Titel: Fatigue Assessment of Concrete Foundations for Wind Power Plants
Författare: Frida Göransson, Anna Nordenmark
Utgivare: Chalmers University of Technology
Årtal: 2011
Sökord: foundation, fatigue, fatigue assessment method, wind power plant, concrete foundation slab, Eurocode 2, fib Model Code 2010
Rapport (Pdf)
Sammanfattning/Abstract:
The demands on cleaner and renewable energy have increased with the depletion of natural resources and a way to meet these demands is to use wind power. With an increasing amount of wind power plants the design of foundation slabs for these are of interest. The foundation slab for a wind power plant is subjected to cyclic loading from the wind and there have been uncertainties concerning the effect of fatigue.From the beginning of 2011 all new structures in Sweden should be designed according to Eurocode and as a result of this a new approach to calculate the influence of fatigue is to be considered.
The aim of this project is to give recommendations for designing concrete foundation slabs with regard to fatigue. This is done by clarifying the issues of fatigue for a foundation slab for a wind power plant, comparing methods for fatigue assessment according to Eurocode 2 and fib Model Code 2010 as well as performing parametric studies of the fatigue design of a foundation slab and identifying parameters that have
significant impact on fatigue of a foundation slab for a wind power plant.
When performing a fatigue assessment the choice of assessment method is important.In this project two fatigue assessment methods regarding reinforcement, according to Eurocode 2, have been included. One of the methods takes the frequency of the load into account and uses the Palmgren-Miner damage summation to estimate the fatigue damage, while the other method uses an equivalent value for the fatigue load and a reference number of cycles. For fatigue assessment of compressed concrete two methods according to Eurocode 2 have been used, as well as a method according to fib Model Code 2010. One of the Eurocode methods and the fib Model Code method are damage calculation methods, while the second Eurocode method just checks for an adequate fatigue life by using the maximum and minimum compressive stress under the frequent load combination.
The fatigue assessment and parametric study performed shows that the dimensions of the slab have an impact on fatigue of the foundation slab. It is concluded that the damage calculation methods are preferable when performing a fatigue assessment based on a spectrum load, like the wind acting on a wind power plant. The fatigue assessment methods that do not take the frequency of the load into account has been seen to not be valid for such a complex load used in this project.