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THEORY STRUCTURES

THEORY OF STRUCTURES DEALS W/ THE PRINCIPLES & METHODS BY W/C

THE DIRECT STRESS, THE SHEAR AND

BENDING MOMENT AND THE

DEFLECTION AT ANY SECTION OF

EACH CONSTITUENT MEMBER IN THE

STRUCTURE MAYBE CALCULATED

Structural Engineering

Structural Engineering

is a field of engineering dealing with the analysis and design of structures that

support or resist loads.

involved in the design of buildings and large nonbuilding structures

Structural engineers are responsible for engineering design and analysis

Structural Engineering

Structural Engineer may specialize in

bridge engineering,

building engineering,

pipeline engineering,

Industrial structures or

special structures such as vehicles or aircraft.

Building structures

Sydney Opera House, designed by Ove Arup & Partners, with the architect Jorn Utzon

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Building structures

Millennium Dome in London, UK, by Buro Happold and Richard Rogers.

Earthquake engineering

structures

Earthquake-proof and massive pyramid El Castillo, Chichen Itza

Earthquake engineering

structures

napshot of shake-table testing [1] of a base-isolated (right) and a regular (left) building model

Civil Engineering Structures

Civil structural engineering includes all structural engineering related to the built environment. It includes:

Bridges Dams

Earthworks Foundations Offshore structures Pipelines Power stations

Railways Retaining structures and walls

Roads Tunnels Waterway

Civil Engineering Structures Civil Engineering Structures

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Civil Engineering Structures Civil Engineering Structures

Civil Engineering Structures Structural Elements

Any structure is essentially made up of only a small number of different types of elements:\

Columns

Beams

Plates

Arches

Shells

Catenaries

Structural Elements Columns are elements that carry only axial force -

either tension or compression - or both axial force and bending

Beams are elements which carry pure bending only

A beam may be:

cantilevered (supported at one end only with a fixed connection)

simply supported (supported vertically at each end; horizontally on only one to withstand friction, and able to rotate at the supports)

continuous (supported by three or more supports)

a combination of the above (ex. supported at one end and in the middle)

Structural Elements

A truss is a structure comprising two types of structural element, ie struts and ties. A

strut is a relatively lightweight column and

a tie is a slender element designed to

withstand tension forces. In a pin-jointed

truss (where all joints are essentially

hinges), the individual elements of a truss

theoretically carry only axial load

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Structural Elements

Plates carry bending in two directions. A concrete flat slab is an example of a plate

Shells derive their strength from their form, and carry forces in compression in

two directions. A dome is an example of a

shell. They can be designed by making a

hanging-chain model, which will act as a

catenary in pure tension, and inverting the

form to achieve pure compression.

Structural Elements Arches carry forces in compression in one

direction only, which is why it is appropriate to

build arches out of masonry. They are designed

by ensuring that the line of thrust of the force

remains within the depth of the arch.

Catenaries derive their strength from their form, and carry transverse forces in pure tension by

deflecting (just as a tightrope will sag when

someone walks on it). They are almost always

cable or fabric structures. A fabric structure acts

as a catenary in two directions.

Loads on the Structure

live (imposed) loads,

dead loads,

earthquake (seismic) loads,

wind loads,

soil pressure loads,

fluid pressure loads,

impact loads, and

vibratory loads

Live Loads

Live loads are transitory or temporary loads, and are relatively unpredictable in

magnitude. They may include the weight

of a building's occupants and furniture,

and temporary loads the structure is

subjected to during construction.

Dead Loads

Dead loads are permanent, and may include the weight of the structure itself

and all major permanent components.

Dead load may also include the weight of

the structure itself supported in a way it

wouldn't normally be supported, for

example during construction.

Impact Loads

EXTRA OR EXCESS EFFECT DUE TO THE SUDDEN OR ABRUPT

APPLICATION OF LOADS

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Methods of Analysis

FX = 0

FY = 0

M = 0

Statical determinacy

A statically determinate structure can be fully

analysed using only consideration of equilibrium,

from Newton's Laws of Motion.

A statically indeterminate structure has more unknowns than equilibrium considerations can

supply equations for (simultaneous eqn). Such a

system can be solved using consideration of

equations of compatibility between geometry

and deflections in addition to equilibrium

equations.

Materials

Steel

Concrete

Masonry

Timber

Others