Behavior and design of piled raft foundations under dynamic and static loading

Abstract

In the scope of this thesis, piled raft foundation systems wereanalyzed for both static and dynamic cases. The e ect of end bearing and shaft friction piles and also the e ect of pile lengths were evaluated for both piled and conventional raft foundations. Usually, neglecting the contribution of the raft, pile foundations are designed with an assumption that piles are resisted all loads. However, it is obvious that raft is a part of foundation system and if there is a contact between raft and soil, raft carries some proportion of structural loads. Regarding this contribution, it can be lead considerably economy. In this study, static and dynamic behavior and their design criteria of piled raft foundation is evaluated. Two di erent simpli ed approaches which are developed by Poulos and Randolph were used forall hand calculations. Microsoft Excel for numerical analyses and Plaxis 2D 2015 AE commercial software for FEM analyses were used. Both numerical analyses and nite elements analyses were conducted for all static models. In addition to static analyses, by using previous earthquake accelerations, three time history analyses were performed for both conventional and piled raft foundations and their results were compared. The material parameters used in the analysis are selected by personal experience and the analysis method and load levels were obtained from the reference studies. An undrained - drained material models were employed in the short and long term analysis of this study inmodeling the soil to analyze clay behavior for piled raft foundations that designed with both oating and end bearing piles. Within this thesis, the researchers basicly focused on the short term behavior. The behavior of the piled raft foundation systems, de ections and internal forces of the foundation members, elastic displacements of piles etc. were evaluated.