Advances in Civil Engineering
ISSN / EISSN : 1687-8086 / 1687-8094
Published by: Hindawi Limited (10.1155)
Total articles ≅ 3,977
Latest articles in this journal
Advances in Civil Engineering, Volume 2021, pp 1-15; https://doi.org/10.1155/2021/1013188
The use of stainless steel bars can improve the durability and sustainability of building materials. Through the static performance test, this research analyzes the failure pattern and bearing performance of bias stainless steel reinforced concrete (SSRC) column. The influence of reinforcement ratio of longitudinal bars and eccentricity on the mechanical performance of specimens was studied. Different constitutive models of stainless steel bars were used to calculate the ultimate bearing capacity of the section of the column under eccentric compression column. Based on the experimental results, a method to modify the expression of the design specification is proposed. And, the results were compared with the test results. The results showed that the damage patterns and failure modes of SSRC columns are essentially the same as those of traditional reinforced concrete columns. The bearing capacity of SSRC columns rises with the increase in the longitudinal reinforcement ratio, and the ductility of the specimens is enhanced. The ultimate load of the specimen decreases with the rise in eccentricity but the deflection increases gradually. The strain distribution of the mid-span section of the SSRC column conforms to the plane section assumption. The bearing capacity of the specimen can be analyzed by referring to the calculation method of the specification, and some parameters in the calculation formula of the specification are modified to adapt to the design and calculation of the SSRC column.
Advances in Civil Engineering, Volume 2021, pp 1-12; https://doi.org/10.1155/2021/7951646
Stress-strain curve can accurately reflect the mechanical behavior of materials, and it is very important for structural design and nonlinear numerical analysis. Some cube and prism specimens were made to investigate the physical and mechanical properties of steel fiber reinforced alkali activated slag concrete (AASC); test results show that the strength, Young’s Elastic Modulus, and Poisson’s ratio all increase with the increase of steel fiber content. The steel fiber reinforced AASC shows an excellent postcracking behavior. Damage evolution parameter (D) was used to describe the formation and propagation of cracks, and continuum damage evolution model of steel fiber reinforced AASC was established by Weibull and Cauchy distribution. The establishing model can well describe the geometric characteristics of the key points of the concrete materials stress-strain curve. Finally, the accuracy of the model was verified by comparing the test stress-strain relationship curve of steel fiber reinforced AASC.
Advances in Civil Engineering, Volume 2021, pp 1-14; https://doi.org/10.1155/2021/6670559
Fire is the most deadly risk during tunnel operation. Early rapid response and a reasonable smoke control plan are very important to evaluate tunnel fire performance. In order to study the relevant time factors for smoke management in a highway tunnel, firstly, the logical sequence and time of the fire alarm system (FAS) startup are investigated and analyzed. Then, according to the one-dimensional fluid mechanics model, the time rule of adjusting the airflow field in the tunnel from the normal operation stage to the emergency ventilation state is analyzed theoretically. Finally, the abovementioned theoretical formulas are verified through the employment of model experiments. The analysis shows that the time that passes from the start of the fire to when the exhaust fan is activated is close to 3 minutes. The time required to form a stable critical wind speed, however, is close to 7 minutes, which is longer than the 5 minutes it takes for the fire to reach its maximum temperature. Due to inertia, it takes about 0.5 to 2 minutes for the air velocity in tunnels of different lengths to drop from the traffic piston wind speed to the critical wind speed. If reverse smoke extraction is required, however, the duration is between 3 and 8 minutes. The conclusion is of guiding significance for the preparation of the emergency linkage control scheme for tunnels, as well as for the setting of initial boundary conditions for CFD fire simulations.
Advances in Civil Engineering, Volume 2021, pp 1-19; https://doi.org/10.1155/2021/6643064
Dynamic compaction machine (DCM) is a widely adopted ground reinforcement technology. However, dynamic compaction energy has a very significant impact on the surrounding environment. At present, the research on the impact of dynamic compaction mainly focuses on the effect of the tamping behavior of a single compactor in the working state, whereas the research on the impact of multiple compactors working jointly is rare. To study the impact of the dynamic compaction energy of multiple compactors working jointly on the surrounding environment, the dynamic response model for multiple compactors working in the same field was established based on the explicit dynamic analysis module in ABAQUS. The validity of the model was verified by comparison with the measured data. Based on this, the impact of the dynamic compaction energy of multiple compactors with different working conditions in terms of the arrangement, spacing, and working time interval was analyzed. The results showed that the arrangement and spacing of the compactors had a remarkable influence on the distribution of the dynamic compaction energy in the surrounding environment. Under the condition of multiple compactors working with a time interval of less than 10 s, the impact of the superimposed dynamic compaction energy due to the interaction of multiple compactors had to be considered.
Advances in Civil Engineering, Volume 2021, pp 1-13; https://doi.org/10.1155/2021/2977428
Over the last decade, there has been a surge in research into possible cement substitute materials in concrete that are environmentally friendly, cost-effective, and socially beneficial. The alternatives include industrial and agricultural wastes, and their potential advantages can be achieved through recycling, repurposing, and renewing processes. With the use of these wastes as additional and replacement materials, significant energy savings and a reduction in cement use can be achieved, which helps to reduce carbon dioxide (CO2) emissions in the environment. Therefore, the use of rice husk ash (RHA) and wheat straw ash (WSA) as ternary cementitious material (TCM) in concrete can help reduce the impact on the environment and minimize the use of Portland cement (PC) in the concrete mixture. This research work is performed on the concrete blended with 0%, 5%, 10%, 15%, and 20% of RHA and WSA as TCM in the mixture. However, the purpose of this experimental work is to investigate the influence of RHA and WSA as TCM on the fresh (slump), physical (water absorption and density), and hardened properties (compressive strength, splitting tensile strength, and flexural strength) and drying shrinkage of concrete. In this regard, a total of 240 concrete samples (cylinders, cubes, and beams) were prepared with 1 : 2 : 4 mix proportions at 0.50 water-cement ratio and cured at 7 and 28 days, respectively. Moreover, the workability of green concrete is getting reduced as the quantity of TCM increases in the mixture. Besides, the compressive strength, splitting tensile strength, and flexural strength are enhanced by 12.65%, 9.40%, and 9.46% at 10% of TCM (5% RHA and 5% WSA) on 28 days consistently. Furthermore, the density and water absorption of concrete are reduced with the increase in the dosages of TCM on 28 days, respectively. In addition, the drying shrinkage is reduced with the increase in the quantity of TCM in concrete.
Advances in Civil Engineering, Volume 2021, pp 1-13; https://doi.org/10.1155/2021/1264270
The horizontal bracing forces of column-bracing systems derived from past studies and current design codes were considered only located at middle of columns. Actually, the horizontal braces used to reduce the out-of-plane effective column lengths are frequently designed not to locate at middle of columns. In this paper, a large number of column-bracing systems with the horizontal braces unlocated at middle of columns were modelled and analyzed using the finite element method, in which the random initial geometric imperfections of both the columns and the horizontal braces unlocated at middle of columns were well considered by the Monte Carlo method. Based on the numerical calculations, parametric analysis, and probability statistics, the probability density function of the horizontal bracing forces was found, so that the corresponding design forces of horizontal braces unlocated at middle of columns were proposed which were compared with the design mid-height horizontal bracing forces in the previous study and the relevant codes. The results indicate that the design forces of the horizontal braces located at 0.6 column height are smaller than the mid-height horizontal bracing forces in the previous study while the design forces of horizontal braces located at 0.7 column height are larger than the mid-height horizontal bracing forces in the previous study. The proposed design forces of the horizontal braces located and unlocated at middle of columns are both smaller than the mid-height horizontal bracing forces stipulated in GB50017-2017, Eurocode 3-1992, and AS4100-1998. The above conclusions provide references for the engineering applications and further related code revisions.
Advances in Civil Engineering, Volume 2021, pp 1-10; https://doi.org/10.1155/2021/5942838
Hydrostatic levelling system (HLS) is widely used to monitor the settlement of major projects, such as high-speed railways, bridges, tunnels, dams, and nuclear power plants; ambient temperature is the most important influencing factor in the actual engineering settlement detection process. In order to systematically study the influence of ambient temperature TA on the test accuracy of the HLS, a test platform was built in the ambient temperature laboratory, and the influence of factors, including the amount of TA change, the rate of increase/decrease of TA, the expansion coefficient of the connecting pipe, and the distance of the measuring point, on the HLS test accuracy was quantitatively analyzed. The test results show that the elevation of a single HSL case has a linear correlation with the ambient temperature; when the temperature rise rate is greater than 0.1°C/min, the measured data are distorted due to incomplete development of material expansion. The temperature influence coefficient of a single HSL case is linearly related to the expansion coefficient deviation between the refrigerant and pipe; the test error of the double HLS case caused by TA is attributed to the expansion coefficient deviation of the pipe and the refrigerant between the base station and the measuring point. The relative temperature influence coefficient increases as distance measurement increases, and the HLS test error caused by TA will maintain a constant value when the distance measurement exceeds a certain value.
Advances in Civil Engineering, Volume 2021, pp 1-15; https://doi.org/10.1155/2021/9949720
The settlement of the widening of soft soil subgrade highways is typically associated with different treatment positions of cement mixed piles. In order to overcome this, in the current paper we employ the finite element method to simulate and analyze the influence of piles under an existing road slope and under an existing subgrade and new embankment on the settlement characteristics of the subgrade and foundation. In particular, we focus on the influence of the pile length and pile spacing on the subgrade and foundation settlements based on a northern high-speed reconstruction and expansion project. The subgrade and foundation soils in the finite element analysis are considered to be homogeneous, continuous, and isotropic elastoplastic materials. The Mohr–Coulomb ideal elastoplastic constitutive model is implemented as the constitutive soil model. The impact of piles under an existing subgrade and new embankment on the settlement is observed to be more significant than that of piles under the existing road slope. Moreover, the subgrade and foundation settlements increase with the pile spacing under the existing road slope and under the existing subgrade and new embankment. More specifically, an increase of the pile spacing from 200% to 400% of the pile diameter is associated with an increase in the maximum settlement of the foundation surface from 1.76 to 1.85 cm (existing road slope) and from 1.44 to 1.96 cm (existing subgrade and new embankment). In addition, the subgrade and foundation settlements decrease for increasing pile lengths under the existing road slope and under the existing subgrade and new embankment, the pile length increases from 4.7 to 9.2 m, and the maximum foundation surface settlement is reduced from 6.2 to 5.52 cm and from 9.73 to 5.43 cm, respectively. The results can provide reference for future subgrade widening projects.
Advances in Civil Engineering, Volume 2021, pp 1-8; https://doi.org/10.1155/2021/1788691
To verify the effectiveness of the suction-based method for improving flutter stability of long-span bridges, the forced vibration experiments for extracting the flutter derivatives of a section model with and without suction were performed, and the corresponding critical flutter wind speeds of this structure were calculated out. It is shown by the experiment that the flutter stability of the bridge depends on suction configuration. As the suction holes locate at the leeward side of the model, the critical flutter wind speed can attain maximum under the same suction velocity. In the analytical results, it is remarkably effective that the suction control improves the long-span bridge flutter stability.
Advances in Civil Engineering, Volume 2021, pp 1-11; https://doi.org/10.1155/2021/9448436
Combined vacuum and surcharge preloading has gradually been widely used because of its advantages of low cost, green environmental protection, and good treatment effect. The conventional prefabricated vertical drain presents obvious defects in vacuum preloading treatment, such as obvious silting, serious bending of the drainage board, large attenuation of vacuum degree of drainage board along the depth, long construction period, and so on, which affect the final reinforcement effect. In this paper, the MIDAS finite element simulation of combined vacuum and surcharge preloading of prefabricated vertical drains (PVDs) and prefabricated horizontal drains (PHDs) is established through the comparative experiment of the engineering field. The comparative experimental study is carried out from the aspects of the vertical settlement, horizontal displacement, and pore water pressure. The results show that under combined vacuum and surcharge preloading, the consolidation effect of soft soil with PHDs is better than that with PVDs. When PHDs are used, the vertical settlement increases by 7.2% compared with PVDs; the horizontal displacement is larger; and the pore water pressure dissipates faster. This is because when the PHDs are adopted, the consolidation direction of the soil is consistent with the direction of the vacuum suction, which is mainly caused by vertical settlement. With the consolidation, the spacing between PHDs is gradually shortened, and the drainage distance is reduced, which can effectively reduce the consolidation time and improve the reinforcement effect of the soil. In addition, the PHDs can move downward uniformly with the soil during the consolidation process and have almost no bending deformation, which makes the vacuum transfer more uniform and effective.