD ASUMPTION , TAKING IN MIND THE COMPLEXITY OF THIS RELEASES?

WHAT DO YOU THINK ABOUT THIS , ?

[Rafal.Gaweda · Accepted solution]

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