- What is Manning's equation used for?
- Open-channel flow velocity: V = (1.49/n)·R raised to 2/3·S raised to 1/2 in U.S. units (1.0 instead of 1.49 in SI). n = roughness, R = hydraulic radius (area ÷ wetted perimeter), S = channel slope. Q = V·A.
- What is the phase (three-phase) diagram of soil?
- A model splitting a soil sample into solids, water, and air. It is the basis for weight–volume relationships: void ratio, porosity, water content, and unit weight.
- Define void ratio (e).
- Void ratio e = volume of voids ÷ volume of solids (Vv/Vs). Porosity n = Vv ÷ total volume. They relate by n = e/(1+e).
- Define water (moisture) content (w).
- Water content w = weight of water ÷ weight of solids (Ww/Ws), expressed as a percent. Found in the lab by oven-drying a sample.
- Define degree of saturation (S).
- S = volume of water ÷ volume of voids (Vw/Vv). S = 0% is fully dry, S = 100% is fully saturated.
- What is the relationship Se = wGs?
- A core phase identity: degree of saturation × void ratio = water content × specific gravity of solids. It links the four basic phase quantities.
- Total vs effective stress
- Total stress σ = overburden weight per area. Effective stress σ' = σ − u, where u is pore water pressure. Effective stress controls strength and settlement (Terzaghi's principle).
- What does the Atterberg limits test measure?
- The water contents at boundaries of fine-grained soil behavior: liquid limit (LL), plastic limit (PL), shrinkage limit. Plasticity index PI = LL − PL.
- What is the Unified Soil Classification System (USCS)?
- Classifies soils by grain size and plasticity into groups (e.g., GW, SP, CL, MH). Coarse soils use gradation (Cu, Cc); fine soils use the plasticity chart (A-line).
- Mohr–Coulomb shear strength
- Shear strength τ = c + σ'·tan(φ), where c = cohesion, φ = angle of internal friction, σ' = effective normal stress. Sands are c ≈ 0; clays develop cohesion.
- What is Rankine active earth pressure?
- Lateral pressure when a wall moves away from soil. Coefficient Ka = tan²(45° − φ/2). Active pressure < at-rest < passive.
- What is at-rest earth pressure (K0)?
- Lateral pressure when the wall does not move. For normally consolidated soil, K0 ≈ 1 − sin(φ).
- How does a uniform surcharge change earth pressure?
- A uniform surcharge q behind a wall adds a uniform (rectangular) lateral pressure Ka·q over the full wall height (in addition to the triangular soil pressure).
- What is consolidation settlement?
- Time-dependent settlement of saturated clay as pore water is squeezed out under load. Magnitude depends on compression index Cc and stress change; rate depends on coefficient of consolidation Cv.
- Standard Penetration Test (SPT) — what is N?
- N is the number of hammer blows to drive a split-spoon sampler the final 12 in (the middle two 6-in increments). It indicates relative density of sands / consistency of clays.
- What is the angle of repose?
- The steepest stable slope angle of a loose granular material, roughly equal to its drained friction angle φ. Guides safe stockpile and excavation slopes.
- What is bearing capacity?
- The maximum contact pressure soil can support before shear failure. Terzaghi: qult = c·Nc + q·Nq + 0.5·γ·B·Nγ. Allowable = qult ÷ factor of safety (often 3).
- What controls excavation dewatering?
- Lowering the groundwater table below the excavation using well points, deep wells, or sumps so the soil stays workable and stable and uplift/boiling is prevented.
- What is differential leveling?
- Surveying method that finds elevation differences with a level and rod: elevation + backsight (BS) = height of instrument (HI); HI − foresight (FS) = next elevation.
- What is loop closure (misclosure)?
- In a closed level loop returning to a known benchmark, the difference between the measured and known elevation. It quantifies survey error and is distributed back through the loop.
- Stationing — what is station 12+50?
- A distance of 1,250 ft along an alignment from station 0+00. Each full station = 100 ft; the number after '+' is the offset in feet.
- What is a horizontal (circular) curve's degree of curve?
- The central angle subtended by a 100-ft arc (arc definition). Radius R = 5729.58 ÷ D (degrees). Larger D = sharper curve.
- Define the elements of a horizontal curve.
- PC (point of curvature), PI (point of intersection), PT (point of tangency), T (tangent length), L (curve length), R (radius), Δ (deflection/central angle).
- What is a vertical curve?
- A parabolic curve connecting two grades (g1, g2). Used for crest and sag curves; length L is set by sight-distance or comfort criteria. Rate of change r = (g2 − g1)/L.
- What is a cut-and-fill mass diagram?
- A plot of cumulative earthwork volume vs station. Rising = cut, falling = fill; it balances haul, locates borrow/waste, and determines economical haul distance.
- What is the shrinkage/swell factor in earthwork?
- Soil changes volume between states: bank (in place), loose (excavated), compacted. Shrinkage = compacted is less volume than bank; swell = loose is more than bank.
- What is the rule for setting construction stakes (offset)?
- Stakes are set at a known horizontal offset from the line/grade so they survive excavation; the cut/fill to finished grade is marked on each stake.
- What does ALTA/erosion control concern in site development?
- Best management practices (silt fence, sediment basins, stabilized entrances) required by the SWPPP under the Clean Water Act / NPDES to control stormwater and sediment.
- What is a benchmark in surveying?
- A fixed reference point of known elevation used as the basis for differential leveling and vertical control on a project.
- What is grade (slope) expressed as a percent?
- Grade = rise ÷ run × 100%. A 2% grade rises 2 ft per 100 ft horizontal. Drainage and ADA limits are commonly specified in percent.
- What is the groundwater symbol on a boring log?
- An inverted triangle drawn beside the soil column at a noted depth (often with a date) marking the observed groundwater table elevation.
- What is concrete compressive strength f'c?
- The specified 28-day compressive strength of a standard cylinder, in psi (or MPa). The basic design property for concrete; tested per ASTM C39.
- What is the water–cement (w/c) ratio?
- The weight of mixing water ÷ weight of cementitious material. Lower w/c gives higher strength and durability but lower workability.
- What is concrete slump?
- A measure of fresh-concrete workability (ASTM C143): the vertical drop of a molded cone of concrete in inches. Higher slump = more flowable.
- What is the modulus of elasticity of concrete?
- Ec ≈ 57,000·√f'c (psi) for normal-weight concrete (ACI). It relates stress to strain in the elastic range.
- Grade vs yield strength of reinforcing steel
- Rebar grade equals its minimum yield strength in ksi — Grade 60 rebar has fy = 60,000 psi. The most common bar in U.S. construction.
- What is asphalt (HMA) and its key properties?
- Hot-mix asphalt is aggregate bound by asphalt cement (bitumen). Key properties: air voids, asphalt content, density, and stability (Marshall or Superpave mix design).
- What are aggregate gradation and fineness modulus?
- Gradation is the particle-size distribution from a sieve analysis. Fineness modulus = sum of cumulative percent retained on standard sieves ÷ 100; higher = coarser sand.
- What is the function of admixtures in concrete?
- Chemicals that modify fresh/hardened properties: water reducers, retarders, accelerators, air-entraining agents (freeze-thaw durability), and superplasticizers.
- What is steel's stress–strain behavior?
- Linear-elastic to yield (fy), then a yield plateau, strain hardening, and rupture. Mild steel is ductile; E ≈ 29,000 ksi.
- What is the difference between Type I and Type III cement?
- Type I is general-purpose portland cement; Type III is high-early-strength (finer ground) used when fast strength gain is needed in cold or fast-track work.
- What is a quantity takeoff?
- Measuring and counting the materials shown on the drawings (linear feet, square yards, cubic yards, counts) to build the cost estimate. The basis of bid pricing.
- Direct vs indirect costs
- Direct costs are tied to a specific work item (labor, materials, equipment for that task). Indirect costs (overhead) support the whole project: supervision, office, bonds, insurance.
- How is concrete volume estimated?
- Volume in cubic yards = (length × width × thickness in ft) ÷ 27. Add waste allowance. Order ready-mix in whole or quarter cubic yards.
- What is a unit-price contract?
- Payment based on actual measured quantities × bid unit prices. Used when quantities are uncertain (earthwork, paving); contrast with lump-sum.
- What is productivity (production rate)?
- Output per unit time or per crew-hour (e.g., cubic yards/hour). Cost = quantity ÷ production rate × crew or equipment hourly cost.
- What is equipment owning and operating (O&O) cost?
- The hourly cost of equipment: ownership (depreciation, interest, taxes, insurance) plus operating (fuel, lubricants, repairs, tires, operator wages).
- What is a contingency in an estimate?
- A reserve amount added to cover unforeseen but probable costs. It reflects estimate uncertainty; it is not for scope changes.
- What is markup (overhead and profit)?
- A percentage added to direct cost to cover company overhead and desired profit. Bid price = direct cost + indirect cost + markup.
- How do you estimate earthwork haul cost?
- Determine bank/loose/compacted volumes with shrink-swell factors, the haul distance and cycle time, the hauler capacity, then cost = volume ÷ hourly production × hourly rate.
- What is the difference between bank, loose, and compacted yards?
- Bank cubic yards (BCY) = in-place; loose cubic yards (LCY) = after excavation (swelled); compacted cubic yards (CCY) = after placement and compaction (densified).
- What is the Critical Path Method (CPM)?
- A scheduling technique that models activities and dependencies in a network, computes early/late dates by forward and backward passes, and finds the longest (critical) path = the shortest project duration.
- What is total float (slack)?
- The time an activity can be delayed without delaying project completion. Total float = late start − early start = late finish − early finish. Critical activities have zero float.
- What is free float?
- The time an activity can be delayed without delaying the early start of any successor. Free float ≤ total float.
- What is the critical path?
- The longest continuous chain of activities through the network. It has zero (minimum) total float and sets the project duration; delaying any critical activity delays the project.
- Forward pass vs backward pass
- Forward pass computes early start/finish (left to right, taking the max at merges). Backward pass computes late start/finish (right to left, taking the min at bursts).
- Activity-on-node (precedence) relationships
- Finish-to-start (FS, default), start-to-start (SS), finish-to-finish (FF), and start-to-finish (SF). Lags add a delay to the relationship.
- What does a start-to-start lag of 3 days mean?
- Successor B may start no earlier than 3 days after predecessor A starts (SS+3). The two activities overlap rather than running strictly in sequence.
- What is a milestone in a schedule?
- A zero-duration event marking a key point (e.g., 'Foundation complete'). Used for tracking and contract deadlines.
- What is project crashing?
- Shortening the schedule by adding resources to critical activities at extra cost. Crash the lowest cost-slope critical activity first; recheck the critical path after each step.
- What is resource leveling?
- Adjusting the schedule (using float) to smooth resource demand and avoid over-allocation, ideally without extending the critical path.
- Bar (Gantt) chart vs network diagram
- A bar chart shows activities as bars on a timeline (easy to read, weak on logic). A network diagram shows dependencies and computes float and the critical path.
- What is earned value (EV) management?
- Comparing planned value (PV), earned value (EV), and actual cost (AC). SV = EV − PV; CV = EV − AC; CPI = EV/AC; SPI = EV/PV. CPI/SPI < 1 means over budget / behind.
- Why specify a sampling and testing frequency?
- To collect enough representative results across a production run to characterize each lot and decide acceptance, balancing risk against testing cost.
- Quality control (QC) vs quality assurance (QA)
- QC is the contractor's process control (testing, inspection of the work). QA is the owner's independent verification that QC and the product meet specs.
- What is acceptance sampling?
- Testing a sample from a lot to decide whether to accept or reject the whole lot, accepting some statistical risk (producer's and consumer's risk).
- What is a concrete cylinder test set?
- Standard cylinders cast from a placement and broken (ASTM C39) at 7 and 28 days; acceptance compares the average to f'c per ACI strength criteria.
- What is the Proctor compaction test?
- Lab test (standard or modified) giving the maximum dry density and optimum moisture content used as the target for field compaction (percent of max dry density).
- How is field compaction verified?
- Compare in-place dry density (nuclear gauge or sand-cone, ASTM) to the Proctor maximum; relative compaction (e.g., ≥ 95%) must meet the spec.
- What is a control chart?
- A plot of a quality characteristic over time with center line and upper/lower control limits; points outside the limits or trends signal a process out of control.
- Mean and standard deviation in QC
- The mean locates the average result; standard deviation σ measures variability. Lower σ = more uniform production and a higher chance of meeting specs.
- What is a slump test acceptance check?
- Field measurement of fresh-concrete slump compared to the specified range; out-of-range loads may be rejected before placement.
- What is statistical (percent-within-limits) acceptance?
- Pay or acceptance based on the percentage of a lot's results falling within specification limits (PWL), rewarding uniform, on-target production.
- Dead load vs live load
- Dead load is the permanent self-weight of fixed components (structure, roofing, finishes). Live load is movable/temporary (occupants, furniture, snow, construction loads).
- What is a free-body diagram?
- A sketch of a body isolated from its supports showing all applied forces and reactions; the basis for writing equilibrium equations.
- What are the static equilibrium equations?
- For a 2-D body: ΣFx = 0, ΣFy = 0, ΣM = 0. A statically determinate structure is solved with these three equations.
- What is bending (flexural) stress?
- σ = M·c / I, where M = bending moment, c = distance from neutral axis, I = moment of inertia. Max at the extreme fiber.
- What is the section modulus?
- S = I/c. Bending stress σ = M/S. A larger S carries more moment at the same stress; it ranks beam efficiency.
- What is shear stress in a beam?
- τ = V·Q / (I·b), where V = shear force, Q = first moment of area above the point, b = width. Maximum at the neutral axis for a rectangular section.
- Simply supported beam, uniform load — max moment
- For a span L with uniform load w, the maximum moment is M = w·L²/8 at midspan; max shear V = w·L/2 at the supports.
- Simply supported beam, center point load — max moment
- For a center point load P on span L, max moment M = P·L/4 at midspan; max shear V = P/2.
- What is axial stress?
- σ = P/A, the force P divided by cross-sectional area A. Tension is positive, compression negative.
- What is column buckling (Euler load)?
- Critical buckling load Pcr = π²·E·I / (K·L)², where K is the effective-length factor for the end conditions. Slender columns fail by buckling below the yield load.
- What is deflection of a simple beam (uniform load)?
- Max midspan deflection δ = 5·w·L⁴ / (384·E·I). Deflection is very sensitive to span (L⁴) and stiffness E·I.
- What is the moment of inertia of a rectangle?
- I = b·h³/12 about the centroidal axis (b = width, h = depth). Depth dominates because it is cubed — deeper beams are far stiffer.
- What is the rational method Q = CiA?
- Estimates peak runoff: Q = C·i·A, where C = runoff coefficient, i = rainfall intensity, A = drainage area. In U.S. units C·i·A gives cfs when i is in in/hr and A in acres.
- What is the runoff coefficient C?
- The fraction of rainfall that becomes direct surface runoff (rather than infiltrating). Near 0.95 for asphalt/roofs; low (0.1–0.3) for lawns and pervious ground.
- What is time of concentration (tc)?
- The time for runoff to travel from the most remote point of a watershed to the outlet. Rainfall intensity i in the rational method is read at a duration equal to tc.
- What is hydraulic radius (R)?
- R = flow area ÷ wetted perimeter. It represents flow efficiency in Manning's equation; a circular pipe flowing full has R = D/4.
- Continuity equation for flow
- Q = V·A (flow rate = velocity × area). For incompressible steady flow, Q is constant, so velocity rises where the area narrows.
- What is Bernoulli's energy equation?
- Total head = pressure head (p/γ) + velocity head (V²/2g) + elevation head (z), constant along a streamline minus head losses.
- Open-channel vs pressure (pipe) flow
- Open-channel flow has a free surface at atmospheric pressure (gravity-driven, uses Manning). Pressure flow fills the conduit (uses Bernoulli/Darcy-Weisbach with friction losses).
- What is specific energy / critical depth?
- Specific energy E = depth + V²/2g. Critical depth minimizes E for a given Q; flow is subcritical (Fr<1) above it and supercritical (Fr>1) below it.
- What is a hydrograph?
- A plot of discharge vs time at a point during a storm, showing the rising limb, peak, and recession. The unit hydrograph scales runoff for a unit of rainfall excess.
- What is detention vs retention?
- A detention basin temporarily stores stormwater and releases it slowly (peak shaving). A retention basin holds water permanently (a wet pond), releasing mainly by infiltration/evaporation.
- Vertical hitch vs choker hitch — sling capacity
- A choker hitch reduces the rated sling capacity (about 75%–80% of vertical) because the bend and squeezing action lower the sling's effective strength.
- What is a crane's load chart based on?
- Rated capacity depends on the load radius (horizontal distance from the center pin to the hook), boom length/angle, and configuration; capacity drops sharply as radius increases.
- What is the difference between gross and net crane capacity?
- Gross capacity from the chart must be reduced by the weight of rigging, hook block, jib, and other below-the-boom items to get the net load the crane can lift.
- What is a sling angle reduction factor?
- As a sling angle from horizontal decreases, tension in each leg increases. Tension = load ÷ (number of legs × sin θ); shallow angles can overload slings.
- What governs pile driving energy?
- Hammer energy (rated foot-pounds) drives the pile; field capacity is estimated from driving resistance (blows per inch) via a dynamic formula or wave-equation analysis.
- What is mass vs lift placement of concrete?
- Mass concrete requires control of heat of hydration (cooling, low-heat cement, lift heights). Placement is done in controlled lifts to manage temperature and cold joints.
- What is the difference between excavation and trenching (OSHA)?
- An excavation is any man-made cut/cavity; a trench is a narrow excavation deeper than it is wide (≤15 ft wide). Trenches ≥5 ft deep generally require a protective system.
- What are excavation protective systems?
- Sloping/benching (laying back the walls), shoring (supports like hydraulic shores), or shielding (trench boxes) to prevent cave-ins, selected by soil type and depth.
- What is dewatering during construction operations?
- Removing or lowering groundwater (well points, sumps, deep wells) so excavation can proceed in stable, workable soil and to prevent bottom heave/boiling.
- What is the productivity learning curve?
- Repetitive operations gain efficiency as crews learn; unit time decreases by a fixed percent each time output doubles, improving production rates on repetitive work.
- What is a concrete cold joint?
- A discontinuity where fresh concrete is placed against concrete that has already begun to set, creating a weak plane; avoided by continuous placement within set time.
- What is mass haul / hauling cycle time?
- Total cycle = load + haul + dump + return + spot times. Production = (60 min/hr ÷ cycle min) × hauler capacity × efficiency.
- What lateral pressure does fresh concrete exert on formwork?
- Fresh (plastic) concrete acts like an equivalent fluid, giving a hydrostatic lateral pressure that increases with depth; ACI 347 caps it by a rate-and-temperature formula (Cw, Cc, pour rate R, temperature T).
- What is formwork and its design loads?
- Temporary molds for fresh concrete. Design for the weight of concrete and reinforcement, construction live loads, and lateral concrete pressure / wind, per ACI 347.
- What is shoring?
- Vertical support carrying the weight of fresh concrete and forms until the slab gains strength. Reshoring redistributes loads to lower floors during multistory construction.
- What is the pour rate's effect on formwork pressure?
- A faster pour rate (ft/hr) and lower temperature keep more concrete plastic at once, raising the lateral form pressure; slower pours let lower concrete set and reduce pressure.
- What is a falsework?
- Temporary framework that supports a permanent structure (e.g., bridge formwork/shoring) during construction until it is self-supporting.
- What loads act on temporary structures?
- Dead (self-weight, materials), construction live loads (workers, equipment, stockpiled materials), lateral loads (wind, concrete pressure, seismic), and impact.
- What is bracing in temporary works?
- Diagonal members that resist lateral loads and prevent buckling/racking of shoring, formwork, scaffolds, and falsework; required for stability.
- What is a cofferdam?
- A temporary watertight enclosure pumped dry to allow construction below the water table or in a waterway (e.g., bridge piers).
- How is allowable load on temporary shoring determined?
- From the shore's rated capacity (often manufacturer tables) reduced for height, eccentricity, and bracing; a factor of safety is applied because failures are catastrophic.
- What is the difference between forms and shoring failure modes?
- Forms fail by excessive deflection, tie/wale overload, or blowout from concrete pressure; shoring fails by buckling, overturning, or foundation settlement.
- What is a scaffold and its OSHA capacity rule?
- A temporary elevated work platform; under OSHA it must support its own weight plus at least 4× the maximum intended load without failure.
- What is the equivalent fluid pressure concept?
- Modeling fresh concrete (or soil) lateral pressure as if it were a fluid of an equivalent unit weight, giving a triangular pressure that increases linearly with depth.
- Which CFR part covers OSHA construction standards?
- 29 CFR 1926 — the OSHA Safety and Health Regulations for Construction. (29 CFR 1910 is general industry.)
- What are the OSHA 'Fatal Four' (Focus Four) hazards?
- Falls, struck-by, caught-in/between, and electrocution — the leading causes of construction fatalities and OSHA's primary enforcement focus.
- When is fall protection required in construction?
- Generally at 6 ft or more above a lower level in construction (OSHA 1926 Subpart M): guardrails, safety nets, or personal fall arrest systems.
- When must a trench have a protective system?
- OSHA requires cave-in protection for excavations 5 ft or deeper (unless in stable rock); a competent person inspects daily and classifies the soil.
- Who is a 'competent person' under OSHA?
- Someone capable of identifying existing and predictable hazards and authorized to take prompt corrective action — required for excavations, scaffolds, and fall protection.
- What is the maximum allowable slope for Type C soil?
- Type C soil (the least stable) must be sloped no steeper than 1.5 horizontal to 1 vertical (about 34°) per OSHA excavation requirements.
- What is a hazard control hierarchy?
- Most to least effective: elimination, substitution, engineering controls, administrative controls, then personal protective equipment (PPE) as the last line.
- What is lockout/tagout (LOTO)?
- Procedures to isolate and de-energize hazardous energy (electrical, hydraulic) and lock/tag controls so equipment cannot start during service, preventing caught-in/electrocution injuries.
- What scaffold safety factor does OSHA require?
- A scaffold and its components must support, without failure, their own weight plus at least 4 times the maximum intended load.
- What is a job hazard analysis (JHA)?
- A step-by-step review of a task that identifies hazards in each step and the controls to eliminate or reduce them before work begins.
- Rankine passive earth pressure coefficient
- Kp = tan²(45° + φ/2). Passive pressure resists a wall pushing into the soil and is the largest of the three earth-pressure states (active < at-rest < passive).
- Terzaghi bearing-capacity equation
- qult = c·Nc + q·Nq + 0.5·γ·B·Nγ, where c = cohesion, q = surcharge at footing base, γ = soil unit weight, B = footing width, and Nc, Nq, Nγ are bearing factors that depend on φ.
- What is factor of safety for slope stability?
- FS = resisting forces (or moments) ÷ driving forces (or moments). FS > 1 is stable; design typically requires FS ≥ 1.3–1.5 depending on conditions.
- What is liquefaction?
- Loss of soil strength when saturated, loose, granular soil under cyclic (seismic) loading builds excess pore pressure until effective stress drops to near zero and the soil behaves like a fluid.
- What is the plasticity index (PI)?
- PI = liquid limit − plastic limit (LL − PL). It is the range of water content over which a fine-grained soil is plastic; high PI indicates highly plastic, expansive clay.
- What is hydraulic conductivity (permeability)?
- The ease with which water flows through soil, k (length/time). Measured by constant-head (sands) or falling-head (silts/clays) tests. Gravels are highly permeable; clays nearly impermeable.
- Darcy's law for soil seepage
- Q = k·i·A, where k = hydraulic conductivity, i = hydraulic gradient (dh/dL), A = cross-sectional area. Governs groundwater flow and seepage.
- What is the difference between cohesive and cohesionless soil?
- Cohesionless (sands, gravels) gets strength from friction (φ) and grain interlock. Cohesive (clays) gets strength largely from cohesion (c) and is affected by water content.
- Normally consolidated vs overconsolidated clay
- Normally consolidated clay has never carried a higher stress than its current overburden. Overconsolidated clay was once loaded more (by ice, erosion, etc.); it settles less under new load.
- What is the relationship between dry unit weight and water content?
- γd = γ / (1 + w), where γ = total (moist) unit weight and w = water content. Dry unit weight is the target measured in compaction control.
- Horizontal curve — degree of curve relation
- R = 5729.58 ÷ D (arc definition, R in ft, D in degrees). Tangent T = R·tan(Δ/2); length L = R·Δ (Δ in radians).
- Horizontal curve middle ordinate (M)
- M = R·(1 − cos(Δ/2)), the distance from the midpoint of the curve to the midpoint of the long chord. Used for clearance and layout.
- Average-end-area earthwork volume
- V = (L/2)·(A1 + A2), where A1 and A2 are the cross-sectional cut/fill areas at two stations a distance L apart. The standard earthwork volume method.
- What is a height of instrument (HI)?
- In leveling, HI = known elevation + backsight (BS). A foresight (FS) then gives the next point's elevation = HI − FS.
- What is superelevation?
- The banking of a roadway on a horizontal curve to counter centrifugal force. Relationship: e + f = V²/(15·R) in U.S. units (V in mph, R in ft).
- What is a vertical curve high/low point?
- On a parabolic vertical curve, the turning point is where grade = 0: distance x = −g1·L/(g2 − g1) from the curve's start (BVC). A crest has a high point; a sag has a low point.
- What is grade staking?
- Setting stakes that mark line and elevation for construction, with cut/fill to finished grade noted, usually at an offset so the stakes survive the work.
- What is a SWPPP?
- A Stormwater Pollution Prevention Plan required under the NPDES program for construction sites disturbing ≥1 acre; it specifies erosion and sediment controls.
- Modulus of rupture of concrete
- fr = 7.5·√f'c (psi) for normal-weight concrete; it is the flexural tensile strength used to predict cracking.
- What does a higher w/c ratio do to concrete?
- Increases workability but lowers strength, durability, and increases permeability. Lower w/c gives stronger, more durable, less permeable concrete.
- What is air entrainment in concrete?
- Intentional microscopic air bubbles added by an admixture to provide freeze-thaw durability by relieving internal pressure from freezing water; it slightly reduces strength.
- Five cement types (ASTM C150)
- Type I general purpose; Type II moderate sulfate resistance/heat; Type III high early strength; Type IV low heat of hydration (mass concrete); Type V high sulfate resistance.
- What is the modulus of elasticity of steel?
- Es ≈ 29,000,000 psi (29,000 ksi), essentially constant for all structural steels regardless of grade.
- What is a sieve analysis?
- Shaking aggregate through a stack of standard sieves to determine the particle-size distribution (gradation), reported as percent passing each sieve.
- What is RQD (Rock Quality Designation)?
- RQD = sum of intact core pieces ≥4 in long ÷ total core run length, as a percent. It rates rock-mass quality; higher RQD means more competent rock.
- What is prestressed concrete?
- Concrete with high-strength tendons tensioned to put the section in compression before service loads, counteracting tensile stresses. Pre-tensioned (cast on stressed strands) or post-tensioned (ducted, stressed after curing).
- Present worth formula
- P = F ÷ (1 + i)ⁿ, the value today of a future amount F received in n periods at interest rate i. The basis of engineering economics comparisons.
- Capital recovery (equivalent annual cost)
- A = P·[ i(1+i)ⁿ ÷ ((1+i)ⁿ − 1) ]. Converts a present cost P into an equivalent uniform annual cost over n years.
- What is life-cycle cost analysis?
- Comparing alternatives by the present worth (or annual cost) of all costs over the life — initial, operating, maintenance, and salvage — not just first cost.
- What is break-even analysis?
- Finding the quantity or time at which two alternatives (or revenue and cost) are equal. Below it one option is cheaper; above it the other is.
- Lump-sum vs unit-price contract
- Lump-sum: one fixed price for a defined scope (best when quantities are known). Unit-price: payment per measured quantity × unit rate (best when quantities are uncertain, like earthwork).
- What is the schedule of values?
- A breakdown of the contract sum into line items used to support progress payments; the contractor bills the percent complete of each item.
- How is labor cost estimated?
- Crew cost per hour ÷ production rate × quantity, plus burden (taxes, insurance, fringe). Productivity (output per crew-hour) is the key driver.
- Early finish (EF) formula in CPM
- EF = ES + duration. The forward pass sets ES = max of predecessors' EF; the backward pass sets LF = min of successors' LS, and LS = LF − duration.
- What is a near-critical path?
- A path with small (low) total float that can become critical if its activities slip; schedulers monitor it because little delay turns it critical.
- What is the cost slope of an activity?
- Cost slope = (crash cost − normal cost) ÷ (normal duration − crash duration) = the extra cost per day saved. Crash the lowest-cost-slope critical activity first.
- What is a lead and a lag?
- A lag delays the successor relative to the predecessor (positive offset); a lead (negative lag) lets it start earlier/overlap. Applied to FS, SS, FF, SF links.
- What is a linear (line-of-balance) schedule?
- A schedule for repetitive work (highways, high-rise floors) plotting location vs time so production rates and crew interference are visible.
- Schedule Performance Index (SPI)
- SPI = EV ÷ PV. SPI < 1 means behind schedule, = 1 on schedule, > 1 ahead. Paired with CPI = EV ÷ AC for cost performance.
- What is a hammock activity?
- A summary activity that spans (hangs between) a start and finish of a group of detailed activities, used for reporting like ongoing supervision.
- Total float vs free float (key difference)
- Total float uses up schedule slack against the project end; free float delays only without affecting any successor's early start. Free float ≤ total float.
- What is the concrete maturity method?
- Estimating in-place concrete strength from its time-temperature history (a maturity index) so forms can be stripped or loads applied based on actual strength gain.
- Relative compaction acceptance
- Field dry density ÷ Proctor maximum dry density × 100%. Specs commonly require ≥ 90–95%; below it the lift is reworked.
- What is a nuclear density gauge?
- A field instrument that measures soil/asphalt in-place density and moisture by gamma/neutron backscatter for rapid compaction QC.
- What is the difference between standard and modified Proctor?
- Modified Proctor uses higher compactive energy (heavier hammer, greater drop, more layers), giving a higher maximum dry density at a lower optimum moisture than standard Proctor.
- What is a weld inspection method?
- Visual plus nondestructive testing: dye penetrant and magnetic particle (surface), ultrasonic and radiographic (internal). Required for critical structural welds.
- What is bolt pretensioning verification?
- Confirming high-strength bolts reach required tension by turn-of-nut, calibrated wrench, direct-tension indicators, or twist-off (tension-control) bolts.
- What is a producer's vs consumer's risk?
- Producer's risk (α) rejects acceptable material; consumer's risk (β) accepts defective material. Acceptance plans balance both.
- What is concrete acceptance per ACI?
- Strength is acceptable if every running average of three consecutive tests ≥ f'c and no single test is more than 500 psi below f'c (for f'c ≤ 5000 psi).
- Cantilever beam point load at free end — max moment
- For load P at the free end of a cantilever of length L: max moment M = P·L at the fixed support; max deflection δ = P·L³/(3·E·I).
- Cantilever beam uniform load — max moment
- For uniform load w on a cantilever of length L: max moment M = w·L²/2 at the support; max deflection δ = w·L⁴/(8·E·I).
- What is the radius of gyration?
- r = √(I/A). It relates a section's moment of inertia to its area and appears in column slenderness, KL/r.
- What is the slenderness ratio?
- KL/r, where K = effective-length factor, L = unbraced length, r = radius of gyration. High slenderness means a column is buckling-controlled.
- Effective length factor K values
- Pinned-pinned K = 1.0; fixed-fixed K = 0.5; fixed-pinned K ≈ 0.7; fixed-free (cantilever) K = 2.0. Higher K lowers the buckling load.
- What is the relationship between load, shear, and moment?
- The slope of the shear diagram equals the negative load (dV/dx = −w); the slope of the moment diagram equals the shear (dM/dx = V). Maximum moment occurs where shear = 0.
- ASD vs LRFD design philosophy
- ASD compares service loads to allowable stress (Rn/Ω). LRFD compares factored loads (Σγi·Qi) to factored resistance (φ·Rn). LRFD applies separate factors to loads and resistance.
- What is a tributary area?
- The floor/roof area whose load is carried by a given member; multiplying it by the unit load gives the member's load. Interior beams collect from both sides.
- What is combined axial and bending stress?
- σ = P/A ± M·c/I — superimpose the axial stress and bending stress; the extreme fiber may be in higher compression or net tension.
- What is a statically indeterminate structure?
- One with more unknown reactions/forces than equilibrium equations; it requires compatibility (deflection) conditions to solve and redistributes load when overloaded.
- Froude number and flow regime
- Fr = V ÷ √(g·D). Fr < 1 is subcritical (tranquil, depth-controlled), Fr = 1 critical, Fr > 1 supercritical (rapid, slope-controlled).
- Hazen-Williams equation
- V = 1.318·C·R raised to 0.63·S raised to 0.54 (U.S. units), used for pressurized water pipe flow; C is the pipe roughness coefficient (higher C = smoother pipe).
- Darcy-Weisbach head loss
- hf = f·(L/D)·(V²/2g), the friction head loss in a pipe; f is the friction factor (from the Moody diagram via Reynolds number and relative roughness).
- What is NPSH and cavitation?
- Net Positive Suction Head is the suction-side pressure margin above vapor pressure a pump needs. If available NPSH < required, the water vaporizes (cavitation), damaging the pump.
- What is the SCS/NRCS curve number method?
- A runoff method where a curve number (CN, 30–98) based on soil and land use sets the runoff depth from rainfall; higher CN (impervious) yields more runoff.
- What is an IDF curve?
- An Intensity-Duration-Frequency curve giving rainfall intensity for a chosen storm duration and return period (frequency); the source of i in the rational method.
- What is the energy grade line vs hydraulic grade line?
- EGL = pressure head + elevation + velocity head (total energy). HGL = pressure head + elevation (the water surface in open flow). EGL is above HGL by the velocity head V²/2g.
- Reynolds number — laminar vs turbulent
- Re = VD/ν. In pipes, Re < 2000 is laminar, > 4000 turbulent, between is transitional. It sets the friction factor.
- What is a detention pond's purpose?
- To temporarily store stormwater and release it at a controlled (lower) rate so the post-development peak flow does not exceed pre-development, protecting downstream channels.
- What is a culvert and how is its capacity controlled?
- A conduit carrying flow under a road/embankment; capacity is governed by either inlet control (entrance geometry) or outlet control (barrel friction + tailwater), whichever gives the higher headwater.
- Sling leg tension with angle
- Tension per leg = total load ÷ (number of legs × sin θ), where θ is the angle from horizontal. As θ decreases, tension increases sharply — a 30° sling roughly doubles leg tension vs vertical.
- What is crane load radius?
- The horizontal distance from the crane's center of rotation to the hook. Rated capacity drops rapidly as radius increases; load charts are read by radius and boom configuration.
- What is outrigger float / mat sizing?
- Outrigger loads can exceed the crane's weight at one corner; mats spread the load so ground bearing pressure stays below the soil's allowable bearing capacity.
- What governs equipment selection for earthmoving?
- Material type, haul distance, grade, production needed, and cost. Scrapers suit medium hauls; trucks/loaders long hauls; dozers short pushes; excavators for trenching.
- What is a drilled shaft (caisson)?
- A deep foundation formed by drilling a hole and filling it with reinforced concrete; carries load by end bearing and side friction. Used for heavy loads or where driving piles is impractical.
- What is pile-driving refusal?
- When a pile no longer advances appreciably under hammer blows (a specified small set per blow), indicating it has reached required capacity or hit a hard layer.
- Borrow-pit volume by the grid method
- Average the corner cut/fill depths weighted by how many grid cells share each corner, multiply by the grid area: V = (area/4)·Σ(weighted heights).
- What is the difference between sloping, shoring, and shielding?
- Sloping/benching cuts back the excavation walls; shoring supports the walls (hydraulic/timber); shielding uses a trench box to protect workers without preventing wall collapse.
- What is a slurry wall / diaphragm wall?
- A reinforced-concrete wall built in a bentonite-slurry-supported trench, used for deep excavation support and cutoff in soft ground or below the water table.
- What is well-point dewatering?
- A line of closely spaced shallow wells connected to a header and vacuum pump to lower the water table around an excavation in sandy soils.
- ACI 347 formwork pressure cap factors
- Lateral pressure of fresh concrete is capped using Cw (unit-weight factor) and Cc (chemistry factor) with pour rate R and temperature T; faster pours and colder temps give higher pressure.
- What is reshoring?
- Shores reinstalled snug (not preloaded) under a slab after the original shores are removed, transferring the slab's self-weight and construction loads to lower floors during multistory work.
- ASCE 37 — design loads on construction
- ASCE 37 'Design Loads on Structures During Construction' gives load combinations and magnitudes for temporary conditions (construction live loads, materials, equipment, environmental).
- What construction live load is typical for formwork decks?
- ACI 347 commonly uses a minimum construction live load (often 50 psf, increased for motorized buggies) plus the concrete and form dead load when designing form decks and shores.
- What is lateral bracing of shoring?
- Diagonal/horizontal bracing that resists wind, concrete pressure, and erection forces and prevents shore towers from buckling or racking; required for stability.
- What is the failure consequence of formwork collapse?
- Sudden, catastrophic, often fatal; therefore temporary works use conservative factors of safety and a qualified engineer's design and inspection.
- What is a wale and a tie in formwork?
- Wales are horizontal members backing the studs/sheathing; ties are tension members across the form spacing the two faces and resisting the concrete's lateral pressure.
- What is shoring for excavation (soldier pile and lagging)?
- Vertical steel piles (soldiers) driven/drilled at intervals with horizontal lagging between them retaining the soil face; often tied back with anchors for deep cuts.
- What is the difference between formwork and falsework?
- Formwork is the mold that shapes the concrete; falsework is the temporary support system (shores, towers, framing) that holds the formwork and wet concrete until self-supporting.
- Scaffold load classes (OSHA)
- Light-duty 25 psf, medium-duty 50 psf, heavy-duty 75 psf intended load; plus the 4× safety factor on capacity. The platform must be fully planked.
- OSHA scaffold guardrail height
- Top rails on supported scaffolds are 38–45 in above the platform (newer scaffolds); a midrail is required between the top rail and platform when there is no wall.
- OSHA Type A, B, C soil definitions
- Type A is most stable cohesive soil (unconfined compressive strength ≥1.5 tsf); Type B intermediate; Type C least stable (≤0.5 tsf or submerged) — each has a maximum allowable slope.
- Maximum slope for OSHA Type A soil
- Type A may be sloped at 3/4 horizontal to 1 vertical (about 53°) for excavations ≤20 ft deep, the steepest of the soil types.
- When must a competent person inspect an excavation?
- Daily before work, after any rainstorm or hazard-increasing event, and as conditions warrant — for cave-in, water, atmosphere, and protective-system hazards.
- What is the OSHA confined-space rule for construction?
- 29 CFR 1926 Subpart AA requires permit-required confined-space programs: atmospheric testing, ventilation, attendants, and rescue for spaces with limited entry and hazards.
- What is a personal fall arrest system (PFAS)?
- An anchor, body harness, and connector (lanyard/lifeline) that stops a fall; OSHA limits arrest force to 1,800 lb and total fall distance, and requires a rescue plan.
- What is maintenance of traffic (MOT)?
- Temporary traffic control in work zones per MUTCD Part 6 — signs, channelizing devices, flaggers, and tapers that protect workers and the traveling public.
- What is OSHA's general duty clause?
- Section 5(a)(1) of the OSH Act requires employers to provide a workplace free from recognized hazards that cause or are likely to cause death or serious harm, even absent a specific standard.
- What PPE is standard on a construction site?
- Hard hat, safety glasses, high-visibility vest, steel/composite-toe boots, gloves, and hearing protection as needed — PPE is the last line in the hazard-control hierarchy.
- Struck-by vs caught-in/between hazards
- Struck-by: hit by a moving object (vehicle, falling load, flying particle). Caught-in/between: crushed/pinched between objects or in a collapse (trench, equipment). Both are OSHA Focus Four hazards.
