Sustainable design for steel-concrete bridges

As bridges are of vital importance in the worldwide infrastructure network and significant in economy, the request for sustainable structures is urgent. Sustainability of bridges means lifecycle design, but lifecycle design over a span of more than 100 years. So in contrast to sustainability issues for buildings the durability and the flexibility to adapt to changed conditions and increased traffic volume play a crucial role for the assessment of the overall lifecycle performance (LCP) of bridges. The main reasons for traffic jams are: besides of high traffic density accidents and roadwork. In order to avoid or reduce traffic jams accidents should be minimised and roadwork reduced e.g. by reducing the time of erection and repair or by improving durability. However these aspects are usually not reflected by construction costs. And decisions on bridges are usually only based on minimum construction costs. Therefore the Hessian Road and Traffic Administration ordered an expertise to assess the cost-effectiveness of steel-concrete composite bridges, particularly with regard to the construction method, see Kuhlmann et al. (2006). The task of the project was to investigate evaluation methods for cost-efficiency analyses and to show how far these consider "costs" in a more holistic way, considering e.g. construction costs, maintenance costs, costs for renovation and reconstruction (including demolition), costs of construction duration including the consequences and effects on traffic etc. By these calculations a first step has been realized to assess bridges structures in view of lifetime costs as well as other non-monetary aspects. This path will be continued in future research initiatives.