Forces and Structures

fulcrum

• The fixed point around which a lever pivots

• A type of lever used in construction

• A measurement of force applied to an object

• The distance from the lever to the load

external force

• A force acting on an object or structure from the outside. Eg. gravity; wind; kicking a soccer ball

• A force that is generated within an object, such as tension in a rope.

• A force that opposes motion, such as friction.

• A force that is applied at a distance, such as magnetic force.

lever

• A tool that changes the amount of force needed to move an object

• A type of pulley used in construction

• A device that measures weight

• A tool for cutting materials

dead load

• A temporary force acting on a structure, such as wind or snow

• A permanent force acting on a structure, such as the weight of the structure itself

• A force that varies with time and is not constant

• A force that is applied only during construction

internal force

• A force that acts on an object from the inside. Eg. tension in a stretched elastic; weight of room sitting on walls of building.

• A force that acts on an object from the outside, like wind pushing against a building.

• A force that is always equal to the weight of the object, regardless of its position.

• A force that only occurs in a vacuum, such as gravitational pull.

metal fatigue

• A process where metal becomes stronger over time

• A weakening of metal due to stress, resulting in an accumulation of small cracks and eventually causing metal to break

• A method of testing metal for durability

• A type of metal that is resistant to corrosion

live load

• A type of load that remains constant over time.

• A type of load that changes, such as people walking across a bridge, snow on a roof, etc.

• A type of load that is only applied during construction.

• A type of load that is only relevant in seismic design.

three ways in which materials fail

• Shear (one section slides over another at the weak point)

• Bend/buckle (compression causes material to bend)

• Torsion (twisting materials causes them to break/lose their structure)

• Fracture (sudden break due to excessive stress)

4 types of forces

• Tension, compression, friction, gravity

• Tension (stretch), compression (squish), shear (tear), torsion (twist)

• Magnetism, buoyancy, tension, compression

• Shear (tear), torsion (twist), inertia, acceleration