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Theory of Structure - I

Lecture Outlines  Introduction  History of Structural Engineering

 Forms of Structures  Materials  Loads

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Introduction STRUCTURAL ENGINEERING

1ST YEAR

2ND YEAR

3RD YEAR

4TH YEAR

ENGG. MECHANICS

THEORY OF STRUCTURES I

THEORY OF STRUCTURES II

STRUC. ENGG.

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History of Structural Engineering  Why 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 Engineering  Greek and Egyptian Temples  Made of stone

 Employed beams and columns  Many columns having little useful

space between them

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Greek temple built 2500 years ago 6

Greek temples of Poseidonia (now called Paestum) dating from the sixth century BC. 7

The Temple of Debod built in early 2nd century BC 8

Egypt: Temples of Karnak built 2000 years ago

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History of Structural Engineering  Arch structures were discovered prior

to Roman era.  Roman Empire used arches extensively in construction.  Stone arches had span of 100 ft and more 10

The Colosseum is one of Rome's most distinctive landmarks. Construction of this famous amphitheatre began in 72 AD. 11

Arches

Aqueducts

Aqueduct at Segovia in eastern Spain 12

The arch of Costantino built in 312 AD 13

History of Structural Engineering  From A.D. 500 to A.D.1500, structures

that were built continued to employ the stone arch as the major structural forms.  Gothic Cathedrals  Roof was supported by flying buttresses 14

Flying Buttress Cathedral from North East Chichester

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Flying Buttress Cathedral from South East Chichester

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History of Structural Engineering  Fifteenth and Sixteenth centuries are known as

Renaissance.  Galileo (1564-1642)

Concept of force and moments Robert Hooke (1635-1703)  Law of linear behavior of materials Sir Isaac Newton (1642-1727)  Laws of motion Leonhard Euler (1707-1783)  Buckling of columns Palladio  introduced the use of truss 

   

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GALILEO

ISSAC NEWTON

ROBERT HOOKE

LEONHARD EULER

PALLADIO 18

History of Structural Engineering  Modern Era  Introduction of Iron  Industrial Revolution  First major structure built or iron was Severn

River Bridge Coalbrookdale.  Suspension bridges  Thomas Telford’s Bridge over Menai Straits in

Wales,  Brunel’s Clifton Bridge in Bristol,  Finley’s Bridge over Merrimack River in Newburyport, Massachusetts. 19

Iron bridge, a cast-iron arch bridge built in 1779 across the River Severn near Coalbrookdale, Shropshire, England 20

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. 22

History of Structural Engineering Rank

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 23

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Forms of Structures Structural Forms

Cables

Arches

Trusses

Beams

Surfaces

Membranes

Plates

Shells 25

Cables  Cables 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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Hanger

Tower

Cable

Cable Anchorage

Road Way

Golden Gate Bridge, San Francisco 29

Cables  Grace 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 31

Arches  An 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 33

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. 34

Triangular Arch

Rampant Round Arch

Round Arch

Lancet Arch

Segmental Arch

Shoulder Flat Arch

Equilateral Pointed Arch

Three-Foiled Cusped Arch

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Horseshoe Arch

Inflexed Arch

Three-centered Arch

Ogee Arch

Elliptical Arch

Reverse Ogee Arch

Parabolic Arch

Tudor Arch

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Truss  In 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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Truss All 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

Flat Truss

Truncated Truss

It is characterized by its triangular shape.

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

A combination of the two is a truncated truss.

It is most often used for roof construction.

It is often used for floor construction.

It is used in hip roof construction.

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Support structure under the Auckland Harbour Bridge. 40

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

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Beams  A 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. 42

Beams  It 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 Surfaces

Membranes

Plates

Shells

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Membranes  Thin sheets of material  Resist applied loads by

tension.  Examples are tents, sails,

balloons etc

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Plates  Plates are flat surfaces

that transfer loads by bending in a manner similar to beams.

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Shells  Shell 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.

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

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Materials Properties of Material

Deformation Characteristics

Strength

Comp. Tension Resist.

Strengt h to weight ratio

Stiff

Elastic

Ductile

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Materials  Aggregates  Steel  Concrete

 Wood  Aluminum  Fiber Glass  Composite Materials etc.

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Loads Loads

Static Loads

Loads

Dynamic Loads

Dead

Live

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Loads

Building Live Loads

Bridge Live Loads

Live Loads

Earthquake Loads

Snow Loads

Wind Loads 53

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