FEM-modellering av en vattenkraftstation : Utvärdering av beräkningar i 3D

Abstract

The Finite Element Method (FEM) is a numerical analysis technique for obtaining approximate solutions. Its origin can be tracked back to the 1940s. The technique, which during the second half of the 20th century required programming skills and a deep understanding of its underlying theory, has during the last decade been implemented in more user friendly software. Models are built in CAD-like environment and the results are illustrated in easy to understand color graphics.Advancements in computer technology have made it possible to build and analyze more advanced models. These advancements have initiated a growing interest in going from mostly 2D-analysis to full scale 3D-models that describe whole constructions.The work done in this report has been performed in cooperation with the consulting company SWECO Infrastructure, which during the first half of 2011 has been designing a hydroelectric power station. The hydroelectric power station in question is Kraftstation VI in the Swedish town Hissmofors. By working with the FEM-software Abaqus, a full scale model of Kraftstation VI has been built and analyzed.The first part of the report focus on modeling technique and some potential sources of error that might arise in FEM-models such as the one in the report.The geometry of the power station is complex which motivated the use of solid elements. Since most of the construction is subjected to bending the choice of using 20-node cube elements was made.Dam constructions are subjected to one-sided water pressure; therefore its safety against overturning and sliding must be established. This is done through stability calculations where all the loads acting on the construction is considered. It is desirable to be able to calculate the stability through the use of the FEM-model and therefore a method for doing that is developed.The model is analyzed by studying three different loading scenarios: Loading scenario 1 – A global analysis of the hydroelectric power station when it is subjected to the expected everyday loads. The focus is on investigating the interaction between the different parts of the station and identifying possible stress concentrations. Loading scenario 2 – A stability analysis of the station with complementary hand calculations. The results indicate that the method is accurate and that the station is stable. Loading scenario 3 – Calculation of the design moment in ultimate limit state in one of the walls of the intake. The results are compared to the design values that SWECO used when designing the wall. The comparison shows that the calculations done in Abaqus returns lower design moment that those of SWECO.Validerat; 20110911 (anonymous