FE Civil flashcards

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

Average End Area Method

Earthwork volume formula V = L(A1 + A2)/2, where A1 and A2 are cross-section areas at each end and L is the distance between them.

Total Float

The amount of time an activity can be delayed without delaying project completion; calculated as late start minus early start (LS − ES).

Swell Factor

The percentage increase in volume when soil is excavated from its natural bank state to a loose state; used to convert bank volume to loose volume.

Water-Cement Ratio

The ratio of water mass to cement mass in a concrete mix; lower values increase strength and durability but reduce workability.

Slump Test

ASTM C143 test measuring concrete workability by the vertical settlement of a standard cone of fresh concrete after removal.

Critical Path

The longest-duration sequence of dependent activities through a project network; it determines the minimum project completion time and has zero float.

Effective Stress

The intergranular stress carried by soil particles, equal to total stress minus pore water pressure (σ' = σ − u); it controls soil strength and compression.

Void Ratio

The ratio of the volume of voids to the volume of solids in a soil mass; relates to porosity by e = n/(1−n).

Plasticity Index

The difference between liquid limit and plastic limit (PI = LL − PL); it indicates the range of water content over which soil behaves plastically.

Terzaghi Bearing Capacity

Equation qu = cNc + qNq + 0.5γBNγ giving ultimate bearing capacity of a shallow strip footing on soil with cohesion and friction.

Consolidation Settlement

Time-dependent compression of saturated clay under load as pore water is expelled; computed using compression index Cc and initial and final effective stresses.

Relative Density

Dr = (emax − e)/(emax − emin), expressing how densely a granular soil is packed relative to its loosest and densest states.

Factor of Safety Slope

The ratio of resisting shear strength to driving shear stress along a potential slip surface; values above about 1.5 are typically required.

Section Modulus

The ratio S = I/c of moment of inertia to distance from the neutral axis; bending stress equals moment divided by section modulus.

Euler Buckling Load

Pcr = π²EI/(KL)², the critical axial load at which a slender column becomes unstable, depending on effective length factor K.

LRFD Load Combination

Factored load U = 1.2D + 1.6L + 0.5(Lr or S or R), combining dead, live, and roof or environmental loads with load factors.

Whitney Stress Block

Simplified rectangular compressive stress distribution in concrete with depth a = As·fy/(0.85·f'c·b), used to compute nominal flexural strength.

Nominal Moment Strength

For a singly reinforced concrete section, Mn = As·fy·(d − a/2), the internal couple formed by tension steel and the concrete stress block.

Maximum Beam Deflection

For a simply supported beam with uniform load, midspan deflection is δ = 5wL⁴/(384EI), where EI is flexural rigidity.

Method of Sections

Truss analysis technique that cuts through three members and uses equilibrium equations on one free body to find member forces.

Degree of Curve

The central angle subtended by a 100-ft arc; radius relates to degree of curve by R = 5729.58/D for US customary units.

Superelevation Equation

e + f = V²/(15R), relating superelevation rate, side friction factor, design speed in mph, and curve radius in feet.

Stopping Sight Distance

Distance for a driver to perceive, react, and stop: SSD = 1.47Vt + V²/(30(f ± G)), with reaction time t and grade G.

Traffic Flow Relationship

Fundamental relation q = k·v, where q is flow rate, k is density, and v is space mean speed; also used to compute headways.

Level of Service

A qualitative grade from A to F describing traffic operating conditions; for freeways it is based primarily on density in passenger cars per mile per lane.

ESAL

Equivalent Single Axle Load; converts a mixed traffic stream into the number of 18-kip standard axle loadings used in pavement design.

Rational Method

Peak runoff formula Q = CiA, where C is runoff coefficient, i is rainfall intensity, and A is drainage area in acres yielding cubic feet per second.

Manning's Equation

Open-channel flow formula Q = (1.486/n)·A·R^(2/3)·S^(1/2) in US customary units, using roughness n, area, hydraulic radius, and slope.

Time of Concentration

The time for runoff to travel from the most hydraulically remote point of a watershed to the outlet; estimated by Kirpich or similar methods.

Ultimate BOD

The total oxygen demand exerted by a wastewater sample after complete biological oxidation; related to BODt by BODt = BODu(1 − e^(−kt)).

Solids Retention Time

Average time biomass remains in an activated sludge system; SRT = (V·X)/(Qw·Xr + Qe·Xe), controlling sludge age and treatment performance.

Darcy-Weisbach Head Loss

Pipe friction loss hf = f·(L/D)·(V²/2g), where f is the friction factor, L length, D diameter, and V flow velocity.