B3.2 Structural Systems Applications and Selection

Finite Element Analysis (FEA)

A computerised simulation method that breaks down a model into small elements to analyse how it responds to physical forces.

What FEA Shows

Stress concentration areas (visualised with colour maps), points of failure under load, and deformation behaviour over time.

Interpreting FEA Data

Focus on areas with stress concentrations or unexpected deformations, as these are the first indicators of potential failure.

Force Diagram (Free-Body Diagram)

A diagram showing all forces acting on a structure or object, including applied loads, support reactions, and internal forces like tension and compression.

Key Principles of Force Diagrams

Forces are vectors with magnitude and direction; forces in the same direction add up, while opposing forces subtract to yield a resultant force.

Newton's 2nd Law in Structures

Force equals mass times acceleration (F = m × a); if acceleration is zero, the resultant force is 0 N (balanced).

Three Steps to Read a Force Diagram

1. Find the loads (arrows pushing down), 2. Find the reactions (arrows pushing up at supports), 3. Check equilibrium (up arrows must equal down arrows).

Following the Load Path

Tracing a load from where it is applied to the ground to determine which parts are carrying weight and whether they are in tension, compression, bending, torsion, or shear.

Safety Factor (SF) Formula

Ultimate load (or stress) divided by working or allowable load (or stress).

Ultimate Load

The maximum load or stress at which the structure actually fails.

Allowable

Working Load

Maximum Intended Load

The total weight of all persons, equipment, tools, materials, and external loads anticipated to be applied to a structure at any single point in time.

Dead Loads (Design Load)

Permanent forces such as the weight of the structure itself.

Live Loads (Design Load)

Temporary forces such as people, furniture, or vehicles.

Environmental Loads (Design Load)

Natural forces from wind, snow, earthquakes, etc.

Design Load Formula

Maximum intended load multiplied by the Safety Factor.

Stress Calculation Formula

σ = F

Strain Calculation Formula

ε = ΔL

Area Conversion for Calculations

1 mm² equals 0.000001 m² (10⁻⁶ m²), which must be converted before calculating stress and Young's Modulus.