Pile group design: An investigation and development of a software to optimize the design of pile groups

Abstract

The design of pile groups is a very time consuming and iterative procedure. Piling is also very expensive, hence it is important to keep the number of piles to a minimum. Today, there are no established guidelines how to design a robust pile group and the design differs depending on the load effects and soil conditions.

This thesis investigates a method for designing a pile group based on the definitions of pile center and load center. A stand-alone software was developed to optimize double and single symmetric pile groups for bridges. The software optimizes the pile groups by minimizing the distance between the pile center and the load center while trying to achieve as high moment capacity in the pile group as possible. The software was evaluated by conducting 27 cases studies, where a vast majority of the generated pile groups were designed with either fewer or the same number of piles as the original pile groups. The pile groups were designed without collisions between the piles and the simulation time varied between 2 and 85 seconds.

The placement of the pile center is mainly limited by the dimensions of the pile cap and the inclination of the piles. The load center was sometimes shown to vary substantially between the different load cases, which made it difficult to match the position of the pile center with the load center. The thesis can conclude that designing a pile group based on the definitions of pile center and load center is a good method when the position of the load center is fairly constant. When this is not the case, the moment capacity of the pile group is of high importance.