topic Re: Unwanted moments in columns in Robot Structural Analysis Forum

Unwanted moments in columns

ivo3Q786 — Mon, 12 Dec 2022 16:45:57 GMT

Dear All,

The attached model represents a car park made of steel columns, beams and concrete precast T-planks. The problem we face here is unwanted moments in some of the columns at grids F, G and H. Although that we are pretty sure the column sections are big enough, due to these moments, we cannot verify the members. Perimeter columns are okay.

Where do we go wrong?

Kind regards

Ivo Demirov

Re: Unwanted moments in columns

Simau — Tue, 13 Dec 2022 15:44:04 GMT

@ivo3Q786

For TT Slab Change Panel calculation model to full rigid

Results for internal columns are better:

Re: Unwanted moments in columns

ivo3Q786 — Wed, 14 Dec 2022 10:48:24 GMT

Hello and thank you for the answer!

Please, see the attached screenshots. With full stiffening of TT planks, the situation with the moments in the columns is better but we have illogical support reactions - an end column should have smaller reaction than a middle one, they cannot be the same.

With partial stiffening the support reactions look normally and exactly as we expect but we have moments in the columns...

Strange situation. Maybe we need to work with two models?

Re: Unwanted moments in columns

Simau — Thu, 15 Dec 2022 18:38:10 GMT

@ivo3Q786

I am not sur i really understand how your structure works.

Do precast T-planks actually work like diaphragms???

How are these T-planks linked to the beams and to each other?

In my humble opinion you must first test the stability of the steel structure by using claddings instead of precasts and adding horizontal bracings as diaphragms.

To design columns you must create columns type according according to their buckling principle. Currently only one type is column is used, the Robot default type "column".

Re: Unwanted moments in columns

ivo3Q786 — Mon, 19 Dec 2022 10:22:53 GMT

I will try to change the model as you say. Thank you!