TWI Knowledge Summary

Structural analysis

The civil, chemical, power generation and offshore industries all operate large and complex engineering structures that operate for long periods and, in many cases, under arduous conditions. The engineers who operate these structures must understand the relationship between the expected loading and the resultant stresses and deflections of each structure. This is achieved by structural analysis. The process can be applied to both metal and non-metal materials. In all cases, the engineer aims to keep the stress and deflection histories below recommended values based on the materials of the structure.

Large, complex structures have been built for thousands of years. However, stress analysis only began to be developed in 15 ^th and 16 ^th centuries and has become a mature discipline in the last one hundred years. Computer-based numerical methods have been used more frequently since the early 1990s for complex structures because only experts are able to use analytical methods. Experimental stress analysis is a valuable tool for the review of existing structures. This can be combined with non-destructive testing (NDT) to directly determine the current state of structures.

All structures interact with their surroundings. This means that the applied loads (e.g. wind, wave) and the characteristics of the supports can be complex. It is important to understand these. Effort is being channelled into the development of user-friendly systems that reduce the risk that loading and support issues will be overlooked or wrongly assessed. This includes the more accurate assessment of the size and effect of stresses locked into the structure during manufacture (e.g. welding residual stresses). A more complete understanding of structures is being made via instrumentation that is applied by the original design team. This means that advanced structures will be easier to maintain.

Further information

Towards a simplified assessment procedure for corroded nozzles in pressure vessels (August 1999)

FAQ: How can elevated ('dynamic') loading rates be taken into account in structural and fracture mechanics assessments?

The use of the elastic T-stress and other constraint parameters in fracture mechanics (Technology Briefing 516 - September 1995)