Cost effective designs

Different cost effective design methods have been developed to reduce the cost of buildings, of which structural optimum design methods and cost effective designs methods using estimating data, are the most common. However, there is no record of the use of cost effective design methods in practice. Consequently, potential benefits of such methods remain untapped. This research evaluated the cost savings through cost effective design methods, identified difficulties involved in their use and examined favourable conditions for the implementation of such methods in design practice. The research aimed at investigating whether or not the opinion among practising designers, (structural engineers and architects) that "cost benefits through cost effective designs are insignificant and methods are not practical" is justified. Previous researchers have developed cost effective design methods, but very little has been done to change the opinion of building designers regarding these methods. A proper evaluation of cost effective design methods and a study of the design process are therefore necessary to gain the attention of designers in practice. The opinion among practising designers is that cost savings through optimum methods are less than 10% of elemental cost and 1% of total building cost. The analysis of cost savings of 22 historical buildings have shown that this is not the case. Optimum design methods using the computer to find the minimum cost from a set of feasible designs were developed for reinforced concrete elements; slabs, beams, columns and independent footing foundations. These optimum methods were applied to the design of 22 historical buildings. More than 10% of elemental cost savings were observed. 2.91% of total building cost can be saved using optimum methods for design of reinforced concrete elements, which is more than 45% of the total design fee of a building. The study proved that for a given building, probabilities of total building cost saving exceeding 1%, 2% and 3% are 0.96, 0.79 and 0.47 respectively. Design and build contracts provide not only a facility but also an incentive, to designers to use cost effective design methods. On the contrary, percentage fee contracts act as a disincentive. Therefore, the legal procedures in design practice, may sometimes serve as obstacles for the use of cost effective design methods. Furthermore, current design practice lacks motivating factors to designers to use cost effective design methods. Therefore building construction industry may need to pay additional fee to get benefits from cost effective design methods.