Efficient robust geotechnical design of drilled shafts in clay using a spreadsheet

This paper presents an efficient robust geotechnical design (RGD) approach that considers performance requirements, design robustness, and cost efficiency simultaneously. In this paper, design robustness is measured via the variation in the performance function of concern that can be evaluated using reliability analysis. Furthermore, the performance requirements of the system are also evaluated using reliability analysis. Thus, the evaluation of design robustness and the evaluation of performance requirements share common computational steps, referred to herein as computational coupling. This coupling for computational efficiency is a significant feature of the proposed RGD approach. Within the framework of the proposed RGD approach, design robustness, cost efficiency, and performance requirements can be considered simultaneously by means of multiobjective optimization. Furthermore, a practical and efficient procedure is developed for such optimization using a feature resident in a popular spreadsheet program. Through an example of the design of a drilled shaft in clay, the effectiveness of this new RGD approach is demonstrated. The results show that the hard-to-control variability resulting from construction variation, variable loading conditions, model errors, and uncertain geotechnical parameters in the design of drilled shafts in clay can be effectively considered with the proposed RGD approach.