Large numbers of basic transceiver stations,where the telecommunication room is one of the main components,comprise an important part of the telecommunication system.After earthquakes,considerable economic loss from t...Large numbers of basic transceiver stations,where the telecommunication room is one of the main components,comprise an important part of the telecommunication system.After earthquakes,considerable economic loss from telecommunication systems is often associated with seismic damage and functional loss of the telecommunication room.However,research related to this has been limited.In this study,shaking table tests were conducted for a full-scale typical telecommunication room,including a light-steel house and the necessary communication and power supply equipment.The tests not only focused on the seismic damage to all the structures but also considered the functions of the communication and power supply of the equipment.The interactions between these facilities and their effects on communication function were also investigated.Compared with the damage to structures,the interruption of the power supply due to earthquakes is a weak link.Finally,the damage indexes,together with their threshold values of different damage states for the communication and power supply equipment,were derived from the test results.The results of this research can contribute to the literature gaps regarding seismic performance studies of telecommunication rooms,and can serve as a valuable reference for future research on its seismic fragility and economic losses evaluation.展开更多
In an effort to investigate and quantify the patterns of local scour,researchers embarked on an in-depth study using a systematic experimental approach.The research focused on the effects of local scour around a set o...In an effort to investigate and quantify the patterns of local scour,researchers embarked on an in-depth study using a systematic experimental approach.The research focused on the effects of local scour around a set of four piles,each subjected to different hydromechanical conditions.In particular,this study aimed to determine how different attack angles—the angles at which the water flow impinges on the piles,and gap ratios—the ratios of the spacing between the piles to their diameters,influence the extent and nature of scour.A comprehensive series of 35 carefully designed experiments were orchestrated,each designed to dissect the nuances in how the gap ratio and attack angle might contribute to changes in the local scour observed at the base of pile groups.During these experimental trials,a wealth of local scour data were collected to support the analysis.These data included precise topographic profiles of the sediment bed around the pile groups,as well as detailed scour time histories showing the evolution of scour at strategic feature points throughout the test procedure.The analysis of the experimental data provided interesting insights.The study revealed that the interplay between the gap ratio and the attack angle had a pronounced influence on the scouring dynamics of the pile groups.One of the key observations was that the initial phases of scour,particularly within the first hour of water flow exposure,were characterized by a sharp increase in the scour depth occurring immediately in front of the piles.After this initial rapid development,the scour depth transitioned to a more gradual change rate.In contrast,the scour topography around the piles continuously evolved.This suggests that sediment displacement and the associated sculpting of the seabed around pile foundations are sustained and progressive processes,altering the underwater landscape over time.The results of this empirical investigation have significant implications for the design and construction of offshore multi-pile foundations,providing a critical reference for engineers and designers to estimate the expected scour depth around such structures,which is an integral part of decisions regarding foundation design,selection of structural materials,and implementation of scour protection measures.展开更多
In order to characterize the impacts of key factors on the low-temperature fracture performance of dense-graded asphalt concrete, the virtual bending fracture test is simulated by using the discrete element method( DE...In order to characterize the impacts of key factors on the low-temperature fracture performance of dense-graded asphalt concrete, the virtual bending fracture test is simulated by using the discrete element method( DEM) and emulation software PFC3D( particle flowcode in three-dimension). A virtual specimen generation procedure consisting of aggregate gradation, irregular clumps, asphalt mortar and air void content is performed based on the random generation algorithm and irregular coarse aggregates library. Then, the virtual fracture test is conducted after adding the micro mechanical contact models to the specimen, and the validity of virtual modeling is verified by the comparison of simulation test data and lab test data. Additionally, an orthogonal test is designed to investigate the impacts of the volume fraction of coarse aggregates and air voids, stiffness of coarse aggregates and asphalt mortar, internal bond strength of asphalt mortar and distribution of coarse aggregates and air voids on low-temperature fracture performance based on virtual simulation.The results showthat all the factors have effects on fracture performance to various degrees, while the value of the bond strength of asphalt mortar is found to be the most important determinant of tensile strength and strain-energy density. The volume fraction of coarse aggregates is considered to be the most important determinant of tensile strain. Therefore, to obtain a high low-temperature fracture performance of densegraded asphalt concrete, it is important to consider the microstructure and properties of asphalt mortar and aggregates.展开更多
Three transformation models (Bursa-Wolf, Molodensky, and WTUSM) are generally used between two data systems transformation. The linear models are used when the rotation angles are small; however, when the rotation a...Three transformation models (Bursa-Wolf, Molodensky, and WTUSM) are generally used between two data systems transformation. The linear models are used when the rotation angles are small; however, when the rotation angles get bigger, model errors will be produced. In this paper, we present a method with three main terms:① the traditional rotation angles θ,φ,ψ are substituted with a,b,c which are three respective values in the anti-symmetrical or Lodrigues matrix; ② directly and accurately calculating the formula of seven parameters in any value of rotation angles; and ③ a corresponding adjustment model is established. This method does not use the triangle function. Instead it uses addition, subtraction, multiplication and division, and the complexity of the equation is reduced, making the calculation easy and quick.展开更多
The steel-bamboo composite structure is a newly developed structure,combining phyllostachys pubescens(also called Moso bamboo)plywood and cold-formed thin-walled steel with structural adhesive.The reliability of steel...The steel-bamboo composite structure is a newly developed structure,combining phyllostachys pubescens(also called Moso bamboo)plywood and cold-formed thin-walled steel with structural adhesive.The reliability of steelbamboo interface is the premise of composite effect.13 specimens were prepared to investigate the failure modes and mechanism of the steel-bamboo interface on the basis of push-out test,and the strain difference analysis method was proposed to study the distribution of shear stress.The results show that the main failure modes of steel-bamboo interface are adhesion failure and splitting of bamboo plywood.The shear stress is not evenly distributed along the longitudinal direction of the interface,showing a shape of“larger at two ends and smaller in the middle”.The lower end of the interface is the initial location of the interface failure and the shear stress concentration degree is positively correlated with the thickness of the externally bonded bamboo plate.The shear resistance of steel-bamboo interface can be enhanced by improving the adhesion between steel and structural adhesive and ameliorating the quality of bamboo products.展开更多
In view of the collapse of a deep excavated foundation pit of the Xianghu subway underground station in Hangzhou of China,the main features of the accident are analyzed,and the induced factors of the accident are summ...In view of the collapse of a deep excavated foundation pit of the Xianghu subway underground station in Hangzhou of China,the main features of the accident are analyzed,and the induced factors of the accident are summarized. Then,a 3-D FEM analysis model is created to demonstrate the soil-support structures interaction system,and the effect of the main factors,such as the volume replacement ratio of the bottom soil reinforcing,the asymmetric ground overload,the embedded depth of the diaphragm wall,the shear strength of the bottom soils disturbed by the construction,and the excessive excavation of the bottom soil,are analyzed and compared. The results show that the ineffective original reinforcement plan for the bottom soft soil is the most prominent factor for the accident,and the disturbance effect of the deep excavation on the shear strength of the bottom soft soil is another significant factor for the accident. Meanwhile,if the reinforcement of the bottom soft soil is canceled,an appropriate extension of the diaphragm retaining walls to the under lying harder soil layer can also effectively prevent the collapse of the deep excavated foundation pit. In addition,the partly excessive excavation in the process has a great influence on the axial force of the most nearby horizontal support but few effect on the stability of the diaphragm wall. Thus,the excessive excavation of the bottom soils should not be the direct inducing factor for the accident. To the asymmetric ground overload,it should be the main factor inducing the different damage conditions of the diaphragm walls on different sides. According to the numerical modeling and actual engineering accident condition,the development process of the accident is also identified.展开更多
The adsorption behaviors and dispersing properties of polycarboxylate superplasticizer(PCE) with different functional groups were systematically analyzed to reveal the theory and methods of modifying PCE molecular str...The adsorption behaviors and dispersing properties of polycarboxylate superplasticizer(PCE) with different functional groups were systematically analyzed to reveal the theory and methods of modifying PCE molecular structures and regulating PCE performances. By substituting carboxylic groups with sulfonic groups, ester groups or acylamino groups, respectively, modified PCEs with different functional groups were synthesized. Results show that introducing low amount of ester groups or sulfonic groups into the PCE molecules has no negative effects on the fluidity of cement paste, while introducing acylamino groups into PCE molecules significantly weakens the fluidity of cement paste. At low amount(when the molar ratio of sodium methallyl sulfonate to TPEG is lower than 0.4), the rapid adsorption of sulfonic groups onto the cement particles contributes to the high dispersing performance of the sulfonic group modified PCEs. When the substitution ratio of acrylic acid by sulfonic acid is higher than 0.4, the viscosity and the yield stress of cement paste increases sharply. Redundant sulfonic groups lead to the excessive charge density of the PCE, which contributes to the inhomogeneous adsorption on the cement grains and hence results in the decline of the dispersing performance. Substitution of carboxylic group by acylamino group or ester group slightly changes the viscosity as well as the yield stress of cement paste. Introducing sulfonic group into PCE molecule improves the adsorption behavior of PCEs, while introducing ester group or acylamino group into PCE depresses the adsorption properties.展开更多
Biaxial compression tests on plain concrete suffered high temperature ranging from 200 ℃ to 600 ℃ were carried out using the large-scale dynamic-static tri-axial concrete test system at the State Key Laboratory of C...Biaxial compression tests on plain concrete suffered high temperature ranging from 200 ℃ to 600 ℃ were carried out using the large-scale dynamic-static tri-axial concrete test system at the State Key Laboratory of Coastal and Offshore Engineering with designated stress ratios of 0, 0.25, 0.5, 0.75 and 1, respectively. The measured strength and strain were reported and the changes in both biaxial compressive failure envelopes and strains at peak stresses were analyzed. The regressive equation of initial elastic modulus in the biggest principal compressive stress direction was derived from test results. With the published results from previous biaxial tension-compression experiments, a three-parameter failure criterion has been proposed. A biaxial nonlinear elastic incremental constitutive model was developed for the compressive stress directions by using the equivalent uniaxial strain values deduced from test results. Analytical results obtained from the proposed biaxial constitutive model achieve good agreement with the experimental results.展开更多
Effects of organosilane-modified PCE (OS-PCE) on the fluidity and the hydration properties of cement-fly ash (FA) composite binder were systematically analyzed.The experimental results show that OS-PCE possesses respe...Effects of organosilane-modified PCE (OS-PCE) on the fluidity and the hydration properties of cement-fly ash (FA) composite binder were systematically analyzed.The experimental results show that OS-PCE possesses respectively 36.98% and 36.67% higher saturated adsorption amount on cement and FA,in comparison with ordinary PCE,and can contribute to higher fluidity of cement-FA composite binder.The addition of OS-PCE retards hydration process of cement-FA composite binder proportionally with the dosage of OS-PCE,but promotes the hydration kinetics of the composite binder.The reactivity enhancement is attributed to the well-dispersed FA by OS-PCE,which provides more nucleation sites for the reaction of heterogeneous C-S-H and enhances the contact with water to react with CH forming pozzolanic C-S-H.Well-distributed hydration products are exhibited in the hardened binder added with OS-PCE,with a large number of hydrated gels uniformly fill in the pores and gaps,which improves the compaction of the hardened structure.展开更多
Spatial data uncertainty can directly affect the quality of digital products and GIS-based decision making. On the basis of the characteristics of randomicity of positional data and fuzziness of attribute data, taking...Spatial data uncertainty can directly affect the quality of digital products and GIS-based decision making. On the basis of the characteristics of randomicity of positional data and fuzziness of attribute data, taking entropy as a measure, the stochastic entropy model of positional data uncertainty and fuzzy entropy model of attribute data uncertainty are proposed. As both randomic-ity and fuzziness usually simultaneously exist in linear segments, their omnibus effects are also investigated and quantified. A novel uncertainty measure, general entropy, is presented. The general entropy can be used as a uniform measure to quantify the total un-certainty caused by stochastic uncertainty and fuzzy uncertainty in GIS.展开更多
In order to investigate the behavior characteristics of asphalt components during the process of nano-cracks temperature self-healing(NTS),molecular simulation technology was used to simulate the temperature self-heal...In order to investigate the behavior characteristics of asphalt components during the process of nano-cracks temperature self-healing(NTS),molecular simulation technology was used to simulate the temperature self-healing of asphalt.Based on the determination of asphalts(virgin asphalt and aged asphalt),the proportional changes of asphalt components were confirmed.The distribution characteristics of asphalt components were obtained by marking different components in the process of NTS.At the same time,the rationality of the micro simulation findings was confirmed by asphalt performance tests and infrared spectroscopy results.The results show that different asphalt components have different behavior characteristics in the process of NTS.The content of asphaltene and resin plays a key role in the process of NTS,while saturation and aromatics play an active role in the temperature self-healing before and after aging.The NTS is the result of the comprehensive action of different components,and the self-healing efficiency is proportional to the relative molecular mass.The effect of aging on the NTS is also realized by changing the proportion of asphalt components.展开更多
This paper mainly investigates the effects of initial static shear stress and grain shape on the liquefaction induced large deformation of saturated sand under torsional shear.Nanjing sand,mainly composed of platy gra...This paper mainly investigates the effects of initial static shear stress and grain shape on the liquefaction induced large deformation of saturated sand under torsional shear.Nanjing sand,mainly composed of platy grains,is tested with different initial static shear stress ratio(SSR)using a hollow column torsional shear apparatus.The tests find that the saturated Nanjing sand reaches full liquefaction under the superposition of initial static shear stress and cyclic stress for both stress reversal and non-reversal cases.However,it requires a large number of loading cycles to reach full liquefaction if stress reversal does not occur.With increasing the initial static stress,the large deformation of the Nanjing sand should mainly induced by the cyclic liquefaction firstly under a smaller initial shear stress,and then it should be induced by the residual deformation failure.The critical point occurs approximately when the initial shear stress is close to the amplitude of the cyclic shear stress.Meanwhile,it shows that grain angularity increases the liquefaction resistance when the initial static shear stress is zero.A small initial static shear stress causes the larger loss of liquefaction resistance for angular sand than rounded sand.At a high initial SSR,the angular sand is more resistant to the large residual deformation failure than the rounded sand.展开更多
To find out the local buckling behaviors of glass fiber reinforced plastic(GFRP)-foam sandwich pipe suffering axial loading,a series of quasi-static axial compression tests are carried out in the laboratory.Comparing ...To find out the local buckling behaviors of glass fiber reinforced plastic(GFRP)-foam sandwich pipe suffering axial loading,a series of quasi-static axial compression tests are carried out in the laboratory.Comparing with the test data,systematic numerical analysis on the local buckling behavior of this sandwich pipe is also conducted,and the buckling failure mechanism is revealed.The influences of the key parameters on bearing capacity of the sandwich structure are discussed.Test and numerical results show that the local buckling failure of the GFRPfoam sandwich pipe is dominated basically by two typical modes,i.e.,the conjoint buckling and the layered buckling.Local buckling at the end,shear failure at the end and interface peeling failure are less efficient than the local buckling failure at the middle height,and ought to be restrained by appropriate structural measures.The local buckling bearing capacity increases linearly with the core density of the sandwich pipe structure.When the core density is relatively high(higher than 0.05 g/cm3),the effect of increasing the core density on improving the bearing efficiency is less on the specimens with a large ratio of the wall thickness to the radius than on those with a small one.Local layered buckling is another failure mode with lower bearing efficiency than the local conjoint buckling,and it can be restrained by increasing the core density to ensure the cooperation of the inner and the outer GFRP surface layer.The bearing capacity of the GFRP-foam sandwich pipe increases with the height-diameter ratio;however,the bearing efficiency decreases with this parameter.展开更多
The bench-scale EGSB (expanded granular sludge bed) reactor was operated to study the effect of sludge loading rate, pH value and nutrient element on the operation of the EGSB reactor and the control rule of these fac...The bench-scale EGSB (expanded granular sludge bed) reactor was operated to study the effect of sludge loading rate, pH value and nutrient element on the operation of the EGSB reactor and the control rule of these factors. Continuous flow was used to treat synthetic wastewater containing dextrose and beer, and the temperature of reactor was controlled at mesophiles temperature (33 ℃). The experimental results demonstrated that the proper sludge loading rate was 0.9-1.42 kg COD/(kg VSS·d); the pH value in the reactor was controlled by adding sodium bicarbonate, the proper additive quantity was 1000-1200 mg/L; the additive quantity of nutrient element was as follows: 41.3 mg/(SS·d) of FeCl2·4H2O, 4.3 mg/(SS·d) of CoCl2·6H2O, 8.2 mg/(SS·d) of NiCl2·6H2O, 7.5-13 mg/(SS·d) of CaCO3,and 56.7-22.7 mg/(SS·d) of 7Na2S·9H2O, respectively. When these parameters were properly determined, the EGSB reactor could treat wastewater with 400-5000 mg/L COD concentration. The COD removal efficiency was over 85%. The operation of the EGSB reactor was steady and the EGSB reactor had strong anti-shock load ability.展开更多
The grain size of AZ91 alloy was investigated in terms of the effects of cooling rate, superheat and steel gauze. It was found that rapid cooling rate and low superheat favoured the achievement of fine grain structure...The grain size of AZ91 alloy was investigated in terms of the effects of cooling rate, superheat and steel gauze. It was found that rapid cooling rate and low superheat favoured the achievement of fine grain structures. The gauze had a less profound effect on the grain size in AZ91 magnesium alloy than that in A356 aluminum alloy. The mechanisms by which these factors affect grain refinement of AZ91 have also been discussed.展开更多
Rapid urbanization has led to a surge in the number of towering structures,and overturning is widely used because it can better accommodate the construction of shaped structures such as variable sections.The complexit...Rapid urbanization has led to a surge in the number of towering structures,and overturning is widely used because it can better accommodate the construction of shaped structures such as variable sections.The complexity of the construction process makes the construction risk have certain randomness,so this paper proposes a cloudbased coupled matter-element model to address the ambiguity and randomness in the safety risk assessment of overturning construction of towering structures.In the pretended model,the digital eigenvalues of the cloud model are used to replace the eigenvalues in the matter–element basic element,and calculate the cloud correlation of the risk assessment metrics through the correlation algorithm of the cloud model to build the computational model.Meanwhile,the improved hierarchical analysis method based on the cloud model is used to determine the weight of the index.The comprehensive evaluation scores of the evaluation event are then obtained through the weighted average method,and the safety risk level is determined accordingly.Through empirical analysis,(1)the improved hierarchical analysis method based on the cloud model can incorporate the data of multiple decisionmakers into the calculation formula to determine theweights,which makes the assessment resultsmore credible;(2)the evaluation results of the cloud-basedmatter-element coupledmodelmethod are basically consistent with those of the other two commonly used methods,and the confidence factor is less than 0.05,indicating that the cloudbased physical element coupled model method is reasonable and practical for towering structure overturning;(3)the cloud-based coupled element model method,which confirms the reliability of risk level by performing Spearman correlation on comprehensive assessment scores,can provide more comprehensive information of instances compared with other methods,and more comprehensively reflects the fuzzy uncertainty relationship between assessment indexes,which makes the assessment results more realistic,scientific and reliable.展开更多
In recent years, the phenomenon of the middle-aged and old people vying for the venue in the park has been frequently exposed, reflecting the uneven distribution of urban parks and the lack of activity space for urban...In recent years, the phenomenon of the middle-aged and old people vying for the venue in the park has been frequently exposed, reflecting the uneven distribution of urban parks and the lack of activity space for urban block parks. That phenomenon also shows that the grouping activity habits of the middle-aged and elderly people have affected the fair use of public resources. Based on the current situation of land use in urban block parks, this study explored the site-constrained design method in combination with behavioral scene theory, and proposed to create more equal opportunities for individuals to share public space by limiting the activity scale of middle-aged and old people.展开更多
In this paper,three kinds of shear walls with full sleeve grouting,fully defective sleeve and partially defective are designed for finite element analysis to analyze the influence of defects on the seismic performance...In this paper,three kinds of shear walls with full sleeve grouting,fully defective sleeve and partially defective are designed for finite element analysis to analyze the influence of defects on the seismic performance of shear walls.The research shows that at the beginning of loading(5 s),the three models begin to appear compressive damage at the bottom of the wall in all three models.The damage of the defect-free model develops rapidly,and the damage of the fully defective model is basically the same as that of the partially defective model.With the gradual increase of displacement control(15 s),the compressive damages at the foot of the wall in the defect-free and partially defective grouting model are obvious,with plastic hinge formed in the foot of the wall,and the phenomenon of development along the pier body showing up.When the structure is damaged,the overall compressive damages of the wall in the defect-free and partially defective models are obvious,and the damage on the defective side of the partially defective model is slightly deficient.While the maximum stress of pre-stressed reinforcement in the defect-freemodel is concentrated at the top of the sleeve,themaximumstress of the pre-stressed steel bar in the fully defective model appears at the end of the steel bar in the sleeve.The hysteresis curve shape of the non-defectmodel and partially defective model are basically the same,showing a“shuttle”shape with a sound energy dissipation effect.The hysteresis curve shape of the fully defective model appears an obvious“pinch”phenomenon.The yield displacement levels of the defect-free and partially defective models are smaller than that of the fully defective model structure.The stiffness degradation curves of the three models basically overlap with one another.Before the limit displacement,the stiffness results of the non-defect model and the partially defective model are greater than that of the fully defective model.When the displacement is loaded to 20 mm,the stiffness degradation of the three models is equivalent.展开更多
With the aim of studying the anti-rutting performance of Thiopave modified asphalt mixture applied to the upper layer of pavement, the strain-hardening creep model in ABAQUS finite element software was used to analyze...With the aim of studying the anti-rutting performance of Thiopave modified asphalt mixture applied to the upper layer of pavement, the strain-hardening creep model in ABAQUS finite element software was used to analyze the rutting under the condition of introducing temperature field. Compared with the calculation results of the rutting of ordinary asphalt pavement, it is found that Thiopave can improve the temperature sensitivity of asphalt mixture. With the increase of temperature, the rutting change of Thiopave modified asphalt pavement is smaller than that of ordinary asphalt. Thiopave also has a certain degree of improvement in the fatigue resistance of asphalt pavements, which can be applied to sections with high traffic volume in high temperature areas.展开更多
Based on the analysis of the form characteristics and construction of the public space of oasis traditional settlements in Turpan,and from the analysis and summary of the types,elements,scales and functions of the pub...Based on the analysis of the form characteristics and construction of the public space of oasis traditional settlements in Turpan,and from the analysis and summary of the types,elements,scales and functions of the public space of the traditional settlements,this study put forward that the public space of the oasis villages can be divided into point space,line space and plane space,and the formation and evolution rules of the public space of oasis traditional settlements in Turpan were obtained.Explore the role of public space in the construction of traditional settlements’ overall space,so as to provide reference for the development and renewal of public space of the current similar oasis settlements.展开更多
基金Key Project of the Key Laboratory of Earthquake Engineering and Engineering Vibration,China Earthquake Administration under Grant Nos.2020EEEVL0502 and 2019EEEVL0304。
文摘Large numbers of basic transceiver stations,where the telecommunication room is one of the main components,comprise an important part of the telecommunication system.After earthquakes,considerable economic loss from telecommunication systems is often associated with seismic damage and functional loss of the telecommunication room.However,research related to this has been limited.In this study,shaking table tests were conducted for a full-scale typical telecommunication room,including a light-steel house and the necessary communication and power supply equipment.The tests not only focused on the seismic damage to all the structures but also considered the functions of the communication and power supply of the equipment.The interactions between these facilities and their effects on communication function were also investigated.Compared with the damage to structures,the interruption of the power supply due to earthquakes is a weak link.Finally,the damage indexes,together with their threshold values of different damage states for the communication and power supply equipment,were derived from the test results.The results of this research can contribute to the literature gaps regarding seismic performance studies of telecommunication rooms,and can serve as a valuable reference for future research on its seismic fragility and economic losses evaluation.
基金financially supported by the National Natural Science Foundation of China(Grant No.51890913)the Natural Science Foundation of Sichuan Province of China(Grant No.2023YFQ0111)。
文摘In an effort to investigate and quantify the patterns of local scour,researchers embarked on an in-depth study using a systematic experimental approach.The research focused on the effects of local scour around a set of four piles,each subjected to different hydromechanical conditions.In particular,this study aimed to determine how different attack angles—the angles at which the water flow impinges on the piles,and gap ratios—the ratios of the spacing between the piles to their diameters,influence the extent and nature of scour.A comprehensive series of 35 carefully designed experiments were orchestrated,each designed to dissect the nuances in how the gap ratio and attack angle might contribute to changes in the local scour observed at the base of pile groups.During these experimental trials,a wealth of local scour data were collected to support the analysis.These data included precise topographic profiles of the sediment bed around the pile groups,as well as detailed scour time histories showing the evolution of scour at strategic feature points throughout the test procedure.The analysis of the experimental data provided interesting insights.The study revealed that the interplay between the gap ratio and the attack angle had a pronounced influence on the scouring dynamics of the pile groups.One of the key observations was that the initial phases of scour,particularly within the first hour of water flow exposure,were characterized by a sharp increase in the scour depth occurring immediately in front of the piles.After this initial rapid development,the scour depth transitioned to a more gradual change rate.In contrast,the scour topography around the piles continuously evolved.This suggests that sediment displacement and the associated sculpting of the seabed around pile foundations are sustained and progressive processes,altering the underwater landscape over time.The results of this empirical investigation have significant implications for the design and construction of offshore multi-pile foundations,providing a critical reference for engineers and designers to estimate the expected scour depth around such structures,which is an integral part of decisions regarding foundation design,selection of structural materials,and implementation of scour protection measures.
基金The National Natural Science Foundation of China(No.51378006,51378121)
文摘In order to characterize the impacts of key factors on the low-temperature fracture performance of dense-graded asphalt concrete, the virtual bending fracture test is simulated by using the discrete element method( DEM) and emulation software PFC3D( particle flowcode in three-dimension). A virtual specimen generation procedure consisting of aggregate gradation, irregular clumps, asphalt mortar and air void content is performed based on the random generation algorithm and irregular coarse aggregates library. Then, the virtual fracture test is conducted after adding the micro mechanical contact models to the specimen, and the validity of virtual modeling is verified by the comparison of simulation test data and lab test data. Additionally, an orthogonal test is designed to investigate the impacts of the volume fraction of coarse aggregates and air voids, stiffness of coarse aggregates and asphalt mortar, internal bond strength of asphalt mortar and distribution of coarse aggregates and air voids on low-temperature fracture performance based on virtual simulation.The results showthat all the factors have effects on fracture performance to various degrees, while the value of the bond strength of asphalt mortar is found to be the most important determinant of tensile strength and strain-energy density. The volume fraction of coarse aggregates is considered to be the most important determinant of tensile strain. Therefore, to obtain a high low-temperature fracture performance of densegraded asphalt concrete, it is important to consider the microstructure and properties of asphalt mortar and aggregates.
文摘Three transformation models (Bursa-Wolf, Molodensky, and WTUSM) are generally used between two data systems transformation. The linear models are used when the rotation angles are small; however, when the rotation angles get bigger, model errors will be produced. In this paper, we present a method with three main terms:① the traditional rotation angles θ,φ,ψ are substituted with a,b,c which are three respective values in the anti-symmetrical or Lodrigues matrix; ② directly and accurately calculating the formula of seven parameters in any value of rotation angles; and ③ a corresponding adjustment model is established. This method does not use the triangle function. Instead it uses addition, subtraction, multiplication and division, and the complexity of the equation is reduced, making the calculation easy and quick.
基金supported by National Key R&D Program of China[grant number 2017YFC0703502]the National Natural Science Foundation of China(NSFC)[grant numbers 51978345,51678310 and 51708304]K.C.Wong Magna Fund at the Ningbo University.
文摘The steel-bamboo composite structure is a newly developed structure,combining phyllostachys pubescens(also called Moso bamboo)plywood and cold-formed thin-walled steel with structural adhesive.The reliability of steelbamboo interface is the premise of composite effect.13 specimens were prepared to investigate the failure modes and mechanism of the steel-bamboo interface on the basis of push-out test,and the strain difference analysis method was proposed to study the distribution of shear stress.The results show that the main failure modes of steel-bamboo interface are adhesion failure and splitting of bamboo plywood.The shear stress is not evenly distributed along the longitudinal direction of the interface,showing a shape of“larger at two ends and smaller in the middle”.The lower end of the interface is the initial location of the interface failure and the shear stress concentration degree is positively correlated with the thickness of the externally bonded bamboo plate.The shear resistance of steel-bamboo interface can be enhanced by improving the adhesion between steel and structural adhesive and ameliorating the quality of bamboo products.
基金funded by the China Postdoctoral Science Foundation(No. 2014M551909)the Jiangsu Geology & Mineral Exploration Bureau’s Science Foundation(No.2013-KY-13)
文摘In view of the collapse of a deep excavated foundation pit of the Xianghu subway underground station in Hangzhou of China,the main features of the accident are analyzed,and the induced factors of the accident are summarized. Then,a 3-D FEM analysis model is created to demonstrate the soil-support structures interaction system,and the effect of the main factors,such as the volume replacement ratio of the bottom soil reinforcing,the asymmetric ground overload,the embedded depth of the diaphragm wall,the shear strength of the bottom soils disturbed by the construction,and the excessive excavation of the bottom soil,are analyzed and compared. The results show that the ineffective original reinforcement plan for the bottom soft soil is the most prominent factor for the accident,and the disturbance effect of the deep excavation on the shear strength of the bottom soft soil is another significant factor for the accident. Meanwhile,if the reinforcement of the bottom soft soil is canceled,an appropriate extension of the diaphragm retaining walls to the under lying harder soil layer can also effectively prevent the collapse of the deep excavated foundation pit. In addition,the partly excessive excavation in the process has a great influence on the axial force of the most nearby horizontal support but few effect on the stability of the diaphragm wall. Thus,the excessive excavation of the bottom soils should not be the direct inducing factor for the accident. To the asymmetric ground overload,it should be the main factor inducing the different damage conditions of the diaphragm walls on different sides. According to the numerical modeling and actual engineering accident condition,the development process of the accident is also identified.
基金Funded by the National Natural Science Foundation of China(No.51808369)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.18KJB560016)+3 种基金the Opening Project of State Key Laboratory of Green Building Materials(No.YA-615)the State Key Laboratory of Silicate Materials for Architectures(No.SYSJJ2018-09)Science and Technology Project of Jiangsu Provincal Department of Housing and Urban-Rural Construction(No.2018ZD049)the Natural Science Foundation of Suzhou University of Science and Technology(No.XKQ2018009)
文摘The adsorption behaviors and dispersing properties of polycarboxylate superplasticizer(PCE) with different functional groups were systematically analyzed to reveal the theory and methods of modifying PCE molecular structures and regulating PCE performances. By substituting carboxylic groups with sulfonic groups, ester groups or acylamino groups, respectively, modified PCEs with different functional groups were synthesized. Results show that introducing low amount of ester groups or sulfonic groups into the PCE molecules has no negative effects on the fluidity of cement paste, while introducing acylamino groups into PCE molecules significantly weakens the fluidity of cement paste. At low amount(when the molar ratio of sodium methallyl sulfonate to TPEG is lower than 0.4), the rapid adsorption of sulfonic groups onto the cement particles contributes to the high dispersing performance of the sulfonic group modified PCEs. When the substitution ratio of acrylic acid by sulfonic acid is higher than 0.4, the viscosity and the yield stress of cement paste increases sharply. Redundant sulfonic groups lead to the excessive charge density of the PCE, which contributes to the inhomogeneous adsorption on the cement grains and hence results in the decline of the dispersing performance. Substitution of carboxylic group by acylamino group or ester group slightly changes the viscosity as well as the yield stress of cement paste. Introducing sulfonic group into PCE molecule improves the adsorption behavior of PCEs, while introducing ester group or acylamino group into PCE depresses the adsorption properties.
基金Sponsored by the Science Foundation of Educational Department of Liaoning Province(Grant No.2023901023)
文摘Biaxial compression tests on plain concrete suffered high temperature ranging from 200 ℃ to 600 ℃ were carried out using the large-scale dynamic-static tri-axial concrete test system at the State Key Laboratory of Coastal and Offshore Engineering with designated stress ratios of 0, 0.25, 0.5, 0.75 and 1, respectively. The measured strength and strain were reported and the changes in both biaxial compressive failure envelopes and strains at peak stresses were analyzed. The regressive equation of initial elastic modulus in the biggest principal compressive stress direction was derived from test results. With the published results from previous biaxial tension-compression experiments, a three-parameter failure criterion has been proposed. A biaxial nonlinear elastic incremental constitutive model was developed for the compressive stress directions by using the equivalent uniaxial strain values deduced from test results. Analytical results obtained from the proposed biaxial constitutive model achieve good agreement with the experimental results.
基金Funded by the Natural Science Foundation of China(51808369)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(18KJB560016)+4 种基金the Opening Project of State Key Laboratory of Green Building Materials(YA-615)the State Key Laboratory of Silicate Building Materials(SYSJJ2018-09)Hubei Key Laboratory of Water System Science for Sponge City Construction(2019-01)the Construction System Science and Technology Project of Jiangsu Province(2018ZD049)the Natural Science Foundation of Suzhou University of Science and Technology(XKQ2018009)。
文摘Effects of organosilane-modified PCE (OS-PCE) on the fluidity and the hydration properties of cement-fly ash (FA) composite binder were systematically analyzed.The experimental results show that OS-PCE possesses respectively 36.98% and 36.67% higher saturated adsorption amount on cement and FA,in comparison with ordinary PCE,and can contribute to higher fluidity of cement-FA composite binder.The addition of OS-PCE retards hydration process of cement-FA composite binder proportionally with the dosage of OS-PCE,but promotes the hydration kinetics of the composite binder.The reactivity enhancement is attributed to the well-dispersed FA by OS-PCE,which provides more nucleation sites for the reaction of heterogeneous C-S-H and enhances the contact with water to react with CH forming pozzolanic C-S-H.Well-distributed hydration products are exhibited in the hardened binder added with OS-PCE,with a large number of hydrated gels uniformly fill in the pores and gaps,which improves the compaction of the hardened structure.
基金Supported by the Open Research Fund Program of Geomatics and Application Laboratory, Liaoning Technical University (No.2005004).
文摘Spatial data uncertainty can directly affect the quality of digital products and GIS-based decision making. On the basis of the characteristics of randomicity of positional data and fuzziness of attribute data, taking entropy as a measure, the stochastic entropy model of positional data uncertainty and fuzzy entropy model of attribute data uncertainty are proposed. As both randomic-ity and fuzziness usually simultaneously exist in linear segments, their omnibus effects are also investigated and quantified. A novel uncertainty measure, general entropy, is presented. The general entropy can be used as a uniform measure to quantify the total un-certainty caused by stochastic uncertainty and fuzzy uncertainty in GIS.
基金Funded by the Fundamental Research Funds for the Central Universities(No.2572021AW10)。
文摘In order to investigate the behavior characteristics of asphalt components during the process of nano-cracks temperature self-healing(NTS),molecular simulation technology was used to simulate the temperature self-healing of asphalt.Based on the determination of asphalts(virgin asphalt and aged asphalt),the proportional changes of asphalt components were confirmed.The distribution characteristics of asphalt components were obtained by marking different components in the process of NTS.At the same time,the rationality of the micro simulation findings was confirmed by asphalt performance tests and infrared spectroscopy results.The results show that different asphalt components have different behavior characteristics in the process of NTS.The content of asphaltene and resin plays a key role in the process of NTS,while saturation and aromatics play an active role in the temperature self-healing before and after aging.The NTS is the result of the comprehensive action of different components,and the self-healing efficiency is proportional to the relative molecular mass.The effect of aging on the NTS is also realized by changing the proportion of asphalt components.
基金supported by the National Natural Science Foundation of China(Nos.51778290,51778386)the National Science Fund for Distinguished Young Scholars(No.51725802)the Natural Science Foundation of Jiangsu High School(No.16KJA560001)。
文摘This paper mainly investigates the effects of initial static shear stress and grain shape on the liquefaction induced large deformation of saturated sand under torsional shear.Nanjing sand,mainly composed of platy grains,is tested with different initial static shear stress ratio(SSR)using a hollow column torsional shear apparatus.The tests find that the saturated Nanjing sand reaches full liquefaction under the superposition of initial static shear stress and cyclic stress for both stress reversal and non-reversal cases.However,it requires a large number of loading cycles to reach full liquefaction if stress reversal does not occur.With increasing the initial static stress,the large deformation of the Nanjing sand should mainly induced by the cyclic liquefaction firstly under a smaller initial shear stress,and then it should be induced by the residual deformation failure.The critical point occurs approximately when the initial shear stress is close to the amplitude of the cyclic shear stress.Meanwhile,it shows that grain angularity increases the liquefaction resistance when the initial static shear stress is zero.A small initial static shear stress causes the larger loss of liquefaction resistance for angular sand than rounded sand.At a high initial SSR,the angular sand is more resistant to the large residual deformation failure than the rounded sand.
基金supported by the National Key R&D Program of China(No.2017YFC0405103)the Natural Science Foundation of China(No. 51978166)the Construction System Science and Technology Guidance Project of Jiangsu(Nos.2017ZD131,2017ZD132).
文摘To find out the local buckling behaviors of glass fiber reinforced plastic(GFRP)-foam sandwich pipe suffering axial loading,a series of quasi-static axial compression tests are carried out in the laboratory.Comparing with the test data,systematic numerical analysis on the local buckling behavior of this sandwich pipe is also conducted,and the buckling failure mechanism is revealed.The influences of the key parameters on bearing capacity of the sandwich structure are discussed.Test and numerical results show that the local buckling failure of the GFRPfoam sandwich pipe is dominated basically by two typical modes,i.e.,the conjoint buckling and the layered buckling.Local buckling at the end,shear failure at the end and interface peeling failure are less efficient than the local buckling failure at the middle height,and ought to be restrained by appropriate structural measures.The local buckling bearing capacity increases linearly with the core density of the sandwich pipe structure.When the core density is relatively high(higher than 0.05 g/cm3),the effect of increasing the core density on improving the bearing efficiency is less on the specimens with a large ratio of the wall thickness to the radius than on those with a small one.Local layered buckling is another failure mode with lower bearing efficiency than the local conjoint buckling,and it can be restrained by increasing the core density to ensure the cooperation of the inner and the outer GFRP surface layer.The bearing capacity of the GFRP-foam sandwich pipe increases with the height-diameter ratio;however,the bearing efficiency decreases with this parameter.
基金the National High Technology Research and Development Program of China(Grant No.2003AA601090).
文摘The bench-scale EGSB (expanded granular sludge bed) reactor was operated to study the effect of sludge loading rate, pH value and nutrient element on the operation of the EGSB reactor and the control rule of these factors. Continuous flow was used to treat synthetic wastewater containing dextrose and beer, and the temperature of reactor was controlled at mesophiles temperature (33 ℃). The experimental results demonstrated that the proper sludge loading rate was 0.9-1.42 kg COD/(kg VSS·d); the pH value in the reactor was controlled by adding sodium bicarbonate, the proper additive quantity was 1000-1200 mg/L; the additive quantity of nutrient element was as follows: 41.3 mg/(SS·d) of FeCl2·4H2O, 4.3 mg/(SS·d) of CoCl2·6H2O, 8.2 mg/(SS·d) of NiCl2·6H2O, 7.5-13 mg/(SS·d) of CaCO3,and 56.7-22.7 mg/(SS·d) of 7Na2S·9H2O, respectively. When these parameters were properly determined, the EGSB reactor could treat wastewater with 400-5000 mg/L COD concentration. The COD removal efficiency was over 85%. The operation of the EGSB reactor was steady and the EGSB reactor had strong anti-shock load ability.
文摘The grain size of AZ91 alloy was investigated in terms of the effects of cooling rate, superheat and steel gauze. It was found that rapid cooling rate and low superheat favoured the achievement of fine grain structures. The gauze had a less profound effect on the grain size in AZ91 magnesium alloy than that in A356 aluminum alloy. The mechanisms by which these factors affect grain refinement of AZ91 have also been discussed.
基金funded by China Railway No.21 Bureau Group No.1 Engineering Co.,Ltd.,Grant No.202209140002.
文摘Rapid urbanization has led to a surge in the number of towering structures,and overturning is widely used because it can better accommodate the construction of shaped structures such as variable sections.The complexity of the construction process makes the construction risk have certain randomness,so this paper proposes a cloudbased coupled matter-element model to address the ambiguity and randomness in the safety risk assessment of overturning construction of towering structures.In the pretended model,the digital eigenvalues of the cloud model are used to replace the eigenvalues in the matter–element basic element,and calculate the cloud correlation of the risk assessment metrics through the correlation algorithm of the cloud model to build the computational model.Meanwhile,the improved hierarchical analysis method based on the cloud model is used to determine the weight of the index.The comprehensive evaluation scores of the evaluation event are then obtained through the weighted average method,and the safety risk level is determined accordingly.Through empirical analysis,(1)the improved hierarchical analysis method based on the cloud model can incorporate the data of multiple decisionmakers into the calculation formula to determine theweights,which makes the assessment resultsmore credible;(2)the evaluation results of the cloud-basedmatter-element coupledmodelmethod are basically consistent with those of the other two commonly used methods,and the confidence factor is less than 0.05,indicating that the cloudbased physical element coupled model method is reasonable and practical for towering structure overturning;(3)the cloud-based coupled element model method,which confirms the reliability of risk level by performing Spearman correlation on comprehensive assessment scores,can provide more comprehensive information of instances compared with other methods,and more comprehensively reflects the fuzzy uncertainty relationship between assessment indexes,which makes the assessment results more realistic,scientific and reliable.
文摘In recent years, the phenomenon of the middle-aged and old people vying for the venue in the park has been frequently exposed, reflecting the uneven distribution of urban parks and the lack of activity space for urban block parks. That phenomenon also shows that the grouping activity habits of the middle-aged and elderly people have affected the fair use of public resources. Based on the current situation of land use in urban block parks, this study explored the site-constrained design method in combination with behavioral scene theory, and proposed to create more equal opportunities for individuals to share public space by limiting the activity scale of middle-aged and old people.
基金The authors are grateful for the financial support received from the National Natural Science Foundation of China(No.52078038)Basic Scientific Research Business of Central University(No.FRF-MP-20-20).
文摘In this paper,three kinds of shear walls with full sleeve grouting,fully defective sleeve and partially defective are designed for finite element analysis to analyze the influence of defects on the seismic performance of shear walls.The research shows that at the beginning of loading(5 s),the three models begin to appear compressive damage at the bottom of the wall in all three models.The damage of the defect-free model develops rapidly,and the damage of the fully defective model is basically the same as that of the partially defective model.With the gradual increase of displacement control(15 s),the compressive damages at the foot of the wall in the defect-free and partially defective grouting model are obvious,with plastic hinge formed in the foot of the wall,and the phenomenon of development along the pier body showing up.When the structure is damaged,the overall compressive damages of the wall in the defect-free and partially defective models are obvious,and the damage on the defective side of the partially defective model is slightly deficient.While the maximum stress of pre-stressed reinforcement in the defect-freemodel is concentrated at the top of the sleeve,themaximumstress of the pre-stressed steel bar in the fully defective model appears at the end of the steel bar in the sleeve.The hysteresis curve shape of the non-defectmodel and partially defective model are basically the same,showing a“shuttle”shape with a sound energy dissipation effect.The hysteresis curve shape of the fully defective model appears an obvious“pinch”phenomenon.The yield displacement levels of the defect-free and partially defective models are smaller than that of the fully defective model structure.The stiffness degradation curves of the three models basically overlap with one another.Before the limit displacement,the stiffness results of the non-defect model and the partially defective model are greater than that of the fully defective model.When the displacement is loaded to 20 mm,the stiffness degradation of the three models is equivalent.
文摘With the aim of studying the anti-rutting performance of Thiopave modified asphalt mixture applied to the upper layer of pavement, the strain-hardening creep model in ABAQUS finite element software was used to analyze the rutting under the condition of introducing temperature field. Compared with the calculation results of the rutting of ordinary asphalt pavement, it is found that Thiopave can improve the temperature sensitivity of asphalt mixture. With the increase of temperature, the rutting change of Thiopave modified asphalt pavement is smaller than that of ordinary asphalt. Thiopave also has a certain degree of improvement in the fatigue resistance of asphalt pavements, which can be applied to sections with high traffic volume in high temperature areas.
基金the National Natural Science Foundation of China(51768066)Funded Project of Doctoral Start-up Fund of Xinjiang University(620312355).
文摘Based on the analysis of the form characteristics and construction of the public space of oasis traditional settlements in Turpan,and from the analysis and summary of the types,elements,scales and functions of the public space of the traditional settlements,this study put forward that the public space of the oasis villages can be divided into point space,line space and plane space,and the formation and evolution rules of the public space of oasis traditional settlements in Turpan were obtained.Explore the role of public space in the construction of traditional settlements’ overall space,so as to provide reference for the development and renewal of public space of the current similar oasis settlements.