Civil Engineering - Structural, Geotechnical and Hydraulic Structures
Civil Engineering covers structural analysis and design, soil mechanics and foundations, and hydraulic structures. The exam tests bending and shear, concrete and steel design basics, effective stress, bearing capacity, dams and spillways.
Structural
For a simply supported beam with UDL w over L, M_max = wL²/8 and V_max = wL/2. A balanced RCC section uses concrete and steel reaching permissible strains together; an under-reinforced section fails by steel yielding and gives warning. Limit-state design uses partial safety factors.
Geotechnical
Effective stress: σ′ = σ − u. Terzaghi bearing capacity: q_u = cN_c + γD_fN_q + 0.5γBN_γ. Compaction increases dry density; consolidation is time-dependent settlement. Shear strength: τ = c + σ′tan φ.
Hydraulic structures
Gravity dams resist overturning, sliding and uplift; spillways must pass the design flood. Weirs and barrages use creep and exit-gradient checks. Canal design uses Kennedy or Lacey silt theories.
Worked example
Soil has γ = 18 kN/m³; the water table is 2 m below ground; find effective stress at 5 m. Total stress = 18 × 5 = 90 kPa. Pore pressure = 9.81 × (5 − 2) = 29.43 kPa. Effective stress = 90 − 29.43 = 60.57 kPa. If capillary rise is present above the water table, negative pore pressure increases effective stress, a common trap.
Traps
Using total unit weight below the water table instead of submerged unit weight; forgetting uplift in dam stability; mixing working-stress and limit-state methods; and ignoring the difference between bearing capacity and allowable bearing pressure.