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INRAT practice questions

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Question 1Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which structural member is a planar framework of straight elements arranged in triangles and assumed to be pinned at its joints?

  1. A beam
  2. A truss Correct answer.
  3. An arch
  4. A cable

Explanation

A truss is a framework of straight members connected at joints to form triangles. Because the triangular units resist distortion, the members act mainly in axial tension or compression rather than bending.

Question 2Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

On an architectural floor plan, how is the location of a section cut normally indicated?

  1. A wavy break line with a small label and hatch
  2. A dotted centerline with a circle at each end and a note
  3. A heavy line with arrows that show the viewing direction Correct answer.
  4. A light dashed line with a circled number and no arrow

Explanation

A section mark on a plan is drawn as a heavy line, often with arrows, to show where the building is cut and which direction the cut is viewed. A label identifies the corresponding section drawing.

Question 3Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which material property describes resistance to local indentation, scratching, or abrasion?

  1. Toughness
  2. Hardness Correct answer.
  3. Ductility
  4. Elasticity

Explanation

Hardness is the resistance of a surface to local indentation, scratching, or abrasion. It is distinct from strength, which concerns load-carrying capacity, and from toughness, which concerns energy absorption.

Question 4Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which passive strategy most improves thermal comfort in a hot-dry climate with large day-to-night temperature swings?

  1. Using continuous carpet over a thin, uninsulated slab
  2. Using high thermal mass with night ventilation Correct answer.
  3. Reducing wall and roof insulation
  4. Increasing west-facing glazing without shading

Explanation

In hot-dry climates, daytime heat gain and cool nights create a large temperature swing. Heavy walls can absorb daytime heat and release it at night, and night ventilation flushes stored heat, reducing daytime overheating.

Question 5Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

What is the primary purpose of fire compartmentation in a building?

  1. Increase daylight penetration into corridors
  2. Limit the spread of fire and smoke Correct answer.
  3. Reduce the dead load on the structural frame
  4. Improve speech privacy between offices

Explanation

Fire compartmentation divides a building into fire-resistant zones using walls, floors, and doors. Its main purpose is to contain fire and smoke long enough for occupants to escape and for firefighters to operate.

Question 6Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A heavy building is to be founded on soft clay overlying a deep firm stratum. Which foundation type is most suitable for transferring the load to that stratum?

  1. Isolated spread footings bearing on the soft upper clay
  2. Pile foundations driven to the deep firm stratum Correct answer.
  3. Strip footings following the external walls
  4. A raft foundation covering the entire footprint

Explanation

Piles transfer heavy loads through weak upper soil to a deeper firm stratum by end bearing, skin friction, or both. A raft spreads load over a wide area but does not by itself reach a deep bearing stratum.

Question 7Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which measure most directly reduces airborne sound transmission through a shared wall between two rooms?

  1. Installing a sound-reflecting panel on the shared wall
  2. Reducing the volume of the source room
  3. Increasing wall mass and sealing all gaps Correct answer.
  4. Adding absorptive material inside the source room

Explanation

Airborne sound through a shared wall is reduced by adding mass and eliminating gaps, because sound leaks through cracks and lightweight panels. Absorptive treatment in the source room mainly reduces reflected sound, not transmission.

Question 8Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

In the northern hemisphere, what building orientation best supports passive solar heating in winter?

  1. North-south, with major glazing facing west
  2. East-west, with major glazing facing north
  3. East-west, with major glazing facing south Correct answer.
  4. North-south, with major glazing facing east

Explanation

In the northern hemisphere, the winter sun is low in the south. An east-west long axis allows major glazing to face south, maximizing winter solar gain while making summer shading easier.

Question 9Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A uniform cantilever beam carries a single point load at its free end. Where does the maximum bending moment occur?

  1. At the fixed support Correct answer.
  2. At midspan
  3. At one-quarter of the span from the support
  4. At the free end

Explanation

For a cantilever with a point load at the free end, the bending moment increases linearly from zero at the free end to a maximum at the fixed support. The fixed support must resist the full overturning moment.

Question 10Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which statement about structural steel under fire conditions is correct?

  1. Steel is combustible and contributes fuel to a fire
  2. Steel expands so little under fire conditions that movement is negligible
  3. Steel is noncombustible but loses strength when heated Correct answer.
  4. Steel has inherent fire resistance and needs no protection

Explanation

Structural steel is noncombustible, but it loses stiffness and strength as it heats, so it usually needs fire protection to achieve a required fire-resistance rating. Its substantial thermal expansion can also damage connections and adjacent construction.

Question 11Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which classical column order is distinguished by a capital with paired spiral volutes?

  1. Corinthian
  2. Tuscan
  3. Doric
  4. Ionic Correct answer.

Explanation

The Ionic capital is recognized by two opposing spiral volutes, often separated by a molded echinus and set above a slender shaft. Doric capitals are plain and flared, while Corinthian capitals are carved with acanthus leaves. Tuscan is a simplified Roman version of the Doric order.

Question 12Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A wall measures 4 cm on a drawing produced at a scale of 1:50. What is its real length?

  1. 0.8 m
  2. 20.0 m
  3. 8.0 m
  4. 2.0 m Correct answer.

Explanation

At 1:50 one unit on the drawing represents 50 units in reality, so 4 cm multiplied by 50 gives 200 cm, which equals 2.0 m. Converting the drawing measurement to metres first (0.04 m × 50) produces the same answer.

Question 13Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

What does the U-value of a building assembly measure?

  1. The fraction of incident solar radiation admitted through the glazing assembly
  2. Heat flow per unit area per degree of temperature difference Correct answer.
  3. The amount of air leakage per metre of joint
  4. The resistance of a material to diffusion of water vapour

Explanation

U-value, or thermal transmittance, is the steady-state heat flow in watts through one square metre of an assembly for each kelvin of temperature difference across it. It is the reciprocal of the assembly's total thermal resistance, so lower values indicate better insulation.

Question 14Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A deep room is lit only by a single side window. Which change most increases daylight at the back of the room?

  1. Raising the window head height Correct answer.
  2. Adding a reflective floor finish near the window
  3. Widening the window while keeping its head height
  4. Increasing the visible transmittance of the glazing slightly

Explanation

Daylight penetration from a side window is governed mainly by the height of the window head, because light from the upper sky reaches farther across the ceiling and toward the rear wall. Raising the head height therefore extends the daylight zone more than modest changes in width or glazing transmittance.

Question 15Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Why is a minimum concrete cover specified over reinforcing steel?

  1. To make the concrete easier to compact
  2. To reduce the self-weight of the slab and the beams
  3. To allow the steel to bond only at the beam ends
  4. To protect the steel from corrosion and fire Correct answer.

Explanation

Cover places a durable layer of concrete between the steel and the environment, limiting the ingress of moisture, chlorides and carbon dioxide that would corrode the bars. It also insulates the reinforcement from fire so the member retains its strength for the required fire period.

Question 16Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

In a building air-handling system, what is the function of an economizer cycle?

  1. It cools with outdoor air instead of running chillers Correct answer.
  2. It recovers heat from exhaust air to preheat the incoming ventilation air
  3. It varies fan speed to maintain duct static pressure
  4. It dehumidifies supply air with a desiccant wheel

Explanation

An economizer compares outdoor and return air conditions and, when outdoor air is cool enough, increases the outdoor-air fraction to meet the cooling load without operating chillers. It is a free-cooling strategy rather than a heat-recovery or humidity-control device.

Question 17Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A 2,000 m² site has a permitted floor area ratio of 2.5. What is the maximum gross floor area that may be built?

  1. 8,000 m²
  2. 5,000 m² Correct answer.
  3. 4,500 m²
  4. 1,250 m²

Explanation

Floor area ratio is total gross floor area divided by site area, so permitted floor area equals site area multiplied by FAR: 2,000 m² × 2.5 = 5,000 m². Coverage limits and setbacks may further constrain the footprint, but they do not change this overall floor-area cap.

Question 18Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

In a cold climate with heated interiors, where should a vapour retarder normally be placed in a wall assembly?

  1. On the cold side of the insulation, so the wall can dry inward
  2. Between two layers of rigid insulation
  3. On the exterior face of the insulation, where it stays dry
  4. On the warm interior side of the insulation Correct answer.

Explanation

In cold climates water vapour diffuses from the warm interior toward the cold exterior, so the retarder belongs on the warm side of the insulation. This keeps the dew point out of the insulation and framing and reduces the risk of interstitial condensation.

Question 19Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A simply supported beam of span L carries a uniform load w. If the span is doubled while w remains unchanged, by what factor does the midspan deflection increase?

  1. 8
  2. 16 Correct answer.
  3. 2
  4. 4

Explanation

For a uniformly loaded simply supported beam, midspan deflection is 5wL⁴ divided by 384EI, so deflection varies with the fourth power of span. Doubling the span therefore multiplies deflection by 2⁴, which is 16.

Question 20Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

For a single-leaf homogeneous partition, approximately how much does doubling the surface mass increase the sound reduction index?

  1. 6 dB Correct answer.
  2. 10 dB
  3. 20 dB
  4. 2 dB

Explanation

The mass law gives about a 6 dB increase in sound reduction index for each doubling of surface mass, and likewise for each doubling of frequency, in the mass-controlled region. This is why heavy dense walls outperform light ones of similar construction quality.

Question 21Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which load type is defined as the self-weight of permanent building components and fixed equipment?

  1. Dead load Correct answer.
  2. Wind load
  3. Snow load
  4. Live load

Explanation

Dead load is the permanent self-weight of structural and non-structural components, including fixed equipment such as partitions and services. It remains essentially constant over the building's life and is calculated from material densities and volumes.

Question 22Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

On an architectural floor plan, which convention indicates the swing and opening direction of a door?

  1. A solid filled triangle at the threshold
  2. A dashed centreline through the wall
  3. An arc with a leaf line at the jamb Correct answer.
  4. A grid bubble beside the opening

Explanation

A door is conventionally drawn in plan as a leaf line at the open position connected to an arc that traces the swing. This shows the hinge side, opening direction, and clear width without needing a separate schedule.

Question 23Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which material is most commonly used for a damp-proof course in a masonry wall?

  1. Untreated timber
  2. Clear glass
  3. Bituminous felt Correct answer.
  4. Loose gravel

Explanation

A damp-proof course must be impermeable to water and capable of accommodating minor movement in masonry. Bituminous felt or a similar flexible sheet material is widely used because it forms a continuous barrier at the base of the wall.

Question 24Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

In a reinforced concrete beam, what is the primary function of vertical stirrups?

  1. Providing surface fire protection to the beam
  2. Carrying primary bending tension at the soffit
  3. Resisting diagonal shear and positioning bars Correct answer.
  4. Resisting longitudinal compression at midspan

Explanation

Stirrups are shear reinforcement; they resist diagonal tension caused by shear and also confine and position the longitudinal bars. They are not the main reinforcement for bending compression or tension.

Question 25Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which natural ventilation strategy depends primarily on the buoyancy of warm air rising through a vertical shaft?

  1. Wind scoop
  2. Cross ventilation
  3. Single-sided ventilation
  4. Stack effect Correct answer.

Explanation

The stack effect relies on temperature differences: warm indoor air is less dense and rises, creating a pressure difference that draws fresh air in at low openings and exhausts stale air at high openings.

Question 26Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

In a sanitary drainage system, what is the main purpose of a water-seal trap?

  1. To prevent sewer gases from entering the building Correct answer.
  2. To reduce noise from draining fixtures
  3. To increase flow velocity in the branch drain
  4. To store water for firefighting use

Explanation

The water seal isolates the drainage system from room air by maintaining a small water plug in the trap. This prevents sewer gases and odours from travelling back through the fixture into the building.

Question 27Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A large exhibition hall requires a 60 m clear span with a lightweight roof and minimal intermediate columns. Which structural system is most suitable?

  1. Load-bearing masonry walls with timber joists
  2. Reinforced concrete cantilever slabs
  3. Space frame or truss roof Correct answer.
  4. Flat slab on a regular column grid

Explanation

A space frame or truss roof can span large distances economically because its triangulated geometry carries loads primarily as axial forces. This allows a 60 m clear span with a lightweight roof and few or no intermediate columns.

Question 28Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which detail most effectively reduces thermal bridging at a concrete balcony slab that projects through an insulated wall?

  1. Painting the interior slab soffit with reflective paint
  2. Adding a row of small air bricks near the slab
  3. Increasing the thickness of interior floor finishes
  4. Installing continuous insulation around the slab edge Correct answer.

Explanation

Thermal bridging occurs where a highly conductive material bypasses insulation. Wrapping the projecting slab edge with continuous insulation breaks the conductive path and reduces heat loss and condensation risk.

Question 29Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A room has a volume of 300 m³ and total sound absorption of 30 m² sabins. Using the Sabine formula RT = 0.161V/A, what is the approximate reverberation time?

  1. 0.16 s
  2. 16.1 s
  3. 5.00 s
  4. 1.61 s Correct answer.

Explanation

Substitute the values into Sabine's equation: RT = 0.161 × 300 / 30. This equals 1.61 seconds, which is a plausible reverberation time for a medium-sized room.

Question 30Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A simply supported beam of span 6 m carries a uniform load of 20 kN/m. What is the maximum bending moment at midspan?

  1. 180 kNm
  2. 60 kNm
  3. 120 kNm
  4. 90 kNm Correct answer.

Explanation

For a simply supported beam with a uniformly distributed load, the maximum moment is wL²/8. Substituting w = 20 kN/m and L = 6 m gives 20 × 36 / 8 = 90 kNm.

Question 31Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

What is the primary structural role of a reinforced concrete shear wall in a multi-storey building?

  1. Resist lateral loads from wind and earthquakes Correct answer.
  2. Provide a continuous damp-proof membrane
  3. Improve the acoustic insulation of the façade
  4. Support the weight of the roof cladding only

Explanation

Shear walls are stiff vertical elements designed mainly to resist horizontal forces such as wind and seismic action, transferring them to the foundation. They may also carry gravity load, but lateral resistance is their defining structural role.

Question 32Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A masonry wall has a window opening. What is the main function of a lintel installed above the opening?

  1. Serve as a horizontal damp-proof course
  2. Anchor the window frame to the foundation
  3. Increase the amount of daylight entering the room
  4. Transfer the weight above the opening to the jambs Correct answer.

Explanation

A lintel spans the opening and carries the masonry or other load above it, transferring that load to the supports on each side. Without a lintel, the wall above a window or door would be unsupported.

Question 33Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which quantity is measured in lux?

  1. Illuminance on a surface Correct answer.
  2. Colour temperature of a light source
  3. Luminous intensity emitted by a lamp
  4. Total luminous flux leaving a luminaire

Explanation

Lux is the SI unit of illuminance, equal to one lumen per square metre. It describes the amount of light falling on a surface, not the total output of a lamp or its colour.

Question 34Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A 40 m² room needs an average illuminance of 300 lx. Ignoring losses, what total luminous flux must the luminaires deliver?

  1. 7,500 lm
  2. 120,000 lm
  3. 1,200 lm
  4. 12,000 lm Correct answer.

Explanation

Illuminance equals luminous flux divided by area, so required flux is 300 lx multiplied by 40 m². That gives 12,000 lm before allowing for maintenance and utilisation losses.

Question 35Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

For ordinary concrete, what is the general effect of increasing the water–cement ratio while other components remain unchanged?

  1. Strength increases and permeability decreases
  2. Strength decreases and permeability increases Correct answer.
  3. Strength is unaffected but colour changes
  4. Permeability decreases while strength increases

Explanation

In normal concrete, more water than needed for hydration increases capillary porosity. This reduces compressive strength and makes the concrete more permeable to water and aggressive agents.

Question 36Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

What is the main purpose of dividing a large building into fire compartments?

  1. Provide expansion movement in the structural frame
  2. Reduce the heating load on the central plant
  3. Improve airborne sound insulation across floors
  4. Slow the spread of fire and smoke between areas Correct answer.

Explanation

Fire compartments use fire-resisting walls and floors to contain a fire for a stated period. This limits fire and smoke spread, protects escape routes, and reduces damage to other parts of the building.

Question 37Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Why is a vent pipe connected to a sanitary drainage system?

  1. To increase the flow velocity in the discharge pipes
  2. To equalise pressure and protect trap seals from siphonage Correct answer.
  3. To filter solid waste before it reaches the sewer
  4. To supply clean water to the fixtures

Explanation

A vent pipe allows air to enter or leave the drainage system so pressure stays close to atmospheric. This prevents water seals in traps from being sucked out by siphonage when fixtures discharge.

Question 38Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A studio is separated from a noisy corridor by a high-mass wall, but the measured sound reduction is much lower than the wall's laboratory rating. Which condition most likely explains this?

  1. A continuous ceiling void bypasses the wall Correct answer.
  2. The wall's laboratory transmission loss is too low
  3. The wall has a very high surface mass
  4. The corridor has a long reverberation time

Explanation

Flanking transmission is sound that reaches the receiving room by a path other than the separating wall, such as a continuous ceiling void or duct. It can dominate the measured performance even when the wall itself has a high laboratory rating.

Question 39Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A long reinforced concrete frame building in a region with large seasonal temperature swings is likely to require movement joints primarily to do what?

  1. Accommodate thermal expansion and contraction Correct answer.
  2. Allow uniform foundation settlement
  3. Improve the fire resistance of the structure
  4. Increase the lateral stiffness of the frame

Explanation

Movement joints provide deliberate gaps that let long concrete frames expand and contract with temperature changes. Without them, restrained movement can cause cracking or damage at connections.

Question 40Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A paved courtyard slopes toward a building entrance. Which measure best reduces the risk of water entering the building?

  1. Seal the paving with a vapour barrier
  2. Regrade paving away from the door with a drain Correct answer.
  3. Raise the threshold and leave the slope unchanged
  4. Increase the paving thickness near the door

Explanation

Surface water should be directed away from the building by sloping paving and collected in a drainage channel. A threshold alone does not remove water from the entrance zone and may be overtopped.

Question 41Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A building site has a deep layer of loose fill overlying firm ground. Which foundation type transfers column loads through the weak layer to the firmer stratum beneath?

  1. Pad footing
  2. Raft foundation
  3. Strip foundation
  4. Pile foundation Correct answer.

Explanation

Piles are slender members that are driven or bored through the weak deposit so that their load is carried by a competent stratum or by friction along their shafts. Because they bypass the loose fill, they limit settlement that a shallow foundation would suffer. Rafts and pad footings spread load close to the surface and would still bear on the unsuitable material.

Question 42Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Which property of fresh concrete is assessed by the slump test?

  1. Permeability
  2. Workability Correct answer.
  3. Setting time
  4. Compressive strength

Explanation

The slump test measures the downward settlement of a moulded cone of fresh concrete and is used as an indirect index of consistency, that is, how workable the mix is. It says nothing about hardened properties, so strength, permeability and setting time must be determined by other tests.

Question 43Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

In a low-voltage domestic installation, against which hazard does a residual current device (RCD) primarily protect?

  1. Voltage surges caused by lightning
  2. Reverse power flow from a generator
  3. Overloading of circuit conductors
  4. Earth-leakage currents that could cause electric shock Correct answer.

Explanation

An RCD continuously compares the current flowing in the live and neutral conductors. Any imbalance indicates current leaking to earth, and the device trips at a very low threshold, typically 30 mA, so that contact with a live part is interrupted before it becomes lethal. Overcurrent and surges require different protective devices.

Question 44Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A rectangular concrete section 200 mm wide and 400 mm deep carries a shear force of 60 kN at a section. Taking the gross cross-sectional area, what is the average shear stress?

  1. 1.50 N/mm²
  2. 0.30 N/mm²
  3. 0.75 N/mm² Correct answer.
  4. 3.00 N/mm²

Explanation

Average shear stress is the shear force divided by the cross-sectional area resisting it. Here the area is 200 mm × 400 mm = 80 000 mm², so the stress is 60 000 N ÷ 80 000 mm² = 0.75 N/mm².

Question 45Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

Concrete is to be placed and finished in hot, windy weather where the mix is expected to stiffen rapidly. Which admixture is most appropriate?

  1. Air entrainer
  2. Accelerator
  3. Pigment
  4. Retarder Correct answer.

Explanation

A retarding admixture slows the hydration reactions and so extends the period during which the concrete remains workable, which is valuable when high temperature and wind speed up moisture loss and stiffening. An accelerator does the opposite, and other admixtures address different properties.

Question 46Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

In a pitched roof, which term denotes the lower horizontal edge of a sloping roof surface that overhangs the wall and discharges water clear of it?

  1. Ridge
  2. Soffit
  3. Eaves Correct answer.
  4. Verge

Explanation

The eaves form the lowest edge of a sloping roof, where the roof covering projects beyond the wall face and water drips free of the building. The ridge is the apex where two slopes meet, the verge is the edge along a gable, and the soffit is the underside surface.

Question 47Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A staircase in a public building has 150 mm risers and 300 mm goings. Using the common 2R + G rule, what value is obtained?

  1. 450 mm
  2. 550 mm
  3. 500 mm
  4. 600 mm Correct answer.

Explanation

The rule substitutes the riser R and going G into the expression 2R + G to check that the proportions give a comfortable stride. With R = 150 mm and G = 300 mm, the result is 2 × 150 + 300 = 600 mm, which lies within the usual acceptable range.

Question 48Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A wall of 12 m² has a sound reduction index of 50 dB. A door of 2 m² with a sound reduction index of 30 dB is inserted into it. What is the approximate composite sound reduction index of the combined element?

  1. 44 dB
  2. 30 dB
  3. 50 dB
  4. 38 dB Correct answer.

Explanation

Transmission coefficients are averaged by area: the wall contributes 12 × 10⁻⁵ and the door 2 × 10⁻³, giving a total of 2.12 × 10⁻³ over 14 m², or about 1.5 × 10⁻⁴. Converting back with −10 log₁₀ of that average gives roughly 38 dB, showing how a small weak element drags down the performance of the whole partition.

Question 49Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A rectangular slab is supported by beams on all four edges, and its long span is only 1.2 times its short span. How is the load predominantly carried to the supports?

  1. Entirely in the short direction, to the two long beams
  2. Directly to the columns at the corners only
  3. In both directions, to all four supporting beams Correct answer.
  4. Entirely in the long direction, to the two short beams

Explanation

When the ratio of long to short span is below about two, the slab deflects into a dished surface and distributes load in two orthogonal directions, so all four edge beams share it. Only when the ratio is larger does the slab behave essentially as a one-way element spanning the short way.

Question 50Unverified - official content outline for INRAT was not supplied; single placeholder domain pending source verification

A retaining wall 4 m high retains soil of unit weight 18 kN/m³ with an angle of internal friction of 30°. Using Rankine theory, ignoring surcharge and wall friction, what is the total active thrust per metre length of wall?

  1. 48 kN/m Correct answer.
  2. 24 kN/m
  3. 96 kN/m
  4. 36 kN/m

Explanation

For φ = 30°, the active pressure coefficient is (1 − sin φ)/(1 + sin φ) = 1/3, so the lateral pressure at the base is 1/3 × 18 × 4 = 24 kPa. The pressure distribution is triangular, so the resultant thrust is half the base pressure times the height: 0.5 × 24 × 4 = 48 kN per metre.