Six Months in Copenhagen

One of the most important aspects of my final Danish project was to estimate the cost of the eventual construction. Given the complexity of the structure and the many work restrictions, any guess is a total shot in the dark. It usually takes the expertise of an experienced construction estimator to produce a realistic estimate, but even they need a starting point. Therefore, I was asked to complete our schematic drawings and estimate the quantity of materials being used.

Recall that the Oerestad Overdecking project involves covering a six lane highway and two active rail lines with a structural deck for recreation, parking and even a hospital. This covered area is over 38,000 m2 (410,000 sft). Despite some very long spans, necessary to bridge transit lines, over 150 columns and many long walls are required. As big as the project looks on the plan, the size of these numbers made me do a double-take.

Each one of the columns and walls also requires a substantial foundation to carry the heavy hospital loading into the stiff chalky soil. The largest spread footing is almost 20 ft wide. We also needed to provide retaining walls in several locations where the plans actually called for new rail lines to be added. In fact, more concrete is expected to be used underground than in the rest of the overdecking (assuming a steel hospital construction). Construction of the below-grade structure will be especially difficult with the transit lines in operation.

Above ground, a system of concrete inverted-T beams will span between the concrete columns and walls. Precast double-T concrete deck slabs will sit on these beams and provide the platform to connect the neighborhoods currently separated by the transit corridor.

Clearly, this project is an ambitious undertaking. The volume of material grows even more impressive with the addition of the 20-story hospital. For now, though, the client is just focused on the first phase - decking over the transit lines. Hopefully these quantity estimates help them estimate a realistic project cost and allow them to make a smart cost-benefit decision on whether to proceed with the project.