Civil Engineering - Combined Technical Services

1. Engineering Mechanics

Engineering Mechanics is the foundation of Civil Engineering. It deals with forces acting on bodies and the effects produced by them.

Important Topics – Force

A force is a push or pull acting on a body.

Characteristics:

Magnitude
Direction
Line of action
Point of application

Units:

Newton (N)
Kilonewton (kN)

Types of Forces

Coplanar forces
Concurrent forces
Parallel forces
Collinear forces
Non-concurrent forces

Resolution of Forces

Breaking a force into horizontal and vertical components.

Formula: Horizontal = F cos θ, Vertical = F sin θ

Equilibrium

A body is in equilibrium when ΣFx = 0, ΣFy = 0, ΣM = 0. Frequently asked in TNPSC.

Moment of Force

Moment = Force × Perpendicular Distance. Unit: N-m. Clockwise moments are generally taken negative, counter-clockwise positive.

Couple

Two equal and opposite forces separated by a distance form a couple. Moment of Couple: M = F × d.

Centre of Gravity

The point through which the entire weight acts.

Rectangle: At center.
Triangle: One-third height from base.
Semicircle: 4R/3π from diameter.

Centroid

Centroid is the geometric center of an area. Frequently asked for Triangle, Rectangle, Circle, Trapezium, and Composite sections.

Friction

Friction opposes motion.

Static friction
Limiting friction
Kinetic friction
Rolling friction

Coefficient of Friction: μ = F/N. Angle of Friction: tan θ = μ.

Simple Machines

Lever
Pulley
Wheel and axle
Screw jack

Efficiency: Efficiency = Mechanical Advantage / Velocity Ratio.

2. Strength of Materials

This subject studies the behavior of materials under different loads.

Stress

Stress = Load / Area. Units: N/mm².

Tensile stress
Compressive stress
Shear stress

Strain

Change in length / Original length. No unit.

Tensile strain
Compressive strain
Shear strain
Volumetric strain

Hooke's Law

Within elastic limit, Stress ∝ Strain. Stress = E × Strain, where E is Young's Modulus.

Elastic Constants

Young's Modulus (E)
Bulk Modulus (K)
Shear Modulus (G)
Poisson's Ratio (μ)

Relationship: E = 2G(1 + μ). Frequently asked.

Elastic Limit

Maximum stress without permanent deformation.

Factor of Safety

Factor of Safety = Ultimate Stress / Working Stress. Higher factor means safer design.

Thermal Stress

Produced due to temperature changes. Formula: σ = E α ΔT, where α = coefficient of thermal expansion.

Bending Stress

Formula: σ = My/I, where M = Bending Moment, I = Moment of Inertia, y = Distance from neutral axis.

Shear Stress in Beams

Maximum shear occurs at neutral axis.

Torsion

Applied to circular shafts. Formula: T/J = τ/R = Gθ/L.

Columns

Types: Short column, Long column
Failure: Crushing, Buckling

Euler Formula is frequently asked.

3. Building Materials

Very important in TNPSC.

Stone

Properties: Hard, Durable, Strong, Weather resistant.

Uses: Masonry, Foundations, Bridges.

Common stones: Granite, Basalt, Sandstone, Limestone.

Bricks

Good brick properties:

Uniform shape
Sharp edges
Metallic ringing sound
Water absorption below 20%
Free from cracks

Classification: First class, Second class, Third class, Fourth class.

Lime

Types: Fat lime, Hydraulic lime, Poor lime.

Uses: Mortar, White washing, Plastering.

Cement

Most important topic.

Manufacturing stages: Crushing, Mixing, Burning, Clinker formation, Grinding, Packing.

Types of Cement: OPC, PPC, Rapid Hardening Cement, Sulphate Resistant Cement, White Cement, Low Heat Cement, Quick Setting Cement.

Initial Setting Time: Minimum 30 minutes
Final Setting Time: Maximum 600 minutes
Fineness Test: Measured using sieve or Blaine apparatus.
Soundness Test: Le Chatelier apparatus.
Consistency Test: Vicat apparatus.
Compressive Strength Test: Cube size 70.6 mm mortar cube.

Aggregates

Fine Aggregate: Sand
Coarse Aggregate: Gravel, Crushed stone

Properties: Hard, Clean, Durable.

Mortar

Mixture of Cement, Sand, Water.

Types: Cement mortar, Lime mortar, Mud mortar.

Uses: Brick masonry, Plastering, Pointing.

Concrete

Mixture of Cement, Fine aggregate, Coarse aggregate, Water. Sometimes admixtures.

Advantages: High compressive strength, Fire resistant, Durable, Economical.

Grades of Concrete: M10, M15, M20, M25, M30, M35, M40. Very frequently asked.

Water-Cement Ratio

Controls Strength, Durability, Workability. Lower ratio generally increases strength if proper compaction is ensured.

Workability

Ease of placing concrete.

Tests: Slump test, Compaction factor test, Vee Bee test, Flow table test.

Curing

Purpose: Maintain moisture for hydration.

Methods: Ponding, Sprinkling, Wet covering, Membrane curing.

Minimum curing is usually 7 days for OPC under normal conditions; longer curing improves strength and durability.

4. Structural Analysis

Structural Analysis deals with determining the reactions, internal forces, bending moments, shear forces, and deflections in structures.

Types of Structures

Beam
Truss
Frame
Arch
Cable
Portal Frame

Classification of Beams

Simply Supported Beam
Cantilever Beam
Fixed Beam
Continuous Beam
Overhanging Beam
Propped Cantilever Beam

Types of Loads

Dead Load: Permanent load due to self-weight of structure. Examples: Concrete, Brick walls, Roof slabs.

Live Load: Temporary loads. Examples: People, Furniture, Vehicles.

Wind Load: Acts horizontally on structures. Important for High-rise buildings, Water tanks, Towers.

Earthquake Load: Dynamic load produced during earthquakes. Structures are designed considering seismic zones.

Support Conditions

Roller Support: One reaction, allows horizontal movement.
Hinged (Pinned) Support: Two reactions, allows rotation.
Fixed Support: Three reactions, restrains both translation and rotation.

Shear Force (SF)

Shear force is the algebraic sum of vertical forces on one side of a section.

Positive SF causes clockwise rotation of the left portion.
Maximum shear generally occurs near supports.

Bending Moment (BM)

Bending moment is the algebraic sum of moments acting about a section. Formula: BM = Force × Distance.

Maximum BM occurs where Shear Force = 0.
Sagging Moment → Positive
Hogging Moment → Negative

Shear Force Diagram (SFD) & Bending Moment Diagram (BMD)

SFD shows variation of shear force throughout the beam. Frequently asked: Point load, Uniformly Distributed Load (UDL), Uniformly Varying Load (UVL).

BMD shows variation of bending moment. Important observations:

Point Load → Straight line
UDL → Parabolic curve
UVL → Cubic curve

Deflection of Beams

Deflection means displacement of a beam due to loading. Methods: Double Integration Method, Macaulay's Method, Moment Area Method, Conjugate Beam Method.

Influence Line Diagram (ILD)

Used for moving loads. Applications: Bridges, Crane girders, Railway bridges.

Trusses

A truss consists of straight members connected by pin joints.

Assumptions: Members carry only axial force. Loads act only at joints.

Methods of Analysis: Method of Joints, Method of Sections.

5. Reinforced Cement Concrete (RCC)

Concrete is strong in compression but weak in tension. Steel reinforcement is added to resist tensile stresses.

Advantages of RCC

High strength
Long life
Fire resistant
Economical
Low maintenance
Easily moulded

Components

Cement
Sand
Aggregate
Water
Reinforcement steel

Types of Reinforcement

Main bars
Distribution bars
Stirrups
Bent-up bars
Ties
Spiral reinforcement

Limit State Method

Currently used for RCC design. Checks: Ultimate Limit State, Serviceability Limit State.

RCC Beams

Types: Singly Reinforced Beam, Doubly Reinforced Beam.

Slabs

Types: One-way slab, Two-way slab, Flat slab, Ribbed slab.

Columns

Classification: Short column, Long column, Tied column, Spiral column.

Footings

Types: Isolated footing, Combined footing, Strap footing, Raft footing, Pile cap.

Development Length

Provides proper bond between steel and concrete. Frequently asked in TNPSC.

Cover to Reinforcement

Purpose: Prevent corrosion, Fire resistance, Proper bonding.

6. Steel Structures

Steel is widely used because of high tensile strength and speed of construction.

Advantages

High strength
Light weight
Ductile
Easy fabrication
Recyclable

Structural Steel Sections

Angle
Channel
I-section
T-section
Box section
Circular section

Connections

Riveted Connection: Older method.
Bolted Connection: Easy installation. Types: Ordinary bolts, High Strength Friction Grip (HSFG) bolts.
Welded Connection: Most commonly used today. Types: Butt weld, Fillet weld, Groove weld.

Steel Roof Trusses

Common Types: King Post, Queen Post, Pratt, Howe, Fink.

7. Fluid Mechanics

Fluid Mechanics deals with liquids and gases at rest and in motion.

Properties of Fluids

Density
Specific Weight
Specific Gravity
Viscosity
Surface Tension
Vapour Pressure
Compressibility

Pascal's Law

Pressure applied to a confined fluid is transmitted equally in all directions. Applications: Hydraulic jack, Hydraulic press, Hydraulic lift.

Bernoulli's Equation

States conservation of energy in flowing fluid. Applications: Venturimeter, Orificemeter, Pitot tube.

Reynolds Number

Determines type of flow. Re = VD/ν.

Laminar: Re < 2000
Transition: 2000–4000
Turbulent: > 4000

Frequently asked.

8. Hydraulics

Flow Through Pipes

Major losses: Friction loss.

Minor losses: Entrance, Exit, Bends, Valves.

Pumps

Centrifugal Pump: Most common. Used for water supply and irrigation.
Reciprocating Pump: High pressure, low discharge.

Turbines

Convert water energy into mechanical energy.

Pelton Wheel: High head, low discharge
Francis Turbine: Medium head, medium discharge
Kaplan Turbine: Low head, high discharge

Frequently asked combination.

9. Environmental Engineering

Environmental Engineering focuses on public health and pollution control.

Water Supply

Requirements: Safe, Clear, Odourless, Tasteless, Free from pathogens.

Sources of Water: River, Lake, Reservoir, Well, Groundwater.

Water Treatment Steps

Screening
Aeration
Coagulation
Flocculation
Sedimentation
Filtration
Disinfection
Storage

Disinfection: Most common method is Chlorination. Types: Plain chlorination, Breakpoint chlorination, Super chlorination.

Wastewater Engineering

Stages: Collection, Conveyance, Treatment, Disposal.

Sewer Systems: Separate system, Combined system, Partially separate system.

Sewage Treatment

Primary Treatment: Screening, Sedimentation.
Secondary Treatment: Biological treatment, Activated sludge process, Trickling filters.
Tertiary Treatment: Advanced treatment, Nutrient removal, Disinfection.

Solid Waste Management

Methods: Composting, Incineration, Sanitary landfill, Recycling, Waste-to-energy.

10. Irrigation Engineering

Irrigation supplies water to crops when rainfall is insufficient.

Types of Irrigation

Surface irrigation
Sprinkler irrigation
Drip irrigation
Lift irrigation

Dams

Purpose: Irrigation, Flood control, Hydroelectric power, Water supply.

Types: Gravity dam, Arch dam, Earth dam, Buttress dam.

Canals

Types: Main canal, Branch canal, Distributary, Watercourse.

11. Transportation Engineering

Transportation Engineering deals with planning, design, construction, operation, and maintenance of transport systems.

Highway Engineering – Road Classification

National Highways (NH)
State Highways (SH)
Major District Roads (MDR)
Other District Roads (ODR)
Village Roads (VR)

Pavements

Flexible Pavement: Bituminous roads, lower initial cost, easier maintenance.
Rigid Pavement: Cement concrete roads, higher initial cost, longer service life.

Road Cross-Section Elements

Formation width
Carriageway
Shoulder
Median
Camber
Kerb
Side drain

Camber: Purpose is quick drainage of rainwater and to protect pavement from water damage.

Sight Distance

Types: Stopping Sight Distance (SSD), Overtaking Sight Distance (OSD), Intermediate Sight Distance (ISD), Headlight Sight Distance.

Traffic Signs

Regulatory signs
Warning signs
Informatory signs

Railway Engineering

Components: Rails, Sleepers, Ballast, Formation.

Gauge Types: Broad Gauge, Metre Gauge, Narrow Gauge.

Airport Engineering

Important Components: Runway, Taxiway, Apron, Terminal building, Hangar.

Runway orientation is decided mainly based on prevailing wind direction.

12. Surveying

Surveying is the science of determining the relative positions of points on, above, or below the earth's surface.

Principles of Surveying

Work from Whole to Part: First establish accurate control points, then fill in the details. This minimizes cumulative errors.
Fix a Point by at Least Two Measurements: A new point should always be determined from two independent references.

Types of Survey

Plane Surveying: Curvature of earth neglected. Suitable for small areas.
Geodetic Surveying: Curvature considered. Used for large areas and national mapping.

Chain Surveying

Suitable for small level areas and simple field measurements. Instruments: Chain, Tape, Arrows, Pegs, Cross staff, Offset rod.

Compass Surveying

Uses: Traverse surveys, Forest surveys, Route surveys. Important Terms: Bearing, Meridian, Declination, Local attraction.

Levelling

Purpose is to determine the difference in elevation between points. Types: Simple leveling, Differential leveling, Fly leveling, Reciprocal leveling, Profile leveling. Instrument: Dumpy level, Automatic level.

Contouring

A contour is a line joining points having equal elevation. Applications: Dam site selection, Reservoir planning, Highway alignment, Canal alignment.

Theodolite Survey

Measures horizontal and vertical angles. Applications: Triangulation, Traversing, Curve setting.

Modern Surveying

Total Station
GPS
GIS
Drone Survey
LiDAR

Frequently asked in recent TNPSC exams.

13. Soil Mechanics

Soil Mechanics studies the engineering behavior of soil.

Soil Formation

Residual soil
Transported soil

Soil Classification

Coarse-grained soils: Gravel, Sand
Fine-grained soils: Silt, Clay
Organic soils

Index Properties

Water content
Specific gravity
Void ratio
Porosity
Degree of saturation

Atterberg Limits

Liquid Limit (LL)
Plastic Limit (PL)
Shrinkage Limit (SL)

Plasticity Index: PI = LL − PL. Very important.

Permeability

Ability of soil to allow water flow. Factors affecting: Grain size, Void ratio, Soil structure.

Compaction

Purpose is to increase density, improve strength, and reduce settlement. Test: Proctor Compaction Test.

Consolidation

Settlement due to expulsion of water from saturated clay.

Shear Strength

Depends on cohesion and internal friction. Mohr-Coulomb equation: τ = c + σ tan φ.

14. Foundation Engineering

Foundation transfers structural loads safely to the soil.

Types of Foundations

Shallow Foundations: Isolated footing, Combined footing, Strip footing, Raft foundation.
Deep Foundations: Pile foundation, Well foundation, Caisson.

Bearing Capacity

Maximum load the soil can safely support. Failure Types: General shear failure, Local shear failure, Punching shear failure.

Pile Foundation

Used when weak soil exists near surface or heavy loads are present. Types: End-bearing pile, Friction pile, Timber pile, Steel pile, RCC pile.

15. Building Planning

Good planning ensures safety, comfort, economy, and efficient use of space.

Principles

Aspect
Prospect
Orientation
Privacy
Grouping
Roominess
Flexibility
Lighting
Ventilation
Sanitation

Building Components

Foundation
Plinth
Walls
Lintel
Sill
Doors
Windows
Roof
Staircase
Flooring
Parapet

Stair Design

Important Terms: Rise, Tread, Landing, Flight, Nosing.

Ideal relationship: 2 Rise + Tread ≈ 600–650 mm.

16. Quantity Surveying & Estimation

An estimate is the calculation of quantities and cost before construction.

Objectives: Cost estimation, Material requirement, Labour requirement, Tender preparation.

Types of Estimates

Preliminary estimate
Detailed estimate
Revised estimate
Supplementary estimate

Rate Analysis

Includes: Material cost, Labour cost, Equipment charges, Water charges, Contractor profit.

Measurement Units

Earthwork → m³
Concrete → m³
Brickwork → m³
Plastering → m²
Painting → m²
Steel → kg or tonne

17. Construction Management

Construction management ensures projects are completed on time, within budget, and to the required quality.

Planning Tools

Bar Chart
CPM (Critical Path Method)
PERT (Program Evaluation and Review Technique)

Project Management Triangle

Time
Cost
Quality

Quality Control

Tests on: Cement, Steel, Concrete, Bricks, Aggregates.

Safety Measures

Helmet
Safety shoes
Gloves
Reflective jackets
Safety belts
Scaffolding inspections

18. Engineering Geology

Studies rocks and geological conditions important for engineering projects.

Types of Rocks

Igneous: Granite, Basalt
Sedimentary: Limestone, Sandstone
Metamorphic: Marble, Quartzite, Gneiss

Geological Structures

Fault
Fold
Joint
Unconformity

Applications

Tunnel construction
Dam foundation
Road cutting
Bridge foundation

Important Indian Standards (Frequently Asked)

Some commonly referred IS Codes (subject to updates):

IS 456 – Plain and Reinforced Concrete
IS 800 – General Construction in Steel
IS 875 – Design Loads
IS 1893 – Earthquake Resistant Design
IS 383 – Coarse and Fine Aggregates
IS 10262 – Concrete Mix Design
IS 1786 – High Strength Reinforcing Steel Bars
IS 3370 – Concrete Structures for Storage of Liquids

For the exam, focus more on the purpose of each code rather than memorizing every clause.

TNPSC Quick Revision Sheet

Remember these high-yield facts:

Initial setting time of OPC = Minimum 30 minutes
Final setting time of OPC = Maximum 600 minutes
Slump test measures workability of concrete
Vicat apparatus → consistency and setting time
Le Chatelier apparatus → soundness of cement
Universal Testing Machine (UTM) → tensile/compression tests
Simply supported beam → BM is maximum at mid-span (for symmetric loading)
Maximum shear stress in a beam → neutral axis
Euler's formula → long columns
Reynolds number identifies flow regime
Pelton → High head
Francis → Medium head
Kaplan → Low head
Chlorination → common water disinfection method
Flexible pavement → bituminous
Rigid pavement → cement concrete
Plasticity Index = LL − PL
Plane surveying → small areas
Geodetic surveying → large areas
GPS, GIS, Total Station → modern surveying

Model MCQs with Answers (1–50)

The SI unit of force is Newton.
The SI unit of stress is N/mm² (or MPa).
Hooke's law is valid within the elastic limit.
The neutral axis in a beam has zero bending stress.
Cement is strongest in compression.
Slump test measures workability of concrete.
Le Chatelier apparatus is used for soundness test.
Vicat apparatus is used for consistency and setting time.
The minimum initial setting time of OPC is 30 minutes.
The maximum final setting time of OPC is 600 minutes.
RCC combines concrete and steel.
A cantilever beam is fixed at one end only.
Maximum bending moment occurs where shear force is zero.
Pratt truss is a type of steel truss.
Bernoulli's theorem is based on conservation of energy.
Reynolds number classifies fluid flow.
Pelton turbine works under high head.
Kaplan turbine works under low head.
Francis turbine is suitable for medium head.
Chlorination is used for water disinfection.
Activated sludge process is a secondary sewage treatment method.
Drip irrigation conserves water efficiently.
National Highways connect major cities and states.
Camber is provided for drainage.
Broad Gauge in India is 1676 mm.
Plane surveying neglects the earth's curvature.
Total Station combines electronic distance measurement and angle measurement.
Liquid Limit is an Atterberg limit.
Plasticity Index = LL − PL.
Compaction increases soil density.
Consolidation mainly occurs in clay.
Bearing capacity refers to the load a soil can safely support.
End-bearing piles transfer load to hard strata.
Raft foundation is used for low bearing capacity soils.
Stair rise is the vertical distance between steps.
Tread is the horizontal surface of a step.
Detailed estimate is prepared before construction begins.
CPM stands for Critical Path Method.
PERT is mainly used when activity durations are uncertain.
Granite is an igneous rock.
Marble is a metamorphic rock.
Limestone is a sedimentary rock.
IS 456 deals with plain and reinforced concrete.
IS 800 deals with steel structures.
IS 875 deals with design loads on buildings.
GPS is used for positioning and surveying.
Concrete is weak in tension.
Steel is strong in tension.
The most common shallow foundation is the isolated footing.
The first principle of surveying is work from whole to part.