What are Standards and Codes?
- Standards are documented technical specifications or guidelines that define materials, dimensions, testing methods, and performance criteria.
- Codes are sets of rules that prescribe how design, fabrication, installation, and inspection should be carried out—often with legal enforceability.
Examples include:
- Bureau of Indian Standards (BIS)
- American Society of Mechanical Engineers
- International Organization for Standardization
- American Society for Testing and Materials
Table of Contents
🔹 Objectives of Design Based on Codes
- Safety Assurance – Prevent failure under expected loads and conditions
- Uniformity – Maintain consistency across industries and projects
- Reliability – Ensure predictable performance over service life
- Quality Control – Standardize materials and manufacturing processes
- Legal Compliance – Meet regulatory and statutory requirements
🔹 Types of Design Approaches in Codes
1. Working Stress Method (WSM)
- Based on elastic theory
- Uses allowable stresses with a factor of safety
- Simpler but often conservative
2. Limit State Design (LSD)
- Considers ultimate and serviceability limit states
- Uses partial safety factors for loads and materials
- Widely adopted in modern codes (e.g., IS, Eurocodes)
3. Load and Resistance Factor Design (LRFD)
- Similar to LSD but more probabilistic
- Common in international practices
🔹 Key Elements in Code-Based Design
✔️ Material Selection
Codes specify acceptable materials, their properties, and testing standards.
✔️ Load Considerations
Includes dead load, live load, wind, seismic, thermal, etc., often defined in separate standards.
✔️ Factors of Safety
Ensures margin against uncertainties in loading, material strength, and workmanship.
✔️ Design Equations
Provided directly in codes to simplify calculations and ensure uniformity.
✔️ Inspection & Testing
Codes outline procedures for quality assurance during and after construction/manufacturing.
🔹 Advantages
- Reduces design errors and ambiguity
- Saves time by providing ready formulas and data
- Ensures compatibility across systems and components
- Facilitates approval from regulatory authorities
🔹 Limitations
- Can restrict innovation due to rigid rules
- May become outdated if not revised regularly
- Sometimes overly conservative, leading to higher costs
🔹 Applications in Mechanical Engineering
- Pressure vessel design (ASME Boiler and Pressure Vessel Code)
- Piping systems (ASME B31 series)
- Machine components (gears, shafts, bearings using ISO/AGMA standards)
- Thermal systems and power plants
- Manufacturing tolerances and fits