Sustainability assessment of reinforced concrete beams under corrosion in life-span utilizing design optimization

Abstract

Minimizing the economic and environmental burden is considered the most critical goal in sustainability assessments, the best approach of which is to implement optimization. In this research, the life-span design of corroded reinforced concrete (RC) beams was addressed through cost and carbon dioxide (CO2) footprint optimizations. Accordingly, the cost-optimized and CO2 footprint-optimized sections were obtained in the presence of corrosion. Displacements were then calculated using a neural network trained on the basis of finite element (FE) modeling results. In addition, the number of required modeling efforts was ensured in key model detection using the Taguchi design containing six control factors of rebar corrosion percentage, beam section height and width, concrete compressive strength, steel yield stress, and reinforcement diameter. Two coding languages were used, in parallel, in order to avoid possible errors and increase accuracy, the results of which were observed to be practically identical. Also, the regression plots displayed an overall R-value of 0.999, indicating the high accuracy of the applied neural network. In addition, the FE modeling results were verified with several experimental RC beams in the literature in terms of load-displacement curves. The results of the numerical approach were in good agreement with the experiments. Furthermore, the FE outputs were compared to those of the neural network demonstrating a relatively good accord. The results of the proposed methodology were found to be more favorable than the previous studies, with a significant cost savings of more than 22%. In this respect, the optimization process was so well balanced that the CO2 footprint resulting from the cost-optimized section was less than 3% different than that from the CO2 footprint-optimized section. Similarly, the cost obtained from the CO2 footprint-optimized section was less than 4.5% different compared to that obtained from the cost-optimized section. It was also revealed that the most economical sections not only do not lead to more pollution, but they are almost the cleanest ones. According to the cost optimization results, short span beams (up to 8 m) were recommended to be designed without regarding corrosion at first. On the other hand, considering the anticipated corrosion from the beginning of the design process is more economical for beams with longer spans (longer than 9 m).