An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study.Mechanical properties ...An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study.Mechanical properties of MFG porous plates change according to the length,width,and thickness directions for various materials and the porosity distribution which can be widely applied in many fields of engineering and defence technology.Especially,new porous rules that depend on spatial coordinates and grading indexes are proposed in the present work.Applying Hamilton's principle and the refined higher-order shear deformation plate theory,the governing equation of motion of an MFG porous rectangular plate in a fluid medium(the fluid-plate system)is obtained.The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to compute the extra mass.The GalerkinVlasov solution is used to solve and give natural frequencies of MFG porous plates with various boundary conditions in a fluid medium.The validity and reliability of the suggested method are confirmed by comparing numerical results of the present work with those from available works in the literature.The effects of different parameters on the thermal vibration response of MFG porous rectangular plates are studied in detail.These findings demonstrate that the behavior of the structure within a liquid medium differs significantly from that within a vacuum medium.Thereby,they offer appropriate operational approaches for the structure when employed in various mediums.展开更多
Fiber reinforced polymers (FRPs), unlike steel, are corrosion-resistant and therefore are of interest;however, their use is hindered because their brittle shear is formulated in most specifications using limited data ...Fiber reinforced polymers (FRPs), unlike steel, are corrosion-resistant and therefore are of interest;however, their use is hindered because their brittle shear is formulated in most specifications using limited data available at the time. We aimed to predict the shear strength of concrete beams reinforced with FRP bars and without stirrups by compiling a relatively large database of 198 previously published test results (available in appendix). To model shear strength, an artificial neural network was trained by an ensemble of Levenberg-Marquardt and imperialist competitive algorithms. The results suggested superior accuracy of model compared to equations available in specifications and literature.展开更多
NT build 443, or profile fitting method, is often used to measure the diffusion coefficient of chloride in concrete. However, this method is quite laborious and needs special equipment. Colorimetric method is a quick ...NT build 443, or profile fitting method, is often used to measure the diffusion coefficient of chloride in concrete. However, this method is quite laborious and needs special equipment. Colorimetric method is a quick and simple method to measure the penetration depth of chloride by spraying 0.1 mol/L silver nitrate solution. The objective of this work is to study the possibility of the use of colorimetric method in the calculation of non-steady-state diffusion coefficient. Twelve concrete mixtures with different supplementary cementitious materials and water-to-cement ratios of 0.35, 0.48 and 0.6 were used for study. According to NT build 443, the concrete specimens were immersed in 165 g/L NaC1 （2.8 mol/L） solution for 42 d. Both water-soluble （convert to free chloride） chloride and acid-soluble chloride at different layers of specimens were measured. The results show that the mean value of free chloride concentration at the color change boundary Cd was 0.306 mol/L. The surface free chloride concentration cs was obtained by profile fitting method, which was 40% lower than the chloride concentration of exposure solution after an immersion period of 42 d. Chloride diffusion coefficients obtained by the colorimetric method was not well correlated with those obtained by profile fitting method.展开更多
In spite of the good performance of the steel plate shear wall(SPSW)in recent earthquakes and experimental studies,the need for huge columns to surround the infill plate is a major shortcoming of the system.This short...In spite of the good performance of the steel plate shear wall(SPSW)in recent earthquakes and experimental studies,the need for huge columns to surround the infill plate is a major shortcoming of the system.This shortcoming can be resolved by using semi-supported SPSW.The semi-supported SPSW has secondary columns that prevent the transfer of stress from the infill plate to the main columns.In spite of extensive experimental and numerical investigations on SPSWs,there are many ambiguities regarding the behavior of the semi-supported SPSW.Although stress in the columns is reduced,incomplete diagonal tension field action is formed in the infill plate that creates new problems.In this paper,a new type of semi-supported SPSW is presented in which the steel plate and the secondary columns are angled.The creation of the angle of the plate and the secondary column makes it possible to use the full capacity of the steel plate as well as the capacity of the secondary columns.Numerical results showed that the wall with a 60°angle has a favorable performance relative to the semi-supported wall.Moreover,with the 60°angle,stiffness,strength and energy absorption is increased.The angle of the secondary columns has little effect on the non-elastic stiffness.Nevertheless,using a wall with an angle of more than 90°can neutralize the wall’s behavior relative to conventional walls.Therefore,the wall with a 60°angle as an optimal angle is recommended.展开更多
The buckling resisting brace(BRB)is an efficient system against lateral loads that enjoy high seismic energy absorption capacity.Although desirable behavior of BRBs has been confirmed,the stiffness of the system is no...The buckling resisting brace(BRB)is an efficient system against lateral loads that enjoy high seismic energy absorption capacity.Although desirable behavior of BRBs has been confirmed,the stiffness of the system is not desirable that it can be compensated by changing the configuration of BRB braces.In so doing,the configuration in the form of double K(DK)is investigated to achieve more favorable behavior.Also,the required mathematical formulas were proposed to design the system.Comparison of DK system with other conventional BRB showed that the DK system has a better structural performance and is more economical(due to needing less core area)than other conventional BRB.Numerical results indicated that the DK system increases the lateral ultimate strength,lateral nonlinear stiffness,and energy absorption.Besides,the DK configuration reduces the axial forces created in columns in the nonlinear zone.Reducing material demand,created forces in the main frame,and also increasing of nonlinear stiffens by DK improve the structure’s safety.展开更多
通过对一个现有建筑的结构动态参数的辨识讨论了土与结构的相互作用。目标建筑是建于1998年的8层的型钢混凝土结构。在此研究中,8自由度的模型被建立以分析微震观测数据,随即,非参数和参数技巧以辨识此结构的自然频率,阻尼率和层硬度等...通过对一个现有建筑的结构动态参数的辨识讨论了土与结构的相互作用。目标建筑是建于1998年的8层的型钢混凝土结构。在此研究中,8自由度的模型被建立以分析微震观测数据,随即,非参数和参数技巧以辨识此结构的自然频率,阻尼率和层硬度等。在考虑土-结构相互作用和不考虑土-结构相互作用的两种情况下,分别辨识结构的参数并对比结果以证实其对辨识结果的影响。在文中非参数方法包括众所周知的传递函数和随机减量法,参数方法是非线性的系统辨识工具ARX(Auto-Regression with extra input)方法。展开更多
文摘An analytical method for analyzing the thermal vibration of multi-directional functionally graded porous rectangular plates in fluid media with novel porosity patterns is developed in this study.Mechanical properties of MFG porous plates change according to the length,width,and thickness directions for various materials and the porosity distribution which can be widely applied in many fields of engineering and defence technology.Especially,new porous rules that depend on spatial coordinates and grading indexes are proposed in the present work.Applying Hamilton's principle and the refined higher-order shear deformation plate theory,the governing equation of motion of an MFG porous rectangular plate in a fluid medium(the fluid-plate system)is obtained.The fluid velocity potential is derived from the boundary conditions of the fluid-plate system and is used to compute the extra mass.The GalerkinVlasov solution is used to solve and give natural frequencies of MFG porous plates with various boundary conditions in a fluid medium.The validity and reliability of the suggested method are confirmed by comparing numerical results of the present work with those from available works in the literature.The effects of different parameters on the thermal vibration response of MFG porous rectangular plates are studied in detail.These findings demonstrate that the behavior of the structure within a liquid medium differs significantly from that within a vacuum medium.Thereby,they offer appropriate operational approaches for the structure when employed in various mediums.
文摘Fiber reinforced polymers (FRPs), unlike steel, are corrosion-resistant and therefore are of interest;however, their use is hindered because their brittle shear is formulated in most specifications using limited data available at the time. We aimed to predict the shear strength of concrete beams reinforced with FRP bars and without stirrups by compiling a relatively large database of 198 previously published test results (available in appendix). To model shear strength, an artificial neural network was trained by an ensemble of Levenberg-Marquardt and imperialist competitive algorithms. The results suggested superior accuracy of model compared to equations available in specifications and literature.
基金Project(2010QZZD018) supported by Central South Universtiy,China,and Ghent University,Belgium
文摘NT build 443, or profile fitting method, is often used to measure the diffusion coefficient of chloride in concrete. However, this method is quite laborious and needs special equipment. Colorimetric method is a quick and simple method to measure the penetration depth of chloride by spraying 0.1 mol/L silver nitrate solution. The objective of this work is to study the possibility of the use of colorimetric method in the calculation of non-steady-state diffusion coefficient. Twelve concrete mixtures with different supplementary cementitious materials and water-to-cement ratios of 0.35, 0.48 and 0.6 were used for study. According to NT build 443, the concrete specimens were immersed in 165 g/L NaC1 （2.8 mol/L） solution for 42 d. Both water-soluble （convert to free chloride） chloride and acid-soluble chloride at different layers of specimens were measured. The results show that the mean value of free chloride concentration at the color change boundary Cd was 0.306 mol/L. The surface free chloride concentration cs was obtained by profile fitting method, which was 40% lower than the chloride concentration of exposure solution after an immersion period of 42 d. Chloride diffusion coefficients obtained by the colorimetric method was not well correlated with those obtained by profile fitting method.
文摘In spite of the good performance of the steel plate shear wall(SPSW)in recent earthquakes and experimental studies,the need for huge columns to surround the infill plate is a major shortcoming of the system.This shortcoming can be resolved by using semi-supported SPSW.The semi-supported SPSW has secondary columns that prevent the transfer of stress from the infill plate to the main columns.In spite of extensive experimental and numerical investigations on SPSWs,there are many ambiguities regarding the behavior of the semi-supported SPSW.Although stress in the columns is reduced,incomplete diagonal tension field action is formed in the infill plate that creates new problems.In this paper,a new type of semi-supported SPSW is presented in which the steel plate and the secondary columns are angled.The creation of the angle of the plate and the secondary column makes it possible to use the full capacity of the steel plate as well as the capacity of the secondary columns.Numerical results showed that the wall with a 60°angle has a favorable performance relative to the semi-supported wall.Moreover,with the 60°angle,stiffness,strength and energy absorption is increased.The angle of the secondary columns has little effect on the non-elastic stiffness.Nevertheless,using a wall with an angle of more than 90°can neutralize the wall’s behavior relative to conventional walls.Therefore,the wall with a 60°angle as an optimal angle is recommended.
文摘The buckling resisting brace(BRB)is an efficient system against lateral loads that enjoy high seismic energy absorption capacity.Although desirable behavior of BRBs has been confirmed,the stiffness of the system is not desirable that it can be compensated by changing the configuration of BRB braces.In so doing,the configuration in the form of double K(DK)is investigated to achieve more favorable behavior.Also,the required mathematical formulas were proposed to design the system.Comparison of DK system with other conventional BRB showed that the DK system has a better structural performance and is more economical(due to needing less core area)than other conventional BRB.Numerical results indicated that the DK system increases the lateral ultimate strength,lateral nonlinear stiffness,and energy absorption.Besides,the DK configuration reduces the axial forces created in columns in the nonlinear zone.Reducing material demand,created forces in the main frame,and also increasing of nonlinear stiffens by DK improve the structure’s safety.
文摘通过对一个现有建筑的结构动态参数的辨识讨论了土与结构的相互作用。目标建筑是建于1998年的8层的型钢混凝土结构。在此研究中,8自由度的模型被建立以分析微震观测数据,随即,非参数和参数技巧以辨识此结构的自然频率,阻尼率和层硬度等。在考虑土-结构相互作用和不考虑土-结构相互作用的两种情况下,分别辨识结构的参数并对比结果以证实其对辨识结果的影响。在文中非参数方法包括众所周知的传递函数和随机减量法,参数方法是非线性的系统辨识工具ARX(Auto-Regression with extra input)方法。
