A singly reinforced concrete beam of 25 cm width and 70 cm effective depth is provided with 18.75 cm2 steel. If the modular ratio (m) is 15, the depth of the neutral axis, is
A. 20 cm
B. 25 cm
C. 30 cm
D. 35 cm
Answer: Option C
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Distribution of shear intensity over a rectangular section of a beam, follows:
A. A circular curve
B. A straight line
C. A parabolic curve
D. An elliptical curve
If the shear stress in a R.C.C. beam is
A. Equal or less than 5 kg/cm2, no shear reinforcement is provided
B. Greater than 4 kg/cm2, but less than 20 kg/cm2, shear reinforcement is provided
C. Greater than 20 kg/cm2, the size of the section is changed
D. All the above
In a pre-stressed member it is advisable to use
A. Low strength concrete only
B. High strength concrete only
C. Low strength concrete but high tensile steel
D. High strength concrete and high tensile steel
In a simply supported slab, alternate bars are curtailed at
A. $${\frac{1}{4}^{{\text{th}}}}$$ of the span
B. $${\frac{1}{5}^{{\text{th}}}}$$ of the span
C. $${\frac{1}{6}^{{\text{th}}}}$$ of the span
D. $${\frac{1}{7}^{{\text{th}}}}$$ of the span
0.36*fck*xu*b=0.87*fy*Ast
xu=0.87*m*Ast/(0.36*b)
=0.87*15*18.75/(0.36*25)
=27.2 cm
=30 cm
0.5*b n^2 = m Ast (d-n).
0.5 25*n^2 = 15 *18.75 (70-n).
12.5*n^2 = 19425-281.25n.
By solving n = 30cm.
Formula : 0.5bn^2=mAst(d-n)
Please give me a solution