Use of stainless reinforcing steel （SRS） in reinforced concrete （RC） structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need ...Use of stainless reinforcing steel （SRS） in reinforced concrete （RC） structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue behavior. Three types of SRSs （Talley S24100, Talley 316LN and Talley 2205） were tested and the results are reported in this paper. They were compared with the properties of A706 carbon reinforcing steel （RS）, which is typical for seismic applications, and MMFX II, which is a high strength, corrosion resistant RS. Low-cycle fatigue tests of the RS coupons were conducted under strain control with constant amplitude to obtain strain life models of the steels. Test results show that the SRSs have slightly lower moduli of elasticity, higher uniform elongations before necking, and better low-cycle fatigue performance than A706 and MMFX II. All five types of RSs tested satisfy the requirements of the ACI 318 code on the lower limit of the tensile to yield strength ratio. Except Talley 2205, the other four types of RSs investigated meet the ACI 318 requirement that the actual yield strength does not exceed the specified yield strength by more than 18 ksi （124 MPa）. Among the three types of SRSs tested, Talley S24100 possesses the highest uniform elongation before necking, and the best low-cycle fatigue performance.展开更多
Small hydropower plants for electricity generation were first built in Spain in the early 1880s. The Spanish peninsula is characterized by its rugged landscape, fast flowing rivers and steep gradients. A clear example...Small hydropower plants for electricity generation were first built in Spain in the early 1880s. The Spanish peninsula is characterized by its rugged landscape, fast flowing rivers and steep gradients. A clear example of this is the remarkable area of the upper Ebro river basin where powerful water flows are found that are ideal for electricity generation. Between 1900 and 1930, the river Ebro was a major source of energy for industrial areas such as Alava, Vizcaya, Vitoria, Miranda de Ebro, Burgos and La Rioja. Between 1951-1965, the use of these small hydropower plants declined due to the construction of alternatives by industrialists in the Basque Country, which in most cases led to their deterioration. They were rescued in the late twentieth century, thanks to private sector initiatives which funded their rehabilitation. This study examines two small-scale hydraulic power plants in the province of Burgos at Medina de Pomar and at Quintanilla Escalada; both buildings were used for generating electricity and had living quarters for the workers and now represent historic architectonic and industrial heritage. The study documents their architectonic features and the restoration processes that have permitted one of them to remain in operation up until the present day.展开更多
Time and cost are two of the most important factors to consider in each construction project. In order to maximize performance, both the client and the contractor will work to optimize both the duration of the project...Time and cost are two of the most important factors to consider in each construction project. In order to maximize performance, both the client and the contractor will work to optimize both the duration of the project and its cost. We show a model of linear entire mixed programming to solve the considered problem. The aim is to minimize the project total time, by means of the assignment of equipments of work to the different production lines of the activities to realizing. The fundamental beginning is to support the same production （rate of production in meters/day of the activity in view of the equipment of work） for tbe different equipments to achieve the maximum efficiency in each period of time. With the limited availability of resources, the work must be continuous and the period of time between operations and final must be kept. However, this paper also presents the bibliographical study on methodologies of the optimization of construction processes in response to the two objectives： time and cost. This will consider the use of recta-heuristic techniques, such as population based algorithms.展开更多
Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak...Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak shear stress-displacement behavior is central to various time-dependent and dynamic rock mechanic problems such as rockbursts and structural instabilities in highly stressed conditions.The complete stress-displacement surface(CSDS)model was developed to describe analytically the pre-and post-peak behavior of rock interfaces under differential loads.Original formulations of the CSDS model required extensive curve-fitting iterations which limited its practical applicability and transparent integration into engineering tools.The present work proposes modifications to the CSDS model aimed at developing a comprehensive and modern calibration protocol to describe the complete shear stressdisplacement behavior of rock interfaces under differential loads.The proposed update to the CSDS model incorporates the concept of mobilized shear strength to enhance the post-peak formulations.Barton’s concepts of joint roughness coefficient(JRC)and joint compressive strength(JCS)are incorporated to facilitate empirical estimations for peak shear stress and normal closure relations.Triaxial/uniaxial compression test and direct shear test results are used to validate the updated model and exemplify the proposed calibration method.The results illustrate that the revised model successfully predicts the post-peak and complete axial stressestrain and shear stressedisplacement curves for rock joints.展开更多
The application of carbon nanomaterials, particularly graphene and carbon nanotubes, in cement-based composites is highly significant. These materials demonstrate the multifunctionality of carbon and offer extensive p...The application of carbon nanomaterials, particularly graphene and carbon nanotubes, in cement-based composites is highly significant. These materials demonstrate the multifunctionality of carbon and offer extensive possibilities for technological advancements. This research analyzes how the integration of graphene into cement-based composites enhances damping and mechanical properties, thereby contributing to the safety and durability of structures. Research on carbon nanomaterials is ongoing and is expected to continue driving innovation across various industrial sectors, promoting the sustainable development of building materials.展开更多
This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical propertie...This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical properties enhancement mechanisms were analyzed and compared through the porosity structure test, XRD analysis, and scanning electron microscope observation. The results show that the introduction of nanosilica significantly improves the dispersion of carbon nanotubes in the cement matrix. At the same time, the addition of nanosilica not only effectively reduces the critical pore size and average pore size of the cement composite material, but also exhibits good synergistic effects with carbon nanotubes, which can significantly optimize the pore structure. Finally, a rationalization suggestion for the co-doping of nanosilica and carbon nanotubes was given to achieve a significant increase in the flexural strength, compressive strength and loss factor of cement-based materials.展开更多
This paper aims to present a comprehensive proposal for project scheduling and control by applying fuzzy earned value.It goes a step further than the existing literature:in the formulation of the fuzzy earned value we...This paper aims to present a comprehensive proposal for project scheduling and control by applying fuzzy earned value.It goes a step further than the existing literature:in the formulation of the fuzzy earned value we consider not only its duration,but also cost and production,and alternatives in the scheduling between the earliest and latest times.The mathematical model is implemented in a prototypical construction project with all the estimated values taken as fuzzy numbers.Our findings suggest that different possible schedules and the fuzzy arithmetic provide more objective results in uncertain environments than the traditional methodology.The proposed model allows for controlling the vagueness of the environment through the adjustment of the α-cut,adapting it to the specific circumstances of the project.展开更多
Energy dissipators, isolated-resistant and specific structural forms for earthquake resistance are popular topics in the research to improve shock-resistance. In this work, experimental methods were used to investigat...Energy dissipators, isolated-resistant and specific structural forms for earthquake resistance are popular topics in the research to improve shock-resistance. In this work, experimental methods were used to investigate the property of low yield strength steel. Carbon content in LYS material is lower than that in other steels; the ultimate stress is three times the yield stress. The ultimate elongation rate is about 62% and the ductility is 23 times that of A36 steel. In order to overcome some defects of ordinary use metallic dampers, the mechanical characteristic of low yield strength steel is used to develop added damping and stiffness for rhombic steel plate absorber. Test of the energy dissipation behavior for this newly de-veloped device indicated that LYS could stably dissipate or absorb the input energy of earthquake. Then, the analytical model for the hysteretic behavior of this new device is proposed. Comparison of experimental data and numerical simulation results showed that this analytical model is suitable for simulating the hysteretic energy behavior of this new device.展开更多
We investigated the structural behavior and bearing capacity of system scaffolds.The research showed that the critical load of a system scaffold structure without diagonal braces is similar to that of a door-shaped st...We investigated the structural behavior and bearing capacity of system scaffolds.The research showed that the critical load of a system scaffold structure without diagonal braces is similar to that of a door-shaped steel scaffold structure.Joint stiffness between vertical props in system scaffolds can be defined based on a comparison between analytical and experimental results.When the number of scaffold stories increases,the critical loads of system scaffolds decrease.Diagonal braces markedly enhance the critical load of system scaffolds.The coupling joint position between vertical props should be kept away from story-to-story joints to prevent a reduction in critical loads.The critical load of a system scaffold decreases as the quantity of extended vertical props at the bottom of the structure increases.A large Christmas tree set up by system scaffolds under various loads was used as an example for analysis and to check the design of system scaffolds.展开更多
Black shale samples were collected from Chimiari Khyber Pakthunkhawa region of Pakistan and were analyzed for elemental compositions. Atomic Absorption Spectrophotometry (AAS) was utilized for the determination of ele...Black shale samples were collected from Chimiari Khyber Pakthunkhawa region of Pakistan and were analyzed for elemental compositions. Atomic Absorption Spectrophotometry (AAS) was utilized for the determination of elements in the digested solutions. The analysis of black shale was performed precisely with relative standard deviation (RSD) lower than 2%. Results showed that the samples contained high concentrations of Ca (11.98 %), Al (7.09%), Fe (3.03%), Mg (0.59%) and Ti (0.58%).展开更多
Structural health monitoring of RC structures under seismic loads has recently attracted much attention in the earthquake engineering research community. In this study, a piezoceramic-based device called ＂smart aggre...Structural health monitoring of RC structures under seismic loads has recently attracted much attention in the earthquake engineering research community. In this study, a piezoceramic-based device called ＂smart aggregate＂ was used for the health monitoring of RC frame structures under earthquake excitations. Three RC moment frames instrumented with smart aggregates were tested using a shaketable with different ground excitation intensities. Distributed piezoceramic- based smart aggregates were embedded in the RC structures and used to monitor their health condition during the tests. The sensitivity and effectiveness of the proposed piezoceramic-based approach were investigated and evaluated by analyzing the measured responses. The displacement ductility demand of the structural members was calculated and compared with the damage index determined from the health monitoring system. The comparison shows that the damage index is compatible with the calculated ductility demand.展开更多
Most serious natural disasters cause fatalities and injuries, and result in infrastructure damage, economic impacts, and social effects. With respect to the nature of impacts, it is important to understand the direct ...Most serious natural disasters cause fatalities and injuries, and result in infrastructure damage, economic impacts, and social effects. With respect to the nature of impacts, it is important to understand the direct and indirect impacts of natural disasters on infrastructure and industries. In this paper, a holistic disaster impact analysis framework is presented to support more understanding of natural disaster events with respect to inter-relation of infrastructure and associated industries. Disaster impact mechanism and inter-relations based on critical function of industries derived from the extensive literature review and case studies. To develop the framework, service factor is chosen to measure the level of inter-relations and proper weights for each inter-relation between infrastructure and associated industries are obtained by surveying experts in the area of disaster mitigation, emergency organizations, and infrastructure management. This paper focuses on the impact analysis of hurricane disaster and the outcome can also be applied to other types of disasters.展开更多
The most significant differences between continuous welded rails （CWRs） and general split-type connectors are axial compression in the longitudinal direction, buckling stability and other issues generated under the ...The most significant differences between continuous welded rails （CWRs） and general split-type connectors are axial compression in the longitudinal direction, buckling stability and other issues generated under the influence of thermal effect. Under thermal effect, a dynamical behavior similar to that of a beam fixed on two sides occurs in the central locked area of the welded rail, as there is axial compression but no possibility of sliding. Continuous welded rails do not contract or expand, and are supported by the dynamical system made up of ballasts and rail clips. The rail-support system mentioned above has the features of non-uniform material distribution and uncertainty of construction quality. Due to these facts, the dynamics method based on the linear elastic hypothesis cannot correctly evaluate the rail＇s buckling conditions. This study is aimed at applying Finite Difference Method （FDM） and Monte Carlo Random Normal Variables Method to the analysis of welded rail＇s buckling behavior during the train＇s acceleration and deceleration, under thermal effect and uncertain factors of ballast and rail clips. The analysis result showed that buckling occurs under the combined effect of thermal effect and the train＇s deceleration force co-effect and the variance ratio of ballast and rail clips is over 0.85, or under the combined effect of thermal effect and the train＇s acceleration force when the ariance ratio is over 0.88.展开更多
The characteristic properties of shell element with similar shapes are used to generate a so-called super element for the analysis of the crack problems for cylindrical pressure vessels. The formulation is processed b...The characteristic properties of shell element with similar shapes are used to generate a so-called super element for the analysis of the crack problems for cylindrical pressure vessels. The formulation is processed by matrix condensation without the involvement of special treatment. This method can deal with various singularity problems and it also presents excellent results to crack problems for cylindrical shell. Especially,the knowledge of the kind of singular order is not necessary in super element generation; it is very economical in terms of computer memory and programming. This method also exhibits versatility to solve the problem of kinked crack at cylindrical shell.展开更多
Many historic buildings in old urban centers in Eastern Canada are made of stone masonry reputed to be highly vulnerable to seismic loads.Seismic risk assessment of stone masonry buildings is therefore the first step ...Many historic buildings in old urban centers in Eastern Canada are made of stone masonry reputed to be highly vulnerable to seismic loads.Seismic risk assessment of stone masonry buildings is therefore the first step in the risk mitigation process to provide adequate planning for retrofit and preservation of historical urban centers.This paper focuses on development of analytical displacement-based fragility curves reflecting the characteristics of existing stone masonry buildings in Eastern Canada.The old historic center of Quebec City has been selected as a typical study area.The standard fragility analysis combines the inelastic spectral displacement,a structure-dependent earthquake intensity measure,and the building damage state correlated to the induced building displacement.The proposed procedure consists of a three-step development process：（1） mechanics-based capacity model,（2） displacement-based damage model and（3） seismic demand model.The damage estimation for a uniform hazard scenario of 2% in 50 years probability of exceedance indicates that slight to moderate damage is the most probable damage experienced by these stone masonry buildings.Comparison is also made with fragility curves implicit in the seismic risk assessment tools Hazus and ELER.Hazus shows the highest probability of the occurrence of no to slight damage,whereas the highest probability of extensive and complete damage is predicted with ELER.This comparison shows the importance of the development of fragility curves specific to the generic construction characteristics in the study area and emphasizes the need for critical use of regional risk assessment tools and generated results.展开更多
Based on the background of navigation lock structure engineering in Changsha Integrated Hub, this study used Parametric Design Language （APDL） compilation command on the t＇mite element program ANSAYS platforms to s...Based on the background of navigation lock structure engineering in Changsha Integrated Hub, this study used Parametric Design Language （APDL） compilation command on the t＇mite element program ANSAYS platforms to simulate the temperature field of the layered pouring process about the lower lock head. The temperature contour map and the change laws of temperature field with time in each different levels of the floor were obtained. And compared with the actual instrument measurement data, the feasibility of the simulation analysis was concluded. Then, this study optimized the pouring process, obtained the suitable methods of layered pouring and put forward the measures to reduce the concrete temperature crack.展开更多
This study proposes a micro vibration mitigation system using viscous dampers to solve the problem of vibration in a high-tech building. Due to the operating frequency of the air conditioners and fundamental mode of t...This study proposes a micro vibration mitigation system using viscous dampers to solve the problem of vibration in a high-tech building. Due to the operating frequency of the air conditioners and fundamental mode of the floors, a resonant phenomenon is occasionally experienced at the upper levels of the structure. Several strategies were considered, and viscous dampers combined with a suspension system were chosen to mitigate this annoying situation. A theoretical analysis was first executed to determine the optimal design value of the damper and the suspension spring. An efficient reduction in floor velocity of approximately 50 % was achieved by the proposed system. Practical verifications including a performance test of the micro-vibration-oriented dampers, the pragmatic application result, and a comparison in one-third octave spectrum was then carried out. The performance of the system was demonstrated by the data measured. It alleviated more trembling than was numerically expected. The energy absorbed by the viscous dampers is illustrated by the hysteresis loops and the one-third octave spectrum. It is found that with the proposed system, the vibration can be effectively captured by the viscous damper and converted to lower frequency-content tremors. The success of this project greatly supports the proposed standard two-stage analysis procedure for mitigating micro-vibration problems in practice. This research extends the use of viscous dampers to a new field.展开更多
The strength and durability properties of concrete with or without three types of rice husk ash （RHA）, namely, amorphous, partial crystalline, and crystalline RHA, were investigates. The three types of RHA were adde...The strength and durability properties of concrete with or without three types of rice husk ash （RHA）, namely, amorphous, partial crystalline, and crystalline RHA, were investigates. The three types of RHA were added into concrete at a 20% replacement level. Consequently, the pozzolanic reactivity of amorphous RHA was higher than that of partial crystalline and crystalline RHA. Concrete added with amorphous RHA showed excellent characteristics in its mechanical and durability properties. The results showed that the higher the amount of crystalline silica in RHA, the lower the concrete resistivity value became. When compared with each other, concretes with 20% of the ce- ment replaced with these types of RHA achieved similar ultrasonic pulse velocity values, but all were lower than that of the control concrete. The incorporation of these kinds of RHA significantly reduced chloride penetration. The results not only encourage the use of amorphous materials, they also support the application of crystalline or partial crystalline RHA as mineral and pozzolanic admixtures for cement.展开更多
Reducing steel slag （RSS） was mainly acquired from five electric-arc furnace （EAF） steelmaking plants （among them, the products of two plants were carbon steel and those of other plants were stainless steel） for...Reducing steel slag （RSS） was mainly acquired from five electric-arc furnace （EAF） steelmaking plants （among them, the products of two plants were carbon steel and those of other plants were stainless steel） for research tests. The chemical properties, compound compositions, activities and contents of main expansive compounds were tested. The results showed that the field sampled RSS had a very high crystallinity and hydraulicity with main chemical compositions close to those of Portland cement. It can be known from the study that in case of C/S ratio higher than 2.0, the main compound compositions are C2S, C3S, C2F and f-CaO. However, after the RSS was stored for six months, an obvious variation occurred with potential pre-hydration in RSS, where the SO3 content was slightly reduced and the compressive activity index was obviously higher than that at the 28th day.展开更多
This paper describes one approach to the design of reinforced concrete (RC) bridge piers, using a three-hybrid multi- objective simulated annealing (SA) algorithm with a neighborhood move based on the mutation operato...This paper describes one approach to the design of reinforced concrete (RC) bridge piers, using a three-hybrid multi- objective simulated annealing (SA) algorithm with a neighborhood move based on the mutation operator from the genetic algorithms (GAs), namely MOSAMO1, MOSAMO2 and MOSAMO3. The procedure is applied to three objective functions: the economic cost, the reinforcing steel congestion and the embedded CO 2 emissions. Additional results for a random walk and a descent local search multi-objective algorithm are presented. The evaluation of solutions follows the Spanish Code for structural concrete. The methodology was applied to a typical bridge pier of 23.97 m in height. This example involved 110 design variables. Results indicate that algorithm MOSAMO2 outperforms other algorithms regarding the definition of Pareto fronts. Further, the proposed procedure will help structural engineers to enhance their bridge pier designs.展开更多
基金Federal Highway Administration Under Contract No.DTFH61-07-R-00121International Molybdenum Association,Nickel Institute,Talley Metals-A Carpenter Company,North American Stainless and Salit Specialty Steel Through MCEER,University at Buffalo
文摘Use of stainless reinforcing steel （SRS） in reinforced concrete （RC） structures is a promising solution to corrosion issues. However, for SRS to be used in seismic applications, several mechanical properties need to be investigated. These include specified and actual yield strengths, tensile strengths, uniform elongations and low-cycle fatigue behavior. Three types of SRSs （Talley S24100, Talley 316LN and Talley 2205） were tested and the results are reported in this paper. They were compared with the properties of A706 carbon reinforcing steel （RS）, which is typical for seismic applications, and MMFX II, which is a high strength, corrosion resistant RS. Low-cycle fatigue tests of the RS coupons were conducted under strain control with constant amplitude to obtain strain life models of the steels. Test results show that the SRSs have slightly lower moduli of elasticity, higher uniform elongations before necking, and better low-cycle fatigue performance than A706 and MMFX II. All five types of RSs tested satisfy the requirements of the ACI 318 code on the lower limit of the tensile to yield strength ratio. Except Talley 2205, the other four types of RSs investigated meet the ACI 318 requirement that the actual yield strength does not exceed the specified yield strength by more than 18 ksi （124 MPa）. Among the three types of SRSs tested, Talley S24100 possesses the highest uniform elongation before necking, and the best low-cycle fatigue performance.
文摘Small hydropower plants for electricity generation were first built in Spain in the early 1880s. The Spanish peninsula is characterized by its rugged landscape, fast flowing rivers and steep gradients. A clear example of this is the remarkable area of the upper Ebro river basin where powerful water flows are found that are ideal for electricity generation. Between 1900 and 1930, the river Ebro was a major source of energy for industrial areas such as Alava, Vizcaya, Vitoria, Miranda de Ebro, Burgos and La Rioja. Between 1951-1965, the use of these small hydropower plants declined due to the construction of alternatives by industrialists in the Basque Country, which in most cases led to their deterioration. They were rescued in the late twentieth century, thanks to private sector initiatives which funded their rehabilitation. This study examines two small-scale hydraulic power plants in the province of Burgos at Medina de Pomar and at Quintanilla Escalada; both buildings were used for generating electricity and had living quarters for the workers and now represent historic architectonic and industrial heritage. The study documents their architectonic features and the restoration processes that have permitted one of them to remain in operation up until the present day.
文摘Time and cost are two of the most important factors to consider in each construction project. In order to maximize performance, both the client and the contractor will work to optimize both the duration of the project and its cost. We show a model of linear entire mixed programming to solve the considered problem. The aim is to minimize the project total time, by means of the assignment of equipments of work to the different production lines of the activities to realizing. The fundamental beginning is to support the same production （rate of production in meters/day of the activity in view of the equipment of work） for tbe different equipments to achieve the maximum efficiency in each period of time. With the limited availability of resources, the work must be continuous and the period of time between operations and final must be kept. However, this paper also presents the bibliographical study on methodologies of the optimization of construction processes in response to the two objectives： time and cost. This will consider the use of recta-heuristic techniques, such as population based algorithms.
基金The authors acknowledge the financial support from Natural Sciences and Engineering Research Council of Canada through its Discovery Grant program(RGPIN-2022-03893)École de Technologie Supérieure(ÉTS)construction engineering research funding.
文摘Conventional numerical solutions developed to describe the geomechanical behavior of rock interfaces subjected to differential load emphasize peak and residual shear strengths.The detailed analysis of preand post-peak shear stress-displacement behavior is central to various time-dependent and dynamic rock mechanic problems such as rockbursts and structural instabilities in highly stressed conditions.The complete stress-displacement surface(CSDS)model was developed to describe analytically the pre-and post-peak behavior of rock interfaces under differential loads.Original formulations of the CSDS model required extensive curve-fitting iterations which limited its practical applicability and transparent integration into engineering tools.The present work proposes modifications to the CSDS model aimed at developing a comprehensive and modern calibration protocol to describe the complete shear stressdisplacement behavior of rock interfaces under differential loads.The proposed update to the CSDS model incorporates the concept of mobilized shear strength to enhance the post-peak formulations.Barton’s concepts of joint roughness coefficient(JRC)and joint compressive strength(JCS)are incorporated to facilitate empirical estimations for peak shear stress and normal closure relations.Triaxial/uniaxial compression test and direct shear test results are used to validate the updated model and exemplify the proposed calibration method.The results illustrate that the revised model successfully predicts the post-peak and complete axial stressestrain and shear stressedisplacement curves for rock joints.
文摘The application of carbon nanomaterials, particularly graphene and carbon nanotubes, in cement-based composites is highly significant. These materials demonstrate the multifunctionality of carbon and offer extensive possibilities for technological advancements. This research analyzes how the integration of graphene into cement-based composites enhances damping and mechanical properties, thereby contributing to the safety and durability of structures. Research on carbon nanomaterials is ongoing and is expected to continue driving innovation across various industrial sectors, promoting the sustainable development of building materials.
文摘This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical properties enhancement mechanisms were analyzed and compared through the porosity structure test, XRD analysis, and scanning electron microscope observation. The results show that the introduction of nanosilica significantly improves the dispersion of carbon nanotubes in the cement matrix. At the same time, the addition of nanosilica not only effectively reduces the critical pore size and average pore size of the cement composite material, but also exhibits good synergistic effects with carbon nanotubes, which can significantly optimize the pore structure. Finally, a rationalization suggestion for the co-doping of nanosilica and carbon nanotubes was given to achieve a significant increase in the flexural strength, compressive strength and loss factor of cement-based materials.
基金Project partially supported by the Spanish Ministry of Science and Innovation (No.BIA2011-23602)the European Community with the European Regional Development Fund (FEDER),Spain
文摘This paper aims to present a comprehensive proposal for project scheduling and control by applying fuzzy earned value.It goes a step further than the existing literature:in the formulation of the fuzzy earned value we consider not only its duration,but also cost and production,and alternatives in the scheduling between the earliest and latest times.The mathematical model is implemented in a prototypical construction project with all the estimated values taken as fuzzy numbers.Our findings suggest that different possible schedules and the fuzzy arithmetic provide more objective results in uncertain environments than the traditional methodology.The proposed model allows for controlling the vagueness of the environment through the adjustment of the α-cut,adapting it to the specific circumstances of the project.
文摘Energy dissipators, isolated-resistant and specific structural forms for earthquake resistance are popular topics in the research to improve shock-resistance. In this work, experimental methods were used to investigate the property of low yield strength steel. Carbon content in LYS material is lower than that in other steels; the ultimate stress is three times the yield stress. The ultimate elongation rate is about 62% and the ductility is 23 times that of A36 steel. In order to overcome some defects of ordinary use metallic dampers, the mechanical characteristic of low yield strength steel is used to develop added damping and stiffness for rhombic steel plate absorber. Test of the energy dissipation behavior for this newly de-veloped device indicated that LYS could stably dissipate or absorb the input energy of earthquake. Then, the analytical model for the hysteretic behavior of this new device is proposed. Comparison of experimental data and numerical simulation results showed that this analytical model is suitable for simulating the hysteretic energy behavior of this new device.
基金Project supported by the National Science Council,Taiwan(No. NSC 93-2211-E-224-002)the Service Center of Construction Tech-nology and Materials,National Yunlin University of Science and Technology,Taiwan(No.95-215)the Hong Kong Polytechnic University(Nos.PolyU 5115/07E and PolyU 5117/06E),Hong Kong,China
文摘We investigated the structural behavior and bearing capacity of system scaffolds.The research showed that the critical load of a system scaffold structure without diagonal braces is similar to that of a door-shaped steel scaffold structure.Joint stiffness between vertical props in system scaffolds can be defined based on a comparison between analytical and experimental results.When the number of scaffold stories increases,the critical loads of system scaffolds decrease.Diagonal braces markedly enhance the critical load of system scaffolds.The coupling joint position between vertical props should be kept away from story-to-story joints to prevent a reduction in critical loads.The critical load of a system scaffold decreases as the quantity of extended vertical props at the bottom of the structure increases.A large Christmas tree set up by system scaffolds under various loads was used as an example for analysis and to check the design of system scaffolds.
文摘Black shale samples were collected from Chimiari Khyber Pakthunkhawa region of Pakistan and were analyzed for elemental compositions. Atomic Absorption Spectrophotometry (AAS) was utilized for the determination of elements in the digested solutions. The analysis of black shale was performed precisely with relative standard deviation (RSD) lower than 2%. Results showed that the samples contained high concentrations of Ca (11.98 %), Al (7.09%), Fe (3.03%), Mg (0.59%) and Ti (0.58%).
基金NSC under Grant No.98-2221-E-027-057-MY2the Center for Research on Earthquake Engineering(NCREE)
文摘Structural health monitoring of RC structures under seismic loads has recently attracted much attention in the earthquake engineering research community. In this study, a piezoceramic-based device called ＂smart aggregate＂ was used for the health monitoring of RC frame structures under earthquake excitations. Three RC moment frames instrumented with smart aggregates were tested using a shaketable with different ground excitation intensities. Distributed piezoceramic- based smart aggregates were embedded in the RC structures and used to monitor their health condition during the tests. The sensitivity and effectiveness of the proposed piezoceramic-based approach were investigated and evaluated by analyzing the measured responses. The displacement ductility demand of the structural members was calculated and compared with the damage index determined from the health monitoring system. The comparison shows that the damage index is compatible with the calculated ductility demand.
基金Project supported by the National Science Foundation of USA (Grant No.0080209)the Innovation Program of the Education Commission of Shanghai Municipality (Grant No.09YZ172)the Consultant Project of Chinese Academy of Engineering(Grant No.200606)
文摘Most serious natural disasters cause fatalities and injuries, and result in infrastructure damage, economic impacts, and social effects. With respect to the nature of impacts, it is important to understand the direct and indirect impacts of natural disasters on infrastructure and industries. In this paper, a holistic disaster impact analysis framework is presented to support more understanding of natural disaster events with respect to inter-relation of infrastructure and associated industries. Disaster impact mechanism and inter-relations based on critical function of industries derived from the extensive literature review and case studies. To develop the framework, service factor is chosen to measure the level of inter-relations and proper weights for each inter-relation between infrastructure and associated industries are obtained by surveying experts in the area of disaster mitigation, emergency organizations, and infrastructure management. This paper focuses on the impact analysis of hurricane disaster and the outcome can also be applied to other types of disasters.
基金Project supported by the National Science Council of Taiwan (No.NSC 93-2211-E-167-002), China
文摘The most significant differences between continuous welded rails （CWRs） and general split-type connectors are axial compression in the longitudinal direction, buckling stability and other issues generated under the influence of thermal effect. Under thermal effect, a dynamical behavior similar to that of a beam fixed on two sides occurs in the central locked area of the welded rail, as there is axial compression but no possibility of sliding. Continuous welded rails do not contract or expand, and are supported by the dynamical system made up of ballasts and rail clips. The rail-support system mentioned above has the features of non-uniform material distribution and uncertainty of construction quality. Due to these facts, the dynamics method based on the linear elastic hypothesis cannot correctly evaluate the rail＇s buckling conditions. This study is aimed at applying Finite Difference Method （FDM） and Monte Carlo Random Normal Variables Method to the analysis of welded rail＇s buckling behavior during the train＇s acceleration and deceleration, under thermal effect and uncertain factors of ballast and rail clips. The analysis result showed that buckling occurs under the combined effect of thermal effect and the train＇s deceleration force co-effect and the variance ratio of ballast and rail clips is over 0.85, or under the combined effect of thermal effect and the train＇s acceleration force when the ariance ratio is over 0.88.
基金Project (No. NSC-95-2221-E-167-002) supported by the National Science Council of Taiwan, China
文摘The characteristic properties of shell element with similar shapes are used to generate a so-called super element for the analysis of the crack problems for cylindrical pressure vessels. The formulation is processed by matrix condensation without the involvement of special treatment. This method can deal with various singularity problems and it also presents excellent results to crack problems for cylindrical shell. Especially,the knowledge of the kind of singular order is not necessary in super element generation; it is very economical in terms of computer memory and programming. This method also exhibits versatility to solve the problem of kinked crack at cylindrical shell.
基金Natural Resources Canada - Geological Survey of Canada Public Safety Geoscience Programthe Chemical,Biological,Radiological-Nuclear and Explosives Research and Technology Initiative,administered by the Defence R&D Canada - Centre for Security Science
文摘Many historic buildings in old urban centers in Eastern Canada are made of stone masonry reputed to be highly vulnerable to seismic loads.Seismic risk assessment of stone masonry buildings is therefore the first step in the risk mitigation process to provide adequate planning for retrofit and preservation of historical urban centers.This paper focuses on development of analytical displacement-based fragility curves reflecting the characteristics of existing stone masonry buildings in Eastern Canada.The old historic center of Quebec City has been selected as a typical study area.The standard fragility analysis combines the inelastic spectral displacement,a structure-dependent earthquake intensity measure,and the building damage state correlated to the induced building displacement.The proposed procedure consists of a three-step development process：（1） mechanics-based capacity model,（2） displacement-based damage model and（3） seismic demand model.The damage estimation for a uniform hazard scenario of 2% in 50 years probability of exceedance indicates that slight to moderate damage is the most probable damage experienced by these stone masonry buildings.Comparison is also made with fragility curves implicit in the seismic risk assessment tools Hazus and ELER.Hazus shows the highest probability of the occurrence of no to slight damage,whereas the highest probability of extensive and complete damage is predicted with ELER.This comparison shows the importance of the development of fragility curves specific to the generic construction characteristics in the study area and emphasizes the need for critical use of regional risk assessment tools and generated results.
文摘Based on the background of navigation lock structure engineering in Changsha Integrated Hub, this study used Parametric Design Language （APDL） compilation command on the t＇mite element program ANSAYS platforms to simulate the temperature field of the layered pouring process about the lower lock head. The temperature contour map and the change laws of temperature field with time in each different levels of the floor were obtained. And compared with the actual instrument measurement data, the feasibility of the simulation analysis was concluded. Then, this study optimized the pouring process, obtained the suitable methods of layered pouring and put forward the measures to reduce the concrete temperature crack.
文摘This study proposes a micro vibration mitigation system using viscous dampers to solve the problem of vibration in a high-tech building. Due to the operating frequency of the air conditioners and fundamental mode of the floors, a resonant phenomenon is occasionally experienced at the upper levels of the structure. Several strategies were considered, and viscous dampers combined with a suspension system were chosen to mitigate this annoying situation. A theoretical analysis was first executed to determine the optimal design value of the damper and the suspension spring. An efficient reduction in floor velocity of approximately 50 % was achieved by the proposed system. Practical verifications including a performance test of the micro-vibration-oriented dampers, the pragmatic application result, and a comparison in one-third octave spectrum was then carried out. The performance of the system was demonstrated by the data measured. It alleviated more trembling than was numerically expected. The energy absorbed by the viscous dampers is illustrated by the hysteresis loops and the one-third octave spectrum. It is found that with the proposed system, the vibration can be effectively captured by the viscous damper and converted to lower frequency-content tremors. The success of this project greatly supports the proposed standard two-stage analysis procedure for mitigating micro-vibration problems in practice. This research extends the use of viscous dampers to a new field.
文摘The strength and durability properties of concrete with or without three types of rice husk ash （RHA）, namely, amorphous, partial crystalline, and crystalline RHA, were investigates. The three types of RHA were added into concrete at a 20% replacement level. Consequently, the pozzolanic reactivity of amorphous RHA was higher than that of partial crystalline and crystalline RHA. Concrete added with amorphous RHA showed excellent characteristics in its mechanical and durability properties. The results showed that the higher the amount of crystalline silica in RHA, the lower the concrete resistivity value became. When compared with each other, concretes with 20% of the ce- ment replaced with these types of RHA achieved similar ultrasonic pulse velocity values, but all were lower than that of the control concrete. The incorporation of these kinds of RHA significantly reduced chloride penetration. The results not only encourage the use of amorphous materials, they also support the application of crystalline or partial crystalline RHA as mineral and pozzolanic admixtures for cement.
文摘Reducing steel slag （RSS） was mainly acquired from five electric-arc furnace （EAF） steelmaking plants （among them, the products of two plants were carbon steel and those of other plants were stainless steel） for research tests. The chemical properties, compound compositions, activities and contents of main expansive compounds were tested. The results showed that the field sampled RSS had a very high crystallinity and hydraulicity with main chemical compositions close to those of Portland cement. It can be known from the study that in case of C/S ratio higher than 2.0, the main compound compositions are C2S, C3S, C2F and f-CaO. However, after the RSS was stored for six months, an obvious variation occurred with potential pre-hydration in RSS, where the SO3 content was slightly reduced and the compressive activity index was obviously higher than that at the 28th day.
基金supported by the Spanish Ministry of Science and Innovation(No. BIA2011-23602)the European Community with the European Regional Development Fund (FEDER), Spain
文摘This paper describes one approach to the design of reinforced concrete (RC) bridge piers, using a three-hybrid multi- objective simulated annealing (SA) algorithm with a neighborhood move based on the mutation operator from the genetic algorithms (GAs), namely MOSAMO1, MOSAMO2 and MOSAMO3. The procedure is applied to three objective functions: the economic cost, the reinforcing steel congestion and the embedded CO 2 emissions. Additional results for a random walk and a descent local search multi-objective algorithm are presented. The evaluation of solutions follows the Spanish Code for structural concrete. The methodology was applied to a typical bridge pier of 23.97 m in height. This example involved 110 design variables. Results indicate that algorithm MOSAMO2 outperforms other algorithms regarding the definition of Pareto fronts. Further, the proposed procedure will help structural engineers to enhance their bridge pier designs.
