BTSC JE Civil flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Modular brick dimensions
- A modular brick measures 190 × 90 × 90 mm; with a 10 mm mortar joint the nominal size becomes 200 × 100 × 100 mm, simplifying masonry quantity calculations.
- Fat lime vs hydraulic lime
- Fat lime is nearly pure calcium oxide, slakes vigorously and doubles in volume; hydraulic lime contains clay impurities that give it the ability to set and harden under water.
- English bond
- A brick masonry bond with alternate courses of headers and stretchers. It is the strongest bond and is preferred for walls of one brick thickness or more.
- Section modulus
- The ratio of moment of inertia to the distance of the extreme fibre from the neutral axis, Z = I/y. Bending stress equals M/Z, so a larger Z reduces stress.
- Euler buckling load
- The critical load at which a slender column buckles elastically: P_cr = π²EI/L_eff², where L_eff depends on end conditions, such as 0.5L for fixed-fixed ends.
- Characteristic strength of concrete
- The compressive strength in N/mm² below which not more than 5 percent of test results fall. M20 concrete has a characteristic cube strength of 20 N/mm² at 28 days.
- Limit state method
- A design approach using partial safety factors on loads and materials, checking collapse and serviceability limit states. It is the current basis of IS 456 reinforced concrete design.
- Development length
- The embedded length of reinforcement needed to develop its design stress in the surrounding concrete without pull-out, computed as φσ_s/(4τ_bd) and used to detail laps and anchorage.
- Plastic section classification
- A steel cross-section that can develop its full plastic moment and rotate without local buckling. IS 800 classifies sections as plastic, compact, semi-compact or slender by width-to-thickness ratios.
- Fillet weld throat thickness
- The effective throat of a fillet weld equals 0.7 times the nominal weld size, measured perpendicular to the weld face, and governs the weld's design strength.
- Void ratio
- The ratio of the volume of voids to the volume of solids in a soil mass, e = V_v/V_s. It relates to porosity by n = e/(1+e).
- Plasticity index
- The difference between the liquid limit and the plastic limit of a soil. It indicates the range of water content over which the soil behaves plastically.
- Terzaghi bearing capacity
- The ultimate bearing pressure of a shallow strip footing: q_u = cN_c + γD_fN_q + 0.5γBN_γ, with factors depending on the soil friction angle.
- Critical hydraulic gradient
- The upward seepage gradient at which effective stress becomes zero and soil loses shear strength, causing quick sand. It equals (G−1)/(1+e).
- Bernoulli's equation
- For steady ideal flow along a streamline, p/γ + V²/2g + z remains constant. It expresses conservation of energy among pressure, velocity and elevation heads.
- Reynolds number
- A dimensionless ratio of inertial to viscous forces, Re = ρVD/μ. Pipe flow is laminar below about 2000 and turbulent above about 4000.
- Hydraulic jump
- A rapid transition from supercritical to subcritical flow that dissipates energy. Conjugate depths satisfy y₂/y₁ = 0.5(√(1+8F₁²) − 1).
- Rational method
- A peak discharge estimate Q = CiA/3.6, where C is the runoff coefficient, i the rainfall intensity in mm/h and A the catchment area in km².
- Duty and delta
- Duty is the irrigated area in hectares served per cumec of canal discharge; delta is the total depth of water applied. They relate as Δ = 8.64B/D.
- Unit hydrograph
- The direct runoff hydrograph produced by one centimetre of rainfall occurring uniformly over a catchment in a specified duration, used to derive flood hydrographs.
- Superelevation
- The transverse slope provided on horizontal curves to counter centrifugal force. Design value e = V²/(127R) − f, limited to 7 percent on plain terrain.
- Stopping sight distance
- The distance needed for a driver to stop a vehicle after seeing an obstruction, equal to the reaction distance plus braking distance. It governs highway geometric design.
- California Bearing Ratio
- A penetration test in which the load to force a standard piston into a soil sample is compared with standard values, expressed as a percentage and used in pavement design.
- Breakpoint chlorination
- The chlorine dose beyond which free residual chlorine increases proportionally with dose, after all reducing matter and ammonia have been oxidised.
- Self-cleansing velocity
- The minimum flow velocity in a sewer that prevents deposition of solids, typically 0.6 to 0.75 m/s. Maximum permissible velocity is about 3 m/s to limit scour.
- BOD of domestic sewage
- The five-day biochemical oxygen demand of typical domestic sewage is about 200 to 300 mg/L, indicating the oxygen needed by microbes to stabilise organic matter.
- Curvature correction
- The correction applied in levelling to reduce staff readings for Earth's curvature, equal to 0.0785d² metres for a distance d in kilometres. Refraction correction is one-seventh of it.
- Bowditch rule
- A traverse adjustment that distributes closing error in latitude and departure proportionally to the length of each side, used when angular and linear measurements are of comparable precision.
- Centre line method
- An estimating method that computes quantities along the centre line of walls of uniform thickness, multiplying length by breadth and depth, then adjusting for junctions.
- PERT expected time
- A probabilistic activity duration estimate using optimistic, most likely and pessimistic times: t_e = (O + 4M + P)/6, used in event-oriented PERT networks.
- Total float
- The amount of time an activity can be delayed without delaying project completion. It equals latest start minus earliest start, or latest finish minus earliest finish.
- Compound interest difference
- For two years, the difference between compound interest and simple interest on a principal P at rate R is P(R/100)², useful for quick aptitude calculations.