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Civil Engineering Formulas and Handbook

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Civil Engineering Formulas and Handbook

 



Section 1) Surveying

Traverse Surveying

 Correction For Sag $$ {C_s} = {{{w^2}{l^3}}\over {24.P^2}} $$ Note:-sag correction is subtractive

Where 

w = weight of tape per meter

l= distance between supports

P = Applied Tension

Correction For Tension $$ {C_p} = {{(P-{P_0})l}\over AE} $$

P0 is tension for which the tape is standardized

A = Cross sectional area

E = Modulus of elasticity of tape material

Correction due to Temperature $${C_T} = L{\alpha}({T_m}-{T_0})$$

Tm is temperature at time of measurement

T0 is temperature at time of standardization of tape

⍺ is coefficient of thermal expansion

L is measured length

Latitude : Projection of a line on N - S direction is called Latitude => L = l.cosÓ¨

Departure : Projection of a line on E - W direction is called Departure => D = l.sinÓ¨

Closing Error:
    if ΣL ≠ 0 and ΣD ≠ 0 then there is closing error

closing error (e) $$e = \sqrt{{(\sum L)}^2 + {(\sum D)}^2 }$$

Direction of Closing error

$$ {\delta} = {tan}^-1 \left({\sum D\over \sum L}\right) $$

The sign of Î£L and Î£D will thus define the quadrant in which closing error lies

Rules of Balancing the Survey
1) Compass Rule :It states that the correction to be applied to the Latitude and Departure of any course is to the total error in Latitude and Departures as the length of the course is to the length of the traverse.

Bowditch method : Error in linear measurement ∝ √L where L is length of line
                                Error in Angular measurement ∝ √(1/L) 
Note:- This method is mostly used to balance a traverse where linear and angular measurements have been taken with equal precision.

correction to a particular line 

$${C_L} = \left({l\over {\sum l}}\right){\times}{\sum L} $$

$${C_D} = \left({l\over {\sum l}}\right){\times}{\sum D} $$

Where, 

CL = correction in Latitude of a line

ΣL = Total error in Latitude

CD = correction in Departure of a line

ΣD = Total error in Departure

Σl = Sum of length of all lines


(Compass rule is most commonly applied)

2) Transit Rule :It states that the correction to be applied to the Latitude and Departure of any course is to the total error in Latitude and Departures as the length of the course is to the Arithmetical sum of all the Latitude and Departures in the Traverse.
Note:- This method is suitable where angular measurement are more precise than linear measurements.

Correction in Latitude of a line $${C_L} = \left({L\over {L_T}}\right){\times}{\sum L} $$

Correction in Departure of a lin$${C_D} = \left({D\over {D_T}}\right){\times}{\sum D} $$

Where, 

LT = Sum of all Latitudes without considering sign

DT = Sum of all Departures without considering sign

ΣL = Total error in Latitude

ΣD = Total error in Departure

L = Latitude of a line

D = Departure of a line

3) Axis Method :
Note:- This method is suitable where Angles are measured very accurately. so correction are done in length of line only, bearing of lines are not changed.

Correction to any length = That length x 1/2 closing error / Length of Axis

Levelling

Height of Instrument = H.I. = R.L. + B.S.

R.L. = H.I. - F.S.

Arithmetic check

ΣB.S. - ΣF.S. = ΣRise - ΣFall = Last R.L. - First R.L.

Reciprocal levelling

Used to check whether instrument is correct or not

Checking --> 

Setup instrument at point A

    Reading on staff at A = a
    Reading on staff at B = b

Setup instrument at point B

    Reading on staff at A = c
    Reading on staff at B = d

if instrument is correct then (a- b)=(c- d)

True difference between RL A and B (H) 
$$H={{(b-a)+(d-c)}\over 2} $$

1️⃣ Area by Cross-Staff Survey  
$$ A = \frac{1}{2} \times \sum (L_1 + L_2) \times d $$  

where:  
\( L_1, L_2 \) = offsets (m)  
\( d \) = distance between offsets (m)  

2️⃣ Area by Trapezoidal Rule  
$$ A = d \left[ \frac{O_1 + O_n}{2} + O_2 + O_3 + \dots + O_{n-1} \right] $$  

where:  
\( d \) = common distance between offsets  
\( O_1, O_2, \dots, O_n \) = offsets  

3️⃣ Area by Simpson’s Rule  
$$ A = \frac{d}{3} \left[ O_1 + O_n + 4(O_2 + O_4 + \dots) + 2(O_3 + O_5 + \dots) \right] $$  

4️⃣ Rise and Fall Method — RL Calculation  
$$ RL_{next} = RL_{previous} + Rise - Fall $$  

5️⃣ Leveling — Arithmetic Check  
$$ \sum \text{Backsight} - \sum \text{Foresight} = \text{Last RL} - \text{First RL} $$  

6️⃣ Distance by Stadia Method  
$$ D = k \times S + C $$  

where:  
\( D \) = horizontal distance  
\( S \) = staff intercept  
\( k \) = multiplying constant (usually 100)  
\( C \) = additive constant  

7️⃣ Height of Instrument (HI) Method  
$$ HI = RL_{BM} + Backsight $$  
$$ RL_{Point} = HI - Foresight $$  

8️⃣ Correction for Curvature  
$$ C_c = 0.0785 \times d^2 $$  

where:  
\( C_c \) = correction in meters  
\( d \) = distance in km  

9️⃣ Correction for Refraction  
$$ C_r = 0.0116 \times d^2 $$  

10️⃣ Combined Correction (Curvature + Refraction)  
$$ C = 0.067 \times d^2 $$  

11️⃣ Tacheometric Horizontal Distance  
$$ D = \frac{f}{i} \times S \times \cos^2 \theta $$  

where:  
\( f \) = focal length  
\( i \) = stadia hair interval  
\( \theta \) = vertical angle  

12️⃣ Tacheometric Vertical Height  
$$ V = \frac{f}{i} \times S \times \frac{\sin 2\theta}{2} $$  

13️⃣ Bearing Conversion — Quadrantal to Whole Circle Bearing (WCB)  
- NE Quadrant: \( \theta \)  
- SE Quadrant: \( 180^\circ - \theta \)  
- SW Quadrant: \( 180^\circ + \theta \)  
- NW Quadrant: \( 360^\circ - \theta \)  

14️⃣ Local Attraction Correction  
$$ \text{Corrected Bearing} = \text{Observed Bearing} \pm \text{Correction} $$  

15️⃣ Prismoidal Volume Formula  
$$ V = \frac{d}{3} (A_1 + 4A_m + A_2) $$  

where:  
\( A_1, A_2 \) = end areas  
\( A_m \) = mid area  
\( d \) = distance between cross-sections  


Section 2) Transportation Engineering

Stopping site distance

 Stopping site distance (SSD in 'metres') of a vehicle is the sum of :

1) The distance travelled by the vehicle during the total reaction time known as lag distance and 

$${\text{Lag distance}}=0.278Vt$$

2) The distance travelled by the vehicle after the application of the brakes, to a dead stop position which is known as braking distance.

$${\text{Braking distance}}={{V^2}\over {254(f\pm S \%)}}$$

$$\text{SSD = Lag distance + Braking distance}$$

$$SSD = 0.278Vt + {{V^2}\over {254(f\pm S \%)}}$$

Where S% is gradient '+' sign for ascending gradient & '-' sign for descending gradient

Overtaking Site Distance (OSD)

The minimum distance open to the vision of a driver of a vehicle intending to overtake slow vehicle ahead with safety against the traffic of opposite direction is known as minimum overtaking sight distance (OSD) or safe passing site distance available.

OSD = d1+ d2+ d3  ...... Where OSD is overtaking site distance in 'm'
$${d_1}={0.278 V_b t}$$

$${d_2}=b+2S$$

OR

$${d_2}={0.278 V_b t}+{{a T^2}\over 2}$$

Where, S = minimum spacing between 2 vehicles

$$S = 0.2{V_b}+6$$ 
here Vis in km/hr.

$$T = {\sqrt{4s\over a}}$$
Where, a = acceleration in 'm/s2'

$$T = {\sqrt{14.4s\over a}}$$
Where, a = acceleration in 'km/hr/sec'

$${d_3}={0.278 V_c T}$$

Where, d3  = distance travelled by on coming vehicle from C1 to C2  during overtaking operation
V= V= Speed of overtaking vehicle or design speed (km/hr)
if Vis not given then
Vb = (V-16) ..................in km/hr
V= (V-4.5) ..................in m/s

For 1 way traffic 
OSD = d1+ d2
For 2 way traffic 
OSD = d1+ d2+ d3
Minimum length of overtaking zone = 3 x OSD

Desirable overtaking zone = 5 x OSD

Terrain Catogory Over taking Sight Distance Safe stopping sight for minimum design speed Safe stopping sight for Rulling design speed
Plain Terrain 475 120 170
Rolling Terrain 310 90 120
Hilly Terrain - 50 60
Steep - 40 50

Super Elevation (e)

The Super Elevation 'e' is expressed as the ratio of the height of outer edge with respect to horizontal width.

$$e={NL\over ML} = tan\theta = {{V^2}\over 225R}$$

$$e+f = {{V^2}\over 127R}$$

Where, 
V= speed in km/hr
R = Radius in 'm'
f = design value of lateral friction = 0.15
e = rate of super elevation

Maximum Super Elevation
emaxTerrain Type
0.07Plain and Rolling Terrain
0.10Hilly Area
0.04
Urban roads with frequent intersections


Ruling minimum radius of the curve


$${R_{Ruling}} = {{V^2}\over {127(e+f)}}$$

Radii for horizontal curves in meters

Terrain Catogory Absolute Rulling
Plain Terrain 250 370
Rolling Terrain 155 250
Hilly Terrain 50 80
Steep 3050

Extra Widening (Ew)

Extra widening of pavement on horizontal curves is divided into 2 parts
1) Mechanical Widening (Wm):- The widening required to account for the off-tracking due to the rigidity of wheel base is called mechanical widening.
$$W_m = {{n{l^2}}\over 2R}$$

2) Psychological Widening (Wp):- Extra width of pavement is also provided for psychological reason such as to provide for greater maneuverability of steering at higher speeds, to allow for extra space requirements for the overhangs of the vehicles and to provide greater clearance for crossing and overtaking vehicles on the curves. Psychological widening is important in pavements with more than 1 lane.
$$W_p = {V\over {9.5\sqrt{R}}}$$

Combined Extra widening required on curves

$$E_w = W_m + W_p $$

$$E_w = {{n{l^2}}\over 2R} +{V\over {9.5\sqrt{R}}}$$

Transition Curve

The Indian road congress (IRC) reccomends the use of spiral as transition curve in the horizontal alignment of highways due to following reasons:
(i) The Spiral Curve satisfies the requirements of ideal transition.
(ii) The geometric properties of spiral is such that the calculations and setting out the curve in the field is simple and easy.

Length of transition curve (L)

(i) According to rate of change of centrifugal acceleration


$$L = {{0.0215 V^3}\over CR}$$

Where, V = Speed of vehicle in (km/hr)
                C = Allovable rate of change of centrifugal acceleration in (m/s2)
                R = Radius of curve in (m)
                L = Length of transition curve in (m)

(ii) According to rate of change of super elevation

$$L = {\text {150x → For Plain & Rolling Terrain}}$$

$$L = {\text {100x → For Built up area}}$$

$$L = {\text {60x → For Hilly area}}$$

Whre, x = Raise of outer line of road

$$x = (w + E_w )e \text{....... if the pavement rotated about inner side}$$

$$x = (w + E_w ){e \over 2} \text{....... if the pavement rotated about centre line}$$

(iii) According to empirical formula

$$L = {{2.7 V^2}\over R}\text{...........For Plain and Rolling terrain}$$

Note:- This is as per IRC and its minimum value of Transition curve.

$$L = {{V^2}\over R}\text{...........For Hilly area}$$




To find out offset length at desired chainage 'x' the equation of cubical parabola

$$Y = {{x^3}\over {6RL}}$$

$${Shift}= {{{L_s}^2}\over {24R}}$$

$${L_s}={{E\times N}\over 2}$$

$${E\over 2} = {\text {Total Raise of outer edge of Pavement}} ={{eB}\over 2}$$

$$N ⟶{\text {Rate of Distribution of super elevation}}$$

Set Back Distance (m)

The clearance distance or set back distance required from the centre lines of a horizontal curve to an obstruction on the inner side of the curve to provide adequate sight distance depends upon the following factors :
(i) Required Sight distance (SSD)
(ii) Radius of horizontal curve, (R)
(iii) Length of the curve (Lc)

1. For Single lane road


(a) When L> SSD

 $$m = R - R.{Cos{{\alpha} \over 2}}$$

&

$${\alpha \over 2}={{180.s}\over {2\Pi R}}$$

Where, Lc = Length of Curve & s = SSD

(b) Lc < SSD

$$m=R\left({1-cos{\alpha \over 2}}\right) + {{S - L_c}\over 2} sin{\alpha \over 2}$$

&

$${\alpha \over 2}={{180.L_c}\over {2\Pi R}}$$

2. For two lane road


(a) When L> SSD

 $$m = R - (R-d){Cos{{\alpha} \over 2}}$$

&

$${\alpha \over 2}={{180.s}\over {2\Pi (R-d)}}$$

Where, Lc = Length of Curve & s = SSD

(b) Lc < SSD

$$m=R-(R-d)\left({1-cos{\alpha \over 2}}\right) + {{S - L_c}\over 2} sin{\alpha \over 2}$$

&

$${\alpha \over 2}={{180.L_c}\over {2\Pi (R-d)}}$$

Grade Compensation

$$\text{Grade Compensation}={{30 + R}\over R}\%$$

And 

$$\text{Maximum value of Grade Compensation}={{75}\over R}\%$$

Where, R = radius of curve in meter

Vertical Curve

Due to changes in grade in vertical alignment of highway, it is necessary to introduce vertical curves at the intersections of different grades to smoothen out the vertical profile and thus ease off changes in gradients for fast moving vehicles.

The vertical curves used in highways may be classified into two categories :
(i) Summit curves or crest curves with convexity upwards
(ii) Valley or sag curves with concavity upwards.

Summit curves (Crest curve with convexity upwards):

Summit curves with convexity upwards are formed in any one of the case illustrated in fig. The deviation angles between the two interacting gradients is equal to the algebraic difference between them. Of all the cases, the deviation angles will be maximum when an ascending gradient meets with a descending gradient. i.e. N = n1 - (- n2) = n1 + n2

(i) Length of Summit curve for SSD

(a) When L > SSD

$$L = {{NS^2}\over {(\sqrt{2H} + \sqrt{2h})^2}}$$


$$L = {{NS^2}\over 4.4}$$

Where, L = Length of summit curve in meter
            S = SSD (m)
            N = Deviation Angle
                = Algebraic deference of grade
            H = Height of eye level of driver above road way surface ≈ 1.2 m
            H = Height of object above Pavement surface ≈ 0.15 m

(a) When L < SSD


$$L = 2S-{{(\sqrt{2H} + \sqrt{2h})^2}\over N}$$

$$L = 2S - {4.4\over N}$$

(ii) Length of Summit curve for Safe Overtaking Distance (OSD) or Intermediate Sight Distance (ISD)

(a) When L > OSD

$$L = {{N{S_o}^2}\over {(\sqrt{2H} + \sqrt{2h})^2}}$$


$$L = {{N{S_o}^2}\over 9.6}$$

Where, So = Overtaking or Intermediate sight distance

(b) When L < OSD

$$L = 2S-{{(\sqrt{2H} + \sqrt{2h})^2}\over N}$$

$$L = 2{S_o} - {9.6\over N}$$

Valley Curves (Sag curve with Concavity Upward):


(i) Length of Valley curve as per comfort condition (Transition curves are provided back to back)
$$L=2\left[NV^3 \over C\right]^{1\over 2}$$

if C = 0.6 m/s2 then 

$$L=0.38(NV^3)^{1\over 2}$$

(ii) Length of Valley curve for head light sight distance (Parabolic Curve is provided)

Summit curves (Crest curve with convexity upwards):

Summit curves with convexity upwards are formed in any one of the case illustrated in fig. The deviation angles between the two interacting gradients is equal to the algebraic difference between them. Of all the cases, the deviation angles will be maximum when an ascending gradient meets with a descending gradient. i.e. N = n1 - (- n2) = n1 + n2

(i) Length of Summit curve for SSD

(a) When L > SSD

$$L = {{NS^2}\over {(2h_1 + 2S.tan\alpha)}}$$


$$L = {{NS^2}\over {1.5+0.035S}}$$

Where, L = Total Length of Valley curve in meter
            S = SSD (m)
            N = Deviation Angle
                = Algebraic deference of grade
            α = Beam Angle ≈ 1o
            h1 = Avg. Height of headlight above Pavement surface ≈ 0.75 m

(a) When L < SSD


$$L = 2S-{{(2h_1 + 2S.tan\alpha)}\over N}$$

$$L = 2S - {{1.5+0.035S}\over N}$$

1️⃣ Vehicle Damage Factor (VDF)  
$$ \text{VDF} = \left( \frac{\text{Axle Load (kN)}}{\text{Standard Axle Load (kN)}} \right)^4 $$  

2️⃣ Cumulative Number of Standard Axles (N)  
$$ N = 365 \times A \times D \times F \times \left( 1 + r \right)^n $$  

where:  
\( A \) = initial commercial vehicles/day  
\( D \) = lane distribution factor  
\( F \) = vehicle damage factor  
\( r \) = growth rate  
\( n \) = design life in years  

3️⃣ California Bearing Ratio (CBR) Modulus  
$$ E_{subgrade} = 17.6 \times (\text{CBR})^{0.64} \text{ MPa} $$  

4️⃣ Flexible Pavement — Structural Number (AASHTO Method)  
$$ SN = a_1 D_1 + a_2 D_2 m_2 + a_3 D_3 m_3 $$  

where:  
\( a \) = layer coefficient  
\( D \) = layer thickness (in inches)  
\( m \) = drainage coefficient  

5️⃣ IRC:37-2018 — Design Traffic (in msa)  
$$ N = \frac{365 \times A \times (1+r)^n - 1}{r} \times F \times D $$  

6️⃣ Deflection-Based Overlay Design (Benkelman Beam Method)  
$$ \text{Overlay Thickness (mm)} = C \times (\text{Measured Deflection} - \text{Permissible Deflection}) $$  

7️⃣ Rigid Pavement — Westergaard's Stress Equation for Edge Load  
$$ \sigma = \frac{3P}{2\pi h^2} \times \left[ \ln \left( \frac{1.6a}{h} \right) + 0.675 \right] $$  

where:  
\( P \) = wheel load  
\( h \) = slab thickness  
\( a \) = radius of contact area  

8️⃣ Radius of Relative Stiffness (l)  
$$ l = \left( \frac{Eh^3}{12(1-\mu^2)k} \right)^{0.25} $$  

where:  
\( E \) = modulus of elasticity  
\( \mu \) = Poisson's ratio  
\( k \) = modulus of subgrade reaction  

9️⃣ Traffic Growth Rate Formula  
$$ T_f = T_0 (1 + r)^n $$  

where:  
\( T_f \) = traffic after \( n \) years  
\( T_0 \) = initial traffic  
\( r \) = growth rate  

🔟 Mean Texture Depth (MTD)  
$$ \text{MTD} = \frac{\text{Volume of Sand (ml)}}{\text{Area (mm}^2)} \times 1000 $$  


Section 3) Mechanics of Materials

 1️⃣ Stress

2️⃣ Strain

$$\varepsilon = \frac{\Delta L}{L}$$

3️⃣ Hooke's Law

$$\sigma = E \times \varepsilon$$

4️⃣ Shear Stress

5️⃣ Bending Stress (Flexure Formula)

6️⃣ Torsional Shear Stress

7️⃣ Deflection of Simply Supported Beam (Center Load)

8️⃣ Euler's Buckling Load (Pinned-Pinned)

9️⃣ Moment of Inertia (Rectangle)

🔟 Torsion Equation

1️⃣1️⃣ Principal Stresses (2D)

1️⃣2️⃣ Maximum Shear Stress

1️⃣3️⃣ Strain Energy (Axial Load)

1️⃣4️⃣ Castigliano's Theorem (Deflection at point of load P)

1️⃣5️⃣ Shear Force (Beam Element)

$$\frac{dV}{dx} = -w(x)$$

1️⃣6️⃣ Bending Moment (Beam Element)

$$\frac{dM}{dx} = V(x)$$

1️⃣7️⃣ Relation between Moment and Slope

1️⃣8️⃣ Slenderness Ratio

1️⃣9️⃣ Radius of Gyration

Section 4) Hydraulics

 The depth at partial flow can be evaluated from equation -

$$ d = ({D\over 2}-{D\over 2}.cos{\alpha\over 2}) $$

Area of cross section while running partially full 

$$ a ={\pi D^2\over 4}({\alpha\over 360^\circ}-{sin\alpha\over 2\pi})$$

Wetted perimeter, while running partially full 
$$P = \pi D{\alpha\over 360^\circ}$$


Hydraulic mean depth, while running partially full

$$ r = {a\over P} $$


Velocity of flow is given by Manning's formula

$$ v = {1\over N}.R^{2\over 3}.s^{1\over 2}$$

Discharge when pipe is running partially full,

q =av

Proportionate discharge  = $$ {q\over Q} = {{a.v}\over {A.v'}}$$

=$$ {q\over Q} =({\alpha\over 360^\circ}-{sin\alpha\over 2\pi}).{(1-{{{360^\circ}sin\alpha}\over {2 \pi \alpha}})}^{2\over 3}$$

for detailed derivation go to link

The broad-crested weir is a type of weir used in open channel flow measurements, which has a rectangular notch on top. The discharge over a broad-crested weir can be calculated using the following equation:

$$Q = CLH^{3/2}$$

where:

  • Q is the discharge over the weir [m^3/s],
  • C is the discharge coefficient, which depends on the shape and size of the weir,
  • L is the width of the weir [m],
  • H is the height of the water above the weir crest [m].

To calculate the value of C, you can use one of the following equations:

  • For a rectangular weir:

$$C = 1.84 - 0.5\left(\frac{H}{L}\right)^{1.5} + 0.25\left(\frac{H}{L}\right)^3$$


For Trapezoidal weir:-

$$C = \frac{2}{3}\left(1 + \frac{2h}{b}\right)\left(1 - \frac{h}{H}\right)^{3/2}$$


where b is the bottom width of the trapezoidal notch, and h is the height of the notch.

The sharp-crested weir is another type of weir commonly used in open channel flow measurements. Unlike the broad-crested weir, it has a sharp edge or crest at the top of the notch. The discharge over a sharp-crested weir can be calculated using the following equation:

Rectangular weir equation:

$$Q = CLH^{3/2}$$ $$C = 1.33\sqrt{\frac{2g}{H}}\left(\frac{L}{H}\right)^{1/2}$$

where g is the acceleration due to gravity (approximately 9.81 m/s^2)
V-notch weir equation:

$$Q = CLH^{3/2}$$ $$C = \frac{1}{2}\sqrt{\frac{2g}{H}}\tan\left(\frac{\theta}{2}\right)$$

Where, Ó¨ is the V-notch angle in degrees.

Note that you will need to provide values for L, H, and either assume a value for C (for a rectangular weir) or measure the V-notch angle Ó¨ (for a V-notch weir) in order to calculate the discharge Q.

The Chezy formula is an empirical equation used to calculate the average velocity of flow in an open channel. The formula is given as:

$$V = C\sqrt{RS}$$

where:

  • V is the average velocity of flow [m/s],
  • C is the Chezy coefficient, which is a dimensionless constant that depends on the roughness of the channel,
  • R is the hydraulic radius, which is the cross-sectional area of flow divided by the wetted perimeter [m],
  • S is the slope of the energy line, which is the change in energy per unit length of the channel [m/m].
Note that you will need to provide values for C, R, and S in order to calculate the average velocity of flow V. The value of C can be determined using experimental data or reference tables, and R can be calculated from the dimensions of the cross section of the channel.

The loss of head due to friction is an important concept in fluid mechanics and is often used in the design of pipelines and other fluid transport systems. The loss of head due to friction is given by the Darcy-Weisbach equation:

$$h_f = \frac{fLV^2}{2gd}$$

where:

  • h_f is the loss of head due to friction [m],
  • f is the Darcy-Weisbach friction factor, which depends on the Reynolds number and the roughness of the pipe,
  • L is the length of the pipe [m],
  • V is the average velocity of flow in the pipe [m/s],
  • g is the acceleration due to gravity (approximately 9.81 m/s^2), and
  • d is the diameter of the pipe [m].
Note that you will need to provide values for f, L, V, g, and d in order to calculate the loss of head due to friction h_f. The value of f can be determined using experimental data or reference tables, and V, L, and d can be measured or determined from the design of the pipe system.

Manning's formula is an empirical equation used to calculate the average velocity of flow in an open channel. The formula is given as:

$$V = \frac{1}{n}R^{2/3}S^{1/2}$$

where:

  • V is the average velocity of flow [m/s],
  • n is the Manning's roughness coefficient, which is a dimensionless constant that depends on the roughness of the channel,
  • R is the hydraulic radius, which is the cross-sectional area of flow divided by the wetted perimeter [m],
  • S is the slope of the energy line, which is the change in energy per unit length of the channel [m/m].
1️⃣ Runoff Coefficient Method (Rational Formula) $$ Q = C \times I \times A $$ where: \( Q \) = peak discharge (m³/s) \( C \) = runoff coefficient \( I \) = rainfall intensity (mm/hr) \( A \) = catchment area (hectares) 2️⃣ Time of Concentration (Kirpich Equation) $$ T_c = 0.01947 \times L^{0.77} \times S^{-0.385} $$ where: \( T_c \) = time of concentration (minutes) \( L \) = length of channel reach (m) \( S \) = slope of channel 3️⃣ Rainfall Intensity-Duration-Frequency (IDF) Equation $$ I = \frac{K \times T_r^n}{(t + b)^m} $$ where: \( I \) = intensity (mm/hr) \( T_r \) = return period (years) \( t \) = duration (minutes) \( K, n, b, m \) = constants from IDF curves 4️⃣ Infiltration Rate (Horton's Equation) $$ f(t) = f_c + (f_0 - f_c) e^{-kt} $$ where: \( f(t) \) = infiltration rate at time \( t \) \( f_0 \) = initial infiltration rate \( f_c \) = final constant infiltration rate \( k \) = decay constant 5️⃣ SCS Curve Number Method — Direct Runoff $$ Q = \frac{(P - 0.2S)^2}{P + 0.8S} $$ where: \( P \) = rainfall (mm) \( S \) = potential maximum retention (mm) and $$ S = \frac{25400}{CN} - 254 $$ \( CN \) = curve number 6️⃣ Unit Hydrograph (UH) Peak Discharge $$ Q_p = \frac{2.78 \times A}{T_r} $$ where: \( Q_p \) = peak discharge (m³/s) \( A \) = area (km²) \( T_r \) = time to peak (hours) 7️⃣ Flood Frequency Analysis (Gumbel’s Formula) $$ X_T = \bar{X} + K \times \sigma $$ where: \( X_T \) = flood magnitude for return period \( T \) \( \bar{X} \) = mean flood value \( \sigma \) = standard deviation \( K \) = frequency factor 8️⃣ Probability of Exceedance $$ P = \frac{m}{(N+1)} \times 100 $$ where: \( m \) = rank of event \( N \) = total number of years of record 9️⃣ Evapotranspiration (Blaney-Criddle Method) $$ ET = p \times (0.46T + 8) $$ where: \( ET \) = evapotranspiration (mm) \( p \) = percentage of total annual daytime hours \( T \) = mean daily temperature (°C) 🔟 Storage Capacity of Reservoir (Prismoidal Formula) $$ V = \frac{h}{3} (A_1 + 4A_m + A_2) $$ where: \( V \) = volume (m³) \( h \) = vertical distance between sections (m) \( A_1, A_2 \) = end areas (m²) \( A_m \) = mid area (m²)








Section 5) Stresses in Structures

 Equation of Pure torsion

$${T\over {I_p}}={\tau \over r}={{G \theta} \over L}$$

Where, 

Ï„ --> Shear stress for example shear stress on wall of a tube subjected to torsion

Ó¨ --> Angle of twist

$$G = {E\over {2(1+\mu)}}$$

1) Circular tube subjected to torsion

$$\text{Polar Moment of Inertia }{I_p} = \text{Area of The section }\times{r^2}$$

$$(\pi D t)\times \left({D \over 2}\right)^2  = {{\pi {D^3} t}\over 4}$$

2) Thin Square tube subjected to torsion

Maximum shear stress Ï„ is given by

$$\tau = {T\over {2A.t}}$$


Normal Stress (Axial)  

$$ \sigma = \frac{P}{A} $$  

Where:  

\( \sigma \) = Normal stress (N/mm² or MPa)  

\( P \) = Axial load (N)  

\( A \) = Cross-sectional area (mm²)



Shear Stress  

$$ \tau = \frac{V}{A} $$  

Where:  

\( \tau \) = Shear stress (N/mm²)  

\( V \) = Shear force (N)  

\( A \) = Area resisting shear (mm²)



Bending Stress (Flexural Formula)  

$$ \sigma = \frac{M y}{I} $$  

Where:  

\( M \) = Bending moment (Nmm)  

\( y \) = Distance from neutral axis (mm)  

\( I \) = Moment of inertia (mm⁴)


Torsional Shear Stress  

$$ \tau = \frac{T r}{J} $$  

Where:  

\( T \) = Applied torque (Nmm)  

\( r \) = Distance from center to outer fiber (mm)  

\( J \) = Polar moment of inertia (mm⁴)


Combined Axial and Bending Stress  

$$ \sigma_{max} = \frac{P}{A} \pm \frac{M y}{I} $$  


Principal Stresses (2D State)  

$$ \sigma_{1,2} = \frac{\sigma_x + \sigma_y}{2} \pm \sqrt{\left(\frac{\sigma_x - \sigma_y}{2}\right)^2 + \tau_{xy}^2} $$  

Where:  

\( \sigma_x, \sigma_y \) = Normal stresses  

\( \tau_{xy} \) = Shear stress


Maximum Shear Stress  

$$ \tau_{max} = \frac{\sigma_1 - \sigma_2}{2} $$  


Bearing Stress  

$$ \sigma_b = \frac{P}{A_b} $$  

Where:  

\( A_b \) = Bearing area (mm²)


Hoop (Circumferential) Stress (Thin Cylindrical Pressure Vessel)  

$$ \sigma_h = \frac{p d}{2 t} $$  

Where:  

\( p \) = Internal pressure (N/mm²)  

\( d \) = Internal diameter (mm)  

\( t \) = Thickness (mm)


Longitudinal Stress (Pressure Vessel)  

$$ \sigma_l = \frac{p d}{4 t} $$  



Section 6) Steel Design

 1️⃣ Design Stress in Steel

2️⃣ Design Tensile Strength (Gross Section)

3️⃣ Design Tensile Strength (Net Section)

4️⃣ Slenderness Ratio

5️⃣ Plastic Section Modulus

6️⃣ Shear Strength (Web Area)

7️⃣ Bolt Shear Strength (Single Plane)

8️⃣ Weld Strength

9️⃣ Factored Load

$$P_u = \gamma_f \times P$$

🔟 Bending Moment — Shear Force Relation

$$\frac{dM}{dx} = V(x)$$

Section 7) Concrete Mix Design

Water-Cement Ratio (Abram’s Law)  

$$ \frac{f_1}{f_2} = \left(\frac{w_2}{w_1}\right)^n $$   


where:  

\( f_1, f_2 \) = compressive strengths  

\( w_1, w_2 \) = water-cement ratios  

\( n \) = constant (usually between 5 to 7)  


Volume of Concrete  

$$ V = \frac{W + \frac{C}{\rho_c} + \frac{F}{\rho_f} + \frac{C.A}{\rho_{ca}} + \frac{F.A}{\rho_{fa}} + \frac{W}{\rho_w}}{1000} $$  


Absolute Volume of Cement  

$$ V_c = \frac{W_c}{\rho_c} $$  


Absolute Volume of Fine Aggregate  

$$ V_{fa} = \frac{W_{fa}}{\rho_{fa}} $$  


Absolute Volume of Coarse Aggregate  

$$ V_{ca} = \frac{W_{ca}}{\rho_{ca}} $$  


Volume of Water  

$$ V_w = \frac{W_w}{\rho_w} $$  


Air Content (as percentage)  

$$ \text{Air \%} = \frac{V_{air}}{V_{total}} \times 100 $$  


Aggregate Proportioning by Weight  

$$ \frac{W_{ca}}{W_{fa}} = \frac{V_{ca} \times \rho_{ca}}{V_{fa} \times \rho_{fa}} $$  


Volume of Cementitious Materials  

$$ V_m = \frac{W_c}{\rho_c} + \frac{W_{fa}}{\rho_{fa}} + \frac{W_{ca}}{\rho_{ca}} + \frac{W_w}{\rho_w} $$  


Adjustment for Moisture Content  

$$ W_{corrected} = W_{SSD} + (MC \times W_{SSD}) $$  


Correction for Aggregate Water Absorption  

$$ W_{adjusted} = W_{SSD} - (Absorption \times W_{SSD}) $$  


Target Mean Strength  

$$ f_{ck'} = f_{ck} + t \times s $$  

where  

\( f_{ck} \) = characteristic strength  

\( t \) = tolerance factor (from IS 456 table)  

\( s \) = standard deviation  


Volume of Entrapped Air  

$$ V_{air} = \text{as per IS 10262 recommendations (usually 1-2\%)} $$  


Modulus of Elasticity of Concrete  

$$ E_c = 5000 \sqrt{f_{ck}} $$  


where:  

\( E_c \) = modulus of elasticity (MPa)  

\( f_{ck} \) = characteristic compressive strength (MPa)  



Bulking of Sand (Approximate Correction)  

$$ \text{Corrected Sand Volume} = \frac{\text{Specified Volume}}{1 + \frac{\text{Bulking Percentage}}{100}} $$  


Mix Proportion by Volume  

**For M20 concrete**  

1 : 1.5 : 3 (Cement : Sand : Aggregate)  

Water-cement ratio as per design requirements.


Fineness Modulus (FM)  

$$ FM = \frac{\text{Cumulative \% retained on standard sieves}}{100} $$  


Slump Test Value Range  

- Very low workability: 0–25 mm  

- Low workability: 25–50 mm  

- Medium workability: 50–100 mm  

- High workability: 100–175 mm  


Degree of Workability — Compaction Factor  

- Very low: 0.70  

- Low: 0.85  

- Medium: 0.92  

- High: 0.95  


Ultimate Creep Strain  

$$ \epsilon_{cr} = \phi \times \epsilon_{e} $$  


where:  

\( \epsilon_{cr} \) = creep strain  

\( \phi \) = creep coefficient  

\( \epsilon_{e} \) = elastic strain  


Maturity of Concrete (Nurse-Saul Equation)  

$$ M = \sum (T_a - T_0) \times \Delta t $$  


where:  

\( T_a \) = average concrete temperature  

\( T_0 \) = datum temperature (usually -11°C)  

\( \Delta t \) = time interval (hours)  


Specific Gravity  

$$ G = \frac{\text{Weight of Aggregate in Air}}{\text{Weight of Equal Volume of Water}} $$  


Water Absorption of Aggregate  

$$ \text{Water Absorption (\%)} = \frac{W_{ssd} - W_{oven}}{W_{oven}} \times 100 $$  


where:  

\( W_{ssd} \) = saturated surface dry weight  

\( W_{oven} \) = oven-dry weight  


Segregation Index (SI)  

$$ SI = \frac{\text{Difference of densities of top & bottom layers}}{\text{Average density}} $$  


Compressive Strength Formula  

$$ f_c = \frac{P}{A} $$  


where:  

\( P \) = failure load (N)  

\( A \) = loaded area (mm²)  


Cement Content per Bag  

**1 bag cement = 50 kg = 0.035 m³**


Section 8) Geotechnical Engineering

 Cohesive soils:- Soil consisting of the finer products of rock weathering. Cohesion is derived from large number of water films associated with the fine grained particles in the soil.

Total force of Attraction between two particle (f) =

$$f={{2 {\pi} rT}\over {1+tan \left({\theta}\over 2 \right) }}$$ 

where   r => Radius of Particle

            T => Surface Tension

Liquidity index:-The difference between natural moisture content and plastic limit expressed as percentage ratio of the plasticity index. 

$$LI={{m-PL}\over {LL-PL}}\times 100$$ 

m => moisture content

Plasticity Index:-The numerical difference between liquid limit and plastic limit of a soil.

$$\text{Plasticity Index}={\text{Liquid Limit }-\text{ Plastic Limit}} $$

1️⃣ Water Content  

$$ w = \frac{W_w}{W_s} \times 100 $$  


2️⃣ Specific Gravity of Soil Solids  

$$ G = \frac{W_s}{W_s - W_w} $$  


3️⃣ Void Ratio  

$$ e = \frac{V_v}{V_s} $$  


4️⃣ Porosity  

$$ n = \frac{V_v}{V} \times 100 $$  


5️⃣ Degree of Saturation  

$$ S_r = \frac{V_w}{V_v} \times 100 $$  


6️⃣ Dry Density  

$$ \rho_d = \frac{W_s}{V} $$  


7️⃣ Bulk Density  

$$ \rho = \frac{W}{V} $$  


8️⃣ Saturated Density  

$$ \rho_{sat} = \frac{W_{sat}}{V} $$  


9️⃣ Submerged Density  

$$ \rho' = \rho_{sat} - \rho_w $$  


🔟 Unit Weight Relationships  

$$ \gamma_d = \frac{G \times \gamma_w}{1+e} $$  


1️⃣1️⃣ Liquidity Index  

$$ LI = \frac{w - PL}{LL - PL} \times 100 $$  


1️⃣2️⃣ Plasticity Index  

$$ PI = LL - PL $$  


1️⃣3️⃣ Flow Index  

$$ FI = \frac{w_1 - w_2}{\log(N_2/N_1)} $$  


1️⃣4️⃣ Consistency Index  

$$ CI = \frac{LL - w}{PI} $$  


1️⃣5️⃣ Shear Strength (Coulomb’s Equation)  

$$ \tau = c + \sigma \tan \phi $$  


1️⃣6️⃣ Terzaghi’s Bearing Capacity Equation  

$$ q_u = c N_c + \gamma D_f N_q + 0.5 \gamma B N_\gamma $$  


1️⃣7️⃣ Settlement of Soil  

$$ S = \frac{C_c}{1+e_0} \log \left( \frac{\sigma'_0 + \Delta \sigma}{\sigma'_0} \right) \times H $$  


1️⃣8️⃣ Factor of Safety (Slope Stability)  

$$ FOS = \frac{\text{Resisting forces}}{\text{Driving forces}} $$

Section 9) Sewerage and Sewage disposal 

1️⃣ Chezy’s Formula

$$ V = C \sqrt{R S} $$

Where:

V = Velocity of flow (m/s)

C = Chezy's coefficient

R = Hydraulic radius (m)

S = Slope of the energy line (m/m)

2️⃣ Manning’s Formula

$$ V = \frac{1}{n} R^{2/3} S^{1/2} $$

Where:

n = Manning’s roughness coefficient

R = Hydraulic radius (m)

S = Slope of the channel (m/m)


3️⃣ Hydraulic Radius  

$$ R = \frac{A}{P} $$​

Where:

A = Area of flow (m²)

P = Wetted perimeter (m)


4️⃣ Discharge in Open Channel  

$$ Q = A \times V $$

Where:

Q = Discharge (m³/s)

A = Area of flow (m²)

V = Velocity (m/s)


  • 5️⃣ Population Forecast (Arithmetic Increase Method)  

    $$ P_n = P_0 + n \times I $$

    Where:

    Pn = Population after nn decades

    P0 = Present population

    II = Average increase per decade

    nn = Number of decades


    6️⃣ Population Forecast (Geometric Increase Method)  

    $$ P_n = P_0 (1 + r)^n $$

    Where:

    Pn = Population after n decades

    P0 = Present population

    r = Growth rate (as decimal)

    n = Number of decades


    7️⃣ Sewage Flow Estimation  

    $$ Q = q \times P $$

    Where:

    Q= Sewage discharge (litres/day)

    q = Per capita sewage generation (litres/person/day)


    $$ P_n = P_0 + n \times I $$

    P = Population


    8️⃣ BOD First Order Reaction  

    $$ BOD_t = BOD_0 \left(1 - e^{-k t}\right) $$

    Where:

    BODt = BOD exerted at time tt

    BOD0 = Ultimate BOD

    k = Reaction rate constant (per day)

    t = Time in days


    9️⃣ Oxygen Demand for Nitrification  

    $$ O_2 = 4.57 \times NH_3 $$


    🔟 Detention Time in Sedimentation Tank  

    $$ t = \frac{V}{Q} $$

    Where:

    t = Detention time (seconds or hours)

    V= Volume of tank (m³)

    Q = Flow rate (m³/s or m³/h)

    Detention Time in Sedimentation Tank  

    $$ t = \frac{V}{Q} $$  


    Where:  

    \( t \) = Detention time (sec or hours)  

    \( V \) = Volume of tank (m³)  

    \( Q \) = Flow rate (m³/sec)



    Surface Loading Rate (Overflow Rate)  

    $$ \text{SLR} = \frac{Q}{A} $$  


    Where:  

    \( Q \) = Flow rate (m³/day)  

    \( A \) = Surface area of tank (m²)



    BOD (Biochemical Oxygen Demand) Removal  

    $$ BOD_t = BOD_0 \left(1 - e^{-k t}\right) $$  


    Where:  

    \( BOD_0 \) = Initial BOD (mg/L)  

    \( k \) = Reaction rate constant (day⁻¹)  

    \( t \) = Time (days)



    BOD Loading on Aeration Tank  

    $$ \text{BOD Loading} = \frac{Q \times BOD}{V} $$  


    Where:  

    \( Q \) = Flow rate (m³/day)  

    \( BOD \) = Concentration (mg/L)  

    \( V \) = Volume of aeration tank (m³)



    Food to Microorganism Ratio (F/M Ratio)  

    $$ F/M = \frac{Q \times S_0}{V \times X} $$  


    Where:  

    \( Q \) = Flow rate (m³/day)  

    \( S_0 \) = Influent BOD (mg/L)  

    \( V \) = Volume of aeration tank (m³)  

    \( X \) = MLSS (Mixed Liquor Suspended Solids) (mg/L)


    Mean Cell Residence Time (MCRT)  

    $$ \theta_c = \frac{V \times X}{Q_w \times X_w + Q_e \times X_e} $$  


    Where:  

    \( Q_w \) = Waste sludge flow rate (m³/day)  

    \( X_w \) = Concentration of solids in waste sludge (mg/L)  

    \( Q_e \) = Effluent flow rate (m³/day)  

    \( X_e \) = Effluent solids concentration (mg/L)


    Sludge Volume Index (SVI)  

    $$ SVI = \frac{\text{Settled Sludge Volume (mL/L)}}{\text{MLSS (mg/L)}} \times 1000 $$  


    Where:  

    SVI in mL/g



    Air Requirement for Aeration  

    $$ Q_{air} = \frac{Q \times BOD \times Y}{C} $$  


    Where:  

    \( Q_{air} \) = Air required (m³/hr)  

    \( Y \) = Oxygen requirement per kg of BOD (kg O₂/kg BOD)  

    \( C \) = Oxygen transfer efficiency



    Chlorine Dose  

    $$ \text{Dose (mg/L)} = \frac{\text{Chlorine applied (mg)}}{\text{Volume (L)}} $$  



    pH Definition  

    $$ pH = -\log[H^+] $$  


    Where:  

    \( [H^+] \) = Hydrogen ion concentration (mol/L)


    Section 10) Water Supply and Purification

     1️⃣ Population Forecasting (Arithmetic Increase Method)  

    $$ P_n = P_0 + n \times I $$  


    2️⃣ Per Capita Demand  

    $$ q = \frac{Q}{P} $$  


    3️⃣ Detention Time in Sedimentation Tank  

    $$ t = \frac{V}{Q} $$  


    4️⃣ Surface Loading Rate (Overflow Rate)  

    $$ SLR = \frac{Q}{A} $$  


    5️⃣ Filter Rate (for Rapid Sand Filter)  

    $$ FR = \frac{Q}{A} $$  


    6️⃣ Chlorine Dose  

    $$ C_d = C_r + D_c $$  


    7️⃣ Disinfection Contact Time (CT Concept)  

    $$ C \times T = \text{constant for effective disinfection} $$  


    8️⃣ Water Pipe Flow (Hazen-Williams Equation)  

    $$ V = 0.85 \times C \times R^{0.63} \times S^{0.54} $$  


    9️⃣ Loss of Head in Filter  

    $$ h_f = \frac{Q^2}{K} $$  


    🔟 Water Demand Formula (General)  

    $$ Q = q \times P $$

    Section 11) Building Materials

    SR. No. Items Unit Materials
    Particulars Quantity Unit
    1 Brick Work 100 cu.m Bricks 50000 Nos
    Mortar 30 cu.m
    2 Rubble stone Masonry 100 cu.m Stone 125 cu.m
    Mortar 42 cu.m
    3 25 mm Cement Concrete 1:2:4 100 sq.m Stone grit 2.4 cu.m
    sand 1.2 cu.m
    cement 24 Bags
    4 12 mm thick plastering 100 sq.m Mortar 2 cu.m
    5 Pointing in brickwork 100 sq.m Mortar 0.6 cu.m
    6 White washing one coat 100 sq.m Lime 10 Kg
    7 Distempring
    i) First coat 100 sq.m Dry distemper 6.5 Kg
    ii) Second coat 100 sq.m Dry distemper 5 Kg
    8 Oil Painting one coat 100 sq.m Ready-made paint 10 Litres
    9 Oil Painting one coat 100 sq.m Paint stiff 10 Kg
    10 20 mm thick Damp-proof course of 1:2:4 cement Mortar 100 sq.m Cement 27 Bags
    Sand 1.8 Cu.m
    Imperno 27 Kg
    11 Painting with bitumen
    i) First coat 100 sq.m Bitumen 150 Kg
    ii) Second coat 100 sq.m Bitumen 100 Kg
    12 C.G.I. Sheet Roofing 100 sq.m C.G.I. sheets 128 Sq.m
    13 A.C. Sheet Roofing 100 sq.m A.C. sheets 115 Sq.m
    14 Panneled door shutter 40 mm thick 100 sq.m Timber 4.5 Cu.m
    15 Battened door shutter 40 mm thick 100 sq.m Timber 5 Cu.m
    16 Partialy Panneled and Glazed shutter 40 mm thick 100 sq.m Timber 3 Cu.m
    17 Fully glazed shutter 40 mm thick 100 sq.m Timber 2 Cu.m

     Fineness Modulus (for Aggregates)  

    $$ \text{FM} = \frac{\text{Cumulative retained on standard sieves}}{100} $$  

    (Fineness modulus indicates average particle size.)

  • Compressive Strength (for Bricks, Cement Cubes etc.)  

    $$ \text{Compressive Strength} = \frac{\text{Ultimate Load}}{\text{Area of Specimen}} $$  

    Units: N/mm²  


    Modulus of Rupture (for Concrete)  

    $$ f_{cr} = \frac{3P}{2bd^2} $$  

    Where:  
    \( P \) = Load at failure (N)  
    \( b \) = Width of specimen (mm)  
    \( d \) = Depth of specimen (mm)  

    Cement Soundness Test  

    Limit: Expansion should not exceed **10 mm** (Le-Chatelier Apparatus)


    Standard Consistency of Cement  

    $$ \text{Consistency (\%)} = \frac{\text{Weight of Water}}{\text{Weight of Cement}} \times 100 $$  

    Standard value: 26% to 33%


    Initial and Final Setting Time (Cement)  

    - **Initial Setting Time** ≥ 30 minutes  
    - **Final Setting Time** ≤ 600 minutes  

    No formula — practical test with Vicat apparatus.

    Section 12) Irrigation Engineering

    1️⃣ Duty (D)  
    $$ D = \frac{8.64 \times B}{\Delta} $$  

    where:  
    \( D \) = duty (hectare/cumec)  
    \( B \) = base period (days)  
    \( \Delta \) = depth of water (cm)  

    ---

    2️⃣ Delta (Δ)  
    $$ \Delta = \frac{8.64 \times B}{D} $$  

    ---

    3️⃣ Base Period (B)  
    $$ B = \frac{\Delta \times D}{8.64} $$  

    ---

    4️⃣ Consumptive Use (U)  
    $$ U = E + T + E_T $$  

    where:  
    \( E \) = evaporation  
    \( T \) = transpiration  
    \( E_T \) = other uses  

    ---

    5️⃣ Crop Water Requirement (WR)  
    $$ WR = IR + ER $$  

    where:  
    \( IR \) = irrigation requirement  
    \( ER \) = effective rainfall  

    ---

    6️⃣ Irrigation Efficiency  
    **a) Water Conveyance Efficiency (Ec)**  
    $$ E_c = \frac{W_f}{W_e} \times 100 $$  

    **b) Water Application Efficiency (Ea)**  
    $$ E_a = \frac{W_s}{W_f} \times 100 $$  

    **c) Water Storage Efficiency (Es)**  
    $$ E_s = \frac{W_s}{W_n} \times 100 $$  

    **d) Water Distribution Efficiency (Ed)**  
    $$ E_d = \left(1 - \frac{y}{d}\right) \times 100 $$  

    where:  
    \( W_e \) = water delivered at field entrance  
    \( W_f \) = water delivered to field  
    \( W_s \) = water stored in root zone  
    \( W_n \) = water needed in root zone  
    \( y \) = average numerical deviation from mean depth  
    \( d \) = mean depth of water stored  

    ---

    7️⃣ Kennedy’s Critical Velocity Formula  
    $$ V_0 = 0.55 \times R^{0.64} $$  

    where:  
    \( V_0 \) = critical velocity (m/s)  
    \( R \) = hydraulic mean depth (m)  

    ---

    8️⃣ Lacey’s Silt Factor  
    $$ f = 1.76 \times \sqrt{d} $$  

    where:  
    \( d \) = mean particle size in mm  

    ---

    9️⃣ Lacey’s Velocity Formula  
    $$ V = \left(\frac{Q f^2}{140}\right)^{1/6} $$  

    ---

    🔟 Lacey’s Regime Perimeter  
    $$ P = 4.75 \times \sqrt{Q} $$  

    ---

    1️⃣1️⃣ Lacey’s Regime Area  
    $$ A = 1.0 \times Q^{5/6} / f^{0.5} $$  

    ---

    1️⃣2️⃣ Crop Factor Method (for estimating Consumptive Use)  
    $$ U = K_c \times E_{pan} $$  

    where:  
    \( K_c \) = crop coefficient  
    \( E_{pan} \) = pan evaporation  

    ---

    1️⃣3️⃣ Delta for Crop  
    $$ \Delta = \frac{WR \times 100}{8.64 \times B} $$  

    ---

    1️⃣4️⃣ Command Area  
    **Gross Commanded Area (GCA):** total area commanded by canal  
    **Culturable Commanded Area (CCA):** area fit for cultivation  
    **Intensity of Irrigation (I):**  
    $$ I = \frac{\text{Net Irrigated Area}}{\text{CCA}} \times 100 $$  

    ---

    1️⃣5️⃣ Canal Lining — Reduction in Seepage Loss  
    $$ \text{Seepage Loss Reduction (\%)} = \frac{S_1 - S_2}{S_1} \times 100 $$  

    where:  
    \( S_1 \) = seepage loss in unlined canal  
    \( S_2 \) = seepage loss in lined canal  

    Section 13) Construction Management

    Time-Cost Trade Off (Crash Cost / Slope of Cost Curve)  

    $$ \text{Crash Cost Slope (CCS)} = \frac{\text{Crash Cost} - \text{Normal Cost}}{\text{Normal Time} - \text{Crash Time}} $$  

    ---

    Total Float (TF)  

    $$ TF = LFT - EFT $$  

    or  

    $$ TF = LST - EST $$  

    where:  
    \( LFT \) = Latest Finish Time  
    \( EFT \) = Earliest Finish Time  
    \( LST \) = Latest Start Time  
    \( EST \) = Earliest Start Time  

    ---

    Free Float (FF)  

    $$ FF = \text{Earliest Start of Following Activity} - \text{Earliest Finish of Current Activity} $$  

    ---

    Independent Float (IF)  

    $$ IF = \text{Earliest Start of Following Activity} - \text{Latest Finish of Current Activity} $$  

    ---

    Critical Path Method (CPM)  

    - Longest duration path through a network  
    - All critical activities have zero float.

    ---

    Cost-Time Optimization Slope  

    $$ \text{Slope} = \frac{\text{Crash Cost} - \text{Normal Cost}}{\text{Normal Time} - \text{Crash Time}} $$  

    ---

    Resource Allocation Formula  

    $$ \text{Resource Required per Day} = \frac{\text{Total Work Quantity}}{\text{Available Working Days}} $$  

    ---

    Labour Productivity  

    $$ \text{Productivity} = \frac{\text{Work Done}}{\text{Man-Hours}} $$  

    ---

    Earned Value (EV)  

    $$ EV = \text{Percent Complete} \times \text{Budget at Completion (BAC)} $$  

    ---

    Schedule Variance (SV)  

    $$ SV = EV - PV $$  

    where:  
    \( PV \) = Planned Value  

    ---

    Cost Variance (CV)  

    $$ CV = EV - AC $$  

    where:  
    \( AC \) = Actual Cost  

    ---

    Performance Indices  

    **Cost Performance Index (CPI)**  
    $$ CPI = \frac{EV}{AC} $$  

    **Schedule Performance Index (SPI)**  
    $$ SPI = \frac{EV}{PV} $$  

    ---

    Bar Bending Schedule (Unit Weight of Steel)  

    $$ \text{Weight (kg)} = \frac{D^2}{162} \times L $$  

    where:  
    \( D \) = Diameter of bar in mm  
    \( L \) = Length in meters  

    ---

    Number of Bricks Required  

    $$ \text{Number of Bricks} = \frac{\text{Volume of Brickwork}}{\text{Volume of 1 Brick with Mortar}} $$  



    Material Requirement in Concrete  

    **For 1 m³ of M20 Concrete (1:1.5:3)**  

    - Cement = 320 kg  
    - Sand = 0.45 m³  
    - Aggregate = 0.90 m³  
    - Water = 160 liters  

    (Ratios may vary based on mix design.)

    Section 14) Fluid Mechanics

    Pressure Intensity  

    $$ p = \frac{F}{A} $$  

    Where:  
    \( F \) = Force (N)  
    \( A \) = Area (m²)


    Hydrostatic Pressure at Depth  

    $$ p = \rho g h $$  

    Where:  
    \( \rho \) = Density of fluid (kg/m³)  
    \( g \) = Acceleration due to gravity (9.81 m/s²)  
    \( h \) = Depth (m)


    Pascal’s Law  

    $$ \text{Pressure is equal in all directions at a point in a static fluid.} $$  

    No equation — principle statement.


    Continuity Equation  

    $$ A_1 V_1 = A_2 V_2 $$  

    Where:  
    \( A \) = Area (m²)  
    \( V \) = Velocity (m/s)


    Bernoulli’s Equation  

    $$ \frac{p}{\rho g} + \frac{V^2}{2g} + z = \text{constant} $$  

    For steady, incompressible, frictionless flow.


    Discharge (Flow Rate)  

    $$ Q = A V $$  

    Where:  
    \( Q \) = Discharge (m³/s)  
    \( A \) = Area (m²)  
    \( V \) = Velocity (m/s)


    Reynolds Number  

    $$ Re = \frac{\rho V D}{\mu} $$  

    Where:  
    \( \rho \) = Fluid density (kg/m³)  
    \( V \) = Mean velocity (m/s)  
    \( D \) = Diameter (m)  
    \( \mu \) = Dynamic viscosity (Pa·s)


    Manning’s Formula (Open Channel Flow)  

    $$ V = \frac{1}{n} R^{2/3} S^{1/2} $$  

    Where:  
    \( V \) = Velocity (m/s)  
    \( n \) = Manning’s roughness coefficient  
    \( R \) = Hydraulic radius (m)  
    \( S \) = Slope of energy line



    Chezy’s Formula  

    $$ V = C \sqrt{R S} $$  

    Where:  
    \( C \) = Chezy’s constant  
    \( R \) = Hydraulic radius (m)  
    \( S \) = Slope of energy line



    Drag Force  

    $$ F_D = C_D \frac{\rho A V^2}{2} $$  

    Where:  
    \( C_D \) = Drag coefficient  
    \( \rho \) = Fluid density (kg/m³)  
    \( A \) = Projected area (m²)  
    \( V \) = Velocity (m/s)

    Section 15) Structural Analysis

    Bending Moment — Shear Force Relation  

    $$ \frac{dM}{dx} = V(x) $$  

    Where:  
    \( M \) = Bending Moment (kNm)  
    \( V(x) \) = Shear force at section x (kN)


    Shear Force — Load Relation  

    $$ \frac{dV}{dx} = -w(x) $$  

    Where:  
    \( w(x) \) = Distributed load at section x (kN/m)


    Moment of Inertia for Rectangular Section  

    $$ I = \frac{b h^3}{12} $$  

    Where:  
    \( b \) = Breadth (mm)  
    \( h \) = Depth (mm)


    Bending Stress (Flexure Formula)  

    $$ \sigma = \frac{M y}{I} $$  

    Where:  
    \( \sigma \) = Bending stress (MPa)  
    \( M \) = Bending moment (kNm)  
    \( y \) = Distance from neutral axis (mm)  
    \( I \) = Moment of inertia (mm⁴)


    Deflection for Cantilever Beam (Point Load at Free End)  

    $$ \delta = \frac{P L^3}{3 E I} $$  

    Where:  
    \( \delta \) = Deflection (mm)  
    \( P \) = Point load (kN)  
    \( L \) = Length of cantilever (mm)  
    \( E \) = Modulus of elasticity (MPa)  
    \( I \) = Moment of inertia (mm⁴)


    Deflection for Simply Supported Beam (Central Point Load)  

    $$ \delta = \frac{P L^3}{48 E I} $$  


    Slope at Free End of Cantilever (Point Load)  

    $$ \theta = \frac{P L^2}{2 E I} $$  


    Moment Area Theorem (First Theorem)  

    $$ \theta_{AB} = \frac{Area \ of \ M/EI \ diagram \ between \ A \ and \ B}{Span} $$  


    Moment Area Theorem (Second Theorem)  

    $$ \delta_{B/A} = \text{Moment of } M/EI \text{ diagram between A and B about point B} $$  


    Principle of Superposition  

    If multiple loads act, total displacement or stress is sum of individual effects:
    $$ \Delta_{total} = \Delta_1 + \Delta_2 + \Delta_3 + \cdots $$  

    Section 16) Reinforced Cement Concrete

    Modular Ratio  

    $$ m = \frac{E_c}{E_s} $$  

    Where:  
    \( E_c \) = Modulus of elasticity of concrete (MPa)  
    \( E_s \) = Modulus of elasticity of steel (MPa)


    Moment of Resistance (Limit State of Collapse — Flexure)  

    $$ M_u = 0.36 f_{ck} b x_u (d - 0.42 x_u) $$  

    Where:  
    \( f_{ck} \) = Characteristic compressive strength of concrete (MPa)  
    \( b \) = Width of beam (mm)  
    \( x_u \) = Depth of neutral axis (mm)  
    \( d \) = Effective depth (mm)


    Limiting Depth of Neutral Axis  

    $$ \frac{x_{u,lim}}{d} = \text{depends on steel grade (as per IS 456:2000)} $$  

    Example:  
    For Fe-500  
    \( \frac{x_{u,lim}}{d} = 0.46 \)


    Lever Arm  

    $$ z = d - 0.42 x_u $$  


    Ultimate Load on Axially Loaded Short Column  

    $$ P_u = 0.4 f_{ck} A_c + 0.67 f_y A_s $$  

    Where:  
    \( A_c \) = Area of concrete (mm²)  
    \( A_s \) = Area of steel (mm²)  
    \( f_y \) = Yield strength of steel (MPa)


    Development Length  

    $$ L_d = \frac{\phi \times \sigma_s}{4 \tau_{bd}} $$  

    Where:  
    \( \phi \) = Diameter of bar (mm)  
    \( \sigma_s \) = Stress in bar at section considered (MPa)  
    \( \tau_{bd} \) = Design bond stress (MPa)


    Design Bond Stress  

    (As per IS 456:2000 — Table 21)

    Example:  
    For M20 concrete & Fe-500  
    \( \tau_{bd} = 1.6 \text{ MPa (plain bars)} \)


    Minimum Reinforcement in Slab  

    $$ A_{s,min} = \frac{0.12}{100} \times b \times D $$  

    For Fe-415/Fe-500  
    \( 0.12\% \) for mild steel  
    \( 0.12\% \) for HYSD bars


    Nominal Cover (IS 456:2000 Table 16)


    Example:  
    Slabs: 20 mm  
    Beams: 25 mm  
    Columns: 40 mm  
    Footings: 50 mm


    Shear Strength of Concrete (without shear reinforcement)  

    $$ V_c = \tau_c b d $$  

    Where:  
    \( \tau_c \) = Design shear strength of concrete (MPa)

    Axial Load Capacity  

    $$ P_u = 0.4 f_{ck} A_c + 0.67 f_y A_s $$  

    Where:  
    \( f_{ck} \) = Characteristic compressive strength of concrete (MPa)  
    \( f_y \) = Yield strength of steel (MPa)  
    \( A_c \) = Area of concrete (mm²)  
    \( A_s \) = Area of steel (mm²)

    ---

    Pure Moment Capacity (No Axial Load)  

    $$ M_u = 0.36 f_{ck} b x_u (d - 0.42 x_u) $$  

    Where:  
    \( b \) = Width of section (mm)  
    \( x_u \) = Neutral axis depth (mm)  
    \( d \) = Effective depth (mm)

    ---

    Interaction Equation for Combined Axial Load and Bending (Limit State Method — Clause 39.6, IS 456:2000)


    $$ \frac{P_u}{P_{uz}} + \frac{M_u}{M_{uz}} \leq 1.0 $$  

    Where:  
    \( P_{uz} \) = Axial load carrying capacity under zero moment  
    \( M_{uz} \) = Moment carrying capacity under zero axial load

    ---

    Moment of Resistance under Combined Load  

    If eccentricity \( e \) is more than minimum eccentricity,  

    $$ M_u = P_u \times e $$  

    Where:  
    \( e \) = Eccentricity of load = \( \frac{M_u}{P_u} \)

    ---

    Minimum Eccentricity  

    $$ e_{min} = \text{greater of } \left( \frac{L}{500} + \frac{D}{30}, 20 \right) \text{ mm} $$  

    Where:  
    \( L \) = Unsupported length (mm)  
    \( D \) = Lateral dimension of column (mm)

    ---

    Slenderness Ratio  

    $$ \lambda = \frac{l_{eff}}{r} $$  

    Where:  
    \( l_{eff} \) = Effective length (mm)  
    \( r \) = Radius of gyration (mm)

    ---

    Radius of Gyration  

    $$ r = \sqrt{\frac{I}{A}} $$  

    Where:  
    \( I \) = Moment of inertia (mm⁴)  
    \( A \) = Area (mm²)

    Load on Slab  

    $$ w = D + L $$  

    Where:  
    \( D \) = Dead load (kN/m²)  
    \( L \) = Live load (kN/m²)


    Short Span and Long Span Ratio  

    $$ \frac{L_y}{L_x} $$  

    If ratio \( \leq 2 \) → Two-way slab  
    If ratio \( > 2 \) → One-way slab  

    \( L_x \) = Shorter span (m)  
    \( L_y \) = Longer span (m)


    Moment Coefficients (from IS 456:2000 Table 26)


    - For simply supported slab with corners free to lift:
      $$ M_x = \alpha_x w L_x^2 $$
      $$ M_y = \alpha_y w L_x^2 $$  

      \( \alpha_x, \alpha_y \) = Coefficients based on span ratio


    Effective Depth (d)  

    Using Limit State Method:  
    $$ d = \sqrt{\frac{M_u}{0.138 f_{ck} b}} $$  

    Where:  
    \( M_u \) = Ultimate Moment (kNm)  
    \( f_{ck} \) = Grade of concrete (MPa)  
    \( b \) = Width (usually 1000 mm)


    Area of Steel (A_s)  

    For balanced section:
    $$ A_s = \frac{M_u}{0.87 f_y j d} $$  

    Where:  
    \( f_y \) = Grade of steel (MPa)  
    \( j \) = Lever arm factor (usually 0.9)


    Minimum Reinforcement as per IS 456:2000  

    $$ A_{s(min)} = \frac{0.12}{100} \times b \times D $$  

    \( D \) = Overall depth (mm)



    Check for Deflection Control  

    Basic span-to-depth ratio:  
    $$ \frac{L}{d} \leq \text{value from IS 456 Table 2 (generally 26-35)} $$  

    Increase or decrease this limit based on percentage tension steel and stress factor.


    Distribution Steel  

    Minimum:
    $$ A_{s(dis)} = \frac{0.12}{100} \times b \times D $$  

    Placed perpendicular to main steel.


    Spacing of Bars  

    Maximum spacing:
    - Main bars:  
      $$ \text{Spacing} \leq 3d \text{ or 300 mm (whichever is less)} $$  

    - Distribution bars:
      $$ \text{Spacing} \leq 5d \text{ or 450 mm (whichever is less)} $$  

    Factored Load on Footing  

    $$ P_u = \gamma_f \times P $$  

    Where:  
    \( P \) = Service Load (kN)  
    \( \gamma_f \) = Load factor (typically 1.5)

    ---

    Required Area of Footing  

    $$ A = \frac{P_u}{q_u} $$  

    Where:  
    \( q_u \) = Factored bearing capacity (kN/m^2)


    Size of Square Footing  

    If square footing,  
    $$ B = \sqrt{A} $$  


    Bending Moment at Face of Column  

    For two-way footing (IS 456:2000 Cl. 34.2.3.2),  
    $$ M_{xx} = \frac{q_u (B - a)^2}{8} $$  
    $$ M_{yy} = \frac{q_u (B - a)^2}{8} $$  

    Where:  
    \( a \) = Size of column in m  
    \( B \) = Size of footing in m


    Effective Depth (d) for Bending  

    $$ d = \sqrt{\frac{M_u}{0.138 f_{ck} b}} $$  

    Where:  
    \( M_u \) = Ultimate moment (kNm)  
    \( f_{ck} \) = Grade of concrete (MPa)


    One-Way Shear Check (at distance d from face)  

    Nominal shear:  

    $$ \tau_v = \frac{V_u}{b \times d} $$  

    Where:  
    \( V_u \) = Factored shear force (kN)  
    \( b \) = Width considered (m)

    Check:  

    $$ \tau_v \leq \tau_c $$  

    \( \tau_c \) from IS 456 Table 19


    Two-Way (Punching) Shear Check  

    Critical perimeter:  

    $$ u = 4 (a + d) $$  

    Nominal shear stress:  

    $$ \tau_v = \frac{V_u}{u \times d} $$  

    Check:  

    $$ \tau_v \leq \tau_c $$  

    \( \tau_c \) from IS 456 Table 20


    Area of Steel (A_s)  

    $$ A_s = \frac{M_u}{0.87 f_y j d} $$  

    \( j \) = Lever arm factor (typically 0.9)


    Minimum Reinforcement  

    As per IS 456:2000  
    $$ A_{s(min)} = \frac{0.12}{100} \times b \times D $$  

    \( D \) = Overall depth (mm)


    Development Length  

    $$ L_d = \frac{\phi \times \sigma_s}{4 \times \tau_{bd}} $$  

    Where:  
    \( \phi \) = Bar diameter (mm)  
    \( \sigma_s \) = Stress in bar (MPa)  
    \( \tau_{bd} \) = Design bond stress (MPa)

    Rise and Tread (As per IS 456:2000)  

    $$ 2R + T = 550 \text{ to } 700 \ \text{mm} $$  

    Where:  
    \( R \) = Rise (mm)  
    \( T \) = Tread (mm)

    Number of Steps  

    $$ N = \frac{H}{R} $$  

    Where:  
    \( H \) = Total floor-to-floor height (mm)


    Horizontal Span of Staircase  

    $$ L = N \times T $$  


    Length of Waist Slab  

    $$ l = \sqrt{(L)^2 + (H)^2} $$  


    Self-Weight of Waist Slab  

    $$ w_s = t \times b \times \gamma_c $$  

    Where:  
    \( t \) = Thickness of waist slab (m)  
    \( b \) = Unit width (1 m)  
    \( \gamma_c \) = Density of concrete (25 kN/m³)


    Load of Steps  

    Per step load:  
    $$ w_{step} = \frac{R \times T \times \gamma_c}{T} $$  

    Uniformly distributed load (UDL) along slope:  
    $$ w_{step} = R \times \gamma_c $$  


    Live Load (as per IS 875 Part 2)  

    Residential = 3 kN/m²  
    Public = 5 kN/m²


    Total Load per Meter on Waist Slab  

    $$ w = w_s + w_{step} + w_{LL} $$  

    \( w_{LL} \) = Live load (kN/m)


    Bending Moment at Mid-Span (Simply Supported)  

    $$ M = \frac{w l^2}{8} $$  


    Effective Depth (d) for Bending  

    $$ d = \sqrt{\frac{M_u}{0.138 f_{ck} b}} $$  

    Where:  
    \( M_u \) = Ultimate moment (kNm)


    Area of Steel (A_s)  

    $$ A_s = \frac{M_u}{0.87 f_y j d} $$  

    \( j \) = 0.9 (lever arm factor)


    Minimum Reinforcement  

    As per IS 456:2000  
    $$ A_{s(min)} = \frac{0.12}{100} \times b \times D $$  

    \( D \) = Overall depth (mm)

    Development Length  

    $$ L_d = \frac{\phi \times \sigma_s}{4 \times \tau_{bd}} $$  

    \( \phi \) = Bar diameter (mm)  
    \( \sigma_s \) = Stress in bar (MPa)  
    \( \tau_{bd} \) = Design bond stress (MPa)

    Section 17) Prestressed Concrete (PSC)

    Loss of Prestress due to Elastic Shortening  

    $$ \Delta f_{es} = m \times \frac{P}{A} $$  

    Where:  
    \( m \) = Modular ratio  
    \( P \) = Prestressing force (N)  
    \( A \) = Area of concrete section (mm²)


    Loss of Prestress due to Creep of Concrete  

    $$ \Delta f_{cr} = f_c \times C_c $$  

    Where:  
    \( f_c \) = Stress in concrete at tendon level (MPa)  
    \( C_c \) = Creep coefficient  


    Loss of Prestress due to Shrinkage of Concrete  

    $$ \Delta f_{sh} = E_s \times \varepsilon_{sh} $$  

    Where:  
    \( E_s \) = Modulus of elasticity of steel (MPa)  
    \( \varepsilon_{sh} \) = Shrinkage strain


    Loss of Prestress due to Relaxation of Steel  

    As per IS 1343, depends on type of steel and initial stress.  
    For example:  
    $$ \Delta f_{relax} = \text{(5\% to 8\% of initial prestress)} $$


    Total Loss of Prestress  

    $$ \text{Total Loss} = \Delta f_{es} + \Delta f_{cr} + \Delta f_{sh} + \Delta f_{relax} $$  


    Final Prestress in Tendon  

    $$ f_p = f_{pi} - \text{Total Loss} $$  

    Where:  
    \( f_{pi} \) = Initial prestress (MPa)


    Ultimate Moment Capacity (Limit State)  

    $$ M_u = f_{pu} \times A_p \times \left( d - \frac{A_p f_{pu}}{2 f_{ck} b} \right) $$  

    Where:  
    \( f_{pu} \) = Ultimate stress in tendon (MPa)  
    \( A_p \) = Area of prestressing steel (mm²)  
    \( d \) = Effective depth (mm)  
    \( b \) = Width of section (mm)  
    \( f_{ck} \) = Characteristic strength of concrete (MPa)


    Eccentricity of Prestressing  

    $$ e = \frac{M}{P} $$  

    Where:  
    \( M \) = Moment (kNm)  
    \( P \) = Prestressing force (kN)



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