# Structures & Forces By: Alfred & Calista

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Structures & Forces By: Alfred & Calista

## 1. Types of loads

### 1.1. Static Loads

1.1.1. A static load is an effect of gravity on a structure

1.1.1.1. Example 1- A dumbbell placed on cardboard

1.1.1.1.1. When the dumbbell is placed on cardboard gravity is pushing down on the dumbbell to exert a force called compression.

1.1.1.2. Example 2- a roof

1.1.1.2.1. A roof is a static load because gravity is putting a force which is putting weight on the house.

### 1.2. Dynamic Load

1.2.1. A load that moves or changes while it affects a structure

1.2.1.1. Example 1-Earthquake

1.2.1.1.1. When a earthquake occurs it moves structures and can also affect them. Ex/ It can move the ground and break houses, streets and street lights It also moves across these places..

1.2.1.2. Example 2- a falling dumbell

1.2.1.2.1. If the dumbbell is dropped then it is a dynamic load because it is moving and will affect a structure like wood of cardboard.

1.3.1. A Permanent Load that can not affect an structure

1.3.1.1. Example 1-Chair

1.3.1.1.1. A chair can be a dead load because it is permanent and the structure has to hold the weight of it.

1.3.1.2. Example 2 - gravity

1.3.1.2.1. Gravity is a dead load because it is always there and it wont affect a structure, because the only thing it does is stick it to the ground

### 1.4. Live Load

1.4.1. A Load that Can affect an Structure, This Load can move or affect the structure.

1.4.1.1. Example 1-Person

1.4.1.1.1. A person is a live load because it can affect a structure. For example a person who is heavy can break the chair because, the chair is unable to withstand the weight of the person and its own.

1.4.1.2. Example 2-Food in a shopping bag

1.4.1.2.1. Food in a shopping bag can be a live load because in the bag it can move and affect the bag when it moves around

## 2. Structures & Safety

### 2.1. Shell structures

2.1.1. A Shell structure is hollow on the inside. Most shell structures are made with strong materials to hold objects inside

2.1.1.1. Example 1-Igloo

2.1.1.1.1. An igloo is a shell structure because it is hollow. People can go in and out of it and forces can applied.

2.1.1.2. Example 2- Container

2.1.1.2.1. A container is a shell structure because it can contain objects and forces like gravity can be applied.

### 2.2. Frame Structures

2.2.1. A frame structure is made up of parts connected together. You can most likely see through the frame

2.2.1.1. Example 1-Eiffel tower

2.2.1.1.1. The Eiffel tower is a frame structure, it is completely made out of iron bars and you can see though some of it.

2.2.1.2. Example 2- Spider Web

2.2.1.2.1. A Spider Web is also a frame Structure you can see most of it and is made out of 1 material which is spider silk

### 2.3. Solid Structures

2.3.1. A solid structure is made with very sturdy materials most of the time and it is usually not flexible. Most solid structures are not see through

2.3.1.1. Example 1- A rock

2.3.1.1.1. A rock is a solid structure because it is very hard to break and is not hollow. You have to have lots of shear force to break a rock

2.3.1.2. `Example 2- A Sandcastle

2.3.1.2.1. A sandcastle is a solid structure because it is completely made out of sand and no can go in nor out.

### 2.4. Combination Structures

2.4.1. Combination Structures are made from all shell, frame and solid structures. With strength it has the ability to withstand forces from an object

2.4.1.1. Example 1- Petra

2.4.1.1.1. The Petra is a combination structure because it is made up of frame ( the Stone pillars) Solid (stone) and shell ( the tomb)

2.4.1.2. Example 2- A house

2.4.1.2.1. A house is a combination structure because it has a frame ( frame of a window ) shell ( roof ) and solid ( door)

### 2.5. Sensor

2.5.1. A Sensor is a object that can sense vibration temperature and sounds.

2.5.1.1. Example 1- a thermometer

2.5.1.1.1. A Thermometer is a Sensor because it can sense temperature in a structure

2.5.1.2. Example 2- A vibration detecter

2.5.1.2.1. A vibration detector is a sensor because it will sense vibrations. This is important because if the vibrations are very strong it will transmit a signal saying the structure may go through structural failure. Structural failure is when a structure will breakdown.

## 3. Internal And External Forces

### 3.1. Compression

3.1.1. Compression is a force when you press or squeeze an object. This is an Internal force

3.1.1.1. Example 1-Accordion

3.1.1.1.1. When you press an accordion, the compression creates air inside the instrument which then makes a sound

3.1.1.2. Example 2-Pencil

3.1.1.2.1. When you hold a pencil, you are creating compression when you squeeze to get a grip on the pencil

### 3.2. Shear

3.2.1. Shear is when you push an object in opposite directions or bending an object. This is a Internal force

3.2.1.1. Example 1-Dough

3.2.1.1.1. When you knead dough, you are pulling and pushing the dough in opposite directions to stretch the dough to make it larger

3.2.1.2. Example 2-Elbow

3.2.1.2.1. Whenever your elbow bends, it creates the internal force shear because shear is when something bends like you elbow.

### 3.3. Torsion

3.3.1. A twisting force that occurs when you pull 2 ends of an object or when you turn/twist the object. This is a Internal force.

3.3.1.1. Example 1-Waist

3.3.1.1.1. Your waist is able to turn right or left but it can not turn a 360. You turn your waist usually when you want to get something or when you exercise.

3.3.1.2. Example 2-Neck

3.3.1.2.1. Your neck does a lot of torsion since you look left and right a lot because then your neck/spinal cord twists or turns. Your neck can also twist for stretching muscles.

### 3.4. Tension

3.4.1. A Pulling force that occurs when 2 parts of and object are pulling away from the center. This is an Internal force.

3.4.1.1. Example 1-Clay

3.4.1.1.1. To soften or smooth clay you pull in opposite ways to stretch the clay and repeat. This is an example of tension.

3.4.1.2. Example 2-Opening A Fan

3.4.1.2.1. When you open a fan, you hold the sides and pull to open it which is tension.

### 3.5. Gravity

3.5.1. An invisible force that pulls a object or structure down. This is an External Force.

3.5.1.1. Example 1-Fruit from a Tree

3.5.1.1.1. Most common examples of gravity is when an apple falls from a tree because the weight of the apple is being affected by gravity which forces the apple to fall down.

3.5.1.2. Example 2-People on the Earth

3.5.1.2.1. Everyone on the earth is not floating because of gravity which is holding us down unless we go to space which is a gravity free zone.

## 4. Applied Forces

### 4.1. Plane of application

4.1.1. The plane of application is the angle you apply to a force. Like if it is 45, 180 or 90 degrees

4.1.1.1. Example 1-Swings

4.1.1.1.1. For swings, the angle/plane of application is important because if you use the swings at a 180 degree angle, you could hit the pole.

4.1.1.2. Example 2-Wrecking Ball

4.1.1.2.1. Wrecking balls needs a plane of application because it needs to know what angle to hit the object.

### 4.2. Point of application

4.2.1. Point of application is where apply the force.If it is top, bottom or right in the middle

4.2.1.1. Example 1-Wrecking Ball

4.2.1.1.1. A wrecking ball also needs a point of application if it is going to hit the top, middle or the bottom of an object

4.2.1.2. Example 2-Archery

4.2.1.2.1. When you aim for the target in archery, you have to aim at the top, middle or bottom to hit the target.

### 4.3. Magnitude

4.3.1. Magnitude is how fast you put the force. From extremely slow to super fast

4.3.1.1. Example 1-Soccer Ball

4.3.1.1.1. When you kick a soccer ball or try to shoot, you have to see how close you are to the net to know how fast you should kick it.

4.3.1.2. Example 2-Paper Plane

4.3.1.2.1. It mostly depends on the speed in order for your paper plane to fly properly because if you do it too fast, the plane will just crash immediately and if it is too slow, it would just fall to the ground

### 4.4. Direction

4.4.1. The direction is if the force is in a pull or push motion

4.4.1.1. Example 1-Pushing & Pulling a door

4.4.1.1.1. To open a door, you need to either push it or pull it which is two different directions.

4.4.1.2. Example 2-Moving Furniture

4.4.1.2.1. Sometimes if something is just too heavy, you would need to push it or pull it in order to move the furniture