AN INTEGRATED KNOWLEDGE-BASED SYSTEM FOR ALTERNATIVE DESIGN AND MATERIALS SELECTION AND COST ESTIMATING

Building design and material type used are the two main parameters tha t have a significant impact on the cost of a building. Therefore, it i s important for a cost estimating tool to have a mechanism that allows the designer to perform a rapid 'what if analysis on design alternati ves and materials selection at the early planning stage without the ac companiment of detailed design and drawings. However, the traditional design cost estimating procedures generally focus on assessing costs a fter design decisions are made and conveyed to the construction drawin g as a quantity take off. On the other hand, comparative cost estimati ng (unit cost per square meter) uses historical data collected by aver aging buildings of different designs, heights and materials. Even toda y's computer aided design (CAD) software incorporates a mechanism to t ake off quantities from completed designs and drawings. However, basic ally they are the same as the traditional quantity take off estimating because a single specified design still controls the resulting costs, and there is no alternative materials selection integrated to the cos t system. This article presents an integrated knowledge-based system f or alternative design decisions, materials selection and cost estimati ng mainly for pre-design analysis. The knowledge-based system also inc ludes materials selection and cost estimating for after-detailed desig n by providing edit tables for inputting the dimensions of building el ements from completed designs and drawings or by directly importing fr om CAD. The system generates activities quantities, costs and lists of materials selected and their respective quantities. An analysis of al ternative design and materials selection for a residential building us ing the integrated system is presented. (C) 1998 Elsevier Science Ltd. All rights reserved.