RCC MCQ Practice Set — 50 Questions with Answers
50 exam-oriented RCC multiple-choice questions with the correct answer and a clear explanation for each. Frequently asked in AE Level Civil Engineering, JE Level Civil Engineering. Solve the full set below for free — no login required.
- 1RCCMEDIUM
The 'ductility' of RC structures is improved under earthquake loading by:
AUsing higher grade concrete onlyBConfinement hoops, under-reinforced sections, strong column-weak beam hierarchy, avoiding laps in hinge zonesCIncreasing rebar diameter onlyDEliminating ties and stirrups for speedAnswer: B. Confinement hoops, under-reinforced sections, strong column-weak beam hierarchy, avoiding laps in hinge zones
Explanation: Ductility in RCC: (1) Confinement reinforcement (IS 13920 — closely spaced hoops/spirals confine concrete, increase ductility in columns and joints); (2) Balanced or under-reinforced section (not over-reinforced); (3) Avoiding lap splices in plastic hinge zones; (4) Strong column — weak beam design (hierarchy of strength); (5) Avoiding abrupt changes in stiffness. Higher ductility = more energy absorption.
- 2RCCHARD
For a circular RC water tank with rigid base, the hoop tension is maximum at:
AAt the base (maximum water pressure)BApproximately mid-height (base restraint reduces hoop tension there; free top — parabolic distribution with max at ~mid)CAt the top (freeboard level)DConstant throughout heightAnswer: B. Approximately mid-height (base restraint reduces hoop tension there; free top — parabolic distribution with max at ~mid)
Explanation: Circular water tank (IS 3370, rigid base): at the base — restrained from expansion → zero hoop tension at base; increases to maximum at mid-height then slightly reduces near top (free). Free top: hoop tension T = γwH×R at that depth. Near rigid base: restraint causes vertical cantilever BM. Critical design: (1) Hoop tension in cylindrical wall; (2) Vertical BM near base. IS 3370 provides design tables.
- 3RCCHARD
The 'end block' in a post-tensioned member is specially designed for:
ANormal bending moment at midspanBBursting tensile stresses in the anchorage zone where concentrated prestress force disperses to full sectionCShear force at supports onlyDFlexural cracking in spanAnswer: B. Bursting tensile stresses in the anchorage zone where concentrated prestress force disperses to full section
Explanation: End block (anchorage zone): high concentrated force from prestressing jack is applied over small bearing plate → spreads to full cross-section over a distance approximately equal to the depth. High bursting (tensile) stresses develop transverse to the tendon direction. End block reinforcement (helical or orthogonal stirrups = 'Magnel zone' reinforcement) resists bursting. IS 1343 provides design guidance.
- 4RCCMEDIUM
The 'minimum clear cover' for reinforcement in a RCC beam in severe exposure (IS 456) is:
A15 mm (same for all exposures)B45 mm nominal cover in severe exposure per IS 456 Table 16 — protects rebar from corrosive environmentC5 mm onlyD100 mm for all conditionsAnswer: B. 45 mm nominal cover in severe exposure per IS 456 Table 16 — protects rebar from corrosive environment
Explanation: IS 456 Table 16: Nominal cover = clear cover + tie/stirrup dia. Mild exposure: 20 mm (beams/slabs). Moderate: 30 mm. Severe: 45 mm. Very severe: 50 mm. Extreme: 75 mm. Nominal cover must also meet development length requirement. Nominal cover ≥ maximum bar dia. Severe exposure includes: alternate wetting/drying, buried below aggressive groundwater, permanently saturated. Cover protects rebar from corrosion.
- 5RCCMEDIUM
A 'shear wall' in a multi-storey RC building acts as:
AOnly carrying vertical floor loads (column alternative)BVertical cantilever resisting lateral (wind/seismic) loads — provides lateral stiffness and overturning resistanceCOnly for acoustic insulationDBeam spanning between columnsAnswer: B. Vertical cantilever resisting lateral (wind/seismic) loads — provides lateral stiffness and overturning resistance
Explanation: Shear walls: RC walls acting as vertical cantilevers (fixed at base) to resist lateral loads (wind, seismic). Provide lateral stiffness and strength. Plan layout: symmetric placement to avoid torsion; core walls (lift shafts, staircases) ideal. Design: bending (lateral force × height = overturning moment), shear (base shear), and sliding. IS 13920: special boundary elements at ends of shear wall for ductility.
- 6RCCMEDIUM
The 'torsion' in RC beams is resisted by:
AOnly longitudinal bars (no stirrups needed)BClosed stirrups (links) + longitudinal bars at corners — space truss analogy; open stirrups cannot resist torsionCPre-stressing force onlyDOnly concrete in pure compressionAnswer: B. Closed stirrups (links) + longitudinal bars at corners — space truss analogy; open stirrups cannot resist torsion
Explanation: IS 456 Cl. 41: torsion resistance by closed stirrups (links around all bars, no open stirrups for torsion) + longitudinal bars at corners. Space truss analogy: concrete diagonal compressive struts + longitudinal tension + transverse tension in ties. Torsion equivalent shear Tve = (Tu + Tu') for design; longitudinal steel Asl = Tve/(2A_oh×fy/γs). Closed stirrups critical — open stirrups cannot resist torsion.
- 7RCCMEDIUM
The 'modular ratio' m used in working stress method (WSM) for RCC is defined as:
Am = fck / fy (concrete to steel grade ratio)Bm = Es/Ec = 280/(3σcbc) — converts steel area to equivalent concrete; used in IS 3370 WSM for liquid-retaining structuresCm = 1.5 for all concrete gradesDm = fy / fckAnswer: B. m = Es/Ec = 280/(3σcbc) — converts steel area to equivalent concrete; used in IS 3370 WSM for liquid-retaining structures
Explanation: Modular ratio m = Es / Ec = 280 / (3σcbc) per IS 456 (older WSM). σcbc = permissible compressive stress in concrete bending (MPa). Typical: M20 concrete: σcbc = 7 MPa → m = 280/21 ≈ 13.3. Used in: transformed section (steel area converted to equivalent concrete = m × Ast). WSM replaced by LSM in IS 456:2000, but WSM retained for water-retaining structures (IS 3370 Part 2). Transformed NA: bx²/2 = m × Ast × (d−x).
- 8RCCMEDIUM
The 'post-tensioning' system requires anchor components to transfer force to concrete because:
ATendons directly bonded to concrete throughout (no anchors needed)BTendon stressed against hardened concrete using wedge/nut anchors bearing on anchor plate — force locked in by anchorCOnly gravity holds tendons in placeDWelding tendons to reinforcement cageAnswer: B. Tendon stressed against hardened concrete using wedge/nut anchors bearing on anchor plate — force locked in by anchor
Explanation: Post-tensioning: tendons (in ducts) stressed after concrete hardening using hydraulic jacks bearing on concrete end face. Force transferred: (1) Friction (along curved tendon path); (2) Bearing (wedge anchors press on anchor plate which bears on concrete). Anchor integrity critical — all prestress locked in by anchor. Loss: anchorage slip (1–5 mm draw-in). IS 1343 covers details; IS 6003 for duct; IS 1785 for wire.
- 9RCCHARD
The 'equivalent frame method' for flat slab design divides the structure into:
AOnly individual column footingsB2D frames (each full floor width strip + columns) in each direction — moments distributed to column and middle stripsC1D simply supported slabsDIsolated columns onlyAnswer: B. 2D frames (each full floor width strip + columns) in each direction — moments distributed to column and middle strips
Explanation: IS 456 Annex D / ACI 318 Equivalent Frame Method: flat slab analysed as a series of 2D frames in each direction. Each frame consists of: (1) Equivalent beam (whole floor slab strip width = centre-to-centre distance); (2) Columns above and below. Stiffness of equivalent beam accounts for torsional flexibility of transverse slab strips. Moments distributed to column strips and middle strips using specified ratios.
- 10RCCMEDIUM
'Thermal cracking' in mass concrete (like dam and raft foundations) is controlled by:
AUsing rapid-setting cementBLow-heat cement, pre-cooling, post-cooling pipes, and pour size limits — reduce temperature rise and gradient during hydrationCAdding more water to concreteDHeating the concrete externallyAnswer: B. Low-heat cement, pre-cooling, post-cooling pipes, and pour size limits — reduce temperature rise and gradient during hydration
Explanation: Mass concrete: heat of hydration causes temperature rise (peak at 2–3 days); subsequent cooling → tensile stress → cracking if ΔT > 20°C (thermal gradient). Control: (1) Low heat cement (LHC/SRC/fly ash blends); (2) Pre-cooling aggregate and mixing water (chilled water, ice); (3) Post-cooling with embedded water pipes; (4) Limiting pour depth/width; (5) Insulation of formwork. IS 7861 covers hot weather concreting.
- 11RCCHARD
A 'corbel' in RC is designed for shear-to-depth ratio a/d ≤ 1 using:
AStandard beam flexure (M/Z) with no shear checkBStrut-and-tie model (STM) — inclined compressive strut + horizontal tensile tie; IS 456 Annex B for a/d ≤ 1CColumn interaction diagramDSimple bending formula M = Vu×aAnswer: B. Strut-and-tie model (STM) — inclined compressive strut + horizontal tensile tie; IS 456 Annex B for a/d ≤ 1
Explanation: Corbel (bracket): short cantilever with a/d ≤ 1. Design by strut-and-tie model (STM): inclined strut carries compressive force; horizontal tie at top carries tension = Vh = Vu×a/z ≈ Vu×a/0.9d. Main reinforcement: closed horizontal ties at top (tension). Framing bars: additional closed links below main bars for confinement. IS 456 Annex B: empirical design chart for a/d ≤ 1. Bearing area: critical at column face.
- 12RCCMEDIUM
The 'minimum reinforcement' in RC beams (IS 456) ensures:
AMaximum strength is achievedBDuctile behaviour after cracking — minimum steel carries tensile force from concrete at cracking, preventing brittle sudden failureCNo deflection under service loadsDCompressive strength governs designAnswer: B. Ductile behaviour after cracking — minimum steel carries tensile force from concrete at cracking, preventing brittle sudden failure
Explanation: IS 456 Cl. 26.5.1.1: Minimum Ast = 0.85/fy × bw × d (in mm²) where fy in MPa. Purpose: prevent sudden (brittle) fracture if concrete cracks — minimum steel takes over tensile force. If Ast = 0, a cracked beam fails suddenly (no ductility). Minimum ensures: Ast_steel can carry at least the tensile force present in concrete just before cracking (M_cr = 0.7√fck × Z). Avoids over-reinforced sections too (Ast_max = 0.04 bD).
- 13RCCMEDIUM
The 'laps' in reinforcement bars are generally NOT recommended for bars larger than:
A12 mmB36 mm — IS 456 recommends mechanical couplers or welded splices for bars > 36 mm diameterC20 mmD50 mmAnswer: B. 36 mm — IS 456 recommends mechanical couplers or welded splices for bars > 36 mm diameter
Explanation: IS 456 Cl. 26.2.5: lap splices should not be used for bars larger than 36 mm diameter. For larger bars: mechanical couplers (threaded sleeve) or welded splices (IS 2751 for welding rebars). Laps: not more than 50% of total steel should be lapped at one section. Lap length = development length × 1.3 (tension); staggered laps preferred. Reason: laps in large bars (> 36 mm) cause excessive congestion and concrete placing problems.
- 14RCCMEDIUM
The 'development length' for a bar in compression (IS 456) compared to tension is:
ASame as tension Ld (no difference)B80% of tension Ld — compression has no splitting tendency and end bearing helps, so shorter development neededC120% of tension LdD50% of tension LdAnswer: B. 80% of tension Ld — compression has no splitting tendency and end bearing helps, so shorter development needed
Explanation: IS 456 Cl. 26.2.1: development length Ld = φ×σs/(4×τbd). In compression: (1) No splitting tendency (bars being pushed in, not pulled); (2) End bearing contributes. IS 456 allows Ld in compression = 80% of Ld in tension. Tension Ld = φ×σs/(4×τbd); Compression Ld = 0.8 × tension Ld. Note: τbd for compression same formula but the 25% reduction factor gives 80% of tension value. Important for column bars passing through slabs.
- 15RCCMEDIUM
Pre-cast concrete elements are preferred over in-situ because:
APre-cast is always cheaper in all casesBBetter quality control, faster erection, less site labour/formwork, repetitive elements — especially for bridges and floorsCPre-cast requires no joints between elementsDPre-cast can only be used for wallsAnswer: B. Better quality control, faster erection, less site labour/formwork, repetitive elements — especially for bridges and floors
Explanation: Pre-cast advantages: (1) Factory quality control (better strength, durability); (2) Faster construction (erection speed); (3) Reduced site formwork and labour; (4) Reduced curing time on site; (5) Repetitive elements (economy). Disadvantages: heavy lifting, joints between elements (design challenge), transportation limits (max ~25 m length on road), not easily modified. Used for: bridge girders, hollow-core slabs, columns, spun poles.
- 16RCCHARD
The 'pre-stressed concrete' advantage of 'load balancing' concept means:
AUsing pre-stress to replace all steelBCurved tendon vertical components balance gravity loads — at balanced load, beam experiences only uniform axial compression (no bending)CPre-stressing eliminates the need for formworkDBalancing the mix design of concreteAnswer: B. Curved tendon vertical components balance gravity loads — at balanced load, beam experiences only uniform axial compression (no bending)
Explanation: Load balancing (Lin, 1963): in PSC, curved tendon with vertical component (upward) balances a portion of gravity load. At balanced load: beam is under uniform axial compression only (no bending). Practical: pre-stress cable profile shaped to balance ~80% DL → beam acts in pure compression for DL → only remaining (unbalanced) load causes bending/shear. Reduces deflection, cracking. Very elegant concept for two-way slabs and flat plates.
- 17RCCMEDIUM
'Shrinkage' of concrete is the volumetric reduction due to:
AThermal expansion reversal onlyBMoisture loss (drying shrinkage primary), autogenous (low w/c), and plastic (before set) — affects PSC loss, deflection, crackingCIncrease in curing temperatureDCompressive loadingAnswer: B. Moisture loss (drying shrinkage primary), autogenous (low w/c), and plastic (before set) — affects PSC loss, deflection, cracking
Explanation: Concrete shrinkage types: (1) Drying shrinkage — loss of moisture to ambient air (most significant; 400–800 microstrain); (2) Autogenous — self-desiccation in low w/c concrete (capillary suction); (3) Plastic shrinkage — rapid surface drying before set (craze cracking); (4) Carbonation shrinkage — CaCO3 formation. Total shrinkage strain affects: prestress loss, deflection of beams, crack width. Reduced by: aggregate, lower w/c.
- 18RCCHARD
The 'push-over analysis' of RC buildings under earthquake is a:
ALinear elastic response spectrum analysisBNon-linear static analysis — incrementally increasing lateral load to generate capacity curve and identify hinge sequenceCTime-history dynamic analysisDLimit state design for bending onlyAnswer: B. Non-linear static analysis — incrementally increasing lateral load to generate capacity curve and identify hinge sequence
Explanation: Push-over analysis (IS 1893 Annex A): non-linear static procedure. Monotonically increasing lateral load applied in proportion to mode shape; track: (1) Capacity curve (base shear vs roof displacement); (2) Sequential plastic hinge formation; (3) Capacity spectrum method to find performance point (intersection with demand spectrum). Identifies weak storey, non-linear deformation capacity. Required for irregular buildings in IS 1893.
- 19RCCMEDIUM
The 'construction joint' in RC structures is treated with water-stop when:
AOnly in decorative facadesBIn water-retaining structures (tanks, basements) — PVC/rubber water-stop prevents water seepage through construction jointsCAll construction joints regardless of useDOnly in earthquake-resistant columnsAnswer: B. In water-retaining structures (tanks, basements) — PVC/rubber water-stop prevents water seepage through construction joints
Explanation: Construction joints: planned stopping and restarting of concrete placement. In water-retaining structures (tanks, basements): joints must be water-tight. Water-stop (PVC or rubber profile) embedded at joint centre — when concrete poured on both sides, water-stop provides mechanical barrier against water seepage through joint. Types: centre bulb (most common), dumbbell. IS 3370 requires water-stops for liquid-retaining structures.
- 20RCCHARD
'Strut-and-tie model' (STM) is used for RC design of 'D-regions' where:
AStandard slender beams with uniform momentBD-regions (deep beams, corbels, joints) where plane-sections-remain-plane assumption breaks down — truss analogyCOnly pre-stressed concreteDOnly axially loaded columnsAnswer: B. D-regions (deep beams, corbels, joints) where plane-sections-remain-plane assumption breaks down — truss analogy
Explanation: STM: applicable in D-regions (Disturbed regions) where Bernoulli beam theory (plane sections remain plane) is invalid: deep beams (a/d < 2), corbels (a/d < 1), dapped ends, beam-column joints, pile caps. Replace complex stress state with equivalent truss: struts (concrete in compression), ties (steel in tension). Forces in strut/tie = design forces for concrete/steel. IS 456 provides limited guidance; ACI 318 Ch.23 comprehensive.
- 21RCCMEDIUM
The 'two-way slab' design (IS 456) uses which table for sagging moments in the two directions?
ATable for flat slabs (column head dimensions)BIS 456 Table 26 (Annex D) — αx and αy moment coefficients varying with ly/lx and edge conditionCBeam design table (rectangular section Mu/bd²)DFoundation settlement tableAnswer: B. IS 456 Table 26 (Annex D) — αx and αy moment coefficients varying with ly/lx and edge condition
Explanation: IS 456 Annex D (Table 26): simply supported or restrained two-way slabs — moment coefficients αx and αy for short span and long span directions. Conditions: restrained or not at edges. Moments: Mx = αx × w × lx² (short span); My = αy × w × lx² (long span). Coefficients from Table 26 vary with (ly/lx) ratio (1.0 to 2.0). Edge condition (continuous/discontinuous) affects coefficients. Restrained slabs develop torsional steel at discontinuous corners.
- 22RCCMEDIUM
The 'development length' concept in IS 456 is needed to ensure:
AThe bar can be bent at that pointBFull bar stress can be transferred to concrete by bond — bars must extend at least Ld beyond the critical sectionCOnly to prevent corrosionDThe concrete cures faster near the barAnswer: B. Full bar stress can be transferred to concrete by bond — bars must extend at least Ld beyond the critical section
Explanation: Development length (Ld): minimum bar length embedded in concrete so the bar can be fully stressed (reach design stress). Ld = φ × σs / (4 × τbd) where τbd = design bond stress (IS 456 Table 26), σs = steel stress at section = 0.87×fy. Purpose: bar pulled at one end → bond stress transfers force to concrete over Ld → bar reaches full capacity within Ld. Without adequate Ld: bond failure → bar slips before yielding → sudden brittle failure.
- 23RCCMEDIUM
The 'box girder' bridge cross-section is preferred for curved alignments because:
ABox girders are easier to formwork than T-beamsBClosed section provides very high torsional stiffness (Bredt''s formula) — essential for curved bridge where torsion is dominantCBox girders need no prestressingDOnly for shallow water crossingsAnswer: B. Closed section provides very high torsional stiffness (Bredt''s formula) — essential for curved bridge where torsion is dominant
Explanation: Box girder (hollow rectangular or trapezoidal cross-section): very high torsional stiffness (closed thin-walled section: T = 2×A_enclosed×t×τ per Bredt''s formula). On curved alignment: dead load and live load eccentric → high torsional moments. Box girder: torsional rigidity ~100× I-section → handles curve torsion efficiently. Also: high bending stiffness, reduced self-weight, smooth aerodynamic shape. RC box girder: 30–60 m spans; prestressed: 60–250 m.
- 24RCCMEDIUM
The 'expansion joint' in a long RC structure is provided to:
AProvide additional shear capacity at midspanBAccommodate thermal movement, shrinkage, and differential settlement without causing cracking — IS 456: every 45 mCOnly for aesthetic purposes (joint as design feature)DReduce reinforcement quantityAnswer: B. Accommodate thermal movement, shrinkage, and differential settlement without causing cracking — IS 456: every 45 m
Explanation: Expansion joints: deliberate discontinuity in RC structure to accommodate: (1) Thermal expansion/contraction (temperature cycles); (2) Concrete shrinkage; (3) Differential settlement between parts; (4) Seismic separation. IS 456 Cl. 27: provide movement joints at intervals not exceeding 45 m in general. Joint width: 25–50 mm (allows movement). Filled with compressible filler and waterproofed with sealant. Without joints: restrained movement → cracking, structural damage.
- 25RCCMEDIUM
The 'interaction diagram' for RC column design shows relationship between:
ADeflection vs. span relationshipBCombinations of axial load P and moment M at the failure limit — points inside P-M envelope are safeCOnly shear vs. moment relationshipDConcrete grade vs. rebar grade selectionAnswer: B. Combinations of axial load P and moment M at the failure limit — points inside P-M envelope are safe
Explanation: P-M interaction diagram: for given column (dimensions, reinforcement): plots combinations of axial load P and bending moment M that cause failure (limit state). Points on curve = balanced failure at each eccentricity. Points inside curve = safe. Points outside = failure. Special points: pure compression (P0, M=0), pure bending (M0, P=0), balanced point (extreme fibre strain = εcu, rebar = εy simultaneously). Used for: eccentrically loaded column design check.
- 26RCCHARD
'Segmental bridge construction' using 'balanced cantilever' method means:
ABuilding from both abutments simultaneously without piersBSegments added symmetrically from each pier as paired cantilevers — no mid-span falsework; prestressed progressivelyCAll segments cast at the same time using full formworkDLifting pre-cast deck panels by cranes from the topAnswer: B. Segments added symmetrically from each pier as paired cantilevers — no mid-span falsework; prestressed progressively
Explanation: Balanced cantilever: segments (2–5 m long precast or cast-in-place) built symmetrically in pairs from each pier outward (one segment each side alternately) → balanced overhanging cantilevers grow from pier without falsework touching ground below. Used for: navigable rivers, deep gorges, highways. Pre-stressing: cantilever tendons on top; after closure (midspan): additional bottom tendons. Typical span: 70–200 m. Famous examples: Bandra-Worli Sealink, metro viaducts.
- 27RCCMEDIUM
'Mass concrete' (large dams, pile caps, thick rafts) uses special measures to control:
ALow compressive strengthBThermal cracking — heat of hydration raises core temperature, surface-to-core temperature differential causes tensile cracksCInsufficient workability for pumpingDExcessive shrinkage from low water contentAnswer: B. Thermal cracking — heat of hydration raises core temperature, surface-to-core temperature differential causes tensile cracks
Explanation: Mass concrete: large volume where heat of hydration (cement reactions generate heat) creates thermal gradients → temperature differential between core (hot) and surface (cooler) → tensile stresses on surface → thermal cracks. Control: (1) Low heat cement (LHC) or GGBS/fly ash partial replacement; (2) Chilled water/ice for mixing; (3) Pre-cooling aggregates; (4) Post-cooling pipes (water circulated through embedded pipes); (5) Limit pour thickness; (6) Insulate formwork surface. IS 14268 covers mass concrete.
- 28RCCMEDIUM
The 'waffle slab' (grid slab) is most suitable for:
AShort spans with heavy point loadsBLarge column-free spans (10–20 m) — reduces dead weight while maintaining depth; coffered ceiling is aesthetically pleasingCOnly retaining wall constructionDOnly hydraulic structuresAnswer: B. Large column-free spans (10–20 m) — reduces dead weight while maintaining depth; coffered ceiling is aesthetically pleasing
Explanation: Waffle slab: two-way ribbed slab — hollow moulds (domes) create voids below, leaving ribs in two directions + solid top slab. Benefits: (1) Reduced dead weight (voids remove unnecessary concrete); (2) High structural depth (deep ribs → large I); (3) Aesthetic coffered ceiling. Economical for: large column-free spans (10–20 m), auditoriums, parking garages. Solid band beams at columns: punching shear region. Not suitable for very heavy live loads (prefer flat slab with drop panels).
- 29RCCHARD
The 'cable-stayed bridge' transfers deck loads to the tower by:
AArch action in the deckBInclined cables in tension anchored to towers; towers in compression; horizontal cable component pre-compresses the deckCSteel trusses below the deckDSuspension hangers from main cablesAnswer: B. Inclined cables in tension anchored to towers; towers in compression; horizontal cable component pre-compresses the deck
Explanation: Cable-stayed bridge: deck supported by inclined cables anchored to towers (pylons). Cables are in tension; towers in compression; deck in compression (pre-compressed by cable horizontal component). Different from suspension bridge: cables anchored directly to tower, not to a main cable. Advantages: longer spans than girder (200–500 m), less material than suspension, aesthetically appealing. Examples: Bandra-Worli Sea Link (extradosed), Vidyasagar Setu (Kolkata — cable-stayed).
- 30RCCMEDIUM
The 'shrinkage' of concrete after casting is distinguished into plastic and drying shrinkage as:
ANo difference — both occur after one yearBPlastic: first hours while concrete is fresh (evaporation > bleeding); drying: long-term moisture loss from hardened concreteCPlastic shrinkage only in summer, drying only in winterDBoth are only relevant for high-strength concreteAnswer: B. Plastic: first hours while concrete is fresh (evaporation > bleeding); drying: long-term moisture loss from hardened concrete
Explanation: Concrete shrinkage types: (1) Plastic shrinkage: occurs while concrete still plastic (first few hours) → loss of bleed water + surface evaporation exceeds bleeding rate → surface tension cracks (map cracking); prevent by: fog spray, wind breaks, early covering; (2) Drying shrinkage: slow volume reduction as concrete dries (months to years) → cement paste contracts → restrained by aggregate and reinforcement; (3) Autogenous (chemical) shrinkage: internal self-desiccation, significant in low w/c (<0.4) mixes; (4) Carbonation shrinkage.
- 31RCCMEDIUM
'Hollow-core pre-stressed slabs' are used in buildings because:
AProvide extra mass for earthquake resistanceBReduce self-weight by 30–40% while achieving long spans (up to 20 m) — factory quality, fast erection, no propping neededCAre used only for column designDOnly for coastal structuresAnswer: B. Reduce self-weight by 30–40% while achieving long spans (up to 20 m) — factory quality, fast erection, no propping needed
Explanation: Hollow-core slabs: extruded pre-stressed concrete planks with longitudinal circular/oval voids — reduce self-weight by 30–40%. Pre-stressed: eliminates shear reinforcement needs, long clear spans (up to 20 m). Used in: residential floors, car parks, warehouses. Advantages: (1) Factory-made quality; (2) Fast erection (no formwork, no propping); (3) Sound insulation (hollow cores). Grouted joints between planks. Cannot cantilever freely (no negative bending capacity unless extra rebar added in cores).
- 32Original practiceMEDIUM
A rectangular RCC beam has b=300 mm, effective depth=400 mm and tension steel=1.0% of bd. Steel area is
A2400 mm²B1200 mm²C120000 mm²D600 mm²Answer: B. 1200 mm²
Explanation: Tensile reinforcement area Ast = (pt / 100) * b * d, where pt = steel percentage (%), b = beam width (mm), d = effective depth (mm). IS 456 limits: minimum pt = 0.85*100/fy (for beams); maximum pt = 4% for beams. Ast governs moment capacity and must satisfy both strength and serviceability requirements. Ast = 1.0/100 × b × d = 1200 mm².
- 33Previous-year standardMEDIUM
For a bar diameter 20 mm, design stress 150 N/mm² and bond stress 1.2 N/mm², development length Ld=φσ/(4τ) is
A1250 mmB645 mmC625 mmD312.5 mmAnswer: C. 625 mm
Explanation: Development length Ld = (phi * sigma_s) / (4 * tau_bd), where phi = bar diameter (mm), sigma_s = design tensile stress in steel (N/mm^2), tau_bd = design bond stress per IS 456 (depends on fck and bar type; tau_bd for M20 deformed bars = 1.6 N/mm^2; plain bars = 1.2 N/mm^2). Ensures bar force is fully transferred by bond before the critical section. Ld=φσ/(4τ)=20×150/(4×1.2)=625 mm.
- 34IS 456 CoverMEDIUM
As per IS 456:2000, the minimum nominal cover for a beam in a moderate exposure condition is:
A20 mmB25 mmC30 mmD45 mmAnswer: C. 30 mm
Explanation: As per IS 456:2000 Table 16, the nominal cover for a beam in moderate exposure condition is 30 mm.
- 35RCC and Steel DesignEASY
What is the primary purpose of a lug angle in a tension member connection?
ATo increase the tensile strength of the main memberBTo reduce the length of the connectionCTo provide additional shear resistanceDTo act as a stiffener for the gusset plateAnswer: B. To reduce the length of the connection
Explanation: Lug angles are used to connect the outstanding legs of a tension member to the gusset plate, which allows for a shorter connection length and more efficient load transfer.
- 36RCC and Steel DesignMEDIUM
A corbel is defined as:
Aa type of pile groupBa structural slab openingCa long simply supported beamDa short cantilever projection from a column or wallAnswer: D. a short cantilever projection from a column or wall
Explanation: A corbel is a short cantilever projection from a column or wall used to support concentrated loads.
- 37RCCMEDIUM
A T-beam section has slab width 300 cm, slab depth 10 cm, rib width 30 cm, beam centre-to-centre distance 3 m (300 cm) and span 5 m (500 cm). Effective flange width is
A120 cmB150 cmC180 cmD300 cmAnswer: B. 150 cm
Explanation: According to IS 456:2000, effective flange width bf = (lo/6) + bw + 6Df. Here, lo = 0.7 * span = 350 cm. bf = (350/6) + 30 + 6(10) = 58.33 + 30 + 60 = 148.33 cm, which is approximately 150 cm.
- 38RCCMEDIUM
The spacing of counterforts depends on
AHeight of the wallBRelative cost of steel and concreteCAllowable unit pressure of soilDAll of the aboveAnswer: D. All of the above
Explanation: The economic spacing of counterforts is influenced by the height of the wall, the relative costs of materials, and the soil pressure, making 'All of the above' the correct choice.
- 39RCCMEDIUM
The overall depth of a wall footing is 560 mm and effective depth is 500 mm. The width of the footing is 3000 mm. The spacing of 10 mm bars for longitudinal reinforcement is
AInsufficient data providedB150 mmC200 mmD300 mmAnswer: A. Insufficient data provided
Explanation: The calculation of reinforcement spacing requires the load on the footing, the allowable soil pressure, and the grade of concrete/steel, which are not provided in the question.
- 40Prestressed ConcreteMEDIUM
Prestress losses in a prestressed concrete member include:
AElastic shortening, creep, shrinkage, relaxation (for pre-tensioned)BOnly friction and anchorage slip (for post-tensioned)CElastic shortening, creep, shrinkage, relaxation, friction, anchorage slip — which ones apply depends on pretension/post-tensionDOnly immediate lossesAnswer: C. Elastic shortening, creep, shrinkage, relaxation, friction, anchorage slip — which ones apply depends on pretension/post-tension
Explanation: Immediate losses: elastic shortening, friction (post only), anchorage slip (post only). Long-term losses: creep, shrinkage, relaxation. Total losses typically 15–25% of initial prestress.
- 41Prestressed ConcreteMEDIUM
Kern (core) of a cross-section in prestressed concrete is:
AThe central 1/3 of the sectionBRegion within which prestress must be applied to keep entire section in compressionCThe centroid point onlyDThe plastic neutral axis zoneAnswer: B. Region within which prestress must be applied to keep entire section in compression
Explanation: Kern: the area about the centroid within which a compressive load must be applied to avoid tension anywhere. For rectangular section: kern extends to ±L/6 from centroid (L=depth); for I-section: smaller kern.
- 42Materials and IS 456MEDIUM
As per IS 456, minimum cement content for M25 concrete (nominal mix/design mix) in moderate exposure:
A300 kg/m³B250 kg/m³C350 kg/m³D400 kg/m³Answer: A. 300 kg/m³
Explanation: IS 456 Table 5: Moderate exposure — min cement 300 kg/m³, max w/c 0.50, min fck M25 (20 for structure). Mild: min 300 kg/m³, max w/c 0.55, min M20.
- 43FootingsMEDIUM
The critical section for punching shear in a footing is at:
AFace of columnBd/2 from face of column (perimeter d/2 around column)Cd from face of columnDEdge of footingAnswer: B. d/2 from face of column (perimeter d/2 around column)
Explanation: Punching shear: critical perimeter bo = 4(b+d) for square column (b=column side, d=effective depth). Punching shear stress τv = Vu/(bo×d). IS 456: τc_punch ≤ k×τc.
- 44Materials and IS 456EASY
Characteristic strength of Fe415 steel (yield strength):
A250 N/mm²B415 N/mm²C500 N/mm²D550 N/mm²Answer: B. 415 N/mm²
Explanation: IS 432/IS 1786: Fe415 → fy = 415 N/mm². Fe500: fy=500. Fe250 (mild steel, IS 432): fy=250. Used in design: partial safety factor γm=1.15 → fd=fy/1.15.
- 45RCCMEDIUM
The 'fire resistance' of an RC member depends primarily on:
AOnly the grade of concrete (fck value)BCover (delays heat to steel), section size (thermal mass), and concrete/aggregate type — IS 456 Annex A fire ratingsCOnly the shape of the section (circular vs rectangular)DOnly the yield strength of steel barsAnswer: B. Cover (delays heat to steel), section size (thermal mass), and concrete/aggregate type — IS 456 Annex A fire ratings
Explanation: Fire resistance (IS 456 Annex A; IS 3809): (1) Cover to reinforcement — deeper cover delays heat reaching steel; (2) Concrete type (NWC, LWC — lightweight better insulator); (3) Section size — larger section = longer time before temperature rise; (4) Aggregate type (calcareous better, siliceous spall). Fire rating: 0.5hr, 1hr, 1.5hr, 2hr, 3hr, 4hr. Cover requirement: 20mm (0.5hr), 40mm (2hr), 50mm (4hr). Exposed columns: larger minimum dimension required.
- 46RCCMEDIUM
The 'nominal cover' to outermost reinforcement in RC columns for 'moderate' exposure (IS 456) is:
A10 mmB30 mm for moderate exposure — IS 456 Table 16C25 mmD60 mmAnswer: B. 30 mm for moderate exposure — IS 456 Table 16
Explanation: IS 456 Table 16: nominal cover for different exposure conditions. Mild: 20 mm (footings 40 mm); Moderate: 30 mm (columns 30 mm, beams 30 mm); Severe: 45 mm; Very severe: 50 mm; Extreme: 75 mm. Cover = distance from concrete surface to outermost bar face. Purpose: corrosion protection, fire resistance, bond. Durability minimum cover often governs over structural minimum.
- 47RCCMEDIUM
The 'balanced section' in RC beam design occurs when:
ASteel yields only, concrete is not stressedBExtreme fibre concrete strain = εcu and tensile steel strain = εy simultaneously — balanced reinforcement ratioCApplied moment equals zeroDNo reinforcement is needed in compressionAnswer: B. Extreme fibre concrete strain = εcu and tensile steel strain = εy simultaneously — balanced reinforcement ratio
Explanation: Balanced section: concrete reaches εcu (extreme fibre) simultaneously when steel reaches εy (yield). In LSM: xu_b/d = εcu/(εcu+εy) = 0.0035/(0.0035+fy/(1.15×Es)) = 0.0035/(0.0035+0.87fy/Es). For Fe 415: xu_b/d = 0.479. Above this ratio: over-reinforced (concrete controls, brittle). Below: under-reinforced (steel yields first, ductile). IS 456 limits xu_max/d to ensure ductile failure.
- 48RCCMEDIUM
A 'raft (mat) foundation' is used when:
ARock is available at shallow depthBSoil bearing capacity is low or differential settlement risk is high — raft covers entire footprint distributing load uniformlyCOnly for one-storey light buildingsDOnly for industrial chimneysAnswer: B. Soil bearing capacity is low or differential settlement risk is high — raft covers entire footprint distributing load uniformly
Explanation: Raft/mat foundation: single slab covering entire building footprint. Used when: (1) Soil BC is low and individual footings would cover > 50% of plan area; (2) Differential settlement risk is high (raft distributes load, reduces differential); (3) Basement is needed (raft = basement floor slab); (4) Heavy column loads close together. Raft distributes load over entire building footprint — reduces soil pressure.
- 49RCCEASY
The IS code for seismic design of buildings in India is:
AIS 800 (structural steel design only)BIS 1893 Part 1 (earthquake design criteria) + IS 13920 (ductile detailing for RC) togetherCIS 875 Part 3 (wind load only)DIS 456 alone covers seismic designAnswer: B. IS 1893 Part 1 (earthquake design criteria) + IS 13920 (ductile detailing for RC) together
Explanation: IS 1893 (Part 1): 2016 — Criteria for Earthquake Resistant Design of Structures (general buildings). IS 13920:2016 — Ductile Detailing of RC Structures. IS 4326:2013 — Earthquake Resistant Construction (masonry and timber). IS 1893 Part 2: liquid retaining; Part 3: bridges. IS 13920 mandatory in seismic zones III, IV, V.
- 50RCCHARD
The 'corbel' in RC construction is designed for:
ABending only (same as beam design)BStrut-and-tie action — diagonal concrete strut + horizontal tension tie at top; a/d ≤ 1 governs design methodCColumn bucklingDPunching shear at column headAnswer: B. Strut-and-tie action — diagonal concrete strut + horizontal tension tie at top; a/d ≤ 1 governs design method
Explanation: Corbel (short bracket): a/d ≤ 1 (shear span to depth). Failure mode: diagonal tension / strut-and-tie. Design by IS 456 Cl. 17 / strut-and-tie method: main tension tie (Ast at top), strut in concrete, friction horizontal force (from beam bearing = 0.2V horizontal force on corbel). Main reinforcement: horizontal (primary), plus vertical stirrups. Very different from beam design (very short span).