Structural Engineering

SciTech 11

What is a structure?

• ______________ – something that is ___________________

• Joining parts to meet a certain _______ or perform a _______________

Types of Structures

• Natural Structures

Types of Structures

• Human Structures

http://www.smh.com.au/articles/2007/11/17/1194767025118.html

Design

• Design depends on ______

• -dam must be ___________

• -tower to transmit tv and phone signals must be __________

• -houses built for ___________ and _____________

• -factories and offices for ______________

Who Designs Structures?

• Civil Engineers – ______________________ _____________________________________

• -most work on roads, water systems, sewers, and public structures

• Structural Engineers – civil engineers that focus on _____________________

• Architect – ______________________ and oversees construction

Who Designs Structures?

• Questions they might ask:

• -how many __________ or ____________ on bridge per day

• -how might skyscraper be affected by ____________________

• -how to protect a structure in ____________________

Forces on Structures

• Force – __________________________ ______________ to an object

• External force – come from __________, act _____________ the structure

• Internal force – force that ____________ _____________, act _________ structure

Types of Forces

• 4 types: compression, tension, torsion, shear

• 1. _____________ – shortens or crushes

• 2. __________ – stretches or pulls apart

• 3. ____________ – twists

• 4. ___________ – pushes parts in opposite directions

• 2.3 Internal Forces Within Structures • Compression, Tension, and Shear • Compression forces crush a material by squeezing it

together. Compressive strength measures the largest compression force the material can withstand before it loses its shape or fails.

• Tension forces stretch a material by pulling its ends apart Tensile strength measures the largest tension force the material can withstand before failing.

• Shear forces bend or tear a material by pressing different parts in opposite directions at the same time. Shear strength measures the largest shear force the material can withstand before it rips apart.

• Torsion forces twist a material by turning the ends in opposite directions. Torsion strength measures the largest torsion force the material can withstand and still spring back into its original shape.

Types of Forces

• Load – _________________ acting on an object, eg: ___________, pressure from wind/water

• Static Load – _____________________, eg: bricks in a building, twigs in nest

• Dynamic Load – __________________, eg: car crossing bridge, oil in pipeline

Structural Materials

• Wood• -one of the ______________ used for structures• -still the ________________ materials for

_________ production• -comes in many varieties• -for construction, strong wood used = ________

__________• -________ of wood helps determine _________

(size, shape, direction of fibres)

Structural Materials

• Disadvantages of wood:

• -_______________________ with changes in ________________

• -damaged by _______________________

• -breaks down if not maintained

Engineered Wood

• -_______________ wood strands, fibres, veneers with _____________

• -can __________________________• -formed into panels, laminated beams, I-joists• -structural panels (___________) most common• -made by gluing together ____________• -odd number of layers, _________________• -less likely to ________________________

(_______________________)

Structural Materials

• ________

• -laminated, used for ________ construction in homes

• -light, available up to 60 ft, don’t ______ or _________

• -eliminate ________________ because don’t shrink

Structural Materials

• _____________________

• -glue together ______________ of wood

• -consistently ____________, can be made very long

Steel

• Steel is an ________ (metal made of _____________________)

• made from ________ and _________• may have _____________ and ________ to

_____________• made into _________________ (I-beams,

pipes, wires) and joined many ways (rivet, bolt, weld)

• used as _______ or ________ to strengthen _____________

Concrete

• made by mixing ____________________ ________________________

• hardens into strong material

• examples?

• very _________ in _______________

• poured into forms to make almost ______ ______________

Concrete• _______________• -may be reinforced with steel bars to

make ____________________• _____________ concrete contains ______

that are under __________ all the time• produce beams, floors or bridges with a

_____________ than reinforced concrete• wires produce a ___________________

that offsets ___________ stresses

Structural Members

• Structural Members:

• -building materials joined to make a __________________

• Common shapes include:

•

Bridges

• Before a bridge is built:• -_______ samples• -_______ speed and direction• -_________ levels and speed of water• -models tested in lab or on computer• -community hearings• -planning takes several _________ and

_____________ of dollars!

Bridge Types

Skyscrapers

• History:• -___________________ in ancient Egypt,

which was 146 metres (480 ft) tall and was built in the 26th century BC

• -Ancient __________ housing structures reached 10 stories

• -Medieval times: many towers built for ______________

• -_______________________ built in 1178

Skyscrapers

• -first “skyscraper” was Home Insurance Building in _____________, 1885

• -____ stories

• -load-bearing ____________ instead of load-bearing walls

• -practical with the invention of the ______________ (no more stairs!)

Skyscrapers

• -Current record = ___________ @ ______ __________, 1,670 ft tall

• -has huge ______________ near top to counteract ______________

http://en.wikipedia.org/wiki/Taipei_101

Skyscrapers

• -high quality ________________ bear immense weight

• -beams _________, _________, or _________ together

• -most weight is transferred to _________ _____________, the spreads out at base and substructure

• -_______________ is a major concern

Wind Resistance

• -many tall buildings __________________ in strong wind

• -structure is _____________ constructed to _______ movement

• -_____________ monitor sway and move huge _________________ to compensate

http://www.youtube.com/watch?v=j5j20NSFNcg

http://www.youtube.com/watch?v=j-zczJXSxnw

http://www.youtube.com/watch?v=j-zczJXSxnw

Earthquake Resistance

• -ban construction along ______________

• -many buildings built on layers of _______ ___________ or a ____________ surface

http://www.youtube.com/watch?v=4Y-62Ti5_6s

http://www.youtube.com/watch?v=kzVvd4Dk6sw

http://www.teara.govt.nz/EarthSeaAndSky/NaturalHazardsAndDisasters/Earthquakes/4/ENZ-Resources/Standard/4/en