Abstract

Keywords

1. Introduction

2. Related work

3. Application research of Internet of Things in solar photovoltaic power station monitoring and management system

4. Development of integrated computer-aided design system for solar photovoltaic buildings

5. Conclusion

Declaration of Competing Interest

References

Abstract

At the same time of economic development, the increasing scarcity of energy has had a great impact on people’s development. People’s production and life demand for electricity is also increasing rapidly, and solar power technology has received more and more attention. As a new energy source, solar energy has the advantages of environmental protection and sustainability, and it has no regional restrictions, can be used on-site, and designed to scale. Solar power generation is an important way to use solar energy. As the main component of the grid-connected power generation system, solar grid-connected inverters complete the tracking problem of the maximum power point in the photovoltaic array and transmit electrical energy to the grid through a set of control algorithms. The electrical energy is transmitted to the grid through the inverter, consistent with solar energy. In order to solve the problems of low integration, low energy efficiency, low reliability, high power consumption and lack of effective monitoring measures for solar energy devices. This article starts with the design of the solar cell integrated system, and through detailed analysis of the solar production system and building integrated planning, establishes the shadow radiant energy model of the solar cell system building electrical and solar cell system based on the Internet of Things, and designs an object-based Networked comprehensive auxiliary platform.

1. Introduction

Today’s society is an information society centered on the Internet. Digitization, informationization and world economics are the hallmarks of the current era. With the continuous rapid development of information technology, the process of world economics has been continuously strengthened. The use of computer technology, communication data and the Internet to complete e-logistics and Internet commerce has been widely used in society. The continuous improvement of information technology and information storage is just the prelude to the transformation of the IT industry. The cost of information dissemination is getting less and less, and it is bound to usher in the era of the Internet of Things dominating. As a post-IP product, the Internet of Things is developing rapidly and will become popular in the future. This is a major plan to realize the intelligentization of the world.

Highlights

Abstract

Keywords

1. Introduction

2. Research significance and objectives

3. Experimental program

3.1. Concrete specimens

3.2. Test setup and instrumentation

3.3. Concrete properties and test parameters

4. Results and discussion

4.1. Concrete deformations: Strains and deflections

4.2. Recovery strains

4.3. Deflection recovery

4.4. Analysis of uncracked and cracked concrete beams

5. Conclusions

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgments

References

Abstract

The purpose of this research is to analyse the long-term deformations of reinforced concrete beams made of recycled coarse aggregates (RCA), using four different replacement ratios, 0%, 20%, 50% and 100%. For said purpose, three different loading stages were carried out: firstly, loading and sustained load for 1300 days, secondly, unloading and recovery where the deformations were registered over a one year period, and lastly, testing the concrete beams up to failure in order to analyse the effect of recycled aggregates on pre-cracked concrete members. The results led to the analysis of deformations under sustained load, as well as those produced after removing the load and the performance of pre-cracked members, while identifying the effect of recycled coarse aggregates on concrete performance in terms of plastic deformation, recoverability and concrete stiffness, and also on structural design.

1. Introduction

In recent years, the use of construction and demolition waste as aggregates for structural concrete has been widely studied. Numerous authors have contributed to the increasing knowledge in this field, analysing the structural performance of recycled concrete and its properties, such as mechanical strength, modulus of elasticity, creep and shrinkage or durability [1], [2], [3]. As a result, several expressions and methods have been assessed for the design of structural concrete using recycled aggregates [4], [5], [6], [7], [8], [9], [10], [11], [12]. Most authors deal with the short and long-term behaviour of concrete while considering only the influence of creep and shrinkage [13], [14], [15] and very few include the ageing effect of concrete, its different cracking behaviour or its ability to recover from deformations after a load is varied or removed [16].

As common concrete structures are usually submitted to load variations during their service life, it is important to consider the effect of creep over time, including not only loading periods but also unloading the stages and the recoverability of concrete. As mentioned by Rossi et al. [17] understanding the behaviour of concrete structures is greatly simplified by the numerical modelling of their mechanical behaviour. However, progress needs to be made to predict the long-term behaviour of concrete with sufficient accuracy. In order to determine the deformational mechanism, it is also important to analyse the effect of cracking and residual strain i.e. the irreversible part of strain. Many factors influence deformation and the ability of concrete to recover after unloading. Once the hysteretic recovery has finished, the residual deformation can be defined as plastic deformation. Additionally, it can be assumed that concrete deformations under loading are mainly due to creep, especially for long periods of loading and therefore, the ability of deformations to recover after unloading is closely linked to creep recovery.

Highlights

Abstract

Keywords

1. Introduction

2. Data sources

3. Results

4. Discussion

5. Conclusion

Author statement

Financial disclosure

Declaration of competing interest

Acknowledgments

Appendix A. Survey of adolescents’ travel behavior

References

Abstract

Introduction
The outbreak of COVID-19 has significantly impacted travel behavior. However, few studies have analyzed the impact of COVID-19 on adolescent travel behavior. This article analyzed the impact of COVID-19 on adolescent travel behavior using questionnaire survey data.

Methods
This paper first used confirmatory factor analysis (CFA) to explore the psychological factors related to the adolescents’ perceptions about the severity of COVID-19. The study then established a logit model to study the effects of COVID-19 in different phases (before, during, and after the epidemic peak), demographic characteristics, and the role of psychological factors on their travel behavior.

Results
The results show that the phase of COVID-19 did not significantly impact the adolescents’ choice of short-distance travel. The frequency of outings per week, the number of exercise sessions per week, and willingness to travel by public transportation decreased significantly in the outbreak phase. Meanwhile, the perception of the severity of COVID-19 significantly impacted adolescent travel behavior.

Conclusion
This research demonstrates that COVID-19 has led adolescents to reduce their frequency of outings, and they try not to use public transportation. Adolescents appear to be traveling more cautiously in the outbreak phase and the post-epidemic phase.

1. Introduction

1.1. Impact of COVID-19 on travel behavior
Due to the high infectious power and fatality rate, the World Health Organization (WHO) set the risk level of the coronavirus (COVID-19) as “very high” in 2020 (WHO, 2020). According to the S.I.R. model (Susceptible Infectious Recovered Model), the epidemic includes 5 phases: the normal phase, the incubation phase of the epidemic, the outbreak phase, the post-epidemic phase, and the recovery and improvement phase (Ye et al., 2020). The normal phase is a phase when there is no pandemic to create interference; during these normal times, people in the cities of China usually travel by public transit. During the incubation phase, a small number of infected people appear, but the infection has not spread. During the outbreak phase, the number of infected people increases rapidly, and the risk of cross-infection increases rapidly. In the post-epidemic phase, the number of newly infected people gradually decrease, and the number of existing infected people declines. In the recovery and improvement phase, the epidemic is controlled, but it is difficult to determine whether there are still asymptomatic infections. The epidemic outbreak phase in China ranged from December 2019 to March 2020. China has gradually entered and sustained the post-epidemic phase since March 2020.

The sudden epidemic disrupted people’s lives and significantly impacted the transportation industry and urban transportation systems (Fatmi, 2020). According to the Ministry of Transport of China, only 283 million passengers used the transportation system from January 25 to February 14, 2020. This was an average of 13.49 million passengers per day, representing a year-on-year decrease of 82.3%.1

Abstract

Keywords

References

Abstract

The article is devoted to the study of the main regularities of the normal cracks level formation in reinforced concrete elements and structures. A critical analysis of the latest publications related to the theme of these studies has been carried out. The main characteristics of prototypes, the conditions for their manufacture and storage are given. Based on the experimental studies results, it has been established that in the real design of bending reinforced concrete elements, when calculating their crack resistance, one can restrict oneself to only two levels of normal cracking. A statistical comparison of the calculation results using the author’s and other methods with experimental data confirmed the effectiveness of those calculation methods in which the crack formation step is directly related to the basic laws and parameters of reinforcement to concrete adhesion.

1. Introduction

In general, it is known that the processes of cracks formation and development, including normal ones, significantly affect the operational properties of reinforced concrete elements and structures. Therefore, it is quite obvious that the issues of their crack resistance will always remain one of the main issues in the reinforced concrete deformation theory. And with the introduction of deformation methods for calculating reinforced concrete elements and structures into modern design practice, they acquire even greater weight and relevance. Indeed, using deformation models, it becomes possible to more accurately reproduce the real stress-strain state of reinforced concrete elements and structures in their deformation process.

At the same time, the results of experimental studies indicate that the cracks formation and development in reinforced concrete elements is multilevel and leads to a gradual disruption of the reinforcement with tensioned concrete interaction. Under such circumstances, it would be advisable to build a general methodology for calculating the normal cracks formation and opening on the basis of the reinforcement to concrete adhesion defining laws direct involvement. Otherwise, the calculation of the normal cracks opening width according to the Thomas (1936) hypothesis will continue to remain predominantly declarative. This is due to the fact that it is extremely difficult to perform this calculation from the standpoint of the concrete and reinforcement mutual displacements sequential accumulation. Since the actual dependence of the reinforcement and concrete mutual displacements is very complex and cannot be described by a single function, its direct integration in most cases is practically impossible. However, the calculation of the normal cracks opening width can be significantly simplified if the cracks step and their opening width are directly related to the reinforcement to concrete adhesion forces and take into account that the cracking process is multilevel. Therefore, the possibility and expediency of such an approach to the calculation of the main parameters of reinforced concrete elements and structures crack resistance requires special studies.

Abstract

Keywords

1. Introduction

2. Experimental program

3. Test results and discussions

4. Predictions of shear capacities

5. Conclusions

Declaration of Competing Interest

Acknowledgments

Data availability

References

Abstract

This study investigated the shear performance of large-scale green concrete (GC) beams reinforced with basalt fiber reinforced polymer (BFRP) bars and stirrups. The GC concept was employed in this study by partially substituting the cement content with 35% by weight of industrial by-products (fly ash and silica fume). The main test variables were the reinforcement ratio, the shear span to depth ratio (a/d), and the spacing between stirrups. Three beams were transversely reinforced with steel stirrups to serve as a control. Experimental results indicated that the ultimate shear capacity was significantly increased at higher reinforcement ratios. Such effect was less pronounced in beams with reduced spacing between stirrups. In addition, the BFRP stirrups were effective in reducing the diagonal shear crack width and increasing the ultimate shear capacities of the tested beams. On the other hand, beams with a higher a/d ratio have shown higher deflection and reduced ultimate shear capacity. Comparing the experimental results of the current study with the current design codes and guidelines provisions, the CSA-S806-12 has shown the best predictions with a mean experimental to predicted shear (Vexp/Vpre) ratio of 1.43 ± 0.29.

1. Introduction

There is a growing motivation from researchers and construction practitioners towards the implementation of FRP composites as an alternative to conventional steel reinforcement [1], [2], [3]. Keeping in mind that the corrosion in steel is one of the main reasons behind the deterioration of reinforced concrete (RC) structures [4], the use of anti-corrosive FRP bars can play a crucial role in addressing the corrosion issue in RC structures. Nowadays, basalt FRP (BFRP) bars are gaining more popularity in the literature due to their lower price than carbon FRP bars, and their comparable mechanical features to the glass FRP (GFRP) bars [5], [6], [7], [8], [9], [10]. Moreover, BFRP bars have shown better thermal resistance compared to GFRP bars [11]. The shear behavior of RC beams reinforced with GFRP bars and stirrups has been well documented in the literature [12], [13], [14], [15], [16], [17]. However, a few studies have investigated the shear behavior of RC beams reinforced with BFRP bars [2], [18], [19]. For instance, Tomlinson and Fam [20] demonstrated that for BFRP-RC beams without stirrups, the shear strength has increased by 39.7% as the reinforcement ratio went from 0.39% to 0.84%, whereas it was increased by 47% with stirrups. Likewise, Issa et al. [2] also noted that the BFRP-RC beams with BFRP stirrups exhibited much higher shear capacity than beams with no BFRP stirrups. However, their effect was less pronounced at higher reinforcement ratios. They also observed a significant increase in the shear capacity of 32% when the reinforcement ratio was increased from 0.8 to 1.3%.

Abstract

Keywords

1. Introduction

2. Experimental design

3. Results and discussion

4. Conclusion

5. Data availability

Declaration of Competing Interest

Acknowledgments

References

Abstract

Sustainability in the construction is becoming a major challanges due to the depletion of natural resources and the avialibility of landfill capacity. Additionally, there is an urgent need to improve the properties of concrete and produce environmentally friendly green concrete. From these points, the effect of varying the water-to-cement (w/c) ratios and the soaking time of glass powder (GP) on the activation of the pozzolanic reactivity and the mechanical properties of green concrete were examined. Two w/c ratios (0.6 and 0.7), two glass contents (5% and 30%), and six GP soaking times werer used in this study. The new mixing method (NMM) was used, in which the GP is partially dissolved in water and more Na+ ions than Ca+2 are formed in solution since Na+ ions have higher mobility than Ca2+ ions. The results indicate that greater normalized compressive strength (CS) is achieved under a w/c ratio of 0.7 for 5% and 30% GP content with soaking time of 6 h. This increase is correlated with the formation of more nucleation sites due to the growth of calcium silicate hydrate rather than portlandite. The relative activation index calculation showed that the 30% GP mixes have higher values than 5% GP mixes.

1. Introduction

Sustinable use of natural resources and effective waste utilization in green concrete is becoming increasingly necessary as natural resources become more limited. Further, the exponentially demand of individual habitaion has led to increased demand for new construction. Fabricating new bottles, flasks, or other tools from glass waste is infeasible due to the amount of energy required (collection, transportation and melting). Therefore, researchers have aimed to reuse crushed waste glass or glass powder (GP) as an aggregate in concrete or as a replacement for cement. The amorphous structure and chemical composition of GP and some types of ash are similar to those of cement, and thus induce a similar pozzolanic effect in concrete. The pozzolanic reaction involves the consumption of the weaker portlandite (CH) to produce calcium silicate hydrate (C-S-H), which has a higher CS and density [1–4].

The traditional or conventional mixing method (TMM), in which GP and water are directly mixed into the concrete mixture, has been used extensively to investigate the effect of using GP in concrete [5]. In the new mixing method (NMM), the GP is presoaked in water to partially dissolve it before it is mixed into the concrete mixture, thus activating the pozzolanic reaction earlier in the life (at 90 days for concrete made with TMM) of the concrete via hydrolysis of the GP and producing stronger concrete than the control [6,7].

The mechanical properties of fresh and hardened concrete using GP depend on the chemical composition, the diameter of the GP particles, and the curing conditions [8,9]. The mixing method used also contributes to the mechanical properties; the NMM allows for the partial dissolution o