IB Design Technology Topic B3.2.5 Safety Factors Calculations Revision Notes (HL)

IB Design Technology Topic B3.2.5 Safety Factors Calculations Revision Notes (HL) | RevisionDojo

Written by official IB examiners

Safety Factor: Designing In the Margin for Error

Note

This lesson assumes A3.2.9 and A3.2.10, which introduced what a safety factor is and why structures are designed with one.
Here you calculate it, and use it to size a real structure.

Definition

Safety Factor (SF)

The ratio of the maximum load a structure can bear to its expected load.

Note

Safety factors are not just about adding extra material or making structures heavier.
They are about strategically designing for unpredictable conditions.

The Formula for Safety Factor

Note

$$\text{Safety Factor (SF)} = \frac{\text{Ultimate Load (or Stress)}}{\text{Allowable Load (or Stress)}}$$
The ultimate load is the load at which the structure actually fails.
The allowable load (also called the working load) is the load it is designed to carry in normal use.
SF is a ratio of two loads, so it has no units. You can use loads or stresses, as long as both are the same kind.
SF = 1 means the structure is exactly at its breaking point, with no margin at all. Below 1 it is predicted to fail.

Tip

When calculating safety factors, always ensure that the units for ultimate load and allowable load are consistent.

Calculating Maximum Intended Loads

Identifying the Expected Load: Consider all forces acting on the structure, including:

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Tip

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Safety Factor: Designing In the Margin for Error

Note

This lesson assumes A3.2.9 and A3.2.10, which introduced what a safety factor is and why structures are designed with one.
Here you calculate it, and use it to size a real structure.

Definition

Safety Factor (SF)

The ratio of the maximum load a structure can bear to its expected load.

Note

Safety factors are not just about adding extra material or making structures heavier.
They are about strategically designing for unpredictable conditions.

The Formula for Safety Factor

Note

$$\text{Safety Factor (SF)} = \frac{\text{Ultimate Load (or Stress)}}{\text{Allowable Load (or Stress)}}$$
The ultimate load is the load at which the structure actually fails.
The allowable load (also called the working load) is the load it is designed to carry in normal use.
SF is a ratio of two loads, so it has no units. You can use loads or stresses, as long as both are the same kind.
SF = 1 means the structure is exactly at its breaking point, with no margin at all. Below 1 it is predicted to fail.

Tip

When calculating safety factors, always ensure that the units for ultimate load and allowable load are consistent.

Calculating Maximum Intended Loads

Identifying the Expected Load: Consider all forces acting on the structure, including:

Definition

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Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

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Tip

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Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
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A. Design in theory8 subtopics

B. Design in practice8 subtopics

C. Design in context8 subtopics

IB Design Technology Topic B3.2.5: Safety Factors Calculations Notes

A. Design in theory8 subtopics

B. Design in practice8 subtopics

C. Design in context8 subtopics

Safety Factor: Designing In the Margin for Error

The Formula for Safety Factor

Calculating Maximum Intended Loads

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Duis aute irure dolor in reprehenderit

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Unlock the rest of this chapter with a free account

Safety Factor: Designing In the Margin for Error

The Formula for Safety Factor

Calculating Maximum Intended Loads

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account