Structures and Forces in Engineering

Basic Structures

• Structures are defined by having a definite shape and size
• Form refers to the shape of a structure
• Function describes the purpose of a structure

Forms of Structures

• Solid: Made of one or more solid pieces (e.g., bones)
• Frame: A framework of connected parts like bars or beams (e.g., human body)
• Shell: A panel or interconnected panels, often for protection or containment (e.g., turtle shell)

Forces and Structures

• Force: A push or pull that causes movement or alters shape; creates stress on objects
• Magnitude: The size of a force
• Fatigue: Weakening of a structure due to repeated stress
• Failure: Breakdown of a structure due to excessive stress or fatigue

External Forces

• Forces acting on a structure from outside

Loads

• Dead Loads: Constant, permanent forces on a structure (e.g., weight of the building materials)
• Live Loads: Variable forces on a structure (e.g., people, furniture, vehicles)

Internal Forces

• Compression: A pushing force; structures must support the weight of occupants and themselves.
• Tension: A pulling force; structures must withstand pulling forces.
• Shear: A cutting force; different parts of structures are pressed in different directions.
• Torsion: A twisting force; structures must resist twists from movement.

Amount of Force on an Object

• Magnitude: The amount of force applied.
• Point of Application: The exact location of force application.
• Direction: The line along which the force acts.

Mass and Weight

• Mass: The amount of matter in an object (measured in kg, g, lbs). Mass remains constant.
• Weight: The force of gravity acting on an object's mass (measured in Newtons, lbs). Weight varies based on gravity.

Structural Efficiency

• Comparing the weight supported (grams) to the weight of the structure (grams).

Function, Shape, and Material

• Function: Purpose of the structure (spanning a gap, withstanding wind, supporting vehicles).
• Shape: Structure's shape influences its ability to withstand forces.
• Material: Key factor in a structure's strength and properties.

Material Properties

• Concrete and Iron Rods: Concrete resists compression, iron resists tension.
• Layered Materials: Combine different properties for strength and functionality (e.g., juice boxes).
• Woven or Knit Materials: Flexible materials (e.g., cloth, newspaper).

Joining Technology

• Joints: Where structural parts connect; critical in structural integrity.
• Mobile Joints: Allow movement within a structure.
• Rigid Joints: Prevent movement.
• Joints are often the weakest part of a structure.

Center of Gravity

• Center of Gravity: The point where the structure's mass is concentrated.
• Stability: Keeping a structure in place. A low center of gravity generally increases stability.
• Regular vs. Irregular Objects: Center of gravity differs based on shape.

Orthographic Drawings

• Drawings used to illustrate structures. Essential to specify dimensions accurately and clearly.

Ergonomics

• Designing tools and structures to facilitate human interaction.

Other Definitions

• Truss: A framework of rafters, posts, and struts.
• Beam: A long, sturdy piece of wood across an opening.