Question

A 40-mm cube with its lower face fixed to the ground. A positive shear force of 6.4 kN acts on the top surface of cube. Draw the shear stress distribution on the vertical face of the cube (fig 1.10).

Answer 1

Shear force,

F = 6.4 kN = 6,400 N

Area of the top surface = 40 × 40 = 1,600mm2

hear stress, τ = +6, 400/1,600

= + 4N/mm2 (as shown)

Shear stress on the vertical face CBEF = τ′ = - 4N/mm2

Shear stress distribution on vertical surface is τ′ = - 4MPa (uniform)

Shear stress tends to rotate the body in anticlockwise direction. Figure 1.11 shows the shear stress distribution on face ABCD.

Students should learn how to draw complementary shear stress. Many a times in interviews, they fail to explain the concept of complementary shear stresses.