Analysis of the behavior of piled raft foundations with finite element method

By Turkey Building Earthquake Regulation enacted at beginning of 2019, analysis of piled raft foundations under earthquake forces has been made compulsory. Two approaches adopted in the regulation, namely common system approach and subsystem approach. In the common system approach, the structure-pile-soil is analyzed as a whole. Subsystem approach, on the other hand, is analyzed in two stages: foundation-pile-soil system called kinematic interaction and foundation-structure system called inertial interaction. In the subsystem approach, three methods are proposed for these stages according to the soil and building characteristics. In this thesis, Method III-Kinematic Interaction analysis, which is anticipated to be performed in conditions with less earthquake risk compared to the other two methods, and which is mostly within the scope of the Geotechnics department, is studied. In the analysis, soil springs (load transfer curves) are determined with MS Excel software, site response analyzes are performed with DEEPSOIL software and incremental nonlinear static analyzes performed with SAP2000 software. In this context, under fixed and specific conditions, the effect of pile diameter variation, pile length variation, group effect in pile group, different earthquake data, bedrock depth in the soil, different clay and sand soils to the behavior of friction piled raft foundation has been investigated through pile internal forces and pile head displacement obtained as a result of kinematic interaction analysis. At the end of the study, piled raft foundation behavior is interpreted determining pile normal forces, moments, shear forces and pile head displacements through the variables listed above. As a result of the analysis, it was concluded that the selection of earthquake data in kinematic interaction analysis is very important and it is the most effective data in piled raft foundation behavior.