The effect of slender section (local buckling) in Sap design

[h-badawy]

Dear expert

I noted that Sap is not taken the effect of slender section in design , i did experimental trial by increasing the width of flange and reducing the thickness the local buckling became non-compact then i did it same more time but still the section is non-compact and not jumping to slender ,however as per ASIC if b/2tf is more than (E/fy)^0.5 the section should be slender in local buckling.
Please if anyone faced this issue before advice me otherwise i have to design each section manually.

Thank you

 

[Guest090822]

I have not used SAP, but I have tested dozens of structural software in my career. I have NEVER found a perfect program. My advice is to email tech support for the company and let them know you believe there is an error. They will normally take your question seriously and issue a software update if in fact you found a mistake in the program.

 

[saplanti]

Have you tried increasing the load? Increasing the cross section increases the capacity of the section.

 

[JoshPlumSE]

Post your cross section and load details and I'll do a hand calc and compare to my version of SAP and to RISA. I've done this a lot.... Usually, the programs are correct. But, it is often hard to tell without a very detailed hand calculation.

 

[h-badawy]

saplanti i increased the section only because the equation of local buckling governed by section sizes only

Thank you

 

[saplanti]

I do not know how SAP works. Is is a bar element analysis or full plate element FEA?
In both cases sectional area increase will increase member capacity in the linear analysis.

If you are doing an experiment on the local buckling you cannot see that in bar element analysis. If the code design run performed after, you can see the check against the code rules.
If you run full plate analysis FEA you will see the stresses reduced without changing the load in the linear analysis.

I suggest you increase the load substantially after you change the cross section to non-compact section in the linear analysis. In case you are running full plate element FEA you will see the stresses will change and deformation will increase.

Before doing anything, I suggest you read your analysis program user guide, see the capabilities.
Second, learn about differences between FEA analyses with bar, plate, shell elements for linear and non-linear analyses. Some bar element calculation programs will have additional buckling module, when you run it after the buckling load the program eliminates the buckled member and transfer the load on others. So you need to buy the buckling module for this application.

I do not know anything about SAP so I cannot say further.

This is very big subject, and you need lots of reading to see how to implement analysis.