Optimization Based - Approach for Organizing the Bidding of Nonserial Repetitive Projects A. Samer Ezeldin 1 and Ahmed M. Alhady 2 1 Professor and Graduate Director, Department of Construction and Architectural Engineering, The American University in Cairo, Egypt; AUC Avenue, P.O. Box 74, New Cairo 11835, Egypt; PH (202) 2615-2631; email: aezeldin@aucegypt.edu. 2 PhD Candidate, Department of Construction and Architectural Engineering, The American University in Cairo, Egypt; AUC Avenue, P.O. Box 74, New Cairo 11835, Egypt; PH (201) 00-180-4706; email: hady79@aucegypt.edu. ABSTRACT In practice, the number of contracts and the categories of contractors to be called for bidding on non-serial repetitive projects under one major program are often estimated based on intuition and experience. It may involve emotional reactions to existing surrounding conditions. Accordingly, the factors that form the possible different scenarios should be properly analyzed and evaluated. This paper introduces an analytical model that allows for decisions on the number of contracts and projects per contractors for different contractors’ categories within major construction infrastructure programs. These optimum decisions are reached using an integrated time and cost objective. Genetic Algorithm has been employed for performing optimization. A computer- based model has been developed and validated. Keywords: Nonserial Repetitive Projects; Bidding Analysis; Optimization; Time Cost Trade-Off. INTRODUCTION Nonserial repetitive construction projects, in this paper, are representing multi-subprojects under a major program with one defined budget. Therefore, the word repetitive projects here refers to projects level not activities level. Those sub- projects are typical in their work packages, activities, and construction methods. However, they can have different quantities, locations, list prices, and different contractors. Each subproject is independently related to the others in terms of starting and finishing dates. In other words, it is not a condition for one subproject to start after another one is finished. Examples of this kind of projects can be mostly noticed in infrastructure projects such as roads, railways, tunnels, bridges, pipelines, etc. In this study, the word cost refers to the cost of owner and the word price refers to the bid price of a contractor. In projects that have a nonserial repetitive nature under a grand project, there can be many different scenarios when deciding upon the number of contracts and contractors’ categories to be called for bidding. These estimations have to be properly determined in order to minimize the cost and time of the grand project especially for infrastructure projects that takes a big share of governments’ capital. The dilemma is that if the contracts are divided into a small numbers with high contract value, limited contractors from high categories have to be called for bidding in order to undertake the project. In this case, this category of contractors has a high 1468 Construction Research Congress 2014 ©ASCE 2014