There is certainly some differences between WSD (WORKING STRESS DESIGN) and USD ( ULTIMATE STRESS DESIGN). The differences are stated below:
Difference between WSD and USD design
WSD- WORKING STRESS DESIGN:
- Stress condition of structural member under working load is given attention.
- Full strength of material is not utilized and is reduced by a factor.
- Stresses calculated are within the elastic limit.
- Is less economical than USD.
USD- ULTIMATE STRESS DESIGN:
- Focuses on the strength capacity of the members at conditions corresponds to failure.
- Material properties are assessed and used in design.
- Loads are multiplied by a factor.
- More economical