Minimum longitudinal reinforcement in column as per IS 456

RE: Minimum longitudinal reinforcement in column as per IS 456

DSANJU — Tue, 26 Jul 2022 11:44:07 GMT

Please note that this issue has been passed on to our development team for further action.

RE: Minimum longitudinal reinforcement in column as per IS 456

Amit Anand Agrahari — Tue, 26 Jul 2022 10:37:52 GMT

Hello Mr Abhishek M

As advised by you, I raised a service request on Jul 01 2022.

My SR 7001439902 has been assigned to Mr Sanjib Das.

It is still pending.

Can you please ask Mr Das to resolve the issue at the earliest as there is no option to raise the query to higher levels.

RE: Minimum longitudinal reinforcement in column as per IS 456

Abhisek M — Fri, 01 Jul 2022 09:55:58 GMT

I have explained what is followed in STAAD. Now using those results in your project in your engineering judgement. If you need more discussion please raise a service request. Our team will get in touch with you.

You may go through the attached wiki to know the process of raising SR.

https://communities.bentley.com/products/w/products__wiki/24845/service-request-manager5

RCDC is now used by a lot of practicing engineers all over the world.

RE: Minimum longitudinal reinforcement in column as per IS 456

Amit Anand Agrahari — Fri, 01 Jul 2022 09:39:00 GMT

Dear Sir,

Please do reply. I have to submit my project for execution.

Regards

RE: Minimum longitudinal reinforcement in column as per IS 456

Amit Anand Agrahari — Thu, 30 Jun 2022 06:59:19 GMT

Dear Sir,

I need a specific reply.

When STAAD provides %steel less than as specified in clause 26.5.3.1 (a) of IS 456:2000 in output, if it is justified under clause 26.5.3.1 (b) of IS 456:2000 or not?

If yes, please take up case for update in STAAD software to add remarks to this effect in output file.

If no, please take up case for update in STAAAD software to flash error/warning message post analysis.

Secondly, no one in my knowledge uses RCDC as it provides too conservative result.
Regards

RE: Minimum longitudinal reinforcement in column as per IS 456

Abhisek M — Wed, 29 Jun 2022 08:20:21 GMT

In STAAD minimum reinforcement is considered as 0.8% on the required area of concrete and not the actual area. In your case gross cross section is 400x400mm , which is 160000sqmm area. 0.8% reinforcement of that area will be 1280sqmm. But the required concrete area to resist the direct stress is 14440 sqmm. So, minimum reinforcement required 0.85 of 14440 = 115.52 sqmm. But as per design requirement 4-16dia bar has been prvided whisch is nearly 804sqmm, which corresponds to 804/160000 = 0.5% of gross area.

If you still need to increase the reinforcement to .8% of gross area, please do it manually.

Also, I would recommend using STAAD Advanced Concrete Design (RCDC) to use for such design. Please refer below link to know more about it.

https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/31797/staad-advanced-concrete-design-rcdc

RE: Minimum longitudinal reinforcement in column as per IS 456

Amit Anand Agrahari — Wed, 29 Jun 2022 04:11:19 GMT

Dear sir

I need little more clarification.

Please find below result of concrete design of one of the columns from the project posted in first query.

I understood the design philosophy. However my query is about the above result.

The result says to provide 0.50% of steel i.e.; 804.25 Sq mm (4-16 dia bars) against reqd steel area of 115.63 Sq mm only.

The Interaction Ratio provided also changes from 0.93 to 0.23.

Do you mean to say that only 0.50% steel is OK as against 0.80% steel??

Or do I need to check and change % steel of each and every column??

Please reply at the earliest, my project is being delayed.

Regards.

----------------------------------------------------------------------------------------------------------------------------

IS-13920 L I M I T S T A T E D E S I G N
C O L U M N N O. 321 D E S I G N R E S U L T S

M30 Fe500 (Main) Fe500 (Sec.)

LENGTH: 1500.0 mm CROSS SECTION: 400.0 mm X 400.0 mm COVER: 45.0 mm

** GUIDING LOAD CASE: 146 END JOINT: 183 SHORT COLUMN

REQD. STEEL AREA : 115.53 Sq.mm.
REQD. CONCRETE AREA: 14440.68 Sq.mm.
MAIN REINFORCEMENT : Provide 4 - 16 dia. (0.50%, 804.25 Sq.mm.)
(Equally distributed)
CONFINING REINFORCEMENT : Provide 12 mm dia. rectangular ties @ 95 mm c/c
over a length 450.0 mm from each joint face towards
midspan as per IS-13920.
2 number overlapping hoops or a single hoop
with crossties are provided along Y direction.
(As per IS-13920)
2 number overlapping hoops or a single hoop
with crossties are provided along Z direction.
(As per IS-13920)
Additional 4 nos. longitudinal bars have been introduced.
TIE REINFORCEMENT : Provide 8 mm dia. rectangular ties @ 200 mm c/c

SECTION CAPACITY BASED ON REINFORCEMENT REQUIRED (KNS-MET)
----------------------------------------------------------
Puz : 2201.76 Muz1 : 18.91 Muy1 : 18.91

INTERACTION RATIO: 0.93 (as per Cl. 39.6, IS456:2000)

SECTION CAPACITY BASED ON REINFORCEMENT PROVIDED (KNS-MET)
----------------------------------------------------------
WORST LOAD CASE: 126
END JOINT: 183 Puz : 2450.74 Muz : 66.87 Muy : 66.87 IR: 0.23

RE: Minimum longitudinal reinforcement in column as per IS 456

Abhisek M — Tue, 28 Jun 2022 12:46:35 GMT

Please refer the below link to know the column design methodology adopted in STAAD.

https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/23169/is-456-column-design-philosophy