Design by Analysis (DBA) indicates that 4 failure modes must be checked when applying the code to pressure vessels or other covered equipment. The 4 modes are:

1. Plastic Collapse

2. Local Failure

3. Buckling Failure

4. Cyclic Loading

Each mode involves calculating stresses and then comparing these stresses to acceptable values. In addition, each mode allows for the use of different methods to establish that the failure mode of interest passes code requirements. Future articles will discuss these modes and methods in more detail.