PE Civil flashcards

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

Water-cement ratio

Ratio of water mass to cementitious material mass in a concrete mix; lower values increase compressive strength and durability but reduce workability.

Slump test

ASTM C143 procedure that measures concrete consistency from the vertical settlement of a molded cone, used to judge workability against the specified slump.

Critical path method

Network scheduling technique in which the critical path is the longest-duration path; its activities have zero total float and determine project completion time.

Trench protective system requirement

OSHA requires sloping, benching, shoring, or shielding for excavations 5 ft deep or more, plus a ladder or ramp within 25 ft of lateral travel.

Cost performance index

Earned value divided by actual cost (CPI = EV/AC); a value below 1.0 indicates the completed work cost more than the amount budgeted.

Standard Proctor test

ASTM D698 laboratory compaction test using a 5.5-lb hammer, 12-in. drop, 3 layers and 25 blows; it establishes maximum dry density and optimum moisture content.

Effective stress principle

Total vertical stress minus pore water pressure (sigma' = sigma - u); it governs consolidation, shear strength, and lateral earth pressures in saturated soils.

Terzaghi bearing capacity equation

qu = c*Nc + q*Nq + 0.5*gamma*B*Ngamma for a strip footing; the N factors depend on friction angle and weight cohesion, surcharge, and soil self-weight.

Rankine active earth pressure

Ka = tan^2(45 deg - phi/2); this is the horizontal-to-vertical effective stress ratio when the wall moves away from the soil enough to mobilize failure.

Plasticity index

PI = LL - PL, the range of water content over which a soil behaves plastically; PI of 30 or more with LL of 50 or more indicates a high-plasticity clay.

Standard penetration test

A 2-in. split spoon is driven 18 in. by a 140-lb hammer falling 30 in.; N is the blow count for the final 12 in. of penetration.

Consolidation settlement equation

Sc = [Cc*H/(1 + e0)] * log10[(sigma'0 + delta-sigma)/sigma'0]; it gives one-dimensional primary settlement of a clay layer from an added effective stress.

Liquefaction susceptibility

Saturated loose to medium clean sands with low corrected SPT resistance and a shallow water table can lose shear strength under cyclic seismic loading and flow like a fluid.

Strength reduction factor phi

ACI 318 resistance factor: 0.90 for tension-controlled flexure, 0.75 for shear and torsion, and 0.65 for tied compression-controlled columns (0.75 for spiral columns).

Nominal flexural strength Mn

For a singly reinforced rectangular beam, Mn = As*fy*(d - a/2), where a = As*fy/(0.85*f'c*b) is the equivalent stress block depth.

Minimum flexural reinforcement

As,min = max(3*sqrt(f'c)/fy, 200/fy) * bw * d with stresses in psi; it prevents brittle flexural failure when computed steel area is small.

Tension-controlled section

A reinforced concrete section whose net tensile strain in the extreme steel layer at nominal strength is at least 0.005, permitting phi = 0.90.

LRFD basic load combination

1.2D + 1.6L plus other applicable cases; design requires the factored resistance phi*Rn to equal or exceed the factored load effect Ru.

Concrete shear strength Vc

For nonprestressed members without axial load, Vc = 2*sqrt(f'c)*bw*d in psi units; shear exceeding this requires stirrups or other shear reinforcement.

One-way slab minimum thickness

For fy = 60 ksi and normal-weight concrete: l/20 simply supported, l/24 one end continuous, l/28 both ends continuous, and l/10 for a cantilever.

Stopping sight distance

SSD = 1.47*V*t + V^2/[30*(f +/- G)] with V in mph; it is the distance to perceive a hazard, react, and brake to a stop.

Superelevation equation

e + f = V^2/(15*R) with V in mph and R in feet; it balances centripetal demand against the sum of superelevation rate and side friction factor.

Degree of curve to radius

R = 5729.58/D using the arc definition in U.S. customary units, so a 1-degree curve has a radius of approximately 5,730 ft.

Peak hour factor

PHF = peak-hour volume divided by four times the peak 15-minute volume; a value close to 1.0 indicates uniform flow within the peak hour.

Pavement structural number

SN = a1*D1 + a2*D2*m2 + a3*D3*m3; layer coefficients a and drainage coefficients m convert layer thicknesses into required structural capacity.

Level of service grades

LOS A through F describe traffic operations from free flow with low density (A) through at-capacity conditions (E) to breakdown or forced flow (F).

Manning equation

Q = (1.486/n)*A*R^(2/3)*S^(1/2) in U.S. customary units, where R is hydraulic radius (area divided by wetted perimeter) and S is channel slope.

Rational method

Q = C*i*A estimates peak runoff in cfs when i is rainfall intensity in in/hr and A is drainage area in acres; C is a dimensionless runoff coefficient.

Froude number

Fr = V/sqrt(g*D) with D the hydraulic depth; values below 1 are subcritical, equal to 1 critical, and above 1 supercritical open-channel flow.

BOD exertion equation

BODt = L0*(1 - e^(-k*t)), where L0 is the ultimate carbonaceous demand, k is the first-order rate constant, and t is time in days.

Chlorine demand

The difference between the chlorine dose applied and the residual chlorine remaining after contact; demand reflects consumption by organisms and reducing substances in the water.

SCS curve number runoff

Q = (P - 0.2S)^2/(P + 0.8S) with S = 1000/CN - 10, all in inches; CN ranges from about 30 to 100 by hydrologic soil group and land use.