Optimization of highway vertical alignment by direct search technique

Özkan, Eray
During initial stages of geometric design of highway projects, generally a number of alternative horizontal alignments are developed. For any selected alternative horizontal alignment, the basic features of the geometric design are to be completed by establishing the vertical alignment of the roadway. Since for a given horizontal alignment there would be infinite number of vertical alignments conforming to the specifications, it is essential to use an optimization process in order to achieve the most economic design. This study is focused on optimizing a vertical alignment already established by the designer. The governing cost item in relation to vertical alignment being the earthwork cost, it should be minimized to reach the optimum solution. Since the problem itself is a multivariable, complex and nondifferentiable one, a heuristic search technique; namely the direct search technique is chosen for this purpose. In order to apply the optimization in an efficient and fast manner, AutoCAD Civil 3D software is selected and a program module in Visual Basic programming language is written to optimize the vertical alignment. The program module integrated to AutoCAD Civil 3D software is applied for some virtual projects and for a segment of a real highway project as well. The results showed that the method provides an incredible reduction in the earthwork costs of the projects by adjusting the vertical alignments slightly without changing the basic design features of the project.


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Citation Formats
E. Özkan, “Optimization of highway vertical alignment by direct search technique,” M.S. - Master of Science, Middle East Technical University, 2013.