Page 427 - Pipelines and Risers

394 Chapter 2 I

The resistance consists of characteristic resistance and safety factors (material factors, or
resistance factor) of typically 1.3. The characteristic resistance is defined for the following
failure modes:
- yielding- SMYS
- brittle fracture- material toughness
- fatigue- SN curves

The loads are classified to 3 categories:
- functional loads
- environmental loads
- accidental loads

Loads factors are applied based on the category of the load. Load combination includes a
couple of combinations of different categories of loads with assigned load factors. The load
effect is then calculated using FE models.

For example environmental loads are:
- Surface vessel motion
- Wave
- Current
- SnowandIce
- Earthquake

Wave loads are the most important and complex environmental load:
- Regular waves
- Irregularwaves
- Long-term variation of waves

There are insufficiencies in existing codes, such as:
- Environmental loads effect
- Functional loads effect
- Stress calculation
- Material properties of new material
- Definition of failure modes
- Working stress design format

For deepwater application, there are even more challenges:
- New dominant load combination