PEC EPE Civil flashcards

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

Tension-controlled section

A reinforced concrete section whose extreme tension steel reaches net tensile strain of at least 0.005 at nominal strength, permitting a strength reduction factor of 0.90 for flexure.

Balanced reinforcement ratio

The steel ratio at which concrete crushing and steel yielding occur simultaneously; sections with ratios above this behave brittle and are generally not permitted for flexural design.

Effective moment of inertia

A reduced stiffness value used to compute deflection of a cracked reinforced concrete member; it transitions from gross to cracked moment of inertia as service moment exceeds the cracking moment.

Cracking moment

The bending moment that first produces tensile stress equal to the concrete modulus of rupture, computed as fr times the section modulus of the gross section.

One-way shear capacity

Nominal concrete shear strength for beams without axial load, based on the square root of compressive strength times web width and effective depth, plus contributions from shear reinforcement.

Development length

The embedment distance required to transfer bar force to concrete without pullout, depending on bar size, cover, spacing, concrete strength, and whether the bar is coated or epoxy.

Slenderness ratio in columns

The ratio of effective length to radius of gyration; when it exceeds a moment-dependent threshold, second-order moments must be included in the design.

Block shear rupture

A steel connection failure combining tensile rupture on one plane with shear yielding or rupture on a perpendicular plane, checked with gross and net areas.

Net effective area

The net cross-sectional area of a tension member after deducting bolt holes, multiplied by a shear lag factor that accounts for nonuniform stress transfer.

Shear lag factor

A reduction factor applied to the net area of a tension member, reflecting that stress is not uniform across the section when only part of the cross section is connected.

Plastic section modulus

A property of a steel section computed about the centroid of half the area; multiplied by yield stress, it gives the plastic moment for compact sections.

Effective stress principle

Total vertical stress minus pore water pressure; it governs soil strength, compressibility, and volume change, and can exceed total stress where pore pressure is negative.

Consolidation settlement equation

Settlement of a clay layer computed from compression index, initial void ratio, layer thickness, and the log ratio of final to initial effective vertical stress.

Preconsolidation pressure

The maximum past effective stress a soil has experienced; below it, recompression indices apply and settlement is much smaller, above it virgin compression governs.

Terzaghi bearing capacity factors

Dimensionless coefficients Nc, Nq, and N-gamma used with cohesion, surcharge, and unit weight to compute ultimate bearing capacity of shallow foundations.

Rankine active earth pressure

Lateral pressure coefficient equal to tangent squared of 45 degrees minus half the friction angle, applied to vertical effective stress behind a yielding retaining wall.

Flow net discharge

Seepage quantity per unit width equals permeability times total head times the ratio of flow channels to equipotential drops in a drawn flow net.

Quick condition and boiling

Upward seepage force equal to submerged unit weight of soil causes effective stress to vanish, producing a boiling or quick condition at the excavation base.

Manning equation

Empirical open channel flow formula relating discharge to roughness coefficient, cross-sectional area, hydraulic radius to the two-thirds power, and slope to the one-half power.

Hydraulic radius

Cross-sectional area of flow divided by wetted perimeter; it appears in Manning and Chezy equations and controls conveyance for a given slope and roughness.

Froude number

Ratio of flow velocity to the square root of gravitational acceleration times hydraulic depth; equal to one at critical flow, below one subcritical, above one supercritical.

Rational method runoff

Peak discharge equals runoff coefficient times rainfall intensity for the time of concentration times drainage area, with consistent units and a frequency-matched intensity.

Time of concentration

The travel time for runoff from the hydraulically most distant point to the outlet; it sets the design storm duration for peak flow computations.

Equivalent single axle load

A traffic loading unit converting mixed axle loads and configurations to repetitions of an 18,000-pound single axle using fourth-power-type equivalency factors.

Structural number

A pavement design index equal to the weighted sum of layer thicknesses times layer coefficients and drainage modifiers, representing required structural capacity.

Superelevation and side friction

On a horizontal curve, the centripetal demand is supplied jointly by pavement cross slope and tire-pavement friction; the sum equals velocity squared over fifteen times radius.

Sight distance

The length of roadway visible to a driver; stopping sight distance combines perception-reaction distance with braking distance and must be maintained around curves and crests.

Atterberg limits

Water content boundaries defining soil consistency states: liquid limit, plastic limit, and shrinkage limit, used to classify fine-grained soils and predict behavior.

Standard Proctor compaction

Laboratory test relating dry unit weight to water content for a given compactive effort, producing a maximum dry density at optimum water content.

Curing of concrete

Maintenance of moisture and temperature in freshly placed concrete so cement hydration continues; inadequate curing lowers strength and durability near the surface.

Formwork removal strength

The in-place concrete strength required before shores or forms are removed; it is verified by field-cured cylinders or maturity methods rather than by elapsed days alone.

Water-cementitious ratio

Mass of water divided by mass of cementitious material in a mix; lower values increase strength and reduce permeability but require adequate workability measures.