A cost estimate method for bridge superstructures using regression analysis and bootstrap

Preliminary cost estimates rely on the conceptual design of the project and use only basic design technologies. Although they present the lowest expected accuracy, they are often used by key people involved in the construction process, thus playing a significant role. Bridge construction has increased over the last years, often exhibiting substantial overruns above estimated costs. To overcome this problem, it is crucial for the decision makers to have an early estimate of the final cost based on previous experience. This paper addresses the need for easy-to-use and reliable cost estimates during the early stages of projects for bridge superstructures, presenting a major impact on the total bridge construction cost. It proposes a conceptual cost estimate method that involves the estimation of both the material quantities and the relevant costs. It describes the development of prediction models for the material quantities of concrete and reinforcing and prestressing steel for three major bridge deck construction methods using regression analysis, while a bootstrap resampling method is used to produce estimate ranges. The material estimating models rely on the development of a database after collecting actual data from a large sample of modern bridges. The major assumptions underlying the correct application of the regression methodology were tested, and necessary adjustments were made. The proposed conceptual cost-estimating methodology uses information known before detailed plans are developed to provide fast and reliable results that can be very useful in the early stages of a road project