# Civil Engineering - RCC Structures Design - Discussion

### Discussion :: RCC Structures Design - Section 1 (Q.No.18)

18.

Dimensions of a beam need be changed if the shear stress is more than

 [A]. 10 kg/cm2 [B]. 15 kg/cm2 [C]. 20 kg/cm2 [D]. 25 kg/cm2

Explanation:

No answer description available for this question.

 Dayanand Pathak said: (Oct 3, 2013) As per table-20 in IS-456 maximum shear stress can be taken by M-15 concrete grade beam is 25kg/cm2.

 Arnab Chanda said: (Mar 23, 2014) But here it is not declared what type of grade is used.

 Abhishek said: (Dec 27, 2014) Then how will we guess it?

 Anuj said: (Feb 4, 2015) It is depend only on concrete grade. How can we decide?

 Rahul Yadav said: (Mar 4, 2015) Please anybody clear this question how we can decide grade we take M-25 then?

 Harishankar said: (Mar 9, 2015) How to estimate shear stress?

 Varun said: (Jul 6, 2015) As the maximum shear stress depends on the grade of concrete we use.

 Piyush Singh said: (Sep 3, 2015) First of all the grade of Concrete is not mentioned in the question, Assuming the grade of concrete to be M15 from table no 20 of IS 456, Page no 73, Maximum permissible shear stress for M15 grade is 2.5 N/mm^2 that will be 25 Kg/cm^2.

 Ankit said: (Aug 11, 2016) Please, someone explain permissible shear stress in RCC beam is 5 kg/cm^2 i.e safe in shear. If shear stress exceeds 20 kg/cm^2 then we redesign the section. So how you guys are saying for M15 grade concrete it is 25kg/cm^2?

 Pramit said: (Oct 19, 2016) As per my knowledge, it depends on the grade of concrete.

 Pramit said: (Apr 12, 2017) It's table 20 of IS 456.

 Samiran Mondal said: (Aug 22, 2017) FOR, M-15 SHEAR STRESS 2.8N/MM2.

 Arya. said: (Aug 26, 2017) Shear stress value is more 1.8 N/mm2. Then beam is redesign.

 Shridhar Rai said: (Oct 5, 2017) Acc to clause 40.2.3.1 for solid slabs nominal shear stress should not exceed half of the value of maximum shear stress i.e. (0.5*4)N/mm2 =2 N/mm2.

 Sourab Sharma said: (Oct 26, 2017) Maximum shear stress = 0.63(fck)^(1/2). For M10 grade of concrete = 1.999 n/mm^2.

 Dhruba said: (Feb 11, 2018) From IS 456:2000 table 20. We have, for Concrete grade M40 and above, maximum shear stress is 4 N/mm^2. Also from clause 40.2.3.1, we get to know that for solid slabs nominal shear stress should not exceed half the appropriate values given in Table.20. So, taking the maximum value of shear stress i.e.for M40 and above ----> 4 N/mm^2. We will obtain its half value to be 2 N/mm^2 (or 20kg/cm^2).

 Abhishek said: (Feb 25, 2018) Method is not specified so lets say WSM, Grade is not specified so lets say M15. Max permissible shear stress for M15 under WSM is 1.6 N/mm^2 . so all options are wrong.

 Ghalib said: (Mar 26, 2018) Yes, Agree @Sourab Sharma. Actually it is .63√(fck). So for higher grades, it will be the max.

 Rkrana said: (Mar 30, 2018) For beam, slab, column m15 grade is used and Max shear stress for m15 grade of concrete is 25kg/cm2. So option C is right.

 Ajay Kumar said: (Jun 10, 2018) Max shear stress of concrete= 0.63 under root fck. So, for M15 concert it should be; 0.63 x under root 15 = 2.5 N/mm^2.

 Akshay said: (Sep 11, 2018) As per IS 456-1978 section is redesigned if shear stress is greater than 20 kg/cm2 or 2N/mm2. So, the Given answer is correct.

 Rehan said: (Oct 2, 2018) The section is revised if shear stress is more than 0.4fc or 2 Mpa,and 2 Mpa is equal to 20kgper cm2.

 Biswajit said: (Feb 26, 2019) Here it is mentioned the term beam which is a reinforced concrete. Also as IS-466, for reinforced concrete minimum grade of concrete shall be M20. Hence, by considering this situation, the Tau Max shall be not more than 25 kg/sqcm.

 Niteesh Patel said: (May 28, 2019) M 40 τ max.=2.5 N/mm^2. M 30 τ max. =2.2 N/mm^2, M 15 τ max.= 1.6N/mm^2, Ans =(D)= 2.5N/mm^2.

 Avijit said: (Aug 26, 2019) Use the formula. τ max = 0.625 * √(fck).

 Amjid Ali said: (Sep 27, 2019) What is meant by (fck)? anyone tell me.

 Kamal Lochan Parida said: (Nov 17, 2019) Fck means the characteristic value of concrete. Which expressed in N/square mm.

 Engr Omid said: (Dec 12, 2019) If 5 kg/sq cm then no need of bars. If 5-20 kg/sq cm then use steel bars If more than 20 kg/sq cm then change the section dimension.

 Ramendra Singh said: (Jun 22, 2020) Tv = 20kg/cm^2 convert in N/mm^2, therefore, multiply by it 10^-1 and then convert into L.S.M by multiplying 1.5 =(2*1.5=3). Tcmax = for M20 we take because minimum we take, therefore, Tcmax=2.8 Tv>Tcmax therefore redesign the section.

 Vikram said: (Nov 29, 2020) The method is not specified so assume wsm. Grade not specified so assume m20( because it is the minimum grade for RCC structure) So the answer is 1.9n/mm2.

 Geetesh said: (Feb 4, 2021) The dimension of beam should be changed or the beam has to be redesigned if the value of maximum Shear stress (say tau max) Exceeds 20kg/cm square. This is the limiting value or max. Val of (tau max) for RC Beam.