A large-span steel–concrete composite beam with precast hollow core slabs(CBHCSs)is a relatively new floor structure that can be applied to various long-span structures.However,human-induced vibrations may present se...A large-span steel–concrete composite beam with precast hollow core slabs(CBHCSs)is a relatively new floor structure that can be applied to various long-span structures.However,human-induced vibrations may present serviceability issues in such structures.To alleviate vibrations,both the walking forces excited by humans and the associated floor responses must be elucidated.In this study,150 load–time histories of walking,excited by 25 test participants,are obtained using a force measuring plate.The dynamic loading factors and phase angles in the Fourier series functions for one-step walking are determined.Subsequently,walking tests are performed on seven CBHCS specimens to capture the essential dynamic properties of mode shapes,natural frequencies,damping ratios,and acceleration time histories.The CBHCS floor system generally exhibits a high frequency(>10 Hz)and low damping(damping ratio<2%).Sensitivity studies using the finite element method are conducted to investigate the vibration performance of the CBHCS floor system,where the floor thickness,steel beam type,contact time,and human weight are considered.Finally,analytical expressions derived for the fundamental frequency and peak acceleration agree well with the experimental results and are hence proposed for practical use.展开更多
A general solution is obtained to a canonical problem of the reflection and refraction of an arbitrary shaped beam by using a uniaxially anisotropic chiral slab.The reflected,internal as well as refracted shaped beams...A general solution is obtained to a canonical problem of the reflection and refraction of an arbitrary shaped beam by using a uniaxially anisotropic chiral slab.The reflected,internal as well as refracted shaped beams are expanded in terms of cylindrical vector wave functions,and the expansion coefficients are determined by using the boundary conditions and method of moments procedure.As two typical examples,the normalized field intensity distributions are evaluated for a fundamental Gaussian beam and Hermite-Gaussian beam,and some propagation properties,especially the negative refraction phenomenon,are discussed briefly.展开更多
To promote the application of green renewable materials in concrete composite slabs(CCSs)and study the flexural behavior of CCSs with different shapes,the bending performances of three CCSs with a SFRRAC base plate,on...To promote the application of green renewable materials in concrete composite slabs(CCSs)and study the flexural behavior of CCSs with different shapes,the bending performances of three CCSs with a SFRRAC base plate,one cast-in-site concrete slab of ordinary concrete and one CCS of ordinary concrete by steel bar truss(as recommended in the technical specification for precast concrete structures in Chinese)were compared through experiments.The carrying capacity,flexural behaviour and bi-directional mechanical properties of the specimens were systematically analyzed from the failure modes,load-deflection curves,load-bar strain curves,load-slip curves and crack distributions.Results show that the bending failure process of CCSs with a SFRRAC base plate is similar to that of the cast-in-site concrete slab of ordinary concrete and CCS of ordinary concrete by steel bar truss,as all of them went through the plastic phase,elastic plastic phase and failure phase with fully developed cracks and deflection.No sudden breakage or horizontal cracking of the connecting interface between the base plate and concrete topping was observed.The shape of the base plate has a major impact on the bearing capacity of the CCS with the SFRRAC base plate.When calculating the ultimate bearing capacity with the plastic yield line theory,the influence of the base plate shape on the plastic yield line position should be taken into account.展开更多
An anchor-shaped geometrical design for a Submerged Entry Nozzle for the slab continuous casting of steel is presented in this work. To evaluate its performance, transient 3D multiphase numerical simulations were carr...An anchor-shaped geometrical design for a Submerged Entry Nozzle for the slab continuous casting of steel is presented in this work. To evaluate its performance, transient 3D multiphase numerical simulations were carried out using the Computational Fluid Dynamics technique. The performance of the proposed nozzle is numerically compared with that of a conventional cylindrical nozzle. Computer results show that the chance of formation of Karman’s vortexes and powder entrapment becomes small for the anchor-shaped SEN.展开更多
The method based on transient heat transfer model is adopted to simulate electro-slag remelting process. The calculated results of the model show that the process is in the quasi-steady state, and the shape of pool re...The method based on transient heat transfer model is adopted to simulate electro-slag remelting process. The calculated results of the model show that the process is in the quasi-steady state, and the shape of pool remains unchanged when the height of ingot is approximately 2.5-3 times the thickness of slab ingot. The change in the shape of pool is found to be strongly dependent on the pattern of melting rate, and hence, the power input; the depth of the molten pool increases with the increase in melting speed. It is concluded that a transient heat transfer model has to be used to obtain reliable input information for the entire, operatina time.展开更多
基金The authors acknowledge the financial support provided by the National Natural Science Foundation of China(51890902 and 51708058).
文摘A large-span steel–concrete composite beam with precast hollow core slabs(CBHCSs)is a relatively new floor structure that can be applied to various long-span structures.However,human-induced vibrations may present serviceability issues in such structures.To alleviate vibrations,both the walking forces excited by humans and the associated floor responses must be elucidated.In this study,150 load–time histories of walking,excited by 25 test participants,are obtained using a force measuring plate.The dynamic loading factors and phase angles in the Fourier series functions for one-step walking are determined.Subsequently,walking tests are performed on seven CBHCS specimens to capture the essential dynamic properties of mode shapes,natural frequencies,damping ratios,and acceleration time histories.The CBHCS floor system generally exhibits a high frequency(>10 Hz)and low damping(damping ratio<2%).Sensitivity studies using the finite element method are conducted to investigate the vibration performance of the CBHCS floor system,where the floor thickness,steel beam type,contact time,and human weight are considered.Finally,analytical expressions derived for the fundamental frequency and peak acceleration agree well with the experimental results and are hence proposed for practical use.
基金Project supported by the National Natural Science Foundation of China(Grant No.61771385)the Science Foundation for Distinguished Young Scholars of Shaanxi Province,China(Grant No.2020JC-42)+1 种基金the Fund from the Science and Technology on Solid-State Laser Laboratory,China(Grant No.6142404180301)the Science and Technology Research Plan of Xi’an City,China(Grant No.GXYD14.26).
文摘A general solution is obtained to a canonical problem of the reflection and refraction of an arbitrary shaped beam by using a uniaxially anisotropic chiral slab.The reflected,internal as well as refracted shaped beams are expanded in terms of cylindrical vector wave functions,and the expansion coefficients are determined by using the boundary conditions and method of moments procedure.As two typical examples,the normalized field intensity distributions are evaluated for a fundamental Gaussian beam and Hermite-Gaussian beam,and some propagation properties,especially the negative refraction phenomenon,are discussed briefly.
基金The National Natural Science Foundation of China(No.51578446).
文摘To promote the application of green renewable materials in concrete composite slabs(CCSs)and study the flexural behavior of CCSs with different shapes,the bending performances of three CCSs with a SFRRAC base plate,one cast-in-site concrete slab of ordinary concrete and one CCS of ordinary concrete by steel bar truss(as recommended in the technical specification for precast concrete structures in Chinese)were compared through experiments.The carrying capacity,flexural behaviour and bi-directional mechanical properties of the specimens were systematically analyzed from the failure modes,load-deflection curves,load-bar strain curves,load-slip curves and crack distributions.Results show that the bending failure process of CCSs with a SFRRAC base plate is similar to that of the cast-in-site concrete slab of ordinary concrete and CCS of ordinary concrete by steel bar truss,as all of them went through the plastic phase,elastic plastic phase and failure phase with fully developed cracks and deflection.No sudden breakage or horizontal cracking of the connecting interface between the base plate and concrete topping was observed.The shape of the base plate has a major impact on the bearing capacity of the CCS with the SFRRAC base plate.When calculating the ultimate bearing capacity with the plastic yield line theory,the influence of the base plate shape on the plastic yield line position should be taken into account.
文摘An anchor-shaped geometrical design for a Submerged Entry Nozzle for the slab continuous casting of steel is presented in this work. To evaluate its performance, transient 3D multiphase numerical simulations were carried out using the Computational Fluid Dynamics technique. The performance of the proposed nozzle is numerically compared with that of a conventional cylindrical nozzle. Computer results show that the chance of formation of Karman’s vortexes and powder entrapment becomes small for the anchor-shaped SEN.
文摘The method based on transient heat transfer model is adopted to simulate electro-slag remelting process. The calculated results of the model show that the process is in the quasi-steady state, and the shape of pool remains unchanged when the height of ingot is approximately 2.5-3 times the thickness of slab ingot. The change in the shape of pool is found to be strongly dependent on the pattern of melting rate, and hence, the power input; the depth of the molten pool increases with the increase in melting speed. It is concluded that a transient heat transfer model has to be used to obtain reliable input information for the entire, operatina time.
