With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components ...With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.展开更多
A 3D finite element (FE) model for the Sutong cable-stayed bridge (SCB) is established based on ANSYS. The dynamic characteristics of the bridge are analyzed using a subspace iteration method. Based on recorded wi...A 3D finite element (FE) model for the Sutong cable-stayed bridge (SCB) is established based on ANSYS. The dynamic characteristics of the bridge are analyzed using a subspace iteration method. Based on recorded wind data, the measured spectra expression is presented using the nonlinear least-squares regression method. Turbulent winds at the bridge site are simulated based on the spectral representation method and the FFT technique. The influence of some key structural parameters and measures on the dynamic characteristics of the bridge are investigated. These parameters include dead load intensity, as well as vertical, lateral and torsional stiffness of the steel box girder. In addition, the influence of elastic stiffness of the connection device employed between the towers and the girder on the vibration mode of the steel box girder is investigated. The analysis shows that all of the vertical, lateral and torsional buffeting displacement responses reduce gradually as the dead load intensity increases. The dynamic characteristics and the structural buffeting displacement response of the SCB are only slightly affected by the vertical and torsional stiffness of the steel box girder, and the lateral and torsional buffeting displacement responses reduce gradually as the lateral stiffness increases. These results provide a reference for dynamic analysis and design of super-long-span cable-stayed bridges.展开更多
This work presented the development and validation of an analytical method to predict the transient temperature field in the asphalt pavement.The governing equation for heat transfer was based on heat conduction radia...This work presented the development and validation of an analytical method to predict the transient temperature field in the asphalt pavement.The governing equation for heat transfer was based on heat conduction radiation and convection.An innovative time-dependent function was proposed to predict the pavement surface temperature with solar radiation and air temperature using dimensional analysis in order to simplify the complex heat exchange on the pavement surface.The parameters for the time-dependent pavement surface temperature function were obtained through the regression analysis of field measurement data.Assuming that the initial pavement temperature distribution was linear and the influence of the base course materials on the temperature of the upper asphalt layers was negligible,a close-form analytical solution of the temperature in asphalt layers was derived using Green's function.Finally,two numerical examples were presented to validate the model solutions with field temperature measurements.Analysis results show that the solution accuracy is in agreement with field data and the relative errors at a shallower depth are greater than those at a deeper one.Although the model is not sensitive to dramatic changes in climatic factors near the pavement surface,it is applicable for predicting pavement temperature field in cloudless days.展开更多
The mechanisms of seismically-induced liquefaction of granular soils underhigh confining stresses are still not fully understood. Evaluation of these mechanisms is generallybased on extrapolation of observed behavior ...The mechanisms of seismically-induced liquefaction of granular soils underhigh confining stresses are still not fully understood. Evaluation of these mechanisms is generallybased on extrapolation of observed behavior at shallow depths. Three centrifuge model tests wereconducted at RPI's experimental facility to investigate the effects of confining stresses on thedynamic response of a deep horizontal deposit of saturated sand. Liquefaction was observed at highconfining stresses in each of the tests. A system identification procedure was used to estimate theassociated shear strain and stress time histories. These histories revealed a response marked byshear strength degradation and dilative patterns. The recorded accelerations and pore pressures wereemployed to generate visual animations of the models. These visualizations revealed a liquefactionfront traveling downward and leading to large shear strains and isolation of upper soil layers.展开更多
This paper examines the quasi-static cyclic behavior, lateral strength and equivalent damping capacities of a system of post-tensioned segmental bridge columns tied with large diameter martensitic Shape Memory Alloy ...This paper examines the quasi-static cyclic behavior, lateral strength and equivalent damping capacities of a system of post-tensioned segmental bridge columns tied with large diameter martensitic Shape Memory Alloy (SMA) link-bars. Moment-curvature constitutive relationships are formulated and analysis tools are developed for the PT column, including a modified four-spring model prepared for the SMA bars. The suggested system is exemplified using a column with an aspect ratio of 7.5 and twelve 36.5 mm diameter NiTi martensitic SMA bars. A post-tensioning force of 40% to 60% of the tendon yield strength is applied in order to obtain a self re-centering system, considering the residual stress of the martensitie SMA bars. The cyclic response results show that the lateral strength remains consistently around 10% of the total vertical load and the equivalent viscous damping ratios reach 10%-12% of critical. When large diameter NiTi superelastic SMA bars are incorporated into the column system, the cyclic response varies substantially. The creep behavior of the superelastic SMA bar is accounted for since it affects the re-centering capability of the column. Two examples are presented to emphasize the modeling sensitivities for these special bars and quantify their cyclic behavior effects within the column assembly.展开更多
An analytical seismic fragility assessment framework is presented for the existing low strength reinforced concrete structures more common in the building stock of the developing countries.For realistic modelling of s...An analytical seismic fragility assessment framework is presented for the existing low strength reinforced concrete structures more common in the building stock of the developing countries.For realistic modelling of such substandard structures,low strength concrete stress-strain and bond-slip capacity models are included in calibrating material models.Key capacity parameters are generated stochastically to produce building population and cyclic pushover analysis is carried out to capture inelastic behaviour.Secant period values are evaluated corresponding to each displacement step on the capacity curves and used as seismic demand.A modified capacity demand diagram method is adopted for the degrading structures,which is further used to evaluate peak ground acceleration from back analysis considering each point on the capacity curve as performance point.For developing fragility curves,the mean values of peak ground acceleration are evaluated corresponding to each performance point on the series of capacity curves.A suitable probability distribution function is adopted for the secant period scatter at different mean peak ground acceleration values and probability of exceedance of limit states is evaluated.A suitable regression function is used for developing fragility curves and regression coefficients are proposed for different confidence levels.Fragility curves are presented for a low rise pre-seismic code reinforced concrete structure typical of developing countries.展开更多
Many biodiversity indices were used to indicate the biological contamination degree in studies of lake water or seawater. Some were studied on biodiversity comparison for different areas at the same time, or initial s...Many biodiversity indices were used to indicate the biological contamination degree in studies of lake water or seawater. Some were studied on biodiversity comparison for different areas at the same time, or initial structure succession of some aerial lake water systems. The phytoplankton changed with the development of various dominant species. In this study, the dominant species at these stages were Chlorophyta in the beginning stage, Cyanophyta in the second stage, and Xanthophyta in the last stage. Seven of nine biodiversity indices (Margalef's, IE, Shannon-Wiener, Simpson's, McNaughton's, Species and Odds Measure of Diversity) showed their failure to represent the eutrophication trend, and the other two indices (Menhinick's and Monk) exhibited good efficiency to indicate the eutrophication trend for the static landscaping water body.展开更多
Recent Cryptosporidium outbreaks have highlighted concerns about filter efficiency and in particular particle breakthrough. It is essential to ascertain the causes of Cryptosporidium sized particle breakthrough for Cr...Recent Cryptosporidium outbreaks have highlighted concerns about filter efficiency and in particular particle breakthrough. It is essential to ascertain the causes of Cryptosporidium sized particle breakthrough for Cryptosporidium cannot be destroyed by conventional chlorine disinfection. This research tried to investigate the influence of temperature, flow rate and chemical dosing on particle breakthrough during filtration. The results showed that higher temperatures and coagulant doses could reduce particle breakthrough. The increase of filtration rate made the residual particle counts become larger. There was an optimal dose in filtration and was well correlated to ζ potential.展开更多
External bonding of fiber reinforced polymer (FRP) composites on the concrete structures has been proved to be an effective and efficient way to strengthen concrete structures. For a FRP strengthened concrete beam, ...External bonding of fiber reinforced polymer (FRP) composites on the concrete structures has been proved to be an effective and efficient way to strengthen concrete structures. For a FRP strengthened concrete beam, it is usually observed that the failure occurs in the concrete and a thin layer of concrete is attached on the surface of the debonded FRP plate. To study the debond behavior between concrete and FRP composites, an analytical model based on the three-parameter model is developed to study the debonding behavior for the FRP-to-concrete joint under pure shearing. Then, nonlinear FEM analysis is conducted to verify the PrOposed analytical model. The FEM results shows good agreement with the results from the model. Finally, with the analytical model, sensitivity analyses are performed to study the effect of the interracial parameters or the ~eometric parameters on the debondin~ behavior.展开更多
Wastes yielded in the vintage process and the biological fermentation of itaconic acid and sodium gluconate of a winery in Shandong, such as grain stillage, melon lees, cornstarch protein residues, itaconic acid mothe...Wastes yielded in the vintage process and the biological fermentation of itaconic acid and sodium gluconate of a winery in Shandong, such as grain stillage, melon lees, cornstarch protein residues, itaconic acid mother liquid, itaconic acid mycelium and sodium gluconate mycelium, were studied. High-activity biological protein feed, foliar fertilizer and irrigation fertilizer were generated from these wastes by applying biological/microbial technologies. Meanwhile, a whole set of technological pathways was put forward. As a result, the optimal economical and social benefits can be obtained with low natural resource consumption and environmental costs by converting wastes into useful matters. In conclusion, through the utilization of limited resources in the whole process of reclamation and utilization of wastes, the harmony promotion can be achieved between the economic system and the natural ecosystem.展开更多
A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semi- cylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the...A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semi- cylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the cylindrical wave functions expansion method.The solution is reduced to solving a set of infinite linear algebraic equations.Fourier expansion theorem with the form of complex exponential function and cosine function is used.Numerical solutions are obtained by truncation of the infinite equations.The accuracy of the presented numerical results is carefully verified.展开更多
In order to estimate vehicular queue length at signalized intersections accurately and overcome the shortcomings and restrictions of existing studies especially those based on shockwave theory,a new methodology is pre...In order to estimate vehicular queue length at signalized intersections accurately and overcome the shortcomings and restrictions of existing studies especially those based on shockwave theory,a new methodology is presented for estimating vehicular queue length using data from both point detectors and probe vehicles. The methodology applies the shockwave theory to model queue evolution over time and space. Using probe vehicle locations and times as well as point detector measured traffic states,analytical formulations for calculating the maximum and minimum( residual) queue length are developed. The proposed methodology is verified using ground truth data collected from numerical experiments conducted in Shanghai,China. It is found that the methodology has a mean absolute percentage error of 17. 09%,which is reasonably effective in estimating the queue length at traffic signalized intersections. Limitations of the proposed models and algorithms are also discussed in the paper.展开更多
Evaluation of the cyclic shear modulus of soils is a crucial but challenging task for many geotechnical earthquake engineering and soil dynamic issues. Improper determination of this property unnecessarily drives up d...Evaluation of the cyclic shear modulus of soils is a crucial but challenging task for many geotechnical earthquake engineering and soil dynamic issues. Improper determination of this property unnecessarily drives up design and maintenance costs or even leads to the construction of unsafe structures. Due to the complexities involved in the direct measurement, empirical curves for estimating the cyclic shear modulus have been commonly adopted in practice for simplicity and economical considerations. However, a systematic and robust approach for formulating a reliable model and empirical curve for cyclic shear modulus prediction for clayey soils is still lacking. In this study, the Bayesian model class selection approach is utilized to identify the most significant soil parameters affecting the normalized cyclic shear modulus and a reliable predictive model for normally to moderately over-consolidated clays is proposed. Results show that the predictability and reliability of the proposed model out performs the well-known empirical models. Finally, a new design chart is established for practical usage.展开更多
Shaking table tests of a 1:10 scale arch model performed to investigate the seismic behavior and resistance of concrete filled steel tubular (CFT) arch structures are described in this paper. The El-Centro record and ...Shaking table tests of a 1:10 scale arch model performed to investigate the seismic behavior and resistance of concrete filled steel tubular (CFT) arch structures are described in this paper. The El-Centro record and Shanghai artificial wave were adopted as the input excitation. The entire test process can be divided into three stages depending on the lateral brace configurations, i.e., fully (five) braced, two braces removed, and all braces removed. A total of 46 tests, starting from the elastic state to failure condition, have been conducted. The natural vibration frequencies, responses of acceleration, displacement and strain were measured. From the test results, it is demonstrated that the CFT arch structures are capable of resisting severe ground motions and that CFT arches offer a credible alternative to reinforced concrete arches, especially in regions of high seismic intensity.展开更多
Integral abutment bridges(IABs)minimize deterioration and degradation of the abutment seats and bearings due to water,dirt,and deicing chemicals by eliminating bearings and expansion joints.Although the continuity bet...Integral abutment bridges(IABs)minimize deterioration and degradation of the abutment seats and bearings due to water,dirt,and deicing chemicals by eliminating bearings and expansion joints.Although the continuity between superstructure and abutments in an IAB is beneficial for reducing maintenance costs,it leads to more complex behavior under strength and service loading(temperature and traffic)and extreme loading(earthquake).The coupling of superstructure and substructure behavior necessitates system-level analysis of IABs.Prior seismic IAB studies have typically investigated the behavior of individual IAB components,however a gap of knowledge has developed due to the lack of studies and investigation about the behavior of all IAB components and their interactions with each other in a single analysis model.This study uses nonlinear static and dynamic analyses to investigate and assess the seismic behavior of IABs typical to the state of Illinois.The analyses aim to bridge the gap of knowledge by evaluating IABs as a whole and utilizing the results to indicate potential vulnerabilities in the design and construction of IABs in Illinois during design-level and larger seismic events,which could not be identified by component-level IAB analyses alone.展开更多
Calcareous sand is widely observed in the foundation of off-shore infrastructure.Although a lot of research has been carried out on the mechanical properties of calcareous sand,study into the influence of the stress–...Calcareous sand is widely observed in the foundation of off-shore infrastructure.Although a lot of research has been carried out on the mechanical properties of calcareous sand,study into the influence of the stress–strain path on the mechanical behaviour of calcareous sand is very limited.In this study,a series of triaxial tests were performed on calcareous sand under three different stress paths.The particle morphology of calcareous sand before and after the tests,the stress–strain relationship under different stress paths,and the char-acteristics of shear strength and deformation were investigated.The results show that the consolidation pressure and stress path have significant effects on the volume strain,strength,and particle breakage of calcareous sand.In addition,the underlying mechanisms of the different behaviours of calcareous sand observed in this study were discussed.展开更多
Biological activated carbon (BAC) has been developed on the granular activated carbon by immobilization of selected and acclimated species of bacteria to treat the micro-polluted water. The BAC removal efficiencies fo...Biological activated carbon (BAC) has been developed on the granular activated carbon by immobilization of selected and acclimated species of bacteria to treat the micro-polluted water. The BAC removal efficiencies for nitrobenzene, permanganate index, turbidity and ammonia were investigated. Effects of shock loading and SEM (Scanning Electron Microscope) observation on BAC were studied. Backwashing and its intensity of BAC were also discussed. The results showed that BAC took short time to start up and recover to the normal condition after shock loading. The shock loading studies showed that the removal efficiency of BAC was not completely inhibited even at high concentration of nitrobenzene. Backwashing performed once every 10-20 d, or an average of 15 d. Backwashing intensity was 12-14 L/(s·m2) with air and 3-4 L/(s·m2) with water.展开更多
文摘With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.
基金The National Science Foundation of China under Grant No.51378111the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No.NCET-13-0128+2 种基金the Fok Ying-Tong Education Foundation for Young Teachersin the Higher Education Institutions of China under Grant No.142007the Fundamental Research Funds for the Central Universities under Grant No.2242012R30002the Open Fund of Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering under Grant No.JSKL2011YB02
文摘A 3D finite element (FE) model for the Sutong cable-stayed bridge (SCB) is established based on ANSYS. The dynamic characteristics of the bridge are analyzed using a subspace iteration method. Based on recorded wind data, the measured spectra expression is presented using the nonlinear least-squares regression method. Turbulent winds at the bridge site are simulated based on the spectral representation method and the FFT technique. The influence of some key structural parameters and measures on the dynamic characteristics of the bridge are investigated. These parameters include dead load intensity, as well as vertical, lateral and torsional stiffness of the steel box girder. In addition, the influence of elastic stiffness of the connection device employed between the towers and the girder on the vibration mode of the steel box girder is investigated. The analysis shows that all of the vertical, lateral and torsional buffeting displacement responses reduce gradually as the dead load intensity increases. The dynamic characteristics and the structural buffeting displacement response of the SCB are only slightly affected by the vertical and torsional stiffness of the steel box girder, and the lateral and torsional buffeting displacement responses reduce gradually as the lateral stiffness increases. These results provide a reference for dynamic analysis and design of super-long-span cable-stayed bridges.
基金Project(2012zzts019)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(201306370121)supported by State Scholarship Fund of ChinaProject(51248006)supported by the National Natural Science Foundation,China
文摘This work presented the development and validation of an analytical method to predict the transient temperature field in the asphalt pavement.The governing equation for heat transfer was based on heat conduction radiation and convection.An innovative time-dependent function was proposed to predict the pavement surface temperature with solar radiation and air temperature using dimensional analysis in order to simplify the complex heat exchange on the pavement surface.The parameters for the time-dependent pavement surface temperature function were obtained through the regression analysis of field measurement data.Assuming that the initial pavement temperature distribution was linear and the influence of the base course materials on the temperature of the upper asphalt layers was negligible,a close-form analytical solution of the temperature in asphalt layers was derived using Green's function.Finally,two numerical examples were presented to validate the model solutions with field temperature measurements.Analysis results show that the solution accuracy is in agreement with field data and the relative errors at a shallower depth are greater than those at a deeper one.Although the model is not sensitive to dramatic changes in climatic factors near the pavement surface,it is applicable for predicting pavement temperature field in cloudless days.
基金This research was supported by the National Science Foundation,Grant No.CMS-984754(Dr.C.Astill program manager)the US Army Engineer Research and Development Center.
文摘The mechanisms of seismically-induced liquefaction of granular soils underhigh confining stresses are still not fully understood. Evaluation of these mechanisms is generallybased on extrapolation of observed behavior at shallow depths. Three centrifuge model tests wereconducted at RPI's experimental facility to investigate the effects of confining stresses on thedynamic response of a deep horizontal deposit of saturated sand. Liquefaction was observed at highconfining stresses in each of the tests. A system identification procedure was used to estimate theassociated shear strain and stress time histories. These histories revealed a response marked byshear strength degradation and dilative patterns. The recorded accelerations and pore pressures wereemployed to generate visual animations of the models. These visualizations revealed a liquefactionfront traveling downward and leading to large shear strains and isolation of upper soil layers.
基金Research fund of Hanyang University Under Grant No.HY-2010-N
文摘This paper examines the quasi-static cyclic behavior, lateral strength and equivalent damping capacities of a system of post-tensioned segmental bridge columns tied with large diameter martensitic Shape Memory Alloy (SMA) link-bars. Moment-curvature constitutive relationships are formulated and analysis tools are developed for the PT column, including a modified four-spring model prepared for the SMA bars. The suggested system is exemplified using a column with an aspect ratio of 7.5 and twelve 36.5 mm diameter NiTi martensitic SMA bars. A post-tensioning force of 40% to 60% of the tendon yield strength is applied in order to obtain a self re-centering system, considering the residual stress of the martensitie SMA bars. The cyclic response results show that the lateral strength remains consistently around 10% of the total vertical load and the equivalent viscous damping ratios reach 10%-12% of critical. When large diameter NiTi superelastic SMA bars are incorporated into the column system, the cyclic response varies substantially. The creep behavior of the superelastic SMA bar is accounted for since it affects the re-centering capability of the column. Two examples are presented to emphasize the modeling sensitivities for these special bars and quantify their cyclic behavior effects within the column assembly.
基金financial support provided by the Overseas Research Student (ORS) award scheme of the Vice-Chancellors committee of the United Kingdom's universities as well as the A.G. Leventis Foundation
文摘An analytical seismic fragility assessment framework is presented for the existing low strength reinforced concrete structures more common in the building stock of the developing countries.For realistic modelling of such substandard structures,low strength concrete stress-strain and bond-slip capacity models are included in calibrating material models.Key capacity parameters are generated stochastically to produce building population and cyclic pushover analysis is carried out to capture inelastic behaviour.Secant period values are evaluated corresponding to each displacement step on the capacity curves and used as seismic demand.A modified capacity demand diagram method is adopted for the degrading structures,which is further used to evaluate peak ground acceleration from back analysis considering each point on the capacity curve as performance point.For developing fragility curves,the mean values of peak ground acceleration are evaluated corresponding to each performance point on the series of capacity curves.A suitable probability distribution function is adopted for the secant period scatter at different mean peak ground acceleration values and probability of exceedance of limit states is evaluated.A suitable regression function is used for developing fragility curves and regression coefficients are proposed for different confidence levels.Fragility curves are presented for a low rise pre-seismic code reinforced concrete structure typical of developing countries.
基金Sponsored by the National Basic Research Program of China (Grant No.2004CB418505)
文摘Many biodiversity indices were used to indicate the biological contamination degree in studies of lake water or seawater. Some were studied on biodiversity comparison for different areas at the same time, or initial structure succession of some aerial lake water systems. The phytoplankton changed with the development of various dominant species. In this study, the dominant species at these stages were Chlorophyta in the beginning stage, Cyanophyta in the second stage, and Xanthophyta in the last stage. Seven of nine biodiversity indices (Margalef's, IE, Shannon-Wiener, Simpson's, McNaughton's, Species and Odds Measure of Diversity) showed their failure to represent the eutrophication trend, and the other two indices (Menhinick's and Monk) exhibited good efficiency to indicate the eutrophication trend for the static landscaping water body.
文摘Recent Cryptosporidium outbreaks have highlighted concerns about filter efficiency and in particular particle breakthrough. It is essential to ascertain the causes of Cryptosporidium sized particle breakthrough for Cryptosporidium cannot be destroyed by conventional chlorine disinfection. This research tried to investigate the influence of temperature, flow rate and chemical dosing on particle breakthrough during filtration. The results showed that higher temperatures and coagulant doses could reduce particle breakthrough. The increase of filtration rate made the residual particle counts become larger. There was an optimal dose in filtration and was well correlated to ζ potential.
基金the National Basic Research Program of China (973 Project) (No. 2009CB623200)National Natural Science Foundation of China (No. 50808043)+1 种基金the Doctoral Program of Higher Education of China (No. 20070286024)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘External bonding of fiber reinforced polymer (FRP) composites on the concrete structures has been proved to be an effective and efficient way to strengthen concrete structures. For a FRP strengthened concrete beam, it is usually observed that the failure occurs in the concrete and a thin layer of concrete is attached on the surface of the debonded FRP plate. To study the debond behavior between concrete and FRP composites, an analytical model based on the three-parameter model is developed to study the debonding behavior for the FRP-to-concrete joint under pure shearing. Then, nonlinear FEM analysis is conducted to verify the PrOposed analytical model. The FEM results shows good agreement with the results from the model. Finally, with the analytical model, sensitivity analyses are performed to study the effect of the interracial parameters or the ~eometric parameters on the debondin~ behavior.
文摘Wastes yielded in the vintage process and the biological fermentation of itaconic acid and sodium gluconate of a winery in Shandong, such as grain stillage, melon lees, cornstarch protein residues, itaconic acid mother liquid, itaconic acid mycelium and sodium gluconate mycelium, were studied. High-activity biological protein feed, foliar fertilizer and irrigation fertilizer were generated from these wastes by applying biological/microbial technologies. Meanwhile, a whole set of technological pathways was put forward. As a result, the optimal economical and social benefits can be obtained with low natural resource consumption and environmental costs by converting wastes into useful matters. In conclusion, through the utilization of limited resources in the whole process of reclamation and utilization of wastes, the harmony promotion can be achieved between the economic system and the natural ecosystem.
文摘A closed-form analytic solution of two-dimensional scattering and diffraction of plane SH waves by a semi- cylindrical hill with a semi-cylindrical concentric tunnel inside an elastic half-space is presented using the cylindrical wave functions expansion method.The solution is reduced to solving a set of infinite linear algebraic equations.Fourier expansion theorem with the form of complex exponential function and cosine function is used.Numerical solutions are obtained by truncation of the infinite equations.The accuracy of the presented numerical results is carefully verified.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51138003)
文摘In order to estimate vehicular queue length at signalized intersections accurately and overcome the shortcomings and restrictions of existing studies especially those based on shockwave theory,a new methodology is presented for estimating vehicular queue length using data from both point detectors and probe vehicles. The methodology applies the shockwave theory to model queue evolution over time and space. Using probe vehicle locations and times as well as point detector measured traffic states,analytical formulations for calculating the maximum and minimum( residual) queue length are developed. The proposed methodology is verified using ground truth data collected from numerical experiments conducted in Shanghai,China. It is found that the methodology has a mean absolute percentage error of 17. 09%,which is reasonably effective in estimating the queue length at traffic signalized intersections. Limitations of the proposed models and algorithms are also discussed in the paper.
基金Research Committee of the University of Macao under Grant No.MYRG2015-00048-FST
文摘Evaluation of the cyclic shear modulus of soils is a crucial but challenging task for many geotechnical earthquake engineering and soil dynamic issues. Improper determination of this property unnecessarily drives up design and maintenance costs or even leads to the construction of unsafe structures. Due to the complexities involved in the direct measurement, empirical curves for estimating the cyclic shear modulus have been commonly adopted in practice for simplicity and economical considerations. However, a systematic and robust approach for formulating a reliable model and empirical curve for cyclic shear modulus prediction for clayey soils is still lacking. In this study, the Bayesian model class selection approach is utilized to identify the most significant soil parameters affecting the normalized cyclic shear modulus and a reliable predictive model for normally to moderately over-consolidated clays is proposed. Results show that the predictability and reliability of the proposed model out performs the well-known empirical models. Finally, a new design chart is established for practical usage.
基金This study was supported by the National Natural Science Foundation of China under Grant No.50078016Open Funding of State Key Laboratory for Disaster Reduction in Civil Engineering,China.
文摘Shaking table tests of a 1:10 scale arch model performed to investigate the seismic behavior and resistance of concrete filled steel tubular (CFT) arch structures are described in this paper. The El-Centro record and Shanghai artificial wave were adopted as the input excitation. The entire test process can be divided into three stages depending on the lateral brace configurations, i.e., fully (five) braced, two braces removed, and all braces removed. A total of 46 tests, starting from the elastic state to failure condition, have been conducted. The natural vibration frequencies, responses of acceleration, displacement and strain were measured. From the test results, it is demonstrated that the CFT arch structures are capable of resisting severe ground motions and that CFT arches offer a credible alternative to reinforced concrete arches, especially in regions of high seismic intensity.
基金used the Extreme Science and Engineering Discovery Environment(XSEDE),which is supported by National Science Foundation(NSF)Grant No.ACI-1548562。
文摘Integral abutment bridges(IABs)minimize deterioration and degradation of the abutment seats and bearings due to water,dirt,and deicing chemicals by eliminating bearings and expansion joints.Although the continuity between superstructure and abutments in an IAB is beneficial for reducing maintenance costs,it leads to more complex behavior under strength and service loading(temperature and traffic)and extreme loading(earthquake).The coupling of superstructure and substructure behavior necessitates system-level analysis of IABs.Prior seismic IAB studies have typically investigated the behavior of individual IAB components,however a gap of knowledge has developed due to the lack of studies and investigation about the behavior of all IAB components and their interactions with each other in a single analysis model.This study uses nonlinear static and dynamic analyses to investigate and assess the seismic behavior of IABs typical to the state of Illinois.The analyses aim to bridge the gap of knowledge by evaluating IABs as a whole and utilizing the results to indicate potential vulnerabilities in the design and construction of IABs in Illinois during design-level and larger seismic events,which could not be identified by component-level IAB analyses alone.
基金supported by the National Natural Science Foundation of China(Grant Nos.41877260,41772336).
文摘Calcareous sand is widely observed in the foundation of off-shore infrastructure.Although a lot of research has been carried out on the mechanical properties of calcareous sand,study into the influence of the stress–strain path on the mechanical behaviour of calcareous sand is very limited.In this study,a series of triaxial tests were performed on calcareous sand under three different stress paths.The particle morphology of calcareous sand before and after the tests,the stress–strain relationship under different stress paths,and the char-acteristics of shear strength and deformation were investigated.The results show that the consolidation pressure and stress path have significant effects on the volume strain,strength,and particle breakage of calcareous sand.In addition,the underlying mechanisms of the different behaviours of calcareous sand observed in this study were discussed.
文摘Biological activated carbon (BAC) has been developed on the granular activated carbon by immobilization of selected and acclimated species of bacteria to treat the micro-polluted water. The BAC removal efficiencies for nitrobenzene, permanganate index, turbidity and ammonia were investigated. Effects of shock loading and SEM (Scanning Electron Microscope) observation on BAC were studied. Backwashing and its intensity of BAC were also discussed. The results showed that BAC took short time to start up and recover to the normal condition after shock loading. The shock loading studies showed that the removal efficiency of BAC was not completely inhibited even at high concentration of nitrobenzene. Backwashing performed once every 10-20 d, or an average of 15 d. Backwashing intensity was 12-14 L/(s·m2) with air and 3-4 L/(s·m2) with water.