Optimization of structures byincluding modeling of pilefoundations : A parametric study on using stiff supports orpiles in a model

Abstract: Structural engineers use rules and regulations in the form of Eurocodes and other supplementary guidelines to design different type of structures. However, the uncertainty surrounding each case and the actual outcome that depends on decisions made throughout the design phase are of most importance and must be handled properly from start. Assumptions and simplifications have to be well-founded. The foundation is often one of the first things that has to be investigated in a construction project. When this part is overseen by geotechnical engineers, structural engineers may in some cases proceed with the modelling of the rest of the structure by implementing a stable foundation to build on in the form of stiff supports in a modelling software. This brings out the question of how to model structures in an optimal way in order to present a proposed structural solution that can be correctly applied to the reality of the foundation in question and all the prerequisites affiliated to that specific case. A model can be created either from the ground level and upwards using stiff supports at the bottom or it can include the whole foundation and piles as well creating a larger structure. Perhaps these models have different behavior depending on all the various factors that can affect a building, which may ultimately result in a preferred way of modeling during the design phase. This report investigated the differences between two models like this, case 1 with stiff supports and case 2 with an included pile foundation. The study contains four parts: Support reactions and internal forces in the piles, translational displacements of the structure, global system buckling and eigenfrequencies.