AMIE Section B Civil cheat sheet

Civil Engineering: Structural, Geotechnical, Hydraulic and Materials Essentials

• Flexural design of a singly reinforced rectangular section: Mu = 0.87 fy As (d - 0.42 xu), with xu/d limited to 0.48 (Fe415) or 0.53 (Fe250) for under-reinforced behaviour; lever arm z = d - 0.42 xu.

• Shear: nominal shear stress tv = Vu/(b d); for M20 concrete with 0.15-3.0% steel, tc ranges from 0.28 to 0.82 N/mm2; the maximum shear stress limit is 2.8 N/mm2 for M20 and 3.1 N/mm2 for M25.

• Terzaghi bearing capacity for a strip footing: qult = c Nc + q Nq + 0.5 gamma B Ngamma, with Nq = e^(pi tan phi) tan^2(45 + phi/2), Nc = (Nq - 1) cot phi.

• Standard Proctor test uses a 2.6 kg rammer dropped 310 mm in three layers of 25 blows; Modified Proctor uses a 4.89 kg rammer dropped 450 mm in five layers of 25 blows, giving roughly 15-20% higher maximum dry density.

• Consistency limits: plasticity index PI = LL - PL; a soil is classified as inorganic clay of low to medium plasticity (CL) when LL < 50 and PI > 7 and above the A-line (PI = 0.73(LL - 20)).

• Cement: initial setting time must be at least 30 minutes and final setting time not more than 600 minutes; soundness by Le Chatelier expansion must not exceed 10 mm; ordinary Portland cement 33 grade has 28-day compressive strength of at least 33 MPa.

• Concrete mix design: target mean strength fck' = fck + 1.65 s; water-cement ratio controls strength (Abrams' law); workability measured by slump (25-75 mm for normal RCC) or compaction factor (0.80-0.92).

• Open-channel flow: Manning's equation V = (1/n) R^(2/3) S^(1/2); the most efficient trapezoidal section has hydraulic radius R = y/2 and half the top width equal to the side slope length.

• Surveying and levelling: the rise-and-fall method computes reduced levels from backsight and foresight differences; the prismoidal correction for a level section is (D/6)(h1 - h2)^2 multiplied by the side slope, subtracted from the trapezoidal volume.