Basic Civil interview questions

150 questions with answers (CIV-001 to CIV-150). Try each one aloud before reading the answer.

Building Materials & Concrete Technology

CIV-001 · What is the difference between PCC and RCC?

PCC (plain cement concrete) is cement, sand, aggregate and water with no reinforcement, so it is good only in compression. RCC adds steel reinforcement to carry the tension that concrete cannot.

CIV-002 · What is the slump test?

A field test that measures the workability (consistency) of fresh concrete. A standard cone (300 mm high, 100 mm top, 200 mm base) is filled in layers, rodded and lifted; the drop in height is the slump.

CIV-003 · What does a concrete grade such as M20 mean?

M stands for mix, and 20 is the characteristic compressive strength of 20 N/mm² on 150 mm cubes at 28 days, per IS 456.

CIV-004 · What is the standard curing period for concrete?

Moist curing for at least 7 days for OPC concrete, and at least 10–14 days for blended cements (fly ash, slag) or in hot, dry weather, as recommended in IS 456.

CIV-005 · What are the main compounds in Ordinary Portland Cement?

Tricalcium silicate (C₃S), dicalcium silicate (C₂S), tricalcium aluminate (C₃A) and tetracalcium aluminoferrite (C₄AF). C₃S and C₂S together make up roughly 70–80% and give most of the strength.

CIV-006 · What are the initial and final setting times of OPC?

Initial setting time must be at least 30 minutes and final setting time at most 600 minutes, measured with the Vicat apparatus.

CIV-007 · What is hydration of cement?

The exothermic chemical reaction of cement with water. It forms calcium silicate hydrate (C-S-H) gel, which gives strength, and calcium hydroxide as a by-product.

CIV-008 · How are fine and coarse aggregates distinguished?

By the 4.75 mm IS sieve. Aggregate mostly passing it is fine aggregate (sand); aggregate mostly retained on it is coarse aggregate.

CIV-009 · What is workability of concrete?

The ease with which fresh concrete can be mixed, placed, compacted and finished without segregation. It is measured by slump, compaction factor, Vee-Bee or flow tests.

CIV-010 · What is an admixture?

A material other than cement, water and aggregate added during mixing to modify properties. Examples are plasticizers, superplasticizers, retarders, accelerators and air-entraining agents.

CIV-011 · What is fineness modulus of aggregate?

An index of particle size: the sum of cumulative percentages retained on standard sieves divided by 100. A higher value means coarser aggregate; fine sand is about 2.2–2.6 and coarse sand about 2.9–3.2.

CIV-012 · What is the standard size of a modular brick in India?

190 × 90 × 90 mm actual size, which becomes a nominal 200 × 100 × 100 mm with a 10 mm mortar joint.

CIV-013 · What are bleeding and segregation in concrete?

Bleeding is water rising to the surface of freshly placed concrete. Segregation is separation of coarse aggregate from the mortar. Both come from poor mix proportions, excess water or bad handling.

Structural Analysis

CIV-014 · What are the types of loads on a structure?

Dead load (self-weight), live or imposed load (occupancy), wind load, seismic load and snow load, plus temperature, shrinkage and settlement effects. In India they are given in IS 875 and IS 1893.

CIV-015 · What is the difference between a statically determinate and an indeterminate structure?

A determinate structure can be solved using equilibrium equations alone. An indeterminate structure has more unknowns than equilibrium equations, so compatibility of deformations is also needed.

CIV-016 · What is the difference between a simply supported beam and a cantilever?

A simply supported beam rests on a pin and a roller at its ends. A cantilever is fixed at one end and free at the other, so its maximum moment and shear occur at the fixed support.

CIV-017 · What are shear force and bending moment?

At a section, shear force is the algebraic sum of transverse forces on one side. Bending moment is the algebraic sum of moments of those forces about the section.

CIV-018 · What is a point of contraflexure?

A point where the bending moment changes sign and passes through zero. It occurs in overhanging, continuous and fixed beams.

CIV-019 · What is section modulus?

Z = I / y_max, the ratio of the moment of inertia to the distance of the extreme fibre from the neutral axis. Bending stress is σ = M / Z, so a larger Z means more bending strength.

CIV-020 · How many reactions do roller, hinged and fixed supports provide?

A roller gives 1 reaction (perpendicular to the surface), a hinge gives 2 (horizontal and vertical) and a fixed support gives 3 (two forces and a moment) in a plane structure.

CIV-021 · What are the basic assumptions in analysing a pin-jointed truss?

Members are connected by frictionless pins, loads act only at joints, and members are straight and weightless. Each member therefore carries only axial tension or compression.

CIV-022 · What is Young's modulus?

The ratio of normal stress to normal strain within the elastic limit (Hooke's law). For structural steel E ≈ 2 × 10⁵ N/mm².

CIV-023 · What is Poisson's ratio?

The ratio of lateral strain to longitudinal strain under axial load. It is about 0.3 for steel and about 0.15–0.2 for concrete.

CIV-024 · What is slenderness ratio?

Effective length divided by the least radius of gyration (λ = Le / r_min). A higher slenderness ratio means a column is more prone to buckling.

CIV-025 · What is the difference between static and kinematic indeterminacy?

Static indeterminacy is the number of unknown forces beyond those equilibrium can solve. Kinematic indeterminacy is the number of unknown joint displacements (degrees of freedom).

CIV-026 · What is the maximum bending moment in a simply supported beam under UDL and under a central point load?

Under a UDL w over span L, M_max = wL²/8 at midspan. Under a central point load W, M_max = WL/4 at midspan.

RCC Design

CIV-027 · What is clear cover in RCC and what are typical values?

The concrete thickness between the outer surface and the nearest reinforcement, protecting it from corrosion and fire. IS 456 nominal cover ranges from 20 mm (mild exposure) to 30, 45, 50 and 75 mm (extreme exposure).

CIV-028 · How do you distinguish a one-way slab from a two-way slab?

If the longer-to-shorter span ratio Ly / Lx > 2, the slab bends mainly in the short direction (one-way). If Ly / Lx ≤ 2 and it is supported on all four sides, it acts two-way.

CIV-029 · What is a doubly reinforced beam?

A beam with steel in both tension and compression zones. It is used when the depth is restricted and the moment exceeds the limiting moment of a singly reinforced section.

CIV-030 · What are under-reinforced, balanced and over-reinforced sections?

In an under-reinforced section steel yields before concrete crushes (ductile, preferred). In a balanced section both happen together. In an over-reinforced section concrete crushes first, giving a sudden brittle failure.

CIV-031 · What is development length?

The embedment length needed to develop the full design stress in a bar through bond. Per IS 456, Ld = φσs / (4τbd), where φ is bar diameter and τbd is design bond stress.

CIV-032 · What is characteristic strength?

The strength below which not more than 5% of test results are expected to fall. It is used for both concrete (fck) and steel (fy).

CIV-033 · What partial safety factors does IS 456 use?

For materials at the ultimate limit state, γm = 1.5 for concrete and 1.15 for steel. For loads, 1.5(DL + LL) is the basic combination.

CIV-034 · What is the purpose of stirrups in a beam?

They resist diagonal tension due to shear, hold longitudinal bars in position, and give some confinement to the concrete.

CIV-035 · What is a T-beam?

A beam cast monolithically with a slab so that part of the slab acts as a compression flange. This increases moment capacity in sagging regions.

CIV-036 · What does Fe415 or Fe500 mean?

High-yield deformed steel bars with a characteristic yield (or 0.2% proof) stress of 415 or 500 N/mm², per IS 1786.

CIV-037 · What is the minimum tension reinforcement in a beam per IS 456?

As / (b d) = 0.85 / fy. For Fe415 this is about 0.2% of b·d.

CIV-038 · When is an RCC column classified as short?

When the ratio of effective length to lateral dimension (lex/D and ley/b) is less than 12, per IS 456. Otherwise it is slender and needs additional moments.

CIV-039 · What is effective depth of a beam?

The distance from the extreme compression fibre to the centroid of the tension reinforcement. It is used in all flexure and shear calculations.

Steel Structures

CIV-040 · What are common hot-rolled steel sections in India?

ISMB (medium-weight beams), ISJB, ISLB, ISWB, ISMC (channels), ISA (angles), tees, flats, plates and tubes, listed in SP 6(1) and IS 808.

CIV-041 · What is the yield strength of common structural steel in India?

E250 grade steel to IS 2062 has a yield strength of 250 N/mm² for thin sections, with ultimate strength of about 410 N/mm².

CIV-042 · What are the types of steel connections?

Bolted, welded and (historically) riveted. They can also be classified by behaviour as simple (pinned), rigid (moment) or semi-rigid.

CIV-043 · What is the difference between a fillet weld and a butt weld?

A fillet weld is triangular and joins surfaces at an angle, such as lap or tee joints. A butt (groove) weld joins plates edge to edge in the same plane, usually with full penetration.

CIV-044 · How does IS 800 classify cross-sections?

As plastic, compact, semi-compact or slender, based on width-to-thickness ratios. The class decides whether the section can reach plastic moment, yield moment or only lower capacity due to local buckling.

CIV-045 · What is a gusset plate?

A plate used at truss joints or column bases to connect several members and transfer forces between them.

CIV-046 · What are lacing and battening?

Systems that tie together the components of a built-up column so they act as one unit. Lacing uses diagonal bars; battens are plates placed perpendicular to the column axis.

CIV-047 · What are a tie and a strut?

A tie is a member in tension. A strut is a member in compression, typically in a truss or bracing system.

CIV-048 · What is a purlin?

A horizontal roof member spanning between trusses or rafters that supports the roof sheeting and transfers its load to the trusses.

CIV-049 · What is shape factor?

The ratio of plastic moment to yield moment, Mp / My = Zp / Ze. It is 1.5 for a rectangle, 1.7 for a solid circle and about 1.12–1.14 for I-sections.

CIV-050 · What is a plastic hinge?

A zone where the full section has yielded, so it rotates at a constant moment Mp. Enough plastic hinges form a collapse mechanism.

CIV-051 · What is the difference between bearing-type and friction-type bolts?

Bearing-type bolts transfer load by shear and bearing on the plate after slip. Friction-type (HSFG) bolts are pre-tensioned so friction between plates transfers the load without slip.

Geotechnical Engineering

CIV-052 · What is the three-phase diagram of soil?

A model showing soil as solids, water and air by volume and mass. It is used to derive relations between void ratio, porosity, water content, saturation and unit weights.

CIV-053 · What are void ratio and porosity, and how are they related?

Void ratio e = Vv / Vs; porosity n = Vv / V. They are related by n = e / (1 + e) and e = n / (1 − n).

CIV-054 · What are water content and degree of saturation?

Water content w = Ww / Ws (by mass of solids). Degree of saturation S = Vw / Vv; S = 0 for dry soil and 1 (100%) for fully saturated soil.

CIV-055 · What are Atterberg limits?

The water contents at which fine-grained soil changes state: liquid limit (liquid to plastic), plastic limit (plastic to semi-solid) and shrinkage limit (semi-solid to solid).

CIV-056 · What is plasticity index?

PI = LL − PL, the range of water content over which soil is plastic. A higher PI means a more plastic, compressible clay.

CIV-057 · What is Darcy's law?

For laminar flow through soil, the discharge velocity is v = k·i, where k is the coefficient of permeability and i is the hydraulic gradient. The flow is Q = k·i·A.

CIV-058 · What is the principle of effective stress?

Terzaghi's principle: σ′ = σ − u, where σ is total stress and u is pore water pressure. Effective stress controls soil strength and compressibility.

CIV-059 · What is the typical specific gravity of soil solids?

About 2.65–2.70 for sands and up to about 2.75–2.8 for clays. Organic soils have lower values.

CIV-060 · What is the standard Proctor test?

A laboratory compaction test in which soil is compacted in a mould in 3 layers of 25 blows each with a light rammer (about 2.5–2.6 kg dropped about 300 mm). It gives the dry density versus water content curve.

CIV-061 · What are OMC and MDD?

Optimum moisture content (OMC) is the water content at which a given compactive effort gives the maximum dry density (MDD). They are the peak of the compaction curve.

CIV-062 · What are the coefficient of uniformity and coefficient of curvature?

Cu = D60/D10 and Cc = D30² / (D10 × D60). A well-graded soil has Cc between 1 and 3 with Cu > 4 for gravels or Cu > 6 for sands.

CIV-063 · What is the difference between cohesive and cohesionless soils?

Cohesive soils (clays) have inter-particle attraction, plasticity and low permeability. Cohesionless soils (sands, gravels) get strength mainly from friction and drain freely.

CIV-064 · What is the Mohr–Coulomb failure criterion?

Shear strength τf = c + σ tan φ, where c is cohesion and φ is the angle of internal friction. In effective stress terms, τf = c′ + σ′ tan φ′.

Foundation Engineering

CIV-065 · What is the difference between shallow and deep foundations?

A shallow foundation has depth less than or about equal to its width (Df ≤ B) and transfers load near the surface. A deep foundation (pile, well, caisson) transfers load to deeper strata through end bearing and skin friction.

CIV-066 · What are the types of shallow foundations?

Isolated (pad) footings, combined footings, strip (wall) footings, strap footings and raft (mat) foundations.

CIV-067 · What is the difference between end-bearing and friction piles?

End-bearing piles carry load mainly through the tip resting on a hard stratum. Friction piles carry load mainly by skin friction along the shaft in deep soft or medium soils.

CIV-068 · When is a raft foundation used?

When soil bearing capacity is low, loads are heavy, or individual footings would cover more than about half the plan area. A raft spreads load and reduces differential settlement.

CIV-069 · What is the difference between ultimate, safe and allowable bearing capacity?

Ultimate bearing capacity causes shear failure. Safe bearing capacity is the ultimate value divided by a factor of safety (usually 2.5–3). Allowable bearing pressure also limits settlement to tolerable values.

CIV-070 · What are the components of foundation settlement?

Immediate (elastic) settlement, primary consolidation settlement due to expulsion of pore water, and secondary compression (creep) after pore pressure has dissipated.

CIV-071 · What is a well foundation?

A large hollow caisson sunk by dredging out soil from inside. It is common for bridge piers and abutments in Indian rivers with deep scour.

CIV-072 · What is a plate load test?

A field test in which a steel plate is loaded in increments at foundation level and settlement is measured. It gives bearing capacity and settlement characteristics of the soil.

CIV-073 · What is the Standard Penetration Test?

A split-spoon sampler is driven by a 63.5 kg hammer falling 750 mm. The number of blows for the last 300 mm of a 450 mm drive is the N-value, an index of soil density and strength.

CIV-074 · What are the types of retaining walls?

Gravity, cantilever, counterfort, buttress, crib and reinforced soil walls, plus sheet pile and diaphragm walls for excavations.

CIV-075 · What are earth pressure at rest, active pressure and passive pressure?

At rest (K₀) is pressure with no wall movement. Active (Ka) is the minimum pressure when the wall moves away from the soil. Passive (Kp) is the maximum resistance when the wall pushes into the soil.

CIV-076 · What is negative skin friction?

A downward drag on a pile when the surrounding soil settles more than the pile, for example due to fill on soft clay. It adds load to the pile instead of supporting it.

Surveying

CIV-077 · What is the difference between plane and geodetic surveying?

Plane surveying ignores the Earth's curvature and is used for small areas (up to about 250 km²). Geodetic surveying accounts for curvature and is used for large areas and control networks.

CIV-078 · What is the fundamental principle of surveying?

Work from the whole to the part: establish a framework of accurate control first, then fill in details, so errors are contained and do not accumulate.

CIV-079 · What chains and tapes are used in linear measurement?

Metric chains of 20 m and 30 m, the Gunter's chain (66 ft), the engineer's chain (100 ft), and steel, invar and synthetic tapes. Invar is used for high precision because of its low thermal expansion.

CIV-080 · What is a benchmark?

A fixed reference point of known reduced level. GTS benchmarks are set by the Survey of India; temporary benchmarks are set for local work.

CIV-081 · What are the two methods of reducing levels?

The height of instrument (collimation) method and the rise and fall method. Rise and fall gives a full arithmetic check on intermediate sights; HI is faster when there are many intermediate sights.

CIV-082 · What are a contour and contour interval?

A contour is a line joining points of equal elevation. Contour interval is the constant vertical distance between successive contours on a map.

CIV-083 · What is a theodolite used for?

Measuring horizontal and vertical angles. It is also used for setting out lines and curves, prolonging lines, levelling and tacheometry.

CIV-084 · What is the difference between whole circle bearing and quadrantal bearing?

Whole circle bearing is measured clockwise from north, 0° to 360°. Quadrantal (reduced) bearing is measured from north or south toward east or west, 0° to 90°, for example N30°E.

CIV-085 · What is magnetic declination?

The horizontal angle between true (geographic) north and magnetic north at a place. It varies with location and time.

CIV-086 · What is a total station?

An electronic instrument combining a theodolite with electronic distance measurement (EDM) and a data recorder. It measures angles and distances and computes coordinates directly.

CIV-087 · What is GNSS in surveying?

Global Navigation Satellite Systems such as GPS, GLONASS, Galileo and NavIC. They give 3D positions from satellite signals; differential and RTK methods reach centimetre-level accuracy.

CIV-088 · What are backsight, foresight and intermediate sight?

A backsight is the first staff reading after setting up the level, taken on a point of known RL. A foresight is the last reading before shifting the instrument. Readings in between are intermediate sights.

CIV-089 · What is local attraction in compass surveying?

Deflection of the magnetic needle by nearby iron objects, electric cables or ore deposits. It is detected when fore and back bearings of a line do not differ by 180°.

Transportation Engineering

CIV-090 · What are the layers of a flexible pavement?

From bottom to top: compacted subgrade, granular subbase, base course (such as WMM), and bituminous binder and wearing courses.

CIV-091 · What is camber?

A transverse slope given to the road surface to drain rainwater. Typical values are about 2–2.5% for bituminous surfaces and higher for gravel or earthen roads.

CIV-092 · What is superelevation?

Raising the outer edge of a road or rail relative to the inner edge on a horizontal curve, to counteract centrifugal force.

CIV-093 · What is stopping sight distance?

The minimum sight distance a driver needs to see an obstacle and stop safely. It is the sum of the lag distance (during perception–reaction time) and the braking distance.

CIV-094 · What is the CBR test?

The California Bearing Ratio test measures the penetration resistance of subgrade or granular material relative to a standard crushed stone. It is used in IRC flexible pavement design.

CIV-095 · What are ruling, limiting and exceptional gradients?

The ruling gradient is the normal maximum used in design. The limiting gradient may be used where topography demands. The exceptional gradient is allowed only for short stretches in difficult terrain.

CIV-096 · What are the railway gauges used in India?

Broad gauge (1676 mm), metre gauge (1000 mm) and narrow gauges (762 mm and 610 mm). Standard gauge (1435 mm) is used for many metro systems.

CIV-097 · What is a passenger car unit (PCU)?

A factor that converts different vehicle types into equivalent passenger cars, based on their effect on traffic flow. It is used to express mixed traffic volume and capacity.

CIV-098 · What are the common tests on bitumen?

Penetration, ductility, softening point (ring and ball), viscosity, flash and fire point, and specific gravity tests.

CIV-099 · What are the common tests on road aggregates?

Aggregate impact value, crushing value, Los Angeles abrasion, flakiness and elongation indices, water absorption and soundness tests.

CIV-100 · What is a transition curve?

A curve of gradually changing radius (usually a clothoid spiral) between a straight and a circular curve. It introduces centrifugal force and superelevation gradually.

CIV-101 · What is a wind rose diagram used for in airport planning?

It shows the direction, duration and intensity of wind. It is used to orient runways so that crosswind components stay within allowable limits for most of the time.

CIV-102 · What is the difference between at-grade and grade-separated intersections?

At-grade intersections have all roads at one level, controlled by signs, signals or roundabouts. Grade-separated intersections use flyovers or underpasses, and interchanges add ramps to separate conflicting movements.

Hydraulics & Water Resources

CIV-103 · What is a Newtonian fluid?

A fluid whose shear stress is directly proportional to the rate of shear strain, τ = μ (du/dy). Water and air are Newtonian.

CIV-104 · What is Bernoulli's equation?

For steady, incompressible, frictionless flow along a streamline, p/(ρg) + V²/(2g) + z = constant. The terms are pressure head, velocity head and datum head.

CIV-105 · What is the continuity equation?

Conservation of mass: for incompressible flow, discharge Q = A₁V₁ = A₂V₂ is constant along a pipe or channel.

CIV-106 · What is the difference between laminar and turbulent flow?

Laminar flow moves in smooth layers; turbulent flow has random mixing. In pipes, flow is generally laminar for Reynolds number below about 2000 and turbulent above about 4000.

CIV-107 · What is a hydraulic jump?

An abrupt rise in water surface when supercritical flow changes to subcritical flow. It dissipates a lot of energy and is used below spillways and sluices.

CIV-108 · What is the Froude number?

Fr = V / √(gD), the ratio of inertial to gravity forces in open channels, where D is hydraulic depth. Flow is subcritical if Fr < 1, critical if Fr = 1 and supercritical if Fr > 1.

CIV-109 · What is specific energy in open channel flow?

Energy per unit weight measured from the channel bed, E = y + V²/(2g). It is minimum at critical depth.

CIV-110 · What is Manning's equation?

V = (1/n) R^(2/3) S^(1/2) in SI units, where n is Manning's roughness coefficient, R is hydraulic radius and S is bed slope. It is used for uniform flow in channels and sewers.

CIV-111 · What is the difference between a notch and a weir?

Both measure discharge by flow over a sharp edge. A notch is a small opening in a tank or flume wall, used in labs. A weir is a larger structure built across a river or channel.

CIV-112 · What is a venturimeter?

A device that measures pipe discharge using a converging section, a throat and a diverging section. Discharge comes from the pressure difference between inlet and throat via Bernoulli's equation.

CIV-113 · What is a unit hydrograph?

The direct runoff hydrograph produced by 1 cm of effective rainfall falling uniformly over a catchment in a specified duration.

CIV-114 · What are duty and delta in irrigation?

Duty (D) is the area irrigated per cumec of continuous flow over the base period. Delta (Δ) is the total depth of water a crop needs. They are related by Δ = 8.64 B / D, with Δ in m, B in days and D in ha/cumec.

Water Supply & Sanitation

CIV-115 · What are the sources of water supply?

Surface sources such as rivers, lakes and reservoirs, and groundwater sources such as wells, tube wells, springs and infiltration galleries. Rainwater harvesting is a supplementary source.

CIV-116 · What is the per capita water demand for Indian cities?

IS 1172 recommends about 135 litres per capita per day for communities with full flushing systems. CPHEEO norms give 150 lpcd for metro cities, in addition to fire and other demands.

CIV-117 · What is turbidity?

Cloudiness of water due to suspended particles such as clay, silt and organic matter. It is measured in NTU with a nephelometer.

CIV-118 · What are coagulation and flocculation?

Coagulation is the addition of a chemical such as alum to destabilize colloidal particles by rapid mixing. Flocculation is gentle mixing that makes the destabilized particles grow into settleable flocs.

CIV-119 · What is sedimentation in water treatment?

Removal of suspended particles by gravity settling in tanks. Plain sedimentation removes discrete particles; coagulation-aided sedimentation removes finer colloids as flocs.

CIV-120 · What is the difference between slow sand and rapid sand filters?

Slow sand filters use a low filtration rate and a biological layer (schmutzdecke) and are cleaned by scraping. Rapid sand filters run at much higher rates after coagulation and are cleaned by backwashing.

CIV-121 · What is chlorination and residual chlorine?

Chlorination disinfects water by killing pathogens. Residual chlorine is the free chlorine left after demand is met, typically kept at about 0.2 mg/L at consumer taps to guard against recontamination.

CIV-122 · What is BOD?

Biochemical oxygen demand: the oxygen used by microorganisms to decompose biodegradable organic matter. It is usually measured over 5 days at 20 °C (BOD₅).

CIV-123 · What is COD?

Chemical oxygen demand: the oxygen needed to chemically oxidize organic matter using a strong oxidant such as potassium dichromate. It is measured in about 2–3 hours.

CIV-124 · What is a septic tank?

A watertight settling tank where sewage solids settle and are anaerobically digested. The effluent goes to a soak pit or drain field for further treatment.

CIV-125 · What is the difference between separate and combined sewer systems?

A separate system carries sewage and stormwater in different pipes. A combined system carries both in one pipe, which is cheaper but overloads treatment plants in rain.

CIV-126 · What is the difference between temporary and permanent hardness?

Temporary hardness is caused by calcium and magnesium bicarbonates and is removed by boiling. Permanent hardness is caused by their sulphates and chlorides and needs lime-soda, ion exchange or similar treatment.

Construction Management & Estimation

CIV-127 · What is the difference between CPM and PERT?

CPM uses deterministic activity durations and focuses on time–cost trade-offs. PERT uses three time estimates (optimistic, most likely, pessimistic) to model uncertainty and estimate completion probability.

CIV-128 · What is a critical path?

The longest path through a project network. It sets the minimum project duration, and its activities have zero total float.

CIV-129 · What are total float and free float?

Total float is the time an activity can be delayed without delaying the project. Free float is the time it can be delayed without delaying the early start of any following activity.

CIV-130 · What is a bar chart (Gantt chart)?

A schedule that shows activities as horizontal bars against a time scale. It is simple to read but does not show dependencies clearly.

CIV-131 · What are the types of estimates?

Preliminary (approximate), plinth area, cube rate, detailed, revised, supplementary and annual repair or maintenance estimates.

CIV-132 · What is a Bill of Quantities?

A document listing item-wise quantities of work with descriptions and units. Contractors price it in their bids, and it is used for payment and comparison of tenders.

CIV-133 · What is a tender?

A formal offer by a contractor to execute specified work at stated rates or price under given conditions, submitted in response to a notice inviting tenders.

CIV-134 · What units are used to measure common building items?

Earthwork, concrete and brickwork are measured in m³. Plastering, flooring and painting are measured in m². Reinforcement steel is measured in kg or tonnes, and skirting or pipes in running metres.

CIV-135 · What are lump-sum, item-rate and cost-plus contracts?

A lump-sum contract has a fixed total price. An item-rate contract pays quoted unit rates for measured quantities. A cost-plus contract reimburses actual cost plus a fee or percentage.

CIV-136 · What is rate analysis?

Working out the unit cost of an item of work from the quantities and costs of materials, labour, equipment and sundries, plus overheads and contractor's profit.

CIV-137 · What is plinth area?

The covered built-up area measured at floor level of the basement or any storey, including walls. Plinth area rates are used for quick preliminary estimates.

CIV-138 · What is the difference between earnest money and security deposit?

Earnest money (bid security, about 1–2%) is submitted with the tender to show the bidder is serious. A security deposit (performance security) is taken from the successful bidder to guarantee proper completion.

Earthquake Engineering

CIV-139 · What is the difference between earthquake magnitude and intensity?

Magnitude (Richter or moment magnitude) measures the energy released at the source and has one value per event. Intensity (such as MSK or Modified Mercalli) describes the shaking and damage at a location and varies from place to place.

CIV-140 · What are the hypocentre and epicentre?

The hypocentre (focus) is the point inside the Earth where rupture starts. The epicentre is the point on the surface directly above it.

CIV-141 · What are the seismic zones of India?

IS 1893 (Part 1):2016 divides India into Zones II, III, IV and V with zone factors Z = 0.10, 0.16, 0.24 and 0.36. Zone V is the most severe.

CIV-142 · What are the types of seismic waves?

Body waves, which are P-waves (primary, compressional, fastest) and S-waves (secondary, shear), and surface waves, which are Love and Rayleigh waves and usually cause the most damage.

CIV-143 · What is the natural period of a structure?

The time a structure takes to complete one cycle of free vibration in a given mode. It depends on mass and stiffness, T = 2π√(m/k), and increases with height.

CIV-144 · What is base shear?

The total design lateral force at the base of a structure due to earthquake ground motion. It is calculated as V_B = A_h × W.

CIV-145 · What is ductility?

The ability of a structure or member to undergo large inelastic deformation without significant loss of strength. It allows energy dissipation during earthquakes.

CIV-146 · What is a soft storey?

A storey whose lateral stiffness is much lower than the storey above, such as an open ground floor used for parking. It concentrates drift and damage and often collapses in earthquakes.

CIV-147 · What is a response spectrum?

A plot of the peak response (acceleration, velocity or displacement) of single-degree-of-freedom systems against natural period, for a given damping and ground motion. Design codes give smoothed versions.

CIV-148 · What damping ratio is usually assumed for RC buildings in seismic design?

5% of critical damping, which is the basis of the IS 1893 design spectrum. Steel structures are often taken at 2%.

CIV-149 · What is a shear wall?

A vertical RC (or masonry) wall that resists lateral forces through in-plane stiffness and strength. It greatly reduces storey drift in buildings.

CIV-150 · What is seismic weight of a building?

The full dead load plus a fraction of the imposed load, per IS 1893. The fraction is 25% for imposed loads up to 3 kN/m² and 50% above that. Roof imposed load is usually not included.

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