1. Forces
1.1. External forces
1.1.1. An external force is a force that happens to a structure on it's outside. These forces can from nature and they can happen all the time.
1.1.1.1. Gravity
1.1.1.1.1. Gravity is the pulling of an object towards the center of a planet. In this case, Earth. Gravity is why things on this planet don't go floating away, and it is a force that acts all the time.
1.1.1.2. wind
1.1.1.2.1. Wind is an external force that can push structures over such as buildings or bridges. It is a natural force, and it can come at any time. Some are stronger than others, such as the ones that really do damage compared to the ones that give us a light summer breeze.
1.1.1.3. Simple non-natural forces
1.1.1.3.1. Other external forces such as sitting on a chair works as well. Because a force from a person on a chair is external to the chair, it is therefore an external force.
1.2. Internal forces
1.2.1. An Internal Force is a force that causes the objects to move, accelerate
1.2.1.1. Shear
1.2.1.1.1. Shear is an internal force acting on a parallel surfaces rubbing in different directions on each others.
1.2.1.2. Compression
1.2.1.2.1. Compression is an internal force that acts when an object is squished together by another object, and makes it more dense.
1.2.1.3. Torsion
1.2.1.3.1. Torsion is an internal force which causes an object to get twisted with opposite ends rotating in different directions.
1.2.1.4. Tension
1.2.1.4.1. Tension is an internal force that causes an object to be pulled apart, and with a high tensile strength, it stretches.
2. Stability
2.1. Stability is a structure's ability to remain it's pose or posture when an external force is applied to it. When a structure is stable, it can easily withstand weight and still support itself from toppling over or collapsing onto itself
2.1.1. Strong shapes
2.1.1.1. Often, builders use stronger shapes in their builds to prevent structures from falling over or breaking. One strong shape is the Triangle. It is a stable shape because it has a wide base, making it's centre of gravity lower. It is also hard for the triangle to lean to a side onto itself because of it's meeting points at the top if the shape.
2.1.1.1.1. Circles roll too much, Squares can fold onto itself, so the triangle is the strongest.
2.1.1.1.2. In bridges, you can often see triangles in the design. This is because it is indeed a strong shape.
2.1.1.1.3. When builders think about the forces that will eventually act on their build. In community centres, they use giant horizontal bars to keep the ceilings from collapsing onto the things inside.
2.1.2. Symmetry
2.1.2.1. When a structure is symmetrical, it's weight is in it's centre, so the weight is equal on both sides and the centre of gravity is right in the structure's middle. This prevents it from leaning to a side and falling over.
2.1.2.1.1. But in a structure that's not symmetrical, it often falls.
2.1.2.1.2. symmetry also changes the COG because of where all or most of the weight is.
2.1.3. Material
2.1.3.1. Some materials are stronger than others. This is dependent on their shear strength, tensile strength, compressive strength, and torsion strength. These are all ways to describe how objects survive internal forces.
2.1.3.1.1. suspension bridges use it's strong cables to withstand tension.
2.1.3.1.2. Thick concrete pillars used in parking towers are very strong, so they can withstand compression.
2.1.4. Centre of gravity
2.1.4.1. The centre of gravity of a structure is where all of it's weight is balanced upon. It can shift depending on where weight is added or removed, on high places or low places. This relates to stability because if the weight shifts onto another side, and there isn't a strong enough base for it, then it falls over.
2.1.4.1.1. A low centre of gravity is very stable because the lower part of the object is where all the weight is. With the weight being heavier, it holds down the structure is it were to fall to a side.
2.1.4.1.2. A high centre of gravity is when all or most of the weight of a structure is balanced and stored on top, and it is less stable that a low centre of gravity. A high centre of gravity is unstable because with it's weight on top, a slight lean and gravity acts on it and pulls it down.
3. Types of Structures
3.1. Solid Structures
3.1.1. A solid structure is a type of structure that is made out of its material the whole way through. It is often used as a strong blocker or stabilizer for objects such as the leg of a table.
3.1.1.1. Bricks: used as a main building material when building houses because it is a strong object that can sustain weight.
3.1.1.2. Road: used for heavy vehicles to move safely across.
3.1.1.3. Dam: used to block an hold great amounts of water and stops them from moving.
3.2. Shell Structures
3.2.1. A shell structure is a type of structure that is hollow. It can hold and protect objects inside of it. It can be very strong so it's contents remain good.
3.2.1.1. Eggshell: a natural casing made by the chicken body used in eggs protecting the future of their species.
3.2.1.2. Igloo: an igloo is created by stacking snow bricks onto each other like a dome to create a hollow inside for people to take shelter in.
3.2.1.3. Pencil Box: a shell structure that is used to contain and hold school utensils and it also makes sure the contents are safe.
3.3. Frame Structures
3.3.1. A frame structure is a type of structure that is joined together by more than 1 piece. It can be covered by material to create walls, or it can just alone be a frame.
3.3.1.1. Skeleton: The frame insides in a human used to hold up the flesh while at the same time, it holds organs inside such as the very important human heart.
3.3.1.2. Cobweb: a home of a spider that is made out of web strands formed together into a net type of structure and a trap for prey.
3.3.1.3. Bicycle: is made out of pieces and needs to be strong to hold up the weight of a human.
3.4. Combination Structures
3.4.1. A combination structure is a structure that is made from all the different kinds of other structures.It is used mostly for multitasking.
3.4.1.1. House: is made out of solid walls for protection, a frame structure usually made of wood, to hold up the floors and walls, and it is shell structure because it needs to hold people.
3.4.1.2. Car: It is a shell structure because it needs to hold people inside, it is a frame because it is made from metal pieces attached together, and it has to be solid to protect the people in it to make it safer.
3.4.1.3. Desk: It is solid because it's heavy with a straight side on top, it is a frame structure because it has parts to connect it together, and it is a shell structure because it has books to hold in and on.
4. Applying forces
4.1. Speed of Application
4.1.1. The speed of application is exactly what it's name says. It can also be called the magnitude of application because it is how much force or speed is put into the force. With more force, the faster it goes, and it's more likely to cause more damage.
4.1.1.1. A fast speed is most likely to cause more destruction, so builders use that as a way to break buildings, with a wrecking ball.
4.1.1.2. In golf, a close shot doesn't need much force, so a light speed is fine.
4.2. Direction of force
4.2.1. This is simply which way the force is applied. In a pull, or push. It describes if the direction, such as away or towards where the force is applied.
4.2.1.1. Pushing something big will need more force, like a car stuck in snow.
4.2.1.2. A pull would also use more force, in the opposite direction, such as dragging a luggage container.
4.3. Point/plane of application
4.3.1. The plane of application is where the force is applied on the structure. For example, it could be towards the top, or towards the bottom where the foundation and supports are located.
4.3.1.1. Smashing the top of a structure would only blow off the top. For example, hitting the top off a tower. It would most likely only knock off the top.
4.3.1.2. But is the base of the tower is hit, nothing is there to support the top, so it all comes tumbling down.
4.4. Angle of application
4.4.1. This is related to the point of application, but instead of hitting the structure from straight on, you can make contact at a 45 degrees angle, or any angle. This can also change the destruction of the structure.
4.4.1.1. Destroying a tower can be affected by whether you hit it straight on, or at it's vertical edge.
4.4.1.2. Sometimes, such as in the puzzle dominos, only hitting it from the largest side would work because the base would be wide horizontally but not vertically. This is also because the pieces are placed next to each other in that specific way. Building the pattern in this way is also good because the pieces are as high as possible, and they are resting on the smallest base.
5. Loads
5.1. Dynamic Load
5.1.1. The dynamic load is a load that can move, and it can be a natural force of weather (such as wind) acting on the dead load.
5.1.1.1. Rain: Is a natural force that can hit everything on impact with water. More powerful storms can cause lots of damage to structures such as towers.
5.1.1.2. Snow: Is a dynamic load that is a frozen water that can impact anything in an instant with it's weight and sudden temperature change.
5.2. Static Loads
5.2.1. Dead Load
5.2.1.1. Dead Load is a load that has to support it's own weight from the force, gravity. It is the structure itself, and it can be used to support other structures.
5.2.1.1.1. Bridge: This is a dead load because it is used to support objects on it, including it's own weight.
5.2.1.1.2. Building: A building needs to hold people inside it, along with the things that that people put in it, including it's own weight.
5.2.1.1.3. Road: Roads can support it's own weight as well as the many cars, buses and vans that it can hold in a single street. It doesn't collapse on the space underneath, bend, or break, so it is very useful.
5.2.2. Live Load
5.2.2.1. Live load is a load that's weight is supported and carried by a dead load.
5.2.2.1.1. Car: a car can be a live load in this case because it is a moving weight that a dead load (like a bridge) needs to support.
5.2.2.1.2. Person: a human goes anywhere, so the places it goes to effects the weight supporting of the structure dead loads.