Prestressed Concrete Structures Multiple Choice Questions on “Design of Shear Reinforcement”.
1. The ultimate shear resistance for any given section, vc should be least of values __________
a) vcw and vcf
b) vew and vef
c) vrw and vrf
d) vdw and vdf
Clarification: At any given section, the ultimate shear resistance, vc should be the least of values vcw and vcf where, vcw = ultimate shear resistance of section cracked in web, vcf = ultimate shear resistance of section cracked in flange.
2. What should be provided if the shear force due to ultimate load is less than the shear force of the concrete?
a) Tensile reinforcement
b) Shear reinforcement
c) Principle reinforcement
d) Compressive reinforcement
Clarification: When V the shear force due to ultimate loads is less than the shear force of the concrete vc, the shear force which can be carried by the concrete, a minimum shear reinforcement should be provided in the form of stirrups with spacing.
3. The spacing provided for shear reinforcement is given as __________
a) Sv = (Asv0.87fy/0.4b)
Clarification: The spacing provided for shear reinforcement Sv = (Asv0.87fy/0.4b), Sv = spacing of stirrups along the length of member, Asv = cross sectional area of stirrup legs effective in shear, b = breadth (for T,I,L beams it is taken as breadth of rib, bw).
4. When the shear force due to ultimate loads is less than 0.5 times shear force of concrete then shear reinforcement is?
b) Not provided
c) Made equal
d) Made zero
Clarification: When the shear force due to ultimate loads V is less than 0.5 times the shear force of concrete: (v < 0.5vc)
Then no shear reinforcement is provided in the members of low importance.
5. When v > vc condition exits, then the shear reinforcement provided includes which extra terms than actual spacing equation?
a) fy, dt, v, vc
b) ft, dt, v, vc
c) dt, v, vc
d) fe, dt, v, vc
Clarification: When V exceeds Vc shear reinforcement is required conforming to the relation (V > Vc)
The extra terms used are fy , dt, v, vc these are included in the spacing equation Sv
Sv = (Asv0.87fydt / V-Vc).
6. The term dt in the spacing equation is termed as __________
a) Lowest value of depth
b) Neutral value of depth
c) Highest value of depth
d) Peak value of depth
Clarification: When v > vc, the spacing provided in that:
dt is the highest value of depth from the extreme compression fiber to longitudinal bars and depth from extreme compression fiber to centroid of tendons.
7. The spacing of stirrups for maximum shear stress is __________
Clarification: The spacing of stirrups should exceed neither 0.75dt nor 4 times the web thickness of flanged members, for maximum shear stress the spacing of stirrups:
Sv > 0.75dt = > x web thickness.
8. The maximum spacing (Sv)max is provided for the condition is?
a) V > 1.8Vc
b) V > 1.5Vc
c) V > 2.0Vc
d) V > 3.5Vc
Clarification: When V exceeds 1.8Vc, the maximum spacing should be reduced to 0.5dt, the lateral spacing of the individual legs of the stirrups provided at a cross section should not exceed 0.75dt, if V > 1.8Vc, the maximum spacing is:
(Sv) max = 0.5 dt.
9. The maximum shear stress value for M35 and M50 is?
a) 3.5 and 4.0
b) 3.7 and 4.6
c) 3.8 and 6.0
d) 4.2 and 4.0
Clarification: The maximum shear stress value for M35 grade concrete is 3.7n/mm2, the maximum shear stress value for M50 grade concrete is 4.6n/mm2, M30 grade concrete is 3.5n/mm2, M40 grade concrete is 4.0n/mm2, M45 grade concrete is 4.3, M55 grade concrete is 4.8n/mm2.
10. The section should be redesigned if the nominal shear stresses __________
a) Exceeds the given values
Clarification: When the nominal shear stress, v/bd exceeds the maximum permissible shear stress values for the particular grades of concrete like M-30, M-35, M-40, M-45, M-50, M-55 and above then the section should be redesigned (this is according to table of maximum shear stress(n/mm2) (IS: 1343-1980).