%0 Journal Article
%T Optimum Design of Pile Foundation by Automatic Grouping Genetic Algorithms
%A Xiaofeng Liu
%A Gengdong Cheng
%A Bo Wang
%A Shuzhi Lin
%J ISRN Civil Engineering
%D 2012
%R 10.5402/2012/678329
%X This paper studies the optimum conceptual design of pile foundations at the initial design stage. A modular method is proposed, which divides the foundation into modules and each module is identified by its characteristics of pile length, diameter, number and layout. Modules with the same characteristics may be packed and represented by a design variable. A minimum-cost optimization model with multiple design constraints based on Chinese code and a cardinality constraint is built to achieve the concurrent optimization of pile size and layout. The model is solved by the improved automatic grouping genetic algorithms to obtain the design with optimal variables and optimal variable grouping. A practical example demonstrates the effectiveness of the proposed approach. 1. Introduction Pile foundations widely used in high-rise buildings often arrange identical piles on a regular grid pattern with constant spacing between them. Such design is very conservative and uneconomical. Several design strategies for pile foundations [1¨C3] are presented to achieve an economic design. Pile design optimization may be defined as minimum cost of the foundation, while maintaining satisfactory performance. Comparing with the wide study and application of optimization technique in structural engineering domain, the development of the optimization of pile foundations is relatively late for three main difficulties. Firstly, accurate performance prediction of pile foundation is almost impossible because of the uncertainty of soil parameters, the complexity of pile-soil-raft interaction, and the inaccurate constitutive law of layered soil. Even with many available studies based on the elastic-plastic theory [4¨C6], the nonlinear analysis needs various simplifications and assumptions which may not fit the real situation. As Poulos pointed out, ˇ°engineering theory should be based initially on the experience and extended or modified in the light of further experienceˇ± [7], the theoretical analysis results of pile foundations should be modified according to experience in practical design. Secondly, for the discrete nature of pile characteristics (number, diameter, and length), pile optimization is a discrete problem. In addition, the objective function and constraint conditions may be discontinuous, nondifferentiable or even difficultly expressed mathematically in terms of design variables [8]. As a result, pile optimization must be solved by an effective method. Thirdly, piles of a practical design must be grouped because designs with too many different piles will significantly
%U http://www.hindawi.com/journals/isrn.civil.engineering/2012/678329/