Theory of Structure - I

Lecture OutlinesIntroduction History of Structural Engineering

Forms of StructuresMaterialsLoads

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STRUCTURAL ENGINEERING

1ST YEAR 2ND YEAR 3RD YEAR 4TH YEAR

ENGG. MECHANICS

THEORY OF STRUCTURES

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THEORY OF STRUCTURES

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STRUC. ENGG.

History of Structural EngineeringWhy history is important?

One reason why history is important it that the past has value to our society.

History is the narrative of mankind.

History when presented properly lends itself to critical analysis.

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History of Structural EngineeringGreek and Egyptian Temples

Made of stoneEmployed beams and columnsMany columns having little useful space between them

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Greek temple built 2500 years ago

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Greek temples of Poseidonia (now called Paestum) dating from the sixth century BC.

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The Temple of Debod built in early 2nd century BC

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Egypt: Temples of Karnak built 2000 years ago

History of Structural EngineeringArch structures were discovered prior to Roman era.

Roman Empire used arches extensively in construction.Stone arches had span of 100 ft and more

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The Colosseum is one of Rome's most distinctive landmarks.  Construction of this famous amphitheatre began in 72 AD.

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Arches

Aqueducts

Aqueduct at Segovia in eastern Spain

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The arch of Costantino built in 312 AD

History of Structural EngineeringFrom A.D. 500 to A.D.1500, structures that were built continued to employ the stone arch as the major structural forms.Gothic CathedralsRoof was supported by flying buttresses

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Cathedral from North East Chichester

Flying Buttress

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Cathedral from South East Chichester

Flying Buttress

History of Structural EngineeringFifteenth and Sixteenth centuries are

known as Renaissance.Galileo (1564-1642)

Concept of force and momentsRobert Hooke (1635-1703)

Law of linear behavior of materialsSir Isaac Newton (1642-1727)

Laws of motionLeonhard Euler (1707-1783)

Buckling of columnsPalladio

introduced the use of truss

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GALILEO ROBERT HOOKE

ISSAC NEWTON LEONHARD EULER PALLADIO

History of Structural EngineeringModern Era

Introduction of IronIndustrial Revolution

First major structure built or iron was Severn River Bridge Coalbrookdale.

Suspension bridgesThomas Telford’s Bridge over Menai

Straits in Wales, Brunel’s Clifton Bridge in Bristol, Finley’s Bridge over Merrimack River in

Newburyport, Massachusetts.

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Iron bridge, a cast-iron arch bridge built in 1779 across the River Severn near Coalbrookdale, Shropshire, England

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Thomas Telford built the suspension bridge in the middle in 1826. They had to destroy some of the castle to anchor it to the rock.

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Isambard Kingdom Brunel designs the Clifton Suspension Bridge at Bristol. Two hundred feet above the River Avon, the bridge is 700 feet long.

History of Structural EngineeringRank Building - City - Country Year Stories Height

1. Burj Dubai, Dubai, UAE 2008 189* 850m*

2. Taipei 101, Taipei, Taiwan 2004 101 509m

3. Petronas Tower 1, Kuala Lumpur, Malaysia 1998 88 452m

4. Petronas Tower 2, Kuala Lumpur, Malaysia 1998 88 452m

5. Sears Tower, Chicago, USA 1974 110 442m

6. Jin Mao Building, Shanghai, China 1999 88 421m

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Structural Forms

Cables Arches Trusses Beams

Surfaces

Membranes Plates Shells

CablesCables stretch well and are light, so they

are useful in large structures. They only take tension stresses.

Cables can be crisscrossed and combined with surface materials to achieve light and large structures.

Examples of this technique are Suncoast Dome and Georgia Dome in the United States

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Cable

Road WayCable Anchorage

TowerHanger

Golden Gate Bridge, San Francisco

CablesGrace Memorial Bridge over the Cooper River

Between Charleston, South Carolina (USA) and Mount Pleasant, South Carolina, stands the Grace Memorial Bridge. 

Completed in 1929, the cantilever steel structure has a main span of 1050 ft., or 320 m. and a total length of 3.6 miles or 5.79 Kilometers. 

A parallel bridge, with a similar design but a shorter main span, was built in 1966.  This allowed the old bridge to be converted to one-way traffic. 

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Grace Memorial Bridge over the Cooper River

ArchesAn arch is a curved structure capable of

spanning a space while supporting significant weight (e.g. a doorway in a stone wall).

The arch is significant because, in theory at least, it provides a structure which eliminates tensile stresses in spanning an open space.

All the forces are resolved into compressive stresses.

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Chinese Moon Bridge

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Made by Zhao1974 in Hebei Province, China. Built by the architect Li Chun from 595 to 605 AD. World's oldest fully-stone, open-spandrel, segmental arch bridge.

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Triangular Arch Round Arch Segmental Arch

Rampant Round Arch

Lancet Arch Shoulder Flat Arch

Three-Foiled Cusped Arch

Equilateral Pointed Arch

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Horseshoe Arch Three-centered Arch

Elliptical Arch

Inflexed Arch Ogee Arch Reverse Ogee Arch

Tudor Arch

Parabolic Arch

TrussIn architecture and structural engineering, a

truss is a structure comprising one or more triangular units constructed with straight slender members whose ends are connected at joints.

A plane truss is one where all the members and joints lie within a 2-dimensional plane, while a space truss has members and joints extending into 3 dimensions.

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TrussAll members are assumed in axial compression or tension.

Members are joined with the help of frictionless pins.

Loads are applied at joints only.

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Types of Trusses

Common Truss

It is characterized by its triangular

shape.

It is most often used for roof construction.

Flat Truss

It gets its name from its parallel top and bottom chords.

It is often used for floor construction.

Truncated Truss

A combination of the two is a

truncated truss.

It is used in hip roof construction.

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Support structure under the Auckland Harbour Bridge.

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A Vierendeel bridge; note the lack of diagonal elements in the primary structure and the way bending loads are carried between

elements

BeamsA beam is a structural element that

carries load primarily in bending (flexure).

Beams generally carry vertical gravitational forces but can also be used to carry horizontal loads (i.e. loads due to an earthquake or wind).

The loads carried by a beam are transferred to columns, walls, or girders, which then transfer the force to adjacent structural compression members.

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BeamsIt requires only vertical supports at ends generally.

It is a compact structure.It’s disadvantage is that it sometimes uses materials less economically than other structural systems.

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Surfaces

Membranes ShellsPlates

MembranesThin sheets of

material

Resist applied loads by tension.

Examples are tents, sails, balloons etc

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Plates are flat surfaces that transfer loads by bending in a manner similar to beams.

ShellsShell is rigid surface

that transfers loads in two directions.

The primary difference between a plate and a shell is that the shell has curvature whereas the plate does not.

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TWA Flight Center, John F. Kennedy International Airport, New York.

Materials

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Properties of Material

StrengthDeformation

Characteristics

Comp. Tension Resist.

Strength to

weight ratio

Stiff Elastic Ductile

MaterialsAggregatesSteelConcreteWoodAluminumFiber GlassComposite Materials etc.

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Loads

Static LoadsDynamic

Loads

Loads

Dead Live

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Live Loads

Building Live Loads

Bridge Live Loads

Snow Loads

Wind Loads

Earthquake Loads

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