RPSC AE Civil flashcards

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

Target mean strength formula

Per IS 10262, f'ck = fck + 1.65·s, where s is the assumed standard deviation for the concrete grade; this sets the mix design strength to ensure the required characteristic strength is met.

Limiting xu/d values

Neutral axis depth ratio limits for singly reinforced sections: 0.53 for Fe 250, 0.48 for Fe 415, and 0.46 for Fe 500 steel; beyond these the section must be doubly reinforced.

Mu,lim formula

Limiting moment of resistance: Mu,lim = 0.36·fck·b·xu,lim·(d − 0.42·xu,lim). It defines the maximum moment a singly reinforced rectangular section can carry.

Nominal shear strength τc

Design shear strength of concrete from IS 456 Table 19, based on percentage tension steel pt = 100·Ast/(b·d) and concrete grade; it increases with pt and grade.

Maximum shear stress τc,max

Upper limit on shear stress in concrete from IS 456 Table 20, dependent only on concrete grade; exceeding it requires enlarging the section regardless of stirrup design.

Effective span of simply supported beam

The smaller of clear span plus effective depth, or centre-to-centre distance of supports. This span is used for bending moment and deflection calculations.

Two-way slab coefficient method

IS 456 Annex D gives moment coefficients αx and αy based on ly/lx and edge conditions; a slab with ly/lx ≥ 2 is treated as one-way.

Lacing slenderness limit

In built-up steel columns, the slenderness ratio of the component between lacing points must not exceed 50, and lacing flats are set at an angle not more than 45° to the axis.

Plastic section design moment

Md = βb·Zp·fbd/γm0 for compact/plastic sections, where βb = 1.0, Zp is the plastic section modulus, and fbd is the design bending stress.

Design shear capacity of steel

Vd = Vp/γm0 where Vp = Av·fy/√3; Av is the shear area and fy the yield strength, following IS 800 limit state design.

Tacheometric distance formula

For a fixed-hair tacheometer, horizontal distance D = (f/i)·s + (f + d), where s is staff intercept and f/i is the multiplying constant, typically 100.

Level book arithmetic check

ΣBS − ΣFS must equal the difference between last and first reduced levels, and also equal ΣRise − ΣFall; this validates the level book entries.

Manning's equation

Open-channel velocity V = (1/n)·R^(2/3)·S^(1/2), where n is roughness, R is hydraulic radius (A/P), and S is bed slope.

Chezy's formula

Uniform flow velocity V = C√(RS), where C is the Chezy coefficient, R is hydraulic radius, and S is the channel slope; C relates to Manning's n by C = R^(1/6)/n.

Most economical trapezoidal section

For a trapezoidal channel, the most efficient section has half top width equal to the side slope length, giving hydraulic radius R = y/2 for any given side slope.

Darcy's law

Seepage discharge q = k·i·A, where k is permeability, i is hydraulic gradient, and A is cross-sectional area; valid for laminar flow through soil.

Constant-head permeability test

For coarse soils, k = QL/(A·h·t), where Q is collected volume in time t, L is sample length, A is area, and h is head difference.

Falling-head permeability test

For fine soils, k = (a·L/(A·t))·ln(h1/h2), where a is standpipe area, A is sample area, and h1, h2 are initial and final heads.

Terzaghi bearing capacity equation

Strip footing ultimate capacity qu = c·Nc + q·Nq + 0.5·γ·B·Nγ, with Nc, Nq, Nγ depending on friction angle; local shear uses reduced c and φ.

Standard Proctor compaction

Compaction with 2.6 kg hammer, 310 mm drop, 3 layers and 25 blows per layer; gives lower maximum dry density and higher optimum moisture content than modified Proctor.

Modified Proctor compaction

Compaction with 4.5 kg hammer, 450 mm drop, 5 layers and 25 blows per layer; yields higher maximum dry density and lower optimum moisture content than standard Proctor.

Superelevation formula

IRC design: e = V²/(127R) − f, where V is design speed in km/h, R is curve radius in metres, and f is lateral friction coefficient.

Extra widening at curves

IRC extra widening = (n·L²)/(2R) + V/(9.5√R), combining mechanical widening for vehicle length L and psychological widening for speed V and radius R.

Stopping sight distance

SSD = 0.278·V·t + V²/(254f), where t is reaction time in seconds, V is speed in km/h, and f is longitudinal friction coefficient.

Water-cement ratio durability limit

IS 456 specifies maximum free w/c ratio and minimum cement content per exposure class; severe exposure typically requires w/c ≤ 0.50 and cement ≥ 320 kg/m³ for RC.

One-way vs two-way slab

A slab is one-way when ly/lx ≥ 2, bending mainly in the short direction; below 2, it is two-way and designed with IS 456 Annex D coefficients.

Batten plate design shear

Battened built-up columns are designed for a transverse shear equal to 2.5% of the axial force, applied at the batten connections per IS 800.

Hydraulic radius

R = A/P, the flow area divided by wetted perimeter; it appears in Manning's and Chezy's equations and governs channel conveyance.

Plastic section modulus

Zp = A·ȳ1 + A·ȳ2 about the equal-area axis; it exceeds the elastic modulus and is used in IS 800 plastic design of compact sections.

Characteristic strength of concrete

The value of cube strength below which not more than 5% of test results fall; designated fck and used as the basis for mix design and structural design.

Standard deviation in mix design

An assumed value of s (e.g., 4 N/mm² for M20–M25) used in f'ck = fck + 1.65·s; it is taken from IS 10262 tables based on grade and plant control.

Bearing capacity factor Nq

A Terzaghi factor depending on the soil friction angle φ, used in qu = c·Nc + q·Nq + 0.5·γ·B·Nγ for the surcharge term.