Dimensionering av betongplatta på lös undergrund. En jämförelse mellan tre beräkningsprogram

Abstract

Today more effective computer programs are in use, regarding design of geotechnical constructions. There is a risk that the theoretical background of the computer programs, its limitations and the signification of the choice of soil parameter is forgotten when the computer programs become more user-friendly. This Master thesis deals with simulation and analysis regarding three computer programs, FEM-design, with the addition Raft, Plaxis and BE-slab. Comparisons are made for settlement and maximum moment in a concrete-plate. FEM-design is a three dimensional FEM-program, foremost created for design engineers. Plaxis is a two dimensional FEM-program, intended for geotechnical engineers while BE-Slab is a Boundary elements program in two dimensions that is mainly used by design engineers. Apart from the theoretical computer programs’ models of calculation, some material models and their soil parameter are discussed in this Master thesis. The area treated in this Masters thesis is located in Älvsborgs harbor in Gothenburg. The bed sequence of the soil contains of fill with underlying clay, moraine and bedrock. Four cases of calculations regarding the bed sequence of the soil are being used when simulating. These cases prove the significance of the soil thickness and the thoroughness of soil parameter determination. This Master thesis discusses how the soil parameters for fill and clay are being obtained and which characteristics give the greatest effects on the settlement and maximum moment. Since the soil parameters of the fill often are inhomogeneous with a large variation over a small area, they are the hardest to estimate. For clay, on the other hand, the investigation methods and possibilities to determine the material characteristics are good. Variations in the clay parameters give a big effect on the resulting settlement and maximum moment. The fill, on the other hand, has a much lesser effect on the settlement and the maximum moment. Beside the soil parameters, it is foremost the theoretical computer programs’ models of calculation that effect the resulting settlement and maximum moment. There is a relatively big difference between the three computer programs, which can be due to the models of calculation. Because of that it is very important to be aware of the theoretical computer programs’ models of calculation, and if the computer program see the concrete plate as a part of a bigger plate or not.