Stability of Structures
What is stability?
The ability of a structure to remain in or return to a stable, balanced position when forces act on it.
What's the difference between strut and tie?
Strut is on the bottom of the cantilever; tie is on the top.
What is a dome?
A dome is a shell structure that looks like the top half of a sphere.
What is the most likely reason for structural failure?
Poor design
How is stability achieved in structures?
Stability in structures is achieved by lowering the center of gravity, to lie directly over its base and by using rigid interconnected materials to resist forces.
What are the TWO features for stability?
-low centre of gravity
-wide support base
Define rebar.
Steel - reinforced rods embedded within concrete.
Give four examples of structures that use a truss?
A Ferris wheel, a bridge, a crane, stadium roof, Eiffel Tower, etc.
What is a preventative measure that can be taken to prevent some kind of structural failure from happening?
Regular maintenance for safety is important because materials used in structure may degrade over time.
What are the advantages and disadvantages of a dome?
The main advantages of concrete domes are that they are structurally sound, watertight, durable and easy to maintain, but the disadvantages are that they are heavy and require a strong support structure.
What happens to a vehicle when the vehicle's center of gravity is not above the support base?
The vehicle will become unstable and possibly tip over.
What is it called when concrete contains rebar?
Reinforced concrete
How do triangles in trusses help the structure support more weight?
Triangles in trusses support more weight because they are inherently rigid shapes that do not change shape under load.
How can extraordinary loads affect structural failure?
Causes excessive stress, deformation, instability, and ultimately sudden or progressive structural failure.
What are trusses used for?
Trusses are used to support heavy loads over long spans efficiently, which are mostly in roofs, bridges, and cranes.
Why are people more stable with their feet spread apart rather than with their feet close to each other?
When people have their feet spread apart, it widens their support base and lowers their centre of gravity.
What is a cantilever?
A cantilever is a beam that is only supported on one side.
Explain how compression forces are different in arches and domes?
The compression force for an arch is distributed between one plane of application and a dome distributes it between multiple planes of application.
How can foundation failure happen?
It can be due to the poor soil, poor/bad installation, not strong enough for the load and earthquake.
What are the advantages and disadvantages of a dome?
The main advantages of concrete domes are that they are structurally sound, watertight, durable and easy to maintain, but the disadvantages are that they are heavy and require a strong support structure.
How is an acrobat able to successfully walk across a tightrope?
The pole an acrobat carries is usually weighted on the ends, making the performer's center of gravity lower. The lower center of gravity makes them more stable.
What are four ways to strengthen a beam?
1. Change up the materials
2. Change the form - I Beam
3. Add rebar
4. Add corrugation
What are five real life examples of a dome?
Five examples are the U.S. Capitol, the Taj Mahal, the Eden Project, the Pantheon, and the Montreal Biosphere.
Explain why small homes can be built with simple wood frames, but skyscrapers and other large buildings must be built with metal frames?
Metal frames are much stronger and because larger building experience larger forces, they have to be stronger to prevent failure due to those forces.
"Human factors are the most common cause of structural failure." After reading this chapter, what do you think is meant by this statement?
The most common factors of structural failure are due to bad design, faulty construction and extraordinary loads. These all have a common factor - humans. Even failures that are not directly the result of human actions might have been prevented if people had considered the possible extreme conditions that might occur.