Automatic optimization of piled raft design based on branch and bound method

Piled rafts are foundation systems that combine a shallow raft with the minimum number of piles beneath the raft, in order to achieve the necessary bearing capacity and the acceptable settlement restrictions. Its use is increasing in many countries, especially in skyscrapers in Europe and Asia, for which the foundation design can result in hundreds of piles due to the high load magnitude. However, controlling the most influencing variables on the foundation behaviour, while achieving an acceptable cost, is a challenge for designers. This paper presents an optimization procedure to determine the best raft thickness, number of piles and their location. The branch and bound optimization method was combined with a specific computational programme for piled raft analysis (GARP) providing an automatic technique to obtain the lower cost design. A building in Brazil and theoretical examples of a piled raft with different load sets are presented and analysed using this numerical approach. The results show that the presented automatic procedure provides interesting solutions, economically enhancing the design of piled raft foundation systems. The optimization process provides arrangements using lower number of piles while satisfying the constraints in both analysed cases. Copyright © 2014 John Wiley & Sons, Ltd.