The use of longitudinal steel or spirals independent of each or does not increase ultimate torsional resistance but when both longitudinal steel and spirals are provided in prestressed members, ultimate torsional resistance is enhanced and according can be expressed as T_tp + T_ts, where T_tp is torsional resistance moment of prestressed concrete section and T_ts is additional torsional resistance moment of non-prestressed reinforcement, which must consist of spirals and longitudinal steel.

The maximum shear stress value for M₃₅ grade concrete is 3.7n/mm², 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.

Research over years have shown that re are two major modes of shear cracking in structural concrete beams, web shear cracks, flexure shear cracks and different modes of shear failure patterns are also considered like diagonal tension failure, shear compression failure, web compression failure.

When V shear force due to ultimate loads is less than shear force of concrete v_c, shear force which can be carried by concrete, a minimum shear reinforcement should be provided in form of stirrups with spacing.

In order to protect a member from collapsing suddenly after development of shear crack, a minimum shear reinforcement is provided (A_sv) is provided in form of stirrups which is obtained by satisfying following condition:
A_sv/b_sv = 0.4/0.87f_y
In member without shear reinforcement, inclined shear cracks extend to compression face resulting in sudden explosive failure this is sometimes referred to as diagonal tensile modes of failure.

The failure of a prestressed concrete member without additional un tensioned reinforcement, under pure torsion, is more or less similar to that of plain concrete where sudden failure is imminent almost simultaneously with formation of first crack.

cracks are observed at point of development of maximum shear stresses diagonally. The effect of this maximum shear stress (? _v) also produces principle tensile stresses on diagonal plane, calculation of principle tensile stress resulting from direct at critical sections with or without bending and shear combined shall be carried out it is also done at material change in width of section and should be less than 0.126(f_c)^1/2.

When nominal shear stress, v/bd exceeds maximum permissible shear stress values for particular grades of concrete like M-30, M-35, M-40, M-45, M-50, M-55 and above n section should be redesigned (this is according to table of maximum shear stress(n/mm²) (IS: 1343-1980).

A = (120�300) = 36�10³ mm², I = 27�10⁷ mm⁴, W_d = 5kn/m
Shear force at support V = (5�10/2) = 25kn
Maximum shear stress at support, ?_v = (3v/2bh) = (3/2)x(25�10³ /120�300) = 1.05n/mm².

The relation for computing ultimate shear force, which includes a multiplying factor to multiplying factor to account for type of concrete is given as V_cw = b_w d_p((0.3?)f_cy^1/2 + 0.3f_cp)+ v_p
B_w = breadth of web, d_p = effective depth to tender or 0.8h, ? = 1.0 for nominal weight concrete and less for light weight concrete, f_cy = cylinder compressive strength of concrete(n/mm²), f_cp = compressive prestress at centroid of a section, v_p = vertical component of effective prestressing force at section.