Question

Question:
What total cross sectional area of longitudinal reinforcing steel is required for a cement concrete
pavement slab 3.75 m wide, 15m long and 200 mm thick? The concrete weighs 2400 kg/m3.
working stress in steel is 1400 kg/cm2. coefficient of friction = 1.5.​

Answer 1

Answer:

Density = Weight/Volume.

The weight of slab = Density of concrete * Volume.

Density of concrete= 2400kg/m^3.

Volume = L*B*H = 1*7.5*0.2=1.5 m^3.

Weight of slab = 2400*1.5 = 3600kg.

This weight of slab should be equal to the force generated due to resisting stresses in the concrete slab.

Force generated = stresses * Area of steel (Ast).

Force generated = 1400*Ast = Weight of slab.

Ast = 3600/1400 =2.57 cm^2.

Considering 1cm diameter bars.

Area of 1 bar = (3.14/4)*1^2=0.785.

Spacing =( Area of 1 bar /Ast )*100 = 30.35cm ~ 30cm.