Problem of Steel Column Slenderness and Buckling at Site 1

[alexgan]

Hi!

I am facing some problem at site. Please kindly advice.

I designed the steel column with the size of UB 305 x 102 x 28 with the maximum height of 10.515 m.

However, due to the inexperience contractor, during the installation of the column, he did not prop and braced the column before he loaded the beam/stiffener and purlin on top. We found that the columns are buckling (approximately 75mm) and look terrible at site now.

Any suggestion on what can i do to strengthened the buckling column? Shall i add stiffener plate of the steel column on the flange or web.

Please kindly advice.

Thank you.

 

[hokie66]

This sounds more like a design issue than a site erection problem. What is supposed to brace this very skinny column in the finished structure? How much load does it take? If the column, by design, has adequate bracing, you may be able to pull the bent column into alignment using the bracing, but more information is required before making that decision.

 

[alexgan]

Hi! @Hokie66! Thanks for the prompt reply.

The maximum Axial Load, Pmax = 51.125 kN.

We are having the 75mm x 75 mm angle bar to brace (as cross bracing in between) the column.

In between the column that will be partially with brickwall (3.6m) and the upper part will be cladding.

The column is too skinny, so what should i do to strengthening the column? Can i increase the stiffener plate? Or should i totally remove the column and requested the column to be replaced?

Please kindly advice.

Thank you!

 

[alexgan]

Hi! @Hokie66!

One more additional information, the column is fully encased in the Reinforced Concrete Column due to the local authorities requirement. This will help in term for the problem right? The RC Column size is 450 mm x 300 mm with 8T12 Shear link 2R6-200.

 

[hokie66]

That steel column wouldn't have ANY capacity as a strut over a 10.5 metre length, so it is no wonder that it buckled about the weak axis. The 305 deep x 102 wide section is a very light beam section, not intended for use as a column, particularly not a long column. You may be able to use the concrete encasement, adequately reinforced, to stabilise the situation, but you need a competent structural engineer to check the design.

 

[alexgan]

Thanks, @hokkie66 for the reply!

I will look into it.

 

[alexgan]

Hi! @hokkie66!

One more question, what is the software that you recommend me for the steel structural?

Please advice.

Thank you!

 

[hokie66]

I don't advise on any particular software. Rather, I advise that if you are going to practice engineering, you get a good engineering education, and after that, a good mentor. Software is no substitute for understanding.

 

[homostructural]

Hello Alexgan! In general I agree with all the advices hokie66 gave you. The cross-section of your column is too small comparing to its length and compressive load. I also agree with what he said about structural software. They are just a useful tool only if you know how to use them and if you have the appropriate theoretical background.

Is this structure located in UK? If yes I would recommend you to study some books about Eurocodes. There are also free resources on the web. Check here for relevant bibliography!

All about Eurocodes:

http://www.DesignToEurocodes.com

 

[dik]

A 4" wide HSS column, 35' high is really slender and unless it has intermediat lateral support on the weak axis, you may have a dangerous condition.

You can weld angles to the 12" face to provide stiffness. Alternatively, you may be able to 'cable' it in place and install the necessary bracing for the weak axis.

Dik

 

[BAretired]

UB 305x102x28 is roughly equivalent to W310x28 or W12x19 Imperial size. The flange width is 102mm or 4".

Even when encased in 450x300 concrete, the shape is too slender as a compression member 10.5m long.

The design must be reviewed by a competent structural engineer before continuing with construction. In the meantime, the steel member must be laterally braced to prevent collapse. This is a dangerous job and should be done only be experienced personnel.

BA

 

[alexgan]

Appreciate for all the advice and reply.

Just would like to give some background of the project. The design consultant designed the column as stated above with the detailing of the lateral structure (as tie beam) and stiffener plate (welded) to the section at every 3 m interval.

The contractor did not follow the drawings. As consultant requested for several times, before the installation of the structure, he needs to submit the shop drawing with the competent person endorsement and the mill certificate to ensure the understanding of the engineering drawings. However, the contractor just erected the structure without all the information above before the construction.

This project is located at South East Asia, one small town. The owner and the contractor is not being well educated. They always like to do the works according to their experience and gut feel. Unless that is problem occur like now, then only they will seek for consultant advice.

At site, now, we are requesting them to remove the beam and re-align the structure. Before for the next erection, they will need to do all the proper bracing (laterally).

Besides, as discussed with the competent engineer, we will be utilised the steel column as part of the reinforcement steel of the RC columns with the RC perimeter beam. We are running again on the design and detail today.

Will update this post once the design completed.

Thank you.

 

[hokie66]

It is painful to give advice in a situation like this. First you told us that you designed the column, then you asked for advice as to what software you should be using, and now you refer to the 'design consultant' and 'competent engineer' as being responsible for the design. Good luck.