Concrete structures miscellaneous Easy Questions and Answers

Concrete structures miscellaneous

Which one of the following is categorised as a long-term loss of pre-stress in a pre-stressed concrete member?

1. Loss due to elastic shortening
1. Loss due to friction
1. Loss due to relaxation of strands
1. Loss due to anchorage slip

Consider a reinforcing bar embedded in concrete. In a marine environment this bar undergoes uniform corrosion, which leads to the deposition of corrosion products on its surface and an increase in the apparent volume of the bar. This subjects the surrounding concrete to expansive pressure. As a result, corrosion induced cracks appear at the surface of concrete. Which of the following statements is TRUE?

1. Corrosion causes circumferential tensile stresses in concrete and the cracks will be parallel to the corroded reinforcing bar.
1. Corrosion causes radial tensile stresses in concrete and the cracks will be parallel to the corroded reinforcing bar.
1. Corrosion causes circumferential tensile stresses in concrete and the cracks will be perpendicular to the direction of the corroded reinforcing bar.
1. Corrosion causes radial tensile stresses in concrete and the cracks will be perpendicular to the direction of the corroded reinforcing bar.

Consider two RCC beams, P and Q, each having the section 400 mm × 750 mm (effective depth, d = 750 mm) made with concrete having a &tau_cmax = 2.1 N/mm². For the reinforcement provided and the grade of concrete used, it may be assumed that the &tau_c = 0.75 N/mm². The design shear in beam P is 400 kN and in beam Q is 750 kN. Considering the provisions of IS 456: 2000, which of the following statements is TRUE?

1. Shear reinforcement should be designed for 175 kN for beam P and the section for beam Q should be revised.
1. Nominal shear reinforcement is required for beam P and the shear reinforcement should be designed for 120 kN for beam Q.
1. Shear reinforcement should be designed for 175 kN for beam P and the shear reinforcement should be designed for 525 kN for beam Q.
1. The sections for both beams P and Q need to be revised.

Select the strength parameter of concrete used in design of plain jointed cement concrete pavements from the following choices.

1. Tensile strength
1. Compressive strength
1. Flexural strength
1. Shear strength

The following statements are related to temperature stresses developed in concrete pavement slabs with free edges (without any restraint):
P. The temperature stresses will be zero during both day and night times if the pavement slab is considered weightless
Q. The temperature stresses will be compressive at the bottom of the slab during night time if the self-weight of the pavement slab is considered
R. The temperature stresses will be compressive at the bottom of the slab during day time if the self-weight of the pavement slab is considered
The TRUE statement(s) is (are)

τ_v =	p	=	4 × 10³
	bd		450 × 750

For Q, τ_r =	Q	=	750 × 10³	= 2.5 N/mm²
	bd		750 × 400

τ_v =	p	=	4 × 10³
	bd		450 × 750

For Q, τ_r =	Q	=	750 × 10³	= 2.5 N/mm²
	bd		750 × 400