Power Production Facilities: Is it the time for a “Metathesis” of our design philosophy?

Power Production Facilities: Is it the time for a “Metathesis” of our design philosophy?

Power production facilities are all but immortal. Oil & gas extraction rigs have a life span of 20-30 years while wind turbines are designed to work 120,000 hours –a lifespan of only 20 years. Unlike most of our civil infrastructure (whose lifespan exceeds 50-100 years or even more at a quite reasonable cost and where effects of failure are usually contained), construction of power-related infrastructure requires abundant resources – the lack of which certainly limits their robustness thereby curtailing their life-expectancy (e.g. due to accumulation of deformation at the base of a wind turbine subjected to wind, waves and current; fatigue of structural members of off-shore platforms subjected to millions of cycles of wave loading and current).

But even during their limited lifetime, they may indeed fail as a result of natural phenomena such as earthquakes provoking a plethora of cascading effects not only on the interrelated components (e.g. pipes, tanks, turbines) but also on the very endurance of communities (lack of power supply to homes and industries, immediate effect on energy prices, environmental consequences etc), let alone the human casualties.

It may be bluntly rhetoric to wonder whether it would be feasible to design our power production infrastructure to last longer and be stronger. Technically –and if haphazardly supposing that constructability is granted- it could happen by increasing dimensions, adding more reinforcement and boosting safety factors. But is it economically permitted? As uninspired, ordinary and cynical as it may sound, resources have always been the determining factor.

Recognizing this reality, the idea presented herein constitutes a major shift in the design philosophy for power-related infrastructure by proposing a Metathesis[1] of our design focus from ensuring robustness of the superstructure to developing resilience of the whole structure-foundation system. The core of the concept is not about adding members or improving materials but rather about exploiting what is already there. Shall this concept be adopted the foundation will no longer be treated as merely a boundary condition but rather as a crucial contributor to maintaining operability and increasing the lifespan of the infrastructure.

The envisaged resilient foundation systems will not aim to simply resist the loading, but rather ensure (depending on the case) that:

  • Operability will not be hammered even when the system is subjected to strong (even stronger than its design) earthquake shaking
  • Deformation (i.e. rotation or settlement) is not accumulated by the soil-foundation system despite its being submitted to millions of loading cycles
  • Stressing of structural members is reduced by partially rerouting loading to the soil-foundation system

To address these challenges, novel foundation design schemes will be developed that will be entailing one or a combination of the following characteristics:

  • Self-centering capacity, i.e. ability to revert to their initial position after strong dynamic loading
  • Fail-safe loading adaptivity, i.e. ability to demonstrate superior response as the level of imposed dynamic loading increases by exhibiting over-strength or hardening[2]
  • Diffusion aptitude, i.e. ability to divert major ground displacement minimizing the load to be sustained by the structure.

It is apparent that although each aims at a different kind of threat all three characteristics constitute resilient foundation schemes sharing the same principle: a metathesis of stressing from the superstructure to a properly designed structure-foundation interacting system.

[1] Metathesis: Originating from Greek, the word literally means shift, transposition or transfer

[2] “Although both terms have been borrowed from soil mechanics terminology, they are herein used to describe the response of the foundation system rather than soil itself.