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

Abstract

This paper describes 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 CO2 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, as well as the toe and heel lengths), four material types, and 12 variables for the reinforcement set-up. 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 one euro could save up to 2.28% kg in CO2 emissions.Finally, the cost-optimized walls require about 4.8% more concrete than the best environmental ones, which need 1.9% more steel.

Optimization of concrete I-beams using a new hybrid glowworm swarm algorithm

“…A thorough review of nonheuristic structural concrete optimization studies can be found in Sarma and Adeli (1998). Many later studies have been undertaken to implement evolutionary algorithms to solve structural concrete optimization problems (Kicinger et al, 2005), while the present authors' research group reported on non-evolutionary algorithms to optimize real-life RC structures (Payá-Zaforteza et al, 2010;Yepes et al, 2012;Carbonell et al, 2012;Martí et al, 2013;Martínez-Martín et al, 2013;Torres-Machí et al, 2013).…”

Studies on Environmental Impact Assessment of Reinforced Concrete in Different Life Cycle Phases

“…Considering that recycling concrete is a common practice (for example, in Australia it accounts for 74% of the demolished concrete), the secondgeneration construction following the demolition of the original concrete is to be included in the emissions life cycle estimates of CO 2 . Yepes et al (2012) presented an approach to a methodology for the design of reinforced concrete retaining walls. They used a hybrid multiobjective optimization method, applied to two objective functions: Embodied carbon dioxide (CO 2 ) emissions and economic cost of retaining walls of reinforced concrete at different stages of production, transportation and execution.…”

“…Kim et al (2016) If concrete mix and raw material suppliers were carefully selected, it can be obtained a reduction of 34% in the emission of CO 2 and 1% in the costs Park et al (2012) CO 2 emissions increase linearly with the compressive strength of the concrete; to similar strengths, the concrete produced in the winter presented an increase of approximately 5% in the CO 2 emissions Santoro and Kripka (2016) Higher strength concrete will produce a greater amount of CO 2 ; the CO 2 emissions during transport are significant Choi et al (2016) For smaller loads the increase of the transversal area of concrete is more advantageous for the eduction of O 2 emissions, and for greater loads the increase of the steel profile produces a more sustainable solution Berndt (2015) The use of smaller resistances is advantageous in relation to CO 2 emissions; the choice of the concrete mixture strongly influences the magnitude of the CO 2 emissions Yang et al (2015) The intensity of CO 2 emissions gradually decreases as Portland cement is replaced by complementary cementitious materials (up to 20%) García-Segura et al (2014) In comparison to Portland cement, despite the reduction in CO 2 capture and life time, 80% blast furnace slag cement emitted 20% less CO 2 per year Cabello et al (2016) To reduce the environmental impact generated by a structure, the focus should be on phases of production of raw materials, transportation and production of concrete Oliveira et al (2014) It is not appropriate to base decisions on the emissions of concrete solely on the strength of the concrete and the type of cement used, since the variations are significant Paya-Zaforteza et al (2009) Minimization of embedded CO 2 emissions and economic cost seem to be highly related Park et al (2013) Reducing the amount of steel and increasing the amount of concrete can be an effective way to reduce the structural costs and CO 2 emissions of columns Habert and Roussel (2009) It is also possible to combine cement replacement and increase mechanical strength Possan et al (2016) Concrete during its life time can absorb from 40 to 90% of CO 2 emitted in the manufacturing process; the absorption of CO 2 is directly proportional to the surface area of concrete exposed to CO 2 , and influenced by the type of cement and resistance to concrete. Park et al (2014) Increasing the strength of the structural materials used is more efficient in reducing CO 2 emissions and costs than increasing the quantities of structural materials used Collins (2013) If carbonation is ignored, emission estimates can be overestimated by up to 45% depending on the strength of the concrete that was used as well as the type of construction application that incorporates recycled concrete during the second generation Yepes et al (2012) CO 2 emissions and costs are closely related. Thus, acceptable solutions in terms of CO 2 emissions are also feasible in terms of cost and vice versa…”

Comparison of metaheuristics on multi objective (Cost-C02) optimization of RC cantilever retaining walls

“…However, few researches [28] took into account the environmental effects of retaining wall design. In structural engineering, the environmental aspects have been considered in the recent years [28]- [36]. It is concluded from these studies that RC structure designs having economically low-CO2 emission can be obtained even from complex design problems.…”