ترجمه مقاله نقش ضروری ارتباطات 6G با چشم انداز صنعت 4.0
- مبلغ: ۸۶,۰۰۰ تومان
ترجمه مقاله پایداری توسعه شهری، تعدیل ساختار صنعتی و کارایی کاربری زمین
- مبلغ: ۹۱,۰۰۰ تومان
This paper describes a methodology to optimize cost and CO2 emissions when designing precast–prestressed concrete road bridges with a double U-shape cross-section. To this end, a hybrid glowworm swarm optimization algorithm (SAGSO) is used to combine the synergy effect of the local search with simulated annealing (SA) and the global search with glowworm swarm optimization (GSO). The solution is defined by 40 variables, including the geometry, materials and reinforcement of the beam and the slab. Regarding the material, high strength concrete is used as well as self-compacting concrete in beams. Results provide engineers with useful guidelines to design PC precast bridges. The analysis also revealed that reducing costs by 1 Euro can save up to 1.75 kg in CO2 emissions. Finally, the parametric study indicates that optimal solutions in terms of monetary costs have quite a satisfactory environmental outcome and differ only slightly from the best possible environmental solution obtained.
1. Introduction
Nowadays, global warming and the gradual deterioration of our planet are both causes for concern. Within the global development context, the environmental impact of construction activities is significant. While the embodied greenhouse gas (GHG) emissions were limited by the Kyoto Protocol, the construction industry continues to generate 40–50% of all global GHG emissions [1]. According to the Environmental Protection Agency (EPA), buildings are responsible for 38% of the entire carbon dioxide (CO2) emissions of the United States [2]. Furthermore, the cement industry produces 5% of world's GHG emissions [3]. Consequently, it is not enough to build cheaply and efficiently; construction should save non-renewable natural resources and respect the environment. This has promoted research related to sustainability in the field of construction.
5. Conclusions
In this paper, a hybrid method combining simulated annealing with glowworm swarm optimization (SAGSO) algorithms is presented and employed to optimize PC precast road bridges formed by two isostatic beams with a double U-shaped cross-section. Two objective functions are considered: the CO2 emissions and cost of the PC bridge at the different stages of material production, transportation and construction. The extensive computational experiments with a set of five span lengths for the bridge indicate that SAGSO is an efficient algorithm for the advanced automatic design of real PC precast bridges used in road construction that reduced the CO2 emissions and the cost. The analysis reveals that CO2 emissions and cost are closely related and, as a rule of thumb, a euro reduction in cost results in savings of 1.75 kg in CO2 emissions. Thus, the solutions which are acceptable for emissions are also viable in terms of cost and vice versa. The parametric study shows a good correlation for both the depth of the beam, the thickness of the slab, the number of strands and the characteristic compressive strength of concrete, which can be useful for the day-to-day design of PC precast bridges. Greater and lesser amounts of passive reinforcement are observed in the beams and the slab, respectively, for CO2-optimization. Regarding concrete, larger volumes are used when optimizing the emission. It must be noted that the repetition of the PC structures increases the economic savings. A cost sensitivity analysis applied to a PC precast bridge with a 35 m span indicates that a maximum 20% rise in steel costs leads to a 10.27% increase in the cost, while a 20% rise in concrete costs only increases the cost up to 3.41%; surprisingly, the variation in the volume of concrete is almost insensitive to its rising price. To conclude, this hybrid method, described herein, is quite flexible and can easily be modified and extended so that structural engineers may reduce CO2 emissions in their structural designs.