Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Bulging of CFT walls

Bulging of CFT walls

Bulging of CFT walls

Hi guys, just wondering what you make of this concrete-filled tube that we found during a frame inspection. It looks like all the side of the column are bulging - indeed it looks like the concrete socle at the base is restraining the deformation which is why some concrete is spalling off. At the upper end there is a brace connection and that is also clearly restraining the deformation. Very strange to me that the walls of the column are bulging over such a long distance, I would have expected some buckling deformations to be more local. Anyone seen this kind of thing before? Interestingly, the other similarly loaded columns do not show this same bulging.

It's a 180x180x5 SHS with plain concrete filling, it's total height is around 7,5m. I have included a stick diagram showing the arrangement - the column takes some compression from the top but also resists some bending moment from the entrance canopy brace that is attached between the stiff points formed by the bracing. Sorry it might all be a bit hard to see but hopefully you get the idea.

RE: Bulging of CFT walls

I assume it's restrained at the top. The connection appears to have rotated a bit. It's a thin wall and with 25' of concrete, there could be a slight 'bulge' depending on how concrete was placed. I've never encountered this and I've never done calculations for this. If designed properly, there is little reason to be concerned. pipe

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Do you feel any better?


RE: Bulging of CFT walls

I do not see any buckling in those pictures. The beam is probably restrained at both top and bottom, and since it seems embedded deeply into the socle, it may experience stresses due to thermal gradients and imposed deformation from frame action. A remedy would´ve been (not sure if it´s worth fixing now) to install the column onto a baseplate and not into a hole in the poorly reinforced socle.

RE: Bulging of CFT walls

Thanks for the input, guys. Yes, I agree that this doesn't seem to concerning and it doesn't look like anything is buckling. I think the column is rotating a little and it gives the impression that it is bulging - I think I'll go back on site with a nice long straight edge and have a look myself.


RE: Bulging of CFT walls

Is freezing of entrapped water a possibility? I have seen several instances of freezing water inside a column resulting in the column walls bulging, although not usually over the entire length of the column.

RE: Bulging of CFT walls

I was going to suggest water intrusion and freezing as a possibility. Although it appears to be interior so freezing would be unlikely it is possible. We actually have a project locally where a HSS12x12 filled with water and froze, it split the column right down the weld. It was an interior column, however it was within an exit stair case that was only heating at the bottom floor by a small radiant heater.

RE: Bulging of CFT walls

Hi guys, sorry for not responding earlier my email notifications were going to junk for some reason.

I guess water entry is a possibility, there are some weird connections at the top of the columns and it's possible a weld or two is missing or incomplete, leaving some space for water to get in. As you mentioned, it is unlikely that freezing would be an issue but it's not beyond the realms of possibility if the shop had been empty for some time and the heating switched off. I'll investigate this a little further.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close