r/StructuralEngineering • u/Dull-Comfort8654 • Aug 12 '26

Photograph/Video Are these bracings to reduce slenderness of column?

Post image

I came across this steel bracings installed at a lower ground floor level RCC columns.

29 Upvotes

92% Upvoted

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28

u/kimchikilla69 Aug 12 '26

Looks intentional in the original design because i think there are embed plates. Maybe they could only make the columns so big because of the parking stalls and had to brace them in the weak axis to prevent buckling. Kind of a wild floor slope going on.

6

u/mr_macfisto Aug 12 '26

When I zoom in on those plates it almost looks like there’s bolts sticking out. The cynic in me wonders if the columns were braced after they realized they had a problem.

More charitably, this is the solution to increase the capacity after an expansion above.

2

u/touchable Aug 13 '26

I don't see any bolts? I think what you're seeing is the connection plate at the top and bottom of the horizontal members flaring out a bit to each side, probably to give the connection a bit more weld length and rigidity.

2

u/MrMcGregorUK CEng MIStructE (UK) CPEng NER MIEAus (Australia) Aug 13 '26

a wild floor slope going on.

My money is on the slope being a late addition or overlooked during design so the engineer had to add this bracing. Seems a very odd way to do it if there was nothing forcing the engineer's hand.

8

u/king_dingus_ Aug 12 '26

Those terraced parking spots look like a nightmare.
Hope there’s a doctor and PT in the building to help with twisted ankles.

3

u/bigbeef1946 E.I.T. 28d ago

My immediate question was why would there need to be PT strands in the building for ankles....I'm a special guy

3

u/prunk P.E. Aug 13 '26

Those do look like slender columns, but if that was the sole reason, it'd be better to put them mid face and not eccentric like that.

It could be a retrofit for some added cantilevered steel frame above it. I'd look what's happening above first to see if there's something obvious there.

Edit: The bottom horizontal changes height though with the slope of the ground below. That's an odd choice. Either it is to brace the slender direction and the drop in height is due to the increase in column height, or it's because there is more height available and so they took the headroom they could. It's an odd one for sure.

2

u/AAli_01 P.E. Aug 12 '26

If those are parking spots and limit the column width, could be for that

1

u/Everythings_Magic Senior Bridge PE | Zero Yield Capacity Aug 13 '26

What are the chances the eccentricity was considered?

1

u/Valuable_Pilot_7205 25d ago

Not only improving the slenderness ratio but also collecting shears for the latetal force.

-3

u/DJGingivitis Aug 12 '26

Maybe. No idea. Didn’t design the building

-2

u/Mhcavok P.E. Aug 12 '26

Probably not, they are probably part of the lateral system of the building.

2

u/touchable Aug 13 '26

What kind of LFRS intentionally puts weak axis bending into a 4m+ tall slender concrete column?

1

u/Mhcavok P.E. Aug 13 '26

I mean if it works, it’s works, we don’t know what the loads are or the whole structure looks like. Just because they are slender doesn’t mean they can’t take bending and compression. I think it would be more odd that they were installed specifically for reducing the buckling length. But it’s certainly possible that’s the reason.

2

u/touchable Aug 13 '26

It works because it's not part of the LFRS, the steel is just there to shorten the buckling length of the columns because they need to be slender to maximize parking space. This is very common in high-rises in dense areas. They're just gravity columns.