Microscale Research and Macroscale Life Cycle Analysis Integration
The integration of the microscale research and macroscale modeling comes together primarily in the specific application chosen for investigation. Microscale researchers developing new greener infrastructure materials must design these materials ultimately for use in existing structures. Therefore, these materials must be engineered to have adequate mechanical properties, such as strength or ductility, to resist applied loads from vehicles, people, or environmental conditions on that structure. Once an application is selected, it is evaluated for sections in which new green materials may be introduced. Due to the lower mechanical performance of many green materials, in comparison to their non-green counterparts, green materials may not be acceptable in all applications in every case. The newly developed green materials are mated to the specific application at this stage.
Following identification of green material applications and selection of the appropriate version of the material, the effect of these new materials on the entire infrastructure system can be evaluated. This is done primarily by macroscale researchers performing life-cycle modeling, flow analysis of material components, and spatial analysis of the production and transportation of each material component. Incorporated in this complex analysis are considerations of the deterioration and corrosion rates of new green materials on service life, examinations of sustainability indicators in the areas of social, economic, and environmental sustainability, and the end-of-life characteristics of new materials, among many others. Once completed, these results are then returned to microscale materials developers to further optimize the material sustainability, and creating a closed loop for iterative improvement of the sustainability of the entire infrastructure system.
Case Study: ECC Link Slab for Bridges
For an initial case study, an application involving bridge decks within Michigan was chosen as an excellent candidate for the incorporation of green ECC material.
A serious concern facing bridge owners is the maintenance and repair of bridge expansion joints. While necessary to accommodate large thermal deformations of bridge spans, these joints often fall into disrepair and eventually leak. This leaking is frequently the cause of severe damage to the bridge beams, allowing water and other corrosive agents to penetrate below the deck and corrode the ends of the beams. After a time, this deterioration requires not only a replacement of the joint to stop the leaking, but also the badly damaged beams, which is costly and time consuming. To combat this problem, many bridge owners have looked to eliminate problematic bridge joints through the use of continuous bridge decks and integral abutment bridges, which call for a continuous deck with no expansion joints. While these technologies have been effective, they are only useful for new bridges and cannot be used on the thousands of simple span bridges currently in service across the nation.
To construct a continuous bridge deck surface, without reconstruction of the entire bridge, an excellent alternative is a bridge deck link slab. This slab forms a connector between two adjacent simple bridge spans, creating a continuous deck to prevent leaking, while absorbing the thermal deformations of the spans which are typically accommodated by an expansion joint. By using ECC material, which can strain-harden, or “stretch”, under load as the adjacent bridge spans expand and contract due to temperature changes, a bridge deck with previously had a number of problematic expansion joints can be changed into a continuous deck. This serves to protect the beams, and the supporting structure of the bridge, from de-icing corrosives and water penetration. A schematic of a bridge with both a mechanical joint and ECC link slab is shown below.
Problematic Conventional Expansion Joint and Durable ECC Link Slab
A number of new ECC versions have been developed which meet the various mechanical and structural demands on the link slab application, such as strength or stiffness. Using these materials, macroscale modeling is being done to determine the effect of the green materials, and the extended lifetime of the bridge in terms of the sustainability indicators outlined above. Results of investigations such as this look to provide infrastructure designers, owners, users, and policy makers with viable sustainable alternatives to current infrastructure system construction, management, and planning practices.
University of Michigan
Page Last Updated
October 16, 2006
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