tailieunhanh - True Optimization of Pavement Maintenance Options with What-If Models

A prototypical problem road agencies are faced with is to find the optimal application schedule of maintenance works for a given road section. To solve such problems what-if models such as the road transport investment model (RTIM), the highway economic requirements system (HERS), and the highway development and management tool (HDM-4) are widely used to predict the consequences of different maintenance options. With these models maintenance options to be compared must be exogenously specified by an analyst, and the “optimization” with these routines simply chooses the best among those compared. As there are usually infinite numbers of options, it is impossible to exhaust all of them and only suboptimal optimizers may be found with this approach. The present article proposes the use of gradient search methods with what-if models to find the true optima without requiring exogenously specified alternatives. It demonstrates through a case study the feasibility of the use of the steepest descent method and the conjugate gradient method along with HDM-4 to find the true optimum maintenance options. | Computer-Aided Civil and Infrastructure Engineering 21 2006 193-204 True Optimization of Pavement Maintenance Options with What-If Models Koji Tsunokawa Dinh Van Hiep Riaz Ul-Islam Graduate School of Civil and Environmental Engineering Saitama University 255 Shimo-Okubo Sakura-ku Saitama-shi Saitama-ken 338-8570 Japan Abstract A prototypical problem road agencies are faced with is to find the optimal application schedule of maintenance works for a given road section. To solve such problems what-if models such as the road transport investment model RTIM the highway economic requirements system HERS and the highway development and management tool HDM-4 are widely used to predict the consequences of different maintenance options. With these models maintenance options to be compared must be exogenously specified by an analyst and the optimization with these routines simply chooses the best among those compared. As there are usually infinite numbers of options it is impossible to exhaust all of them and only suboptimal optimizers may be found with this approach. The present article proposes the use of gradient search methods with what-if models to find the true optima without requiring exogenously specified alternatives. It demonstrates through a case study the feasibility of the use of the steepest descent method and the conjugate gradient method along with HDM-4 to find the true optimum maintenance options. 1 INTRODUCTION Background Road managing agencies strive to maintain their networks by selecting maintenance alternatives that minimize total transport cost TTC or maximize benefits to the stakeholders in the long term. This requires the use of analysis systems that can predict the costs and bene- To whom correspondence should be addressed. E-mail koji-t@post. . fits of different maintenance options over time. Accordingly what-if models of pavement management analysis such as RTIM Cundill 1993 HERS FHWA 1998 and the highway development and .