Structural Engineering SciTech 11. What is a structure? ______________ – something that is...
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Transcript of Structural Engineering SciTech 11. What is a structure? ______________ – something that is...
What is a structure?
• ______________ – something that is ___________________
• Joining parts to meet a certain _______ or perform a _______________
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!
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