Free PE Construction Exam Flashcards

Ka = (1 - sin phi) / (1 + sin phi), where phi is the soil's friction angle. Ka gives the lateral pressure a retained soil mass exerts as it moves away from a wall or excavation support - the minimum lateral-pressure condition.

Kp = (1 + sin phi) / (1 - sin phi), the reciprocal of Ka. Kp governs the much larger lateral pressure that develops when soil is pushed INTO a wall or structure - the maximum lateral resistance the soil can offer.

Effective stress = total stress minus pore water pressure. Effective stress, not total stress, controls a soil's shear strength and consolidation behavior - critical whenever groundwater is present at an excavation or foundation.

FS = resisting forces (or moments) divided by driving forces (or moments) along the failure surface. FS greater than 1 means a stable slope; construction cut/fill slopes are typically designed for FS of at least 1.5.

HI = known benchmark elevation + backsight (BS) rod reading. HI is the elevation of the instrument's line of sight and is the reference used to find every other point's elevation from that setup.

New elevation = HI minus the foresight (FS) rod reading. Unlike the backsight, which is added to find HI, the foresight is subtracted to solve for the unknown point's elevation.

R = 5729.58 / D, where D is the degree of curve. A larger degree of curve means a sharper curve and smaller radius - used to stake horizontal curves from PC to PT during site layout.

Potholing (often vacuum excavation) exposes a short section of a buried utility to physically verify its exact horizontal location and depth before larger-scale excavation, reducing the risk of a utility strike from inaccurate as-built records.

A lower w/c ratio produces higher compressive strength and lower permeability (better durability) because less capillary porosity remains after curing - but very low w/c ratios reduce workability unless admixtures are used.

The slump test measures the workability/consistency of fresh concrete, not its strength. A cone is filled and lifted, and the vertical drop (slump) is recorded - low slump means a stiff mix, high slump means a more fluid mix.

Air-entraining admixtures create microscopic air bubbles that give freeze-thaw cycling water somewhere to expand into, protecting hardened concrete from freeze-thaw and de-icer scaling damage in exposed exterior work.

USCS classifies soils with two-letter symbols (e.g., SW, SP, CL, CH, ML) based on grain-size distribution and Atterberg limits (plasticity). It is the standard reference for describing soil suitability as fill, backfill, or foundation material.

Swell is the volume increase that occurs when in-place (bank) soil is excavated and loosened - loose (hauled) volume exceeds bank volume. A soil with 25% swell means 1 bank cubic yard becomes 1.25 loose cubic yards once dug.

Load factor = bank volume divided by loose volume, always less than 1.0 for a swelling soil. It converts a hauled (loose) quantity back into equivalent in-place bank volume for payment and cut/fill balance calculations.

Shrinkage occurs when soil is placed and compacted into an embankment: the compacted volume ends up smaller than the original bank volume because compaction increases density beyond the natural in-situ state - the opposite direction of swell.

A mass haul diagram plots cumulative cut-minus-fill volume against station along an alignment. It identifies balance points (where cut equals fill), the most economical haul direction and distance, and where waste or borrow is needed.

Total Float = Late Start minus Early Start = Late Finish minus Early Finish (LS - ES = LF - EF). It is the amount an activity can slip without delaying the project's overall completion date.

Free float is the amount an activity can be delayed without delaying the early start of its very next successor activity - a narrower, more local measure than total float, which protects the whole project's finish date.

The critical path is the longest continuous chain of dependent activities through the network diagram. Every activity on it has zero total float, so delaying any one of them delays the entire project's completion date.

Crashing shortens one or more critical-path activity durations - typically by adding labor, equipment, or overtime - which increases direct costs but can reduce overall project duration. Time-cost tradeoff analysis finds the least-cost way to compress the schedule.

Finish-to-Start (FS): successor starts after predecessor finishes - the default relationship. Start-to-Start (SS): successor can start once predecessor starts. Finish-to-Finish (FF): successor can't finish until predecessor finishes. Start-to-Finish (SF): successor can't finish until predecessor starts - rare.

The Proctor test determines the maximum dry density and corresponding optimum moisture content a soil can achieve under a standardized compactive effort in the lab. Field compaction specs (e.g., '95% Standard Proctor') are checked against this reference curve.

A nuclear density gauge quickly measures in-place soil density and moisture content on site using a radioactive source, letting inspectors verify a lift meets its Proctor-based compaction spec without waiting on lab test results.

The maturity method (ASTM C1074) estimates in-place concrete strength by combining a pour's temperature history over time into a maturity index, calibrated against lab strength curves - commonly used to decide when forms can safely be stripped.

Field-cast cylinders are cured similarly to the structure and tested in compression - typically at 28 days, often with an early 7-day check - to verify the concrete mix meets the specified compressive strength for acceptance.

Bolted connections are checked with a torque or turn-of-nut method to confirm proper clamping (pretension) force. Welds are verified with nondestructive testing (visual, ultrasonic, radiographic, or magnetic-particle) against acceptance criteria such as AWS D1.1.

Sigma = Mc / I, where M is bending moment, c is the distance from the neutral axis to the extreme fiber, and I is the section's moment of inertia. It gives the maximum normal stress from flexure at a given cross-section.

Tau = VQ / (Ib), where V is shear force, Q is the first moment of area above (or below) the point of interest, I is the moment of inertia, and b is the section width at that point.

Dead load is the permanent self-weight of the finished structure. Construction load is a temporary load present only during erection - formwork, wet concrete, equipment, stored material, workers - that can exceed the structure's final in-service loading and must be checked separately.

Deflection is a serviceability limit state, not a strength limit state - it confirms a member stays within code or owner deflection limits (e.g., L/360 under live load) to prevent cracking, ponding, or occupant discomfort, even if the member is strong enough to avoid failure.

Total stress at a point = axial stress plus or minus bending stress = P/A +/- Mc/I, using superposition. Essential for members like shoring posts or formwork studs that carry both direct compression and eccentric (bending) loads simultaneously.

Q = CiA, where Q is peak discharge, C is a runoff coefficient based on surface type, i is rainfall intensity for the time of concentration, and A is the drainage area. Used for small drainage areas in temporary drainage and erosion-control design.

V = (1.49/n) x R^(2/3) x S^(1/2) in US customary units, where n is the channel's roughness coefficient, R is the hydraulic radius, and S is the channel slope. Used to size temporary ditches, channels, and culverts.

Tc is the time for runoff to travel from the hydraulically most distant point in a drainage area to the point of analysis. A longer Tc generally corresponds to a lower design rainfall intensity used in Rational Method calculations.

A mobile crane's lifting capacity varies with boom length, boom angle, and lift radius (plus configuration and counterweight). Operators and riggers must always read the allowable capacity from the manufacturer's load chart for that specific radius - never the nameplate maximum.

Before a crane pick, the ground-bearing pressure under each outrigger pad must be checked against the soil's allowable bearing capacity, using mats or cribbing to spread the load if needed - a critical setup check to prevent settlement or tip-over.

A wellpoint system uses a header pipe with vacuum-connected points to lower the groundwater table proactively over a broad area before excavation begins. Sump pumping is reactive - it collects and removes water that has already entered a localized low point in the excavation.

A drilled shaft is installed by auguring/excavating a hole (with casing or slurry support if needed) and then placing reinforcement and concrete. A driven pile is a prefabricated member driven into the ground by an impact or vibratory hammer. Choice depends on soil conditions, vibration/noise limits, and required capacity.

Production rate is approximately load/bucket capacity times cycles per hour times an efficiency (job) factor. Cycle time (load, haul, dump, return) and job efficiency - soil conditions, operator skill, downtime - both directly drive achievable output and fleet-sizing decisions.

A borrow pit is an off-site (or designated on-site) fill source used when a project's cut volume can't meet its fill needs. It is the counterpart to a waste/spoil area, which is used when cut volume exceeds what's needed for fill.

Formwork is the temporary mold that shapes fresh concrete and resists its lateral (hydrostatic-like) pressure until it gains strength. Falsework is the temporary structural support system - shoring towers, bents - that carries the load of the formwork, wet concrete, or an unfinished structure.

Shoring is a temporary system carrying vertical and/or lateral loads from a structure, excavation wall, or adjacent property during construction. Bracing instead provides lateral stability against wind, seismic, or unbalanced forces - a vertically strong system can still rack or overturn without adequate bracing.

Reshoring is the reinstallation of shores beneath a concrete member after the original formwork/shoring was removed early (often to speed up form reuse), continuing to carry the member's weight and any construction loads until the concrete gains enough strength to support itself.

Fresh concrete behaves like a fluid initially, so formwork lateral pressure increases with the rate of placement (pour rate) and concrete unit weight, and decreases as concrete temperature rises (faster set). ACI 347R provides design pressure guidance based on these factors.

OSHA 1926 Subpart P recognizes three protective-system types: sloping/benching (cutting the wall back at a safe angle), shoring (installing supports like hydraulic shores), and shielding (using a trench box/shield to protect workers without necessarily supporting the soil).

Support-of-excavation systems - sheet piling, soldier piles with lagging, slurry walls - retain an adjacent soil face so excavation can proceed safely next to property lines, existing structures, or utilities where simply sloping the wall back isn't feasible.

Bracing resists lateral (horizontal) forces - wind, seismic, or unbalanced pressure - to keep a structure, formwork system, or temporary works from racking or overturning, complementing formwork and shoring, which primarily handle concrete shape and vertical/soil loads.

Under OSHA 1926 Subpart P, a protective system (sloping, shoring, or shielding) is required for excavations 5 feet deep or greater, except in stable rock. Excavations deeper than 20 feet require the protective system to be designed by a registered professional engineer.

Type A soil (most stable, e.g., stiff clay) allows a maximum slope of about 3/4:1 (53 degrees); Type B (medium stability) allows 1:1 (45 degrees); Type C (least stable, e.g., saturated or granular soil) requires 1.5:1 (about 34 degrees) - steeper allowable angles go with more stable soil.

Fall protection is generally required at 6 feet for most construction work and at 10 feet for scaffold platforms. A competent person must also inspect excavations and other hazards before each shift begins and as conditions change (OSHA 1926.651(k)(1)); documentation is best practice but not explicitly required by Subpart P.