PE Civil key terms

Scheduling technique that identifies the longest chain of dependent activities through a project network, thereby establishing the minimum possible project duration and highlighting activities with no float.

The amount of time an activity can be delayed from its early start without delaying the project completion date or violating a constraint; also called slack.

A written, formally approved modification to the contract scope, schedule, or price issued after the original agreement is executed, typically authorized by the owner.

A percentage of each progress payment withheld by the owner until substantial completion to protect against incomplete work, defects, or unresolved claims.

A specifically described unit of work in the contract, measured and paid at an agreed unit price or lump sum.

Maintaining adequate moisture and temperature in freshly placed concrete so cement hydration can proceed and design strength and durability develop.

A horizontal layer of soil or aggregate placed and compacted before the next layer is added; thickness is controlled by equipment and compaction requirements.

Water-content thresholds (liquid limit, plastic limit) that describe the consistency and plasticity of fine-grained soils and are used for classification.

Field test in which a split-spoon sampler is driven into soil by a drop hammer; the blow count (N-value) correlates with density and strength.

The intergranular stress carried by soil solids, equal to total stress minus pore water pressure; it controls soil strength and volume change.

Loss of shear strength in saturated loose sands during rapid shaking when pore pressure rises until effective stress approaches zero.

Gradual reduction in the volume of saturated fine-grained soil caused by expulsion of pore water under sustained load, producing time-dependent settlement that must be predicted for structures.

The maximum pressure a soil or rock mass can support at the base of a foundation without shear failure or excessive settlement.

Mechanical densification of soil that reduces air voids and increases unit weight; specifications use moisture-density curves from laboratory Proctor tests.

Lateral pressure exerted by retained soil when a wall yields slightly away from the backfill, reaching the minimum stable pressure state.

Ratio of available shear strength (resisting forces) to shear stress (driving forces) along a potential failure surface; values above one indicate stability margin.

Design philosophy that verifies a structure will not exceed specified states: strength (safety against collapse) and serviceability (acceptable deflection, cracking, vibration).

Multiplier applied to nominal loads in strength design to account for uncertainty and variability, producing factored demand used in LRFD combinations.

Multiplier less than one applied to nominal member strength to account for material, fabrication, and analysis uncertainties; also called phi factor.

The bonded length of reinforcement required to transfer bar force to concrete so the bar can reach its yield strength without pullout or splitting.

Web reinforcement, usually stirrups or ties, provided to resist shear forces, confine concrete, and improve ductility in beams and columns.

The nominal bending moment capacity of a cross section computed from internal compression and tension forces, before applying resistance factors.

Condition in which a structure must remain usable under normal service loads, controlling deflection, crack width, and vibration rather than strength or collapse.

Sudden lateral displacement or instability of a slender compression member when its critical load is reached, abruptly reducing its axial capacity.

The selected maximum safe speed used to determine geometric features such as horizontal curve radius, superelevation, and sight distance along a roadway.

Minimum distance required for a driver to perceive a hazard and stop before reaching it, including perception-reaction distance and braking distance.

The transverse slope of a roadway curve that uses vehicle weight to help offset centrifugal force and improve comfort and safety.

A qualitative letter grade from A to F describing traffic operational quality, based on measures such as travel speed, density, or control delay.

Total two-way traffic volume passing a point over a full year divided by 365, used for highway planning, pavement design, and funding decisions.

A traffic-loading measure that converts mixed vehicle axle loads to the number of 18,000-lb single-axle applications producing equivalent pavement damage.

An index representing the total structural capacity of a flexible pavement, derived from layer thicknesses and coefficients to carry design traffic.

A peak runoff estimation procedure using Q = CiA, where runoff coefficient, rainfall intensity, and drainage area estimate peak flow from small catchments.

The time for water to travel from the hydraulically most distant point of a catchment to the outlet, used to select design rainfall intensity.

A dimensionless fraction of rainfall that becomes surface runoff, reflecting land cover, soil type, slope, and antecedent moisture conditions in a drainage area.

An empirical formula relating open-channel velocity to hydraulic radius, channel slope, and roughness coefficient; widely used for sewers and channels.

A measure of oxygen consumed by microorganisms decomposing organic matter in water over a set period, indicating organic pollution strength.

The average time wastewater or water remains in a treatment tank or basin, equal to tank volume divided by flow rate.

Concentration of particulate matter suspended in water that can be captured by filtration, used to gauge pollution and treatment performance.