What is a Force?
A push or pull on an object that can change its motion
Any push or pull applied to an object.
Define Magnitude.
The measure of how strong a force is
Magnitude quantifies the strength of a force.
What unit is used to measure force?
Newtons (N)
The unit is named after Sir Isaac Newton.
What is an Unbalanced Force?
When forces acting on a structure are not equal in magnitude and direction
Unbalanced forces can cause motion.
What is a Balanced Force?
Force where the effect of one force is cancelled out by another
The forces are equal on both sides, resulting in no motion.
What are external forces acting on structures called?
Loads
Loads can be static or dynamic.
Define Static Load.
A force applied and held in a fixed position for a specific amount of time
Caused by gravity, e.g., a lamppost on the sidewalk.
What is a Dynamic Load?
A force that changes over time because of other forces
Example: Wind blowing on a hydro tower.
What is a Dead Load?
The weight of the structure itself
Caused by gravity acting on the structure, does not change.
What is a Live Load?
The weight of ‘stuff’ on the structure
Can change, e.g., the weight of a rider on a bicycle.
Define a Solid Structure.
Made by piling up or forming similar materials into a particular shape or design
Examples: Wooden telephone pole, concrete parking barriers.
What is a Frame Structure?
Has a skeleton of very strong materials with most of the inside empty space
Examples: Umbrella, goal posts, tent.
Define a Shell Structure.
Hollow, curved shape using a thin outer layer for strength
Examples: Helmet, domed roof, egg.
What is a Combination Structure?
Structures that have solid, shell, and frame parts
Most buildings are combination structures.
What is Tension?
Force that stretches a material apart
Example: Girl on a swing, where the rope shows tension.
Define Compression.
Force that squeezes a material together
Example: Diver on a diving board, where the board bends.
What is Torsion?
An action that twists a material
Occurs when opposite rotational forces are applied.
Define Shear.
When two parallel but opposite forces are at work in the same place
Causes parts of a material to slide past one another.
What is Lamination?
Two or more layers of material glued or bonded together
Example: Laminated wood.
Define Corrugation.
A pleating or rippling of a material
Example: Corrugated metal roof.
What is a Tie in structural terms?
A member that helps to hold a structure up from above
A tie forms a triangle above a structure and is in tension.
What is a Strut?
A member that helps to hold a structure up from below
A strut forms a triangle below a structure and is in compression.
Define a Truss.
A frame made up of many triangles creating a strong structure
Some members are in compression and some in tension.
What is an Arch?
A structure formed in a regular curve
Moves the load down the sides towards the supports at the base.
