Tamil Nadu HSE Second Year Basic Civil Engineering flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Modular brick size

In India, the modular brick measures 190 × 90 × 90 mm; with a 10 mm mortar joint, the nominal size becomes 200 × 100 × 100 mm, which simplifies masonry dimensions.

Efflorescence test

Bricks are soaked in water and dried; white salt deposits on the surface grade the brick as nil, slight, moderate, heavy or serious. Heavy and serious grades are rejected for construction.

Initial setting time

The time from adding water to cement until the paste begins to lose plasticity; for ordinary Portland cement it must not be less than 30 minutes.

Damp-proof course

A waterproof layer laid at plinth level, usually of 1:2 cement mortar with waterproofing compound or bitumen felt, that stops moisture rising through the wall by capillary action.

Well-conditioned triangle

A triangle used in chain surveying in which no angle is less than 30 degrees or more than 120 degrees; such triangles give more accurate chaining and plotting.

Height of instrument

In levelling, the reduced level of the instrument station plus the backsight reading on a known point; subtracting a foresight from it gives the reduced level of the next point.

Rise and fall method

A levelling reduction method where the difference between consecutive staff readings gives a rise or fall; the reduced level of each point is found by adding rises and subtracting falls.

Benchmark

A fixed, permanent point of known reduced level used as a reference for levelling; it may be a government benchmark, a permanent structure, or an assumed temporary point.

Floor area ratio

The total floor area of all storeys divided by the plot area; it limits how much built area a plot may carry and is fixed by local development regulations.

Carpet area

The usable floor area of a room measured between the internal faces of walls, excluding the area occupied by walls, columns and built-in fixtures.

Stair proportions

For comfortable use, the riser should not exceed 190 mm and the tread should not be less than 250 mm; the rule of thumb is riser plus tread equals about 400 to 450 mm.

Building orientation

The placement of a building on its plot so that long walls face north and south; this reduces direct sun on walls and improves comfort in tropical climates like Tamil Nadu.

Hooke's law

Within the elastic limit, stress is directly proportional to strain; the constant of proportionality is Young's modulus E, so σ = Eε.

Section modulus

The ratio of the second moment of area about the neutral axis to the distance of the extreme fibre from it; a beam is safe in bending when M/Z does not exceed the permissible stress.

Bending equation

M/I = σ/y = E/R relates bending moment, second moment of area, bending stress, distance from neutral axis, Young's modulus and radius of curvature of a bent beam.

Euler buckling load

The axial load at which a slender column buckles elastically, given by P = π²EI/L², where L is the effective length depending on end conditions.

Characteristic strength

The strength of concrete below which not more than 5 percent of test results fall; the grade M20 means a characteristic cube strength of 20 N/mm² at 28 days.

Slump test

A workability test in which fresh concrete is placed in a standard cone, the cone is lifted, and the vertical settlement of the concrete is measured in millimetres.

Bulking of sand

The increase in volume of moist sand due to films of water around particles, up to 20 to 30 percent for fine sand; it must be corrected when batching concrete by volume.

Bleeding in concrete

The upward migration of mixing water to the surface of freshly placed concrete, caused by settlement of solid particles; it weakens the top layer and reduces bond with the next lift.

Per capita demand

The average quantity of water consumed per person per day; for Indian towns it is commonly taken as 135 litres per head per day for domestic purposes.

Residual chlorine

The chlorine remaining in treated water after the contact period, ideally about 0.2 mg/l; it protects the water from recontamination in the distribution system.

Self-cleansing velocity

The minimum flow velocity in a sewer, about 0.6 to 0.9 m/s, that prevents deposition of solids; the maximum permissible velocity is about 3 m/s to avoid erosion.

Septic tank

An underground chamber that settles and anaerobically digests domestic sewage; the clarified effluent flows to a soak pit or dispersion trench for disposal.

Superelevation

The transverse slope given to the outer edge of a road curve to counter centrifugal force; it is calculated as e = V²/(127R) and is limited to about 7 percent.

Stopping sight distance

The total distance a vehicle travels during the driver's reaction time plus the braking distance; it must be available so a driver can stop before an obstruction.

California Bearing Ratio

The ratio, in percent, of the load required to penetrate a soil sample to the load required for standard crushed stone at the same penetration; used in flexible pavement design.

Camber

The cross slope provided on a road surface to drain rainwater to the sides; typical values are 2 percent for concrete roads and 4 percent for earth roads.

Plinth area estimate

An approximate estimate obtained by multiplying the plinth area of the building, measured at floor level including walls, by the plinth area rate for that class of building.

Contingency in estimate

An allowance, usually 3 to 5 percent of the estimated cost, added to a detailed estimate to cover unforeseen items and minor changes during construction.

Sinking fund method

A depreciation method in which a fixed annual amount is set aside and invested at compound interest so that the accumulated sum equals the cost of replacing the asset.

Capitalised value

The present worth of a property calculated as net annual income divided by the rate of interest; it is used in valuation when the property earns rent.