Interplay of compression, tension, shear, and bending forces maintains balance and stability.
Enables structures like bridges and tables to carry loads.

Resisting Deformation

Structures undergo slight shape changes under external forces.
Internal forces resist these changes to maintain shape and function.

Load-Bearing Capacity

Structures have a limit to the weight they can hold.
Internal forces distribute weight evenly to prevent overloading.

Safety

Internal forces are vital for structural safety.
Engineers and architects consider these forces to withstand conditions like winds, earthquakes, or heavy traffic.

Everyday Structures

Internal forces work quietly to keep buildings and bridges strong and safe.
Understanding these forces helps create reliable structures.

Types of Internal Forces

Compression

Force that pushes things together.
Essential for structures like bridges and buildings to stay upright.

Tension

Pulling force that keeps parts from sliding apart.
Crucial in suspension bridges where cables support weight.

Shear

Force acting parallel to the surface, trying to slide layers.
Present in beams and columns to maintain shape and strength.

Bending

Force applied when trying to bend a stick.
In structures, helps distribute loads and prevent breaking under pressure.

Effects of Internal Forces on Structures

Internal Forces

Exist inside structures, keeping the various parts together and preventing collapse.

Examples of Structures

Buildings, bridges, towers, chairs, and tables.

External Forces

*Pushes and pulls that come from outside of a structure.
*Affect structures like wind blows leaves off a tree and gravity pulls objects toward the ground.

Examples of External Forces

*Gravity: pulls things to stay on the ground
*Snow and Ice: accumulate on structures and surfaces in the winter
*Wind: exerts pressure on buildings and bridges
*Natural Phenomena: weather events
*Traffic Loads: can cause bending and compression forces

How Internal Forces Maintain Stability

*Internal forces maintain balance within a structure.
*Balanced structures remain in place.

Handling Heavy Weights

*Structures must handle heavy weights to function safely.
*Internal forces distribute weight evenly enabling them to do so.

Role of Engineers and Builders

*Engineers and builders use knowledge of internal forces for safety.
*They consider weather conditions and heavy traffic.

Internal Forces as \"Secret Helpers\"

*Internal forces work quietly inside buildings, maintaining strength and safety.

Internal Forces - Worksheet

1. Role of Internal Forces

Internal forces exist within a structure.
They maintain structural integrity by keeping parts together and ensuring safety.
Examples: buildings, bridges, and towers.

2. Four Types of Internal Forces

Compression: Required for buildings and bridges to stay upright.
Tension: Supports weight and suspends cables.
Shear: Helps maintain shape and strength.
Bending: Distributes loads and prevents breaking under pressure.

Internal Forces Experiment

Question

How do internal forces (tension, compression, shear, torsion) affect a marshmallow or sponge?

Hypothesis

The marshmallow will become soft and squished due to compression.

Directions and Expected Forces

Pinch either end of the sponge/marshmallow and pull it from both directions: tension
Pinch either end of the sponge/marshmallow and twist it from both directions: torsion
Use your hand to place downward pressure on the marshmallow or sponge: compression
Use a pair of scissors to cut your sponge/marshmallow: shear

Plane

Planes vs. Gravity

Planes counteract gravity using lift generated by their wings.
Planes use meters to fly above clouds.

External Forces on Buildings

Gravity influences buildings.
Weight is distributed to keep its structure safe.

Engineer's Considerations

Engineers account for deformation to ensure structural safety against strong winds and natural phenomena.

Importance of Regular Maintenance

Regular maintenance is important because the structure can't take the impact of the external forces

Static and Dynamic LOADS

Definitions

Load: A weight or source of pressure creating an external force on a structure.
Static Load: Something that does not change (size, position, and direction remain the same).
Dynamic Load: A force that can change when acting on a structure.

Examples

Static: The weight of the roof of a building, Blocks of a pyramid, Water current
Dynamic: Landslide, Wind, A push on a swing, A person standing on a bridge, A ball rolling, A person jumping on a trampoline

Load Type

Snow, storm, medioroly guest

Static vs. Dynamic Loads

Wind - Dynamic
Person standing on a bridge - Static
Weight of the roof - Static
Person jumping on a trampoline - Dynamic
Ball rolling - Dynamic
Landslide - Dynamic
Blocks of a pyramid - Static
Water current - Dynamic
Push on a swing - Dynamic

Internal Forces Experiment Results

Tension: Stretches things.
Torsion: Twists things.
Compression: Squishes things.
Shear: Slices things.

Classifying Structures

Key Question: What forms do structures have?
Structures have three basic forms: * Solid * Frame * Shell
- Complex structures are often combinations of these forms.
- Different structural forms can support different loads.

Solid Structures

A solid structure uses solid construction materials to support loads
A solid structure usually has a large mass.
A well-made solid structure can last a long time.

Examples

* Concrete dam
* Wooden telephone pole
* Marble statue

Dams have thick concrete at the bottom where the load forces of the water are huge.

Describe Structures

Pyramid

They are made from hauled stones. shape of pyramids looks like a traingular prisim from houted crushed stones. Priest determines the true north at the Biteile
The first pyramid in Egypt was built around 2700 BCE
Workers hauled limestone blocks and stacked them to form a pyramid structure

Stonehenge

It was made of dug up ditch with tools made of worked and red stone from England.
England is the place people built the Stonehenge. Around 2000 BCE
Workers transported massive stones and arranged them in a specific pattern/circular

Forces Acting On Structures

* Look in science book for assistance; what forces would affect these structures and describe how.
    * Pyrmaids: External and dynamic forces, gravity, and wind can act on pyramids
    * Stonehenge: The forcses that can act on Stonehenge are gravity and weathening

Static and Dynamic Load

* A load is weight or source of pressure that creates an external force on a structure.
    * A Static Load is something that does not change.
    * A Dynamic Load is a force that can change when actng on a structure.