Question

To avoid sudden collapse just after a shear crack, minimum shear reinforcement is provided in prestressed concrete member in the form of stirrups. IS 1343 suggested the relation as ________. 

1. \(\frac{{{A_{sv}}}}{{b.{S_v}}} = \frac{{0 \cdot 4d}}{{0 \cdot 87fy}}\)
2. \(\frac{{{A_{sv}}}}{{bd.{S_v}}} = \frac{{0 \cdot 4d}}{{0 \cdot 87}} \times {f_y}\)
3. \(\frac{{{A_{sv}}}}{{b.{S_v}}} = \frac{{0 \cdot 4}}{{0 \cdot 87fy}}\)
4. \(\frac{{{A_{sv}}}}{{b.{S_v}}} = \frac{{0 \cdot 4{f_{ck}}}}{{0 \cdot 87fy}}\)

Answer 1

Correct Answer - Option 3 : \(\frac{{{A_{sv}}}}{{b.{S_v}}} = \frac{{0 \cdot 4}}{{0 \cdot 87fy}}\)

Concept:

Prestressed Concrete:

• Prestressed concrete is basically concrete in which internal stress of suitable magnitude and distribution are introduced so that. the stress resulting from the external load is counteracted ta the desired degree.
• Prestressed concrete is different from a conventional RCC structure due to the application of an initial load on the structure prior to its use.

Shear Reinforcement:

• According to IS:1343 - 1980, the minimum shear reinforcement is provided,
• When (V), the shear force due to the ultimate loads, is less than (V_C), the shear force which can be carried by the concrete, Minimum shear reinforcement should be provided in the form of stirrups such that:  

\(\frac{{{A_{sv}}}}{{b{s_v}}} = \;\frac{{0.4}}{{0.87{f_y}}}\) Where,

A_sv = Total cross-section area of strirup legs effective in shear.

b = breath of the member which T, I, and L beams should be taken as the breath of the rib,

S_v = Strriup spacing along the length of the member, and

f_y = Characteristic strength of the stirrup reinforcement which shall not be taken greater than 415 N/mm².

 

The shear reinforcement need not be provided in the following cases.

• Where V is less than 0.5 V_c, and,
• In members of minor importance.