Environmental impact assessment and eco-friendly decision-making in civil structures.

This study develops two useful procedures in performing an environmental-impact assessment. One is the advanced life-cycle assessment (LCA) method, which effectively tracks the flow of materials and considers the recycling and demolition of a civil structure. The other is an eco-friendly decision-making procedure, which may effectively apply when determining the prototype of a civil structure. The advanced LCA method differs from traditional LCA procedure, as it classifies the input material prior to the impact assessment. Classification work is performed to establish independent life-cycle stages for each material. The processes of recycling and demolition are appropriately added to the life-cycle stages. The impact assessment is performed separately for the materials, and results are aggregated at the end of the analysis. The eco-friendly decision-making procedure enables designers to choose an economical, and environmentally friendly, alternative during the planning phase of the construction project. This procedure rationally amalgamates economical value and environmental effects into a single indicator. The life cycle cost (LCC) of a structure can be analysed by using conventional LCC tools, whereas the environmental impact is estimated by LCA. The results from LCC and LCA are then integrated by using either a CO2 conversion method or an analytical hierarchy process (AHP). The CO2 conversion method presents the result as a monetary value, whereas the AHP presents the result as a non-dimensional value. A practical example using a steel box girder bridge and a pre-stressed concrete (PSC) box-girder bridge is also given in order to aid the understanding of the presented procedure.