KPSC AE Civil flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Section modulus

Ratio of moment of inertia to the distance of the extreme fibre from the neutral axis, Z = I/y. Bending stress equals bending moment divided by section modulus.

Euler buckling load

Critical axial load for a slender column, P_cr = π²EI/L_eff². The effective length depends on end conditions: fixed-fixed gives 0.5L, fixed-free gives 2L.

Parallel axis theorem

Moment of inertia about any axis equals that about a parallel centroidal axis plus area times the square of the distance between the axes: I = I_c + A d².

Strain energy

Energy stored in a member during elastic deformation, equal to half the product of load and extension for axial loading. Proof resilience is its value at the elastic limit per unit volume.

Müller-Breslau principle

The influence line for a stress resultant or reaction equals the deflected shape obtained when a unit displacement is introduced at the release corresponding to that function.

Static indeterminacy of frames

For a plane frame, degree of static indeterminacy equals 3m + r − 3j, where m is number of members, r reactions and j joints.

Three-hinged arch

A statically determinate arch with hinges at both supports and the crown. Bending moment at any section equals simple beam moment minus horizontal thrust times rise.

Slope-deflection equation

Relates end moments of a member to end rotations and relative displacement, including fixed-end moments. It forms the basis of the slope-deflection method of analysis.

Limiting neutral axis depth

Maximum x_u/d for a singly reinforced section at the limit state of collapse: 0.53 for Fe 250, 0.48 for Fe 415 and 0.46 for Fe 500 steel.

Development length

Embedded length needed to develop bar stress without slip, L_d = φσ_s/(4τ_bd). A standard 90-degree bend provides an anchorage value of eight bar diameters.

Partial safety factor for steel

In IS 800 limit state design, γ_m0 equals 1.10 applied to yield strength and γ_m1 equals 1.25 applied to ultimate strength of steel.

Plastic section modulus

First moment of the full cross-sectional area about the equal-area axis, denoted Z_p. The shape factor is the ratio of plastic to elastic section modulus.

Reynolds number

Dimensionless ratio of inertia to viscous forces, Re = ρVD/μ. Pipe flow is laminar below about 2000 and turbulent above about 4000.

Hydraulic jump

Rapid transition from supercritical to subcritical flow with energy dissipation. Conjugate depths follow y2/y1 = 0.5(√(1+8F1²) − 1).

Most efficient trapezoidal section

Channel section giving maximum discharge for a given area. For a trapezoid, hydraulic radius equals half the flow depth and half the top width equals the side length.

Centre of pressure

Point where the resultant hydrostatic force acts on a submerged plane. Its depth below the free surface exceeds the centroid depth by I_G/(A h̄).

Rational method

Estimates peak runoff as Q = CiA/3.6, where C is runoff coefficient, i rainfall intensity in mm/h and A catchment area in square kilometres.

Unit hydrograph

Direct runoff hydrograph from one unit depth of rainfall over a specified duration. Ordinates scale linearly with rainfall depth while the time base stays unchanged.

Phi index

Constant infiltration loss rate, in mm/h, such that rainfall minus loss equals the observed direct runoff volume for a storm.

Return period risk

Probability that a T-year event is exceeded at least once in n years equals 1 − (1 − 1/T)^n, assuming independent annual events.

Terzaghi bearing capacity

Ultimate bearing pressure of a strip footing equals cN_c + qN_q + 0.5γBN_γ, with shape factors reducing the last term for square and circular footings.

Critical hydraulic gradient

Gradient at which upward seepage reduces effective stress to zero, causing quicksand. It equals (G − 1)/(1 + e) for soil of specific gravity G and void ratio e.

Coefficient of consolidation

C_v = T_v d²/t, obtained from the time-settlement curve. Time factor is 0.197 for 50% and 0.848 for 90% consolidation.

Group efficiency of piles

Ratio of the capacity of a pile group to the sum of individual pile capacities. It may be computed by the Converse-Labarre formula using spacing and number of piles.

Stopping sight distance

Distance for a driver to stop after seeing an obstruction, equal to lag distance plus braking distance. Reaction time of 2.5 s and friction factor are used.

Superelevation

Transverse slope provided on horizontal curves to counter centrifugal force, e = v²/(127R) − f with speed in km/h. Maximum is 7% on plain terrain.

CBR test

California Bearing Ratio compares penetration load of a soil or pavement sample to standard crushed stone load, expressed as a percentage at specified penetrations.

BOD5

Biochemical oxygen demand measured at 20 degrees Celsius over five days. It indicates biodegradable organic matter and follows first-order exertion kinetics.

Overflow rate

Settling tank design parameter equal to discharge divided by surface area. Particles with settling velocity above the overflow rate are completely removed.

Vicat apparatus

Instrument used to determine standard consistency, initial setting time and final setting time of cement paste using a plunger or needle under specified conditions.

Bulking of sand

Increase in apparent volume of moist sand due to water films around particles, maximum near 4–6% moisture. Volume batching must correct for it.

Prismoidal rule

Volume formula V = h/3[(A1 + An) + 4(sum of odd sections) + 2(sum of even sections)], more accurate than the trapezoidal rule for earthwork computation.

Cost performance index

Earned value management ratio CPI = EV/AC. A value below one means the project is spending more than the value earned so far.