It is important and difficult to control the temperature of mass concrete structure during high arch dam construction.A new method with decision support system is presented for temperature control and crack prevention...It is important and difficult to control the temperature of mass concrete structure during high arch dam construction.A new method with decision support system is presented for temperature control and crack prevention.It is a database system with functions of data storage,information inquiry,data analysis,early warning and resource sharing.Monitoring information during construction can be digitized via this system,and the intelligent analysis and dynamic control of concrete temperature can be conducted.This method has been applied in the construction of the Dagangshan Arch Dam in China and has proven to be very convenient.Based on the decision support of this system and the dynamic adjustment of construction measures,the concrete temperature of this project is well-controlled.展开更多
The main concern of this paper is to study the influence of the building slenderness ratio on the structural behavior of the residential concrete tall buildings aiming to deepen structure and architect designers under...The main concern of this paper is to study the influence of the building slenderness ratio on the structural behavior of the residential concrete tall buildings aiming to deepen structure and architect designers understanding for such type of buildings. The study is emphasized only on Kuwait city design conditions for wind and seismic loadings. The paper presents an actual case study for adding two thirty stories residential towers with two different slenderness ratios to an existing residential complex. Wind loading is considered using both code values and wind tunnel results. Three dimensional finite element techniques through ETABS software are used in conducting analysis for structures presented here. A serviceability study is performed to ensure that buildings have sufficient stability to limit lateral drift and peak acceleration within the acceptable range of occupancy comfort. In addition, an ultimate strength study is carried out to verify that all the structural elements are designed to withstand factored gravity and lateral loads in a safe manner according to the international building codes. Analysis results are presented and discussed. A brief idea about foundation design of the new towers and its connection to the existing foundation is presented. Finally conclusions are summarized as guidelines for the structural professions of concrete residential tall buildings.展开更多
To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valle...To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valley were analyzed by using the equivalent-linear model. Statistical analysis was also made to the seismic coefficient, and an empirical formula for calculating the maximum acceleration was provided. The results indicate that under the condition of the same dam height and the same base acceleration excitations, with the increase of the river valley width, the position of the maximum acceleration on the axis of the top of the dam moves from the center to the riversides symmetrically. For the narrow valleys, the maximum acceleration occurs in the middle of the axis at the top of the dam; for wide valleys the maximum acceleration appears near the riversides. The result negates the application of 2D dynamical computation for wide valleys, and shows that for the seismic response of high concrete-faced rockfill dams, the seismic coefficient along the axis should be given, except for that along the dam height. Seismic stability analysis of rockfill dams using pseudo-static method can be modified according to the formula.展开更多
Reactive powder concrete （RPC） is vulnerable to explosive spalling when exposed to high temperature. The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling....Reactive powder concrete （RPC） is vulnerable to explosive spalling when exposed to high temperature. The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling. Applying mercury intrusion po- rosimetry （MIP） and scanning electron microscopy （SEM） techniques, the authors probed the characteristics of micro pore structures of plain RPC200 when heated from 20-350~C. The pore characteristics such as specific pore volume, threshold pore size and most probable pore size varying with temperatures were investigated. A vapor pressure kit was developed to measure the vapor pressure and its variation inside RPC200 at various temperatures. A thin-wall spherical pore model was proposed to ana- lyze the thermo-mechanical mechanism of spalling, by which the stresses varying with the vapor pressure q（T） and the character- istic size of wall （K） at any point of interest were determined. It is shown that the pore characteristics including specific pore volume, average pore size, threshold pore size and most probable pore size rise significantly with the increasing temperature. 200~C appears to be the threshold temperature above which the threshold pore size and the most probable pore size climb up dramatically. The increase in the specific pore volume results from the growth both in quantity and in volume of the transition pores and the capillary pores. The appearance of the explosive spalling in RPC200 is mainly attributed to being unable to form pathways in favor of releasing water steam in RPC and to thin-wall sphere domain where the vapor pressure governs the the rapid accumulation of high vapor pressures as well. The spalling is bounded through the pore model.展开更多
Owing to the deficiency in early warning for high concrete dam,a formula was established to characterize the deformation behavior of high concrete dam as a whole.The early warning index of spatial deformation was calc...Owing to the deficiency in early warning for high concrete dam,a formula was established to characterize the deformation behavior of high concrete dam as a whole.The early warning index of spatial deformation was calculated by low probability principle on the basis of the deformation entropy formula proposed.The steps were as follows.Firstly,the probability method was utilized to define the degree of order and degree of chaos for each survey point.Secondly,the weight distribution among the survey points was calculated by projection pursuit analysis.Thirdly,the formula of holistic deformation entropy,which can represent the degree of order of high concrete dam,was established on the basis of synergetics and information entropy.Lastly,the early warning index of deformation entropy was computed by low probability method based on series of calculated deformation entropy values.An example showed that the dynamic property of deformation entropy is in accordance with both environmental variables and deflection deformation.Moreover,deformation entropy can be used to improve warning ability and safety management for high concrete dam.展开更多
A tremendous amount of non-biodegradable waste is created during mining and processing tasks of layered stones like marble.Over time,this has become a global problem because it harms the environment in multiple ways.H...A tremendous amount of non-biodegradable waste is created during mining and processing tasks of layered stones like marble.Over time,this has become a global problem because it harms the environment in multiple ways.Hence,it is necessary to find an alternate way to securely dispose and reuse marble wastes.The construction sector is one of the significant consumers of natural resources for the production of material binders and aggregates.As a result,in recent years,number of researchers have carried out studies in which various kinds of marble waste have been incorporated into concrete with the intention of substituting either cement or aggregates or both.This paper presents the effect of two locally sourced waste marble powders Kadapa marble powder(KMP)and Bethamcherla marble powder(BMP)as partial replacement of cement on mechanical and durability properties of high strength concrete(HSC).Their effect at different replacement levels in HSC is evaluated in compressive,indirect tensile and flexural strengths,elastic modulus,chloride penetration resistance and freeze-thaw durability properties.Micro-structural investigation is also conducted to evaluate their impact on the matrix of HSC containing waste marble powders as additional cementitious materials.Results show that the HSC consisting of KMP and BMP content of 10%and 15%,respectively exhibited higher mechanical and durability properties than the control HSC.Micro-structural investigation also supports this finding.It can be concluded that the use of marble powders as partial replacement of cement does not have any adverse impact on the properties of concrete.The use of KMP and BMP reduces the vast amount of energy required to produce cement,cost and time with reduction in environmental hazards.展开更多
基金Supported by the National Natural Science Foundation of China(No.50909078)the National Basic Research Program of China("973"Program,No.2013CB035900)
文摘It is important and difficult to control the temperature of mass concrete structure during high arch dam construction.A new method with decision support system is presented for temperature control and crack prevention.It is a database system with functions of data storage,information inquiry,data analysis,early warning and resource sharing.Monitoring information during construction can be digitized via this system,and the intelligent analysis and dynamic control of concrete temperature can be conducted.This method has been applied in the construction of the Dagangshan Arch Dam in China and has proven to be very convenient.Based on the decision support of this system and the dynamic adjustment of construction measures,the concrete temperature of this project is well-controlled.
文摘The main concern of this paper is to study the influence of the building slenderness ratio on the structural behavior of the residential concrete tall buildings aiming to deepen structure and architect designers understanding for such type of buildings. The study is emphasized only on Kuwait city design conditions for wind and seismic loadings. The paper presents an actual case study for adding two thirty stories residential towers with two different slenderness ratios to an existing residential complex. Wind loading is considered using both code values and wind tunnel results. Three dimensional finite element techniques through ETABS software are used in conducting analysis for structures presented here. A serviceability study is performed to ensure that buildings have sufficient stability to limit lateral drift and peak acceleration within the acceptable range of occupancy comfort. In addition, an ultimate strength study is carried out to verify that all the structural elements are designed to withstand factored gravity and lateral loads in a safe manner according to the international building codes. Analysis results are presented and discussed. A brief idea about foundation design of the new towers and its connection to the existing foundation is presented. Finally conclusions are summarized as guidelines for the structural professions of concrete residential tall buildings.
基金Project(90815024) supported by the National Natural Science Foundation of China
文摘To find the distribution patterns of dynamic amplification coefficients for dams subjected to earthquake, 3D seismic responses of concrete-faced rockfill dams with different heights and different shapes of river valley were analyzed by using the equivalent-linear model. Statistical analysis was also made to the seismic coefficient, and an empirical formula for calculating the maximum acceleration was provided. The results indicate that under the condition of the same dam height and the same base acceleration excitations, with the increase of the river valley width, the position of the maximum acceleration on the axis of the top of the dam moves from the center to the riversides symmetrically. For the narrow valleys, the maximum acceleration occurs in the middle of the axis at the top of the dam; for wide valleys the maximum acceleration appears near the riversides. The result negates the application of 2D dynamical computation for wide valleys, and shows that for the seismic response of high concrete-faced rockfill dams, the seismic coefficient along the axis should be given, except for that along the dam height. Seismic stability analysis of rockfill dams using pseudo-static method can be modified according to the formula.
基金supported by the National Science Foundation for Distin-guished Young Scholars of China (Grant No. 51125017)the National Natural Science Foundation of China (Grant No. 50974125)+1 种基金the ResearchFund for Doctoral Programs of Chinese Ministry of Education (Grant No.20110023110015)the National Basic Research Program of China("973" Project)(Grant Nos. 2010CB226804,2011CB201201)
文摘Reactive powder concrete （RPC） is vulnerable to explosive spalling when exposed to high temperature. The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling. Applying mercury intrusion po- rosimetry （MIP） and scanning electron microscopy （SEM） techniques, the authors probed the characteristics of micro pore structures of plain RPC200 when heated from 20-350~C. The pore characteristics such as specific pore volume, threshold pore size and most probable pore size varying with temperatures were investigated. A vapor pressure kit was developed to measure the vapor pressure and its variation inside RPC200 at various temperatures. A thin-wall spherical pore model was proposed to ana- lyze the thermo-mechanical mechanism of spalling, by which the stresses varying with the vapor pressure q（T） and the character- istic size of wall （K） at any point of interest were determined. It is shown that the pore characteristics including specific pore volume, average pore size, threshold pore size and most probable pore size rise significantly with the increasing temperature. 200~C appears to be the threshold temperature above which the threshold pore size and the most probable pore size climb up dramatically. The increase in the specific pore volume results from the growth both in quantity and in volume of the transition pores and the capillary pores. The appearance of the explosive spalling in RPC200 is mainly attributed to being unable to form pathways in favor of releasing water steam in RPC and to thin-wall sphere domain where the vapor pressure governs the the rapid accumulation of high vapor pressures as well. The spalling is bounded through the pore model.
基金supported by the National Natural Science Foundation of China (Grant No 50589025)the National Key Technology R&D Program (Grant No 2008BAB29B03)the Research Foundation of Education Bureau of Hunan Province, China (Grant No 09C087)
文摘Owing to the deficiency in early warning for high concrete dam,a formula was established to characterize the deformation behavior of high concrete dam as a whole.The early warning index of spatial deformation was calculated by low probability principle on the basis of the deformation entropy formula proposed.The steps were as follows.Firstly,the probability method was utilized to define the degree of order and degree of chaos for each survey point.Secondly,the weight distribution among the survey points was calculated by projection pursuit analysis.Thirdly,the formula of holistic deformation entropy,which can represent the degree of order of high concrete dam,was established on the basis of synergetics and information entropy.Lastly,the early warning index of deformation entropy was computed by low probability method based on series of calculated deformation entropy values.An example showed that the dynamic property of deformation entropy is in accordance with both environmental variables and deflection deformation.Moreover,deformation entropy can be used to improve warning ability and safety management for high concrete dam.
文摘A tremendous amount of non-biodegradable waste is created during mining and processing tasks of layered stones like marble.Over time,this has become a global problem because it harms the environment in multiple ways.Hence,it is necessary to find an alternate way to securely dispose and reuse marble wastes.The construction sector is one of the significant consumers of natural resources for the production of material binders and aggregates.As a result,in recent years,number of researchers have carried out studies in which various kinds of marble waste have been incorporated into concrete with the intention of substituting either cement or aggregates or both.This paper presents the effect of two locally sourced waste marble powders Kadapa marble powder(KMP)and Bethamcherla marble powder(BMP)as partial replacement of cement on mechanical and durability properties of high strength concrete(HSC).Their effect at different replacement levels in HSC is evaluated in compressive,indirect tensile and flexural strengths,elastic modulus,chloride penetration resistance and freeze-thaw durability properties.Micro-structural investigation is also conducted to evaluate their impact on the matrix of HSC containing waste marble powders as additional cementitious materials.Results show that the HSC consisting of KMP and BMP content of 10%and 15%,respectively exhibited higher mechanical and durability properties than the control HSC.Micro-structural investigation also supports this finding.It can be concluded that the use of marble powders as partial replacement of cement does not have any adverse impact on the properties of concrete.The use of KMP and BMP reduces the vast amount of energy required to produce cement,cost and time with reduction in environmental hazards.
