STRUCTURAL ENGINEERING FORUM OF INDIA [SEFI]

subhashgandha · SEFI Regulars Joined: 26 Jan 2003 Posts: 37

Resp. Sirs,

I have to strengthen some beams of a only 5 years old G+4, RCC framed building. The building is not designed by me. Structural drawings of majority of beams available. Apparently it seems that many beams have less reinforcement than required. In some of the large beams, minor shear and flexure cracks are visible.

The client wants large beams to be strengthen by steel plates. He is not ready to adopt any other technique. He is okay with either epoxy grout or steel plates but more inclined to plates.

Can anyone guide me how to design steel plates to strengthen an existing RC beam for both shear and flexure. Or kindly suggest some literature/book.

kunalkansara · General Sponsor Joined: 26 Jan 2003 Posts: 196

Dear Subhash

I'm not sure on what extent the building detailing is deficient. Steel plating is not a bad idea per say, but it is not as simple as it sounds. I hope I'm wrong, but it seems your client is taking the issue a bit too casually. Also, the strengthening design needs to be carried out (and of course independently vetted) by the experienced engineers with specific training, knowledge and expertise in structural strengthening.

Haphazard strengthening can be dangerous. For example, a beam strengthened for flexure has increased risk of failing under shear. So often such beams needs to be strengthened in shear complimentarily even if they were originally not deficient in shear. Steel plating could be effective in flexural strengthening, but their effectiveness in shear is questionable.

It also depends on the strength of concrete and possibility of effectively attaching steel plates on the beams. Often the steel plates needs to be bolted into the soffits, so it is partially intrusive method.

The use of FRP for such applications is way more effective and appropriate than steel plating.

Im accessing this website through phone as I'm on vacation at the moment, so can't write details on how to design for strengthening. But if you wish, please send the details of the structure and I might be able to help you with the design.

Kind regards
Kunal

subhashgandha · SEFI Regulars Joined: 26 Jan 2003 Posts: 37

subhashgandha · SEFI Regulars Joined: 26 Jan 2003 Posts: 37

Resp. Krunal Sir,
Thank you very much for the technical reply. My technical knowledge and experience in this regard is very less (almost NIL) compared to yours but I also was worried in the same way as you. But ultimately the client is ready to adopt glass/carbon wrapping (FRP) system.

The wrapping agency will study the existing structural condition with some NDTs, suggest a suitable retrofitting method (in due consultation with me) and execute the work.

But still I am very much interested in designing steel plates for strengthening the existing RCC members. Kindly guide me.

Subhash Gandha
M.Tech. (Structures)

edward_jade · SEFI Member Joined: 01 Aug 2016 Posts: 2

hi sir kunal,

been through that situation of mr. subhashgandha, but i insisted to our management that appropriate professionals shall be employed in addressing our situation because at that moment i'm not well verse in the scenario, they heeded, and moved me to other projects. i was very interested that time with regards to the approach of strengthening our structure but unfortunately i was not in the room for learning. could you give me some reference books or materials pertaining to approaching those kind of retrofittings. thank you.

jai1231 · SEFI Member Joined: 03 Aug 2018 Posts: 3

Please go ahead thorugh Retrofitting Process.I think this is much better than steel plate

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On Sat, 1 Sep 2018 at 23:04, subhashgandha <forum@sefindia.org (forum@sefindia.org)> wrote:

B.S.VIRDI · SEFI Member Joined: 02 Jan 2009 Posts: 5

It is better to rehabilitate beams with carbon fibre raping

Sent from my iPhone

On 21-Aug-2018, at 7:18 PM, subhashgandha <forum@sefindia.org (forum@sefindia.org)> wrote:

kunalkansara · General Sponsor Joined: 26 Jan 2003 Posts: 196

Dear Subhash and Edward

I will write separately in due course on this. Kindly pardon the delay, and I hope this will be ok with you both as the matter is now for understanding only!

Kind regards
Kunal

PS: Kindly refrain from using Sir or respected etc suffixes and prefixes at least while referring to me. I would appreciate if you refer to me solely by my first name, ideally. Let the new generation of Engineers break the orthodox VIP culture and practices that is suffocating India for a pretty long time! I hope you will find it more convenient. Thanks.

subhashgandha · SEFI Regulars Joined: 26 Jan 2003 Posts: 37

Dear Kunal, (hope you allow atleast the word Dear).
Thank you very much for the interest taken. If you prefer, and possible also, You can email any material/reference etc.., to me on parthcon@gmail.com.

P.S. : We are Indians and right from the childhood we are trained and happy to address others with Sir, Respected etc... and secondly you are far richer both in knowledge & experience so you are a "Respected GURUJI" to us and we will be happy to call you that but ultimately at your wish we will not address you in that way, but atleast just allow us to call you Dear. Simply call you Kunal do not suits...This is my wish.......Thanks