Q1: In R.C. sewer pipes, the percentage longitudinal reinforcement to the cross-sectional area of concrete is kept

ANS:D - 0.25

In Reinforced Concrete (R.C.) sewer pipes, the percentage of longitudinal reinforcement to the cross-sectional area of concrete is typically kept around 0.25%. Reinforced concrete sewer pipes are designed to withstand various loads, including the weight of the soil above them, traffic loads, and internal hydrostatic pressure from the wastewater flowing inside. Longitudinal reinforcement, usually in the form of steel bars or rods, is added to enhance the tensile strength and ductility of the concrete pipes. The percentage of longitudinal reinforcement is generally low, typically around 0.25% of the cross-sectional area of the concrete. This level of reinforcement is sufficient to provide adequate tensile strength and structural integrity to the sewer pipes while keeping the overall cost and weight of the pipes manageable. Higher percentages of reinforcement may lead to increased stiffness and reduced flexibility, which can make the pipes more susceptible to cracking and failure under certain conditions. Therefore, the percentage of longitudinal reinforcement is carefully selected based on the specific design requirements and structural considerations of the sewer system.