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Civil Engineering Cheatsheet

A comprehensive cheat sheet covering essential concepts, formulas, and tables in civil engineering. Designed for quick reference for students and professionals.

Structural Analysis & Design

Material Properties

Steel (A36)

 
Fy = 36 ksi
Fu = 58 ksi
E = 29,000 ksi

Concrete (f'c)

 
f'c = Concrete compressive strength (ksi)
E = 57000 * sqrt(f'c) (psi)

Wood

Properties vary widely; refer to specific wood species tables.

Load Combinations (ASCE 7)

LRFD (Load and Resistance Factor Design) Load Combinations:

1.4D
1.2D + 1.6L + 0.5(Lr or S or R)
1.2D + 1.6(Lr or S or R) + (L or 0.5W)
1.2D + 1.0W + L + 0.5(Lr or S or R)
1.2D + 1.0E + L + 0.2S
0.9D + 1.0W + 0.9H
0.9D + 1.0E + 0.9H

Where:
D = Dead Load, L = Live Load, Lr = Roof Live Load, S = Snow Load, R = Rain Load, W = Wind Load, E = Earthquake Load, H = Soil Load

Beam Deflection Formulas

Cantilever Beam, End Load

 
delta = (P*L^3) / (3*E*I)

Cantilever Beam, Uniform Load

 
delta = (w*L^4) / (8*E*I)

Simply Supported Beam, Center Load

 
delta = (P*L^3) / (48*E*I)

Simply Supported Beam, Uniform Load

 
delta = (5*w*L^4) / (384*E*I)

Geotechnical Engineering

Soil Properties

Unit Weight (γ)

 
γ = W / V

Dry Unit Weight (γd)

 
γd = Ws / V

Void Ratio (e)

 
e = Vv / Vs

Porosity (n)

 
n = Vv / V

Degree of Saturation (S)

 
S = Vw / Vv

Water Content (w)

 
w = Ww / Ws

Effective Stress 

σ' = σ - u

Where:
σ’ = Effective stress
σ = Total stress
u = Pore water pressure

Bearing Capacity (Terzaghi)

Strip Footing

 
q_ult = cNc + γDfNq + 0.5γBNγ

Square Footing

 
q_ult = 1.3cNc + γDfNq + 0.4γBNγ

Circular Footing

 
q_ult = 1.3cNc + γDfNq + 0.3γBNγ

Where

 
c = Cohesion
γ = Unit weight of soil
Df = Depth of footing
B = Width or diameter of footing
Nc, Nq, Nγ = Bearing capacity factors

Transportation Engineering

Highway Capacity

Density (D)

 
D = v / s

where v = flow rate, s = space mean speed

Flow Rate (v)

 
v = D * s

Space Mean Speed (s)

 
s = v / D

Traffic Flow Relationships

Fundamental equation of traffic flow:

v = k * u

Where:
v = flow (vehicles/hour)
k = density (vehicles/mile)
u = speed (miles/hour)

Stopping Sight Distance (SSD)

SSD Formula

 
SSD = 1.47*v*t + (v^2) / (30*(f +- g))

Where:
v = speed (mph)
t = perception-reaction time (sec, typically 2.5 sec)
f = coefficient of friction
g = grade (+ for uphill, - for downhill)

Environmental Engineering

Water Quality Parameters

BOD (Biochemical Oxygen Demand)

 
BOD = (DOi - DOf) / P

Where:
DOi = Initial dissolved oxygen
DOf = Final dissolved oxygen
P = Dilution factor

COD (Chemical Oxygen Demand)

Measure of the oxygen equivalent of the organic matter in a water sample that is susceptible to oxidation by a strong chemical oxidant.

pH

Measure of acidity or alkalinity. pH = -log[H+]

Turbidity

Measure of the cloudiness of water. Caused by suspended solids.

Activated Sludge Process

Sludge Volume Index (SVI):

SVI = (Settled Sludge Volume (mL/L) * 1000) / MLSS (mg/L)

Where:
MLSS = Mixed Liquor Suspended Solids

Air Quality

PM10 & PM2.5

Particulate matter with aerodynamic diameter less than 10 μm and 2.5 μm, respectively.

Ozone (O3)

Formed by photochemical reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOCs).

Carbon Monoxide (CO)

A colorless, odorless toxic gas produced by incomplete combustion.
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