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[RGurunathan]

neral@www.buonovino.com(general@www.buonovino.com)>



Dear All,

Sub : RCC members subjected to predominantly bending and low value of axial force (tension or compression)






Reinforcement calculation for beams subjected to predominantly bending along with low value of compression or tension has not been addressed in IS456/SP16 so far.The available charts will give the solution with equal reinforcement i.e Asc=Ast.This is not appropriate due to the following reasons.


#1- For members subjected to high value of M & low value of P, the solution for the reinforcement with Asc=Ast,generally corresponds to Xu= 0.2d approximately and the design is uneconomical since section is not effectively utilized. This attachment gives the procedure for calculation of Asc/Ast for such cases based on equilibrium equations and formulae also given.

#2- For members subjected to high value of M & low value of T,the solution for the reinforcement in SP16 with Asc=Ast is based on totally ignoring the concrete area which is very unfair.If we are to ignore the concrete area completely,then charts are not at all required Based on equilibrium, simple equation Asc=Ast= M/(0.87Fy X d1)+ T/(2 X 0.87Fy) is sufficient which is same as sp-16.This attachment gives the procedure for such cases and formulae also given.(without ignoring the concrete area)


#3 -At present software providers are giving the design without following any standard procedure. For the same member design, we are getting different values by different programmes. The professionals should ask for the validation of the programme used for the design from the vendors.They should also take up this matter with IS code revision committee so that this aspect is addressed in the code IS 456.




I request you to go through the attachment giving the procedure and the formulae for calculation of reinforcements in beams subjected to low value of axial force and share the same to other engineers.After due diligence if found to be correct,please take it forward for incorporation in IS 456 by writing to prof C V R Murthy of IIT Madras who is heading the IS 456 revision committee.


(I have also forwarded this to Prof CVR Murthy of IIT Madras, (Chairman for IS 456 Committee) and requested him to include the same in revised version of IS 456/ or by amendment.Wnen contacted over phone on 13 th dec 2022,he informed that same would be taken up in the next sitting of the committee members.)

With Regards,


RGurunathan-(9444398176)


(Formerly Lecturer in structural Engineering department,Annamalai University &
Retired Joint General Manager,L&T Construction Group)




On Thu, 19 Jan 2023 at 15:58, admin forum@www.buonovino.com)> wrote: