CO2-Optimization Design of Reinforced Concrete Retaining Walls Based on a VNS-Threshold Acceptance Strategy

Abstract

This paper presents one approach to a methodology to design reinforced concrete cantilever retaining walls for road construction using a hybrid multistart optimization strategic method based on a variable neighborhood search threshold acceptance strategy (VNS-MTAR) algorithm. This algorithm is applied to two objective functions: the embedded carbon dioxide (CO 2) emissions and the economic cost of reinforced concrete walls at different stages of materials production, transportation, and construction. The problem involved 20 design variables: four geometric variables (thickness of the stem and the base slab; toe and heel lengths), four material types, and 12 variables for the reinforcement setup. Results first indicate that embedded emissions and cost are closely related and that more environmentally friendly solutions than the lowest cost solution are available at a cost increment of less than 1.28%. The analysis also indicated that reducing costs by 1 Euro could save up to 2.28%kg in CO 2 emissions. Finally, the cost-optimized walls require approximately 4.8% more concrete than the best environmental ones, which need 1.9% more steel. © 2012 American Society of Civil Engineers.