Higher concentration is beneficial for the Paste and Thickened Tailings(PTT)operation in metal mine.Partial paste thickeners are produced lower density underflow.Flocculated tailings are intended to form a water entra...Higher concentration is beneficial for the Paste and Thickened Tailings(PTT)operation in metal mine.Partial paste thickeners are produced lower density underflow.Flocculated tailings are intended to form a water entrapped network structure in thickener,which is detrimental to underflow concentration.In this study,the continuous thickening experiment was carried out for ultra-fine tungsten tailings to study the influence of rake shearing on underflow.The micro pores structure and seepage flow in tailings bed before and after shearing are studied by CT and simulation approach to reveal the shearing enhancement mechanism of thickening process.The results shown that,the underflow concentration is increased from 61.4 wt%to 69.6 wt%by rake shearing in a pilot scale thickener,the porosity decreased from 46.48%to 37.46%.The entrapped water discharged from sticks structure more than sphere spaces.In items of seepage,after shearing,the seepage flow channel of tailings underflow is becoming longer,which caused the decreasing average flow rate decreases and absolute permeability.The absolute permeability is negatively correlated with tortuosity.The rake shearing can destroy the flocs structure;change the effective stress to increase the concentration.Higher underflow concentration improves the waste recycling and water recovery rate,especially for arid areas.展开更多
Considering three longitudinal displacement functions and uniform axial displacement functions for shear lag effect and uniform axial deformation of thin-walled box girder with varying depths,a simple and efficient me...Considering three longitudinal displacement functions and uniform axial displacement functions for shear lag effect and uniform axial deformation of thin-walled box girder with varying depths,a simple and efficient method with high precision to analyze the shear lag effect of thin-walled box girders was proposed.The governing differential equations and boundary conditions of the box girder under lateral loading were derived based on the energy-variational method,and closed-form solutions to stress and deflection corresponding to lateral loading were obtained.Analysis and calculations were carried out with respect to a trapezoidal box girder under concentrated loading or uniform loading and a rectangular box girder under concentrated loading.The analytical results were compared with numerical solutions derived according to the high order finite strip element method and the experimental results.The investigation shows that the closed-form solution is in good agreement with the numerical solutions derived according to the high order finite strip method and the experimental results,and has good stability.Because of the shear lag effect,the stress in cross-section centroid is no longer zero,thus it is not reasonable enough to assume that the strain in cross-section centroid is zero without considering uniform axial deformation.展开更多
Based on the consideration of longitudinal warp caused by shear lag effects on concrete slabs and bottom plates of steel beams,shear deformation of steel beams and interface slip between steel beams and concrete slabs...Based on the consideration of longitudinal warp caused by shear lag effects on concrete slabs and bottom plates of steel beams,shear deformation of steel beams and interface slip between steel beams and concrete slabs,the governing differential equations and boundary conditions of the steel-concrete composite box beams under lateral loading were derived using energy-variational method.The closed-form solutions for stress,deflection and slip of box beams under lateral loading were obtained,and the comparison of the analytical results and the experimental results for steel-concrete composite box beams under concentrated loading or uniform loading verifies the closed-form solution.The investigation of the parameters of load effects on composite box beams shows that:1) Slip stiffness has considerable impact on mid-span deflection and end slip when it is comparatively small;the mid-span deflection and end slip decrease significantly with the increase of slip stiffness,but when the slip stiffness reaches a certain value,its impact on mid-span deflection and end slip decreases to be negligible.2) The shear deformation has certain influence on mid-span deflection,and the larger the load is,the greater the influence is.3) The impact of shear deformation on end slip can be neglected.4) The strain of bottom plate of steel beam decreases with the increase of slip stiffness,while the shear lag effect becomes more significant.展开更多
The acoustic propagation characteristics of axisymmetric waves have been widely used in leak detection of fluid-filled pipes.The related acoustic methods and equipment are gradually coming to the market,but their theo...The acoustic propagation characteristics of axisymmetric waves have been widely used in leak detection of fluid-filled pipes.The related acoustic methods and equipment are gradually coming to the market,but their theoretical research obviously lags behind the field practice,which seriously restricts the breakthrough and innovation of this technology.Based on the fully three-dimensional effect of the surrounding medium,a coupled motion equation of axisymmetric wave of buried liquid-filled pipes is derived in detail,a contact coefficient is used to express the coupling strength between surrounding medium and pipe,then,a general equation of motion was derived which contain the pipe soil lubrication contact,pipe soil compact contact and pipe in water and air.Finally,the corresponding numerical calculation model is established and solved used numerical method.The shear effects of the surrounding medium and the shear effects at the interface between surrounding medium and pipe are discussed in detail.The output indicates that the surrounding medium is to add mass to the pipe wall,but the shear effect is to add stiffness.With the consideration of the contact strength between the pipe and the medium,the additional mass and the pipe wall will resonate at a specific frequency,resulting in a significant increase in the radiation wave to the surrounding medium.The research contents have great guiding effect on the theory of acoustic wave propagation and the engineering application of leak detection technology in the buried pipe.展开更多
Based on Reddy's theory of plates with higher order shear deformations and the Boltzmann superposition principles, the governing equations were established for dynamic stability of viscoelastic plates with finit...Based on Reddy's theory of plates with higher order shear deformations and the Boltzmann superposition principles, the governing equations were established for dynamic stability of viscoelastic plates with finite deformations taking account of shear effects. The Galerkin method was applied to simplify the set of equations. The numerical methods in nonlinear dynamics were used to solve the simplified system. It could be seen that there are plenty of dynamic properties for this kind of viscoelastic plates under transverse harmonic loads. The influences of the transverse shear deformations and material parameter on the dynamic behavior of nonlinear viscoelastic plates were investigated.展开更多
A micromechanics constitutive theory which takes into account both the dilatation and shear ef- fects of the transformation is proposed to describe the macroscopic plastic behavior of structure ceramics during forward...A micromechanics constitutive theory which takes into account both the dilatation and shear ef- fects of the transformation is proposed to describe the macroscopic plastic behavior of structure ceramics during forward transformation under different temperatures.Under some basic assumptions,the analytic expressions of the Helmholtz and complementary free energy of the constitutive element are derived in a self-consistent manner by using the Mori-Tanaka's method which takes into account the interaction between the transformed inclusions.In the framework of Hill-Rice's internal variable constitutive theory,the forward transformation yield function and incremental stress strain relations,in analogy to the theory of metal plasticity,for non-proportional loading histories are obtained.展开更多
In order to resolve the traffic congestion problem, many cable-stayed bridges are designed with a large width to span ratio. This results in significant shear lag effect to cause nonuniform stress distribution along t...In order to resolve the traffic congestion problem, many cable-stayed bridges are designed with a large width to span ratio. This results in significant shear lag effect to cause nonuniform stress distribution along the flanges of the beam of bridge. This paper reports study on the shear lag effect of the Lanzhou Xiaoxihu Yellow River Bridge. A 3D finite element model of the bridge was developed and finite element analysis (FEA) was done to obtain the theoretical results. To evaluate the theoretical results, a scaled model was made to conduct static test in laboratory. The experiment results accorded with the results obtained by FEA. It is proved that FEA is an effective method to predict shear lag effect of bridges of this type.展开更多
The dynamic effective shear strength of saturated sand under cyclic loading is discussed in this paper.The discussion includes the transient time depen- dency behaviors based on the analysis of the results obtained in...The dynamic effective shear strength of saturated sand under cyclic loading is discussed in this paper.The discussion includes the transient time depen- dency behaviors based on the analysis of the results obtained in conventional cyclic triaxial tests and cyclic torsional shear triaxial tests.It has been found that the dy- namic effective shear strength is composed of effective frictional resistance and viscous resistance,which are characterized by the strain rate dependent feature of strength magnitude,the coupling of consolidation stress with cyclic stress and the dependency of time needed to make the soil strength sufficiently mobilized,and can also be ex- pressed by the extended Mohr-Coulomb's law.The two strength parameters of the dynamic effective internal frictional angle φd and the dynamic viscosity coefficient η are determined.The former is unvaried for different number of cyclic loading,dy- namic stress form and consolidation stress ratio.And the later is unvaried for the different dynamic shear strain rate γt developed during the sand liquefaction,but increases with the increase of initial density of sand.The generalization of dynamic effective stress strength criterion in the 3-dimensional effective stress space is studied in detail for the purpose of its practical use.展开更多
A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and...A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom（MDOF） system is approximated by using the modal energy-decomposition. Energybased base shear coefficients are verified by means of both pushover analysis and nonlinear time history（NLTH） analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation.展开更多
In this paper, a formulation for shakedown analysis of elastic-plastic offshore structures under cyclic wave loading is presented. In this formulation, a fast numerical solution method is used, suitable for the Finite...In this paper, a formulation for shakedown analysis of elastic-plastic offshore structures under cyclic wave loading is presented. In this formulation, a fast numerical solution method is used, suitable for the Finite Element Method (FEM) analysis of large offshore structures on which shear effects in addition to bending and axial effects are taken into account. The Morison equation is adopted for converting the velocity and acceleration terms into resultant forces and it is extended to consider arbitrary orientations of the structural members. The theoretical methods of the shakedown analysis are discussed in detail and the formulation is applied to an offshore structure to verify the concept employed and its analytical capabilities.展开更多
The project of Xiaoxihu Yellow River Bridge in Lanzhou is chosen as partial cable-stayed bridge. To get the shear lag effect and anti-earthquake performance of the actual bridge under various loading conditions, organ...The project of Xiaoxihu Yellow River Bridge in Lanzhou is chosen as partial cable-stayed bridge. To get the shear lag effect and anti-earthquake performance of the actual bridge under various loading conditions, organic glass scaled model was adopted to have an experiment and a theory research at one time. The experiment result is the basically same as the theory calculation which proves the FEA method can well calculate shear lag effect and dynamical performance. As a result, because the bridge is located in a seismic area of 8 degree, an elasto-plastic seismic checking is performed by customized FEA program in this paper.展开更多
To investigate the effects of mechanical factors on matrix metalloproteinase9(MMP-9) expressions in rat bone marrow-derived mesenchymal stem cells(MSCs) and possible mechanism signal.Rat bone marrow MSCs were isolated...To investigate the effects of mechanical factors on matrix metalloproteinase9(MMP-9) expressions in rat bone marrow-derived mesenchymal stem cells(MSCs) and possible mechanism signal.Rat bone marrow MSCs were isolated and cultured,then,exposed to laminar shear stress展开更多
Classical bending theories for beams and plates can not be used for short, stubby beams and thick plates since transverse shearing effect is excluded, and ordinary theories with multiple generalized displacements can ...Classical bending theories for beams and plates can not be used for short, stubby beams and thick plates since transverse shearing effect is excluded, and ordinary theories with multiple generalized displacements can not be used for long, slender beams and thin plates since the innate relation between rotation angle and deflection is ignored. These two types of theories are not consistent due to the contradiction of dependence and independence of the rotation angle. Based on several basic assumptions, a new type of theories which not only include the transverse shearing effect is presented, but also the relation between potation angle and deflection is obtained. Analytical solutions of several simple beams are given. It has been testified by numerical examples that the new theories can be used for either long, slender beams and thin plates or short, stubby beams and thick plates.展开更多
Based on Hamilton principle,the governing differential equations and the corresponding boundary conditions of steel-concrete composite box girder with consideration of the shear lag effect meeting self equilibrated st...Based on Hamilton principle,the governing differential equations and the corresponding boundary conditions of steel-concrete composite box girder with consideration of the shear lag effect meeting self equilibrated stress,shear deformation,slip,as well as rotational inertia were induced.Therefore,natural frequency equations were obtained for the boundary types,such as simple support,cantilever,continuous girder and fixed support at two ends.The ANSYS finite element solutions were compared with the analytical solutions by calculation examples and the validity of the proposed approach was verified,which also shows the correctness of longitudinal warping displacement functions.Some meaningful conclusions for engineering design were obtained.The decrease extent of each order natural frequency of the steel-concrete composite box-girder is great under action of the shear lag effect.The shear-lag effect of steel-concrete composite box girder increases when frequency order rises,and increases while span-width ratio decreases.The proposed approach provides theoretical basis for further research of free vibration characteristics of steel-concrete composite box-girder.展开更多
By investigating the shear effect on submerged cultivation of a traditional Chinese medicinal herb Ganoderma lucidum, a relatively high cell concentration of 13.8 g·L-1 by dry mass was obtained in bioreactor at a...By investigating the shear effect on submerged cultivation of a traditional Chinese medicinal herb Ganoderma lucidum, a relatively high cell concentration of 13.8 g·L-1 by dry mass was obtained in bioreactor at an impeller tip speed (ITS) of 0.51m·s-1. At an ITS of 0.51,1.02 and 1.53m·s-1, a maximal production titer of intracellular polysaccharide was 2.64, 2.20 and 2.28g·L-1 and that of ganoderic acid was 306, 299 and 273g·L-1, respectively. Under these ITSs, the maximal mean projected area of dispersed hyphae was 3.70, 2.54 and 2.13×104μm2, and that of pellets was 0.91, 0.67 and 0.55mm2, respectively. The information obtained is useful for efficient submerged cultivation of mushrooms on a large scale.展开更多
At jet pressures ranging from 80 to 120 MPa, submerged water jets are investigated by numerical simulation and experiment. Numerical simulation enables a systematic analysis of major flow parameters such as jet veloci...At jet pressures ranging from 80 to 120 MPa, submerged water jets are investigated by numerical simulation and experiment. Numerical simulation enables a systematic analysis of major flow parameters such as jet velocity, turbulent kinetic energy as well as void fraction of cavitation. Experiments facilitate an objective assessment of surface morphology, micro hardness and surface roughness of the impinged samples. A comparison is implemented between submerged and non-submerged water jets. The results show that submerged water jet is characterized by low velocity magnitudes relative to non-submerged water jet at the same jet pressure. Shear effect serves as a key factor underlying the inception of cavitation in submerged water jet stream. Predicted annular shape of cavity zone is substantiated by local height distributions associated with experimentally obtained footprints. As jet pressure increases, joint contribution of jet kinetic energy and cavitation is demonstrated. While for non-submerged water jet, impingement force stems exclusively from flow velocity.展开更多
Three groups of dynamic triaxial tests were performed for saturated Nanjing fine sand subjected to uniform cyclic loading. The tested curves of the excess pore water pressure （EPWP） ratio variation with the ratio of...Three groups of dynamic triaxial tests were performed for saturated Nanjing fine sand subjected to uniform cyclic loading. The tested curves of the excess pore water pressure （EPWP） ratio variation with the ratio of the number of cycles are provided. The concept of the EPWP increment ratio is introduced and two new concepts of the effective dynamic shear stress ratio and the log decrement of effective stress are defined. It is found that the development of the EPWP increment ratio can be divided into three stages： descending, stable and ascending. Furthermore, at the stable and ascending stages, a satisfactory linear relationship is obtained between the accumulative EPWP increment ratio and natural logarithm of the effective dynamic shear stress ratio. Accordingly, the EPWP increment ratio at the number of cycles N has been deduced that is proportional to the log decrement of effective stress at the cycle number N-l, but is independent of the cyclic stress amplitude. Based on the analysis, a new EPWP increment model for saturated Nanjing fine sand is developed from tested data fitting, which provides a better prediction of the curves of EPWP generation, the number of cycles required for initial liquefaction and the liquefaction resistance.展开更多
Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. ...Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. To analyze the elastic-plastic response of a short-leg shear wall structure during an earthquake, this study modified the multiple-vertical-rod element model of the shear wall, considered the shear lag effect and proposed a multiple-vertical-rod element coupling beam model with a new local stiffness domain. Based on the principle of minimum potential energy and the variational principle, the stiffness matrixes of a short-leg shear wall and a coupling beam are derived in this study. Furthermore, the bending shear correlation for the analysis of different parameters to describe the structure, such as the beam height to span ratio, short-leg shear wall height to thickness ratio, and steel ratio are introduced. The results show that the height to span ratio directly affects the structural integrity; and the short-leg shear wall height to thickness ratio should be limited to a range of approximately 6.0 to 7.0. The design of short-leg shear walls should be in accordance with the ＂strong wall and weak beam＂ principle.展开更多
Based on the stress field distribution rule of the mining floor under abutment pressure, we have established a simplified mechanical model, which contains multiple factors relating to activation and evolution of insid...Based on the stress field distribution rule of the mining floor under abutment pressure, we have established a simplified mechanical model, which contains multiple factors relating to activation and evolution of insidious water-conductive faults. The influence of normal and shear stresses on fault activation and effective shear stress distribution in the fault plane was acquired under mining conditions.Using fracture mechanics theory to calculate the stress intensity factor of an insidious fault front, we have derived the criterion for main fault activation. Results indicate that during the whole working face advance, transpressions are exerted on fault planes twice successively in opposite directions. In most cases, the second transpression is more likely to lead to fault activation. Activation is influenced by many factors, predominant among which are: burial depth of the insidious fault, friction angle of the fault plane, face advance direction and pore water pressure. Steep fault planes are more easily activated to induce a sustained water inrush in the face.展开更多
基金This work was supported by funding from the National Natural Science Foundation of China Projects(51834001,51704094,U170420041)the China Postdoctoral Science Foundation(2020M672226)+2 种基金Program for Science&Technology Innovation Talents in Universities of Henan Province(19HASTIT047)Key Science Research Project in Universities of Henan Province(19B620001,20A620004)Henan Polytechnic University Science Fund for Distinguished Young Scholars(J2020-3).
文摘Higher concentration is beneficial for the Paste and Thickened Tailings(PTT)operation in metal mine.Partial paste thickeners are produced lower density underflow.Flocculated tailings are intended to form a water entrapped network structure in thickener,which is detrimental to underflow concentration.In this study,the continuous thickening experiment was carried out for ultra-fine tungsten tailings to study the influence of rake shearing on underflow.The micro pores structure and seepage flow in tailings bed before and after shearing are studied by CT and simulation approach to reveal the shearing enhancement mechanism of thickening process.The results shown that,the underflow concentration is increased from 61.4 wt%to 69.6 wt%by rake shearing in a pilot scale thickener,the porosity decreased from 46.48%to 37.46%.The entrapped water discharged from sticks structure more than sphere spaces.In items of seepage,after shearing,the seepage flow channel of tailings underflow is becoming longer,which caused the decreasing average flow rate decreases and absolute permeability.The absolute permeability is negatively correlated with tortuosity.The rake shearing can destroy the flocs structure;change the effective stress to increase the concentration.Higher underflow concentration improves the waste recycling and water recovery rate,especially for arid areas.
基金Projects(51078355,50938008) supported by the National Natural Science Foundation of ChinaProject(CX2011B093) supported by the Doctoral Candidate Research Innovation Program of Hunan Province, ChinaProject(20117Q008) supported by the Basic Scientific Research Funds for Central Universities of China
文摘Considering three longitudinal displacement functions and uniform axial displacement functions for shear lag effect and uniform axial deformation of thin-walled box girder with varying depths,a simple and efficient method with high precision to analyze the shear lag effect of thin-walled box girders was proposed.The governing differential equations and boundary conditions of the box girder under lateral loading were derived based on the energy-variational method,and closed-form solutions to stress and deflection corresponding to lateral loading were obtained.Analysis and calculations were carried out with respect to a trapezoidal box girder under concentrated loading or uniform loading and a rectangular box girder under concentrated loading.The analytical results were compared with numerical solutions derived according to the high order finite strip element method and the experimental results.The investigation shows that the closed-form solution is in good agreement with the numerical solutions derived according to the high order finite strip method and the experimental results,and has good stability.Because of the shear lag effect,the stress in cross-section centroid is no longer zero,thus it is not reasonable enough to assume that the strain in cross-section centroid is zero without considering uniform axial deformation.
基金Projects(51078355,50938008) supported by the National Natural Science Foundation of ChinaProject(094801020) supported by the Academic Scholarship for Doctoral Candidates of the Ministry of Education,China+1 种基金Project(CX2011B093) supported by the Doctoral Candidate Research Innovation Project of Hunan Province, ChinaProject(20117Q008) supported by the Central University Basic Scientific Research Business Expenses Special Fund of China
文摘Based on the consideration of longitudinal warp caused by shear lag effects on concrete slabs and bottom plates of steel beams,shear deformation of steel beams and interface slip between steel beams and concrete slabs,the governing differential equations and boundary conditions of the steel-concrete composite box beams under lateral loading were derived using energy-variational method.The closed-form solutions for stress,deflection and slip of box beams under lateral loading were obtained,and the comparison of the analytical results and the experimental results for steel-concrete composite box beams under concentrated loading or uniform loading verifies the closed-form solution.The investigation of the parameters of load effects on composite box beams shows that:1) Slip stiffness has considerable impact on mid-span deflection and end slip when it is comparatively small;the mid-span deflection and end slip decrease significantly with the increase of slip stiffness,but when the slip stiffness reaches a certain value,its impact on mid-span deflection and end slip decreases to be negligible.2) The shear deformation has certain influence on mid-span deflection,and the larger the load is,the greater the influence is.3) The impact of shear deformation on end slip can be neglected.4) The strain of bottom plate of steel beam decreases with the increase of slip stiffness,while the shear lag effect becomes more significant.
基金National Natural Science Foundation of China(Grant No.11774378).
文摘The acoustic propagation characteristics of axisymmetric waves have been widely used in leak detection of fluid-filled pipes.The related acoustic methods and equipment are gradually coming to the market,but their theoretical research obviously lags behind the field practice,which seriously restricts the breakthrough and innovation of this technology.Based on the fully three-dimensional effect of the surrounding medium,a coupled motion equation of axisymmetric wave of buried liquid-filled pipes is derived in detail,a contact coefficient is used to express the coupling strength between surrounding medium and pipe,then,a general equation of motion was derived which contain the pipe soil lubrication contact,pipe soil compact contact and pipe in water and air.Finally,the corresponding numerical calculation model is established and solved used numerical method.The shear effects of the surrounding medium and the shear effects at the interface between surrounding medium and pipe are discussed in detail.The output indicates that the surrounding medium is to add mass to the pipe wall,but the shear effect is to add stiffness.With the consideration of the contact strength between the pipe and the medium,the additional mass and the pipe wall will resonate at a specific frequency,resulting in a significant increase in the radiation wave to the surrounding medium.The research contents have great guiding effect on the theory of acoustic wave propagation and the engineering application of leak detection technology in the buried pipe.
文摘Based on Reddy's theory of plates with higher order shear deformations and the Boltzmann superposition principles, the governing equations were established for dynamic stability of viscoelastic plates with finite deformations taking account of shear effects. The Galerkin method was applied to simplify the set of equations. The numerical methods in nonlinear dynamics were used to solve the simplified system. It could be seen that there are plenty of dynamic properties for this kind of viscoelastic plates under transverse harmonic loads. The influences of the transverse shear deformations and material parameter on the dynamic behavior of nonlinear viscoelastic plates were investigated.
基金The project supported by National Natural Science Foundation of China
文摘A micromechanics constitutive theory which takes into account both the dilatation and shear ef- fects of the transformation is proposed to describe the macroscopic plastic behavior of structure ceramics during forward transformation under different temperatures.Under some basic assumptions,the analytic expressions of the Helmholtz and complementary free energy of the constitutive element are derived in a self-consistent manner by using the Mori-Tanaka's method which takes into account the interaction between the transformed inclusions.In the framework of Hill-Rice's internal variable constitutive theory,the forward transformation yield function and incremental stress strain relations,in analogy to the theory of metal plasticity,for non-proportional loading histories are obtained.
文摘In order to resolve the traffic congestion problem, many cable-stayed bridges are designed with a large width to span ratio. This results in significant shear lag effect to cause nonuniform stress distribution along the flanges of the beam of bridge. This paper reports study on the shear lag effect of the Lanzhou Xiaoxihu Yellow River Bridge. A 3D finite element model of the bridge was developed and finite element analysis (FEA) was done to obtain the theoretical results. To evaluate the theoretical results, a scaled model was made to conduct static test in laboratory. The experiment results accorded with the results obtained by FEA. It is proved that FEA is an effective method to predict shear lag effect of bridges of this type.
基金The project supported by the National Natural Science Foundation of China (10172070)
文摘The dynamic effective shear strength of saturated sand under cyclic loading is discussed in this paper.The discussion includes the transient time depen- dency behaviors based on the analysis of the results obtained in conventional cyclic triaxial tests and cyclic torsional shear triaxial tests.It has been found that the dy- namic effective shear strength is composed of effective frictional resistance and viscous resistance,which are characterized by the strain rate dependent feature of strength magnitude,the coupling of consolidation stress with cyclic stress and the dependency of time needed to make the soil strength sufficiently mobilized,and can also be ex- pressed by the extended Mohr-Coulomb's law.The two strength parameters of the dynamic effective internal frictional angle φd and the dynamic viscosity coefficient η are determined.The former is unvaried for different number of cyclic loading,dy- namic stress form and consolidation stress ratio.And the later is unvaried for the different dynamic shear strain rate γt developed during the sand liquefaction,but increases with the increase of initial density of sand.The generalization of dynamic effective stress strength criterion in the 3-dimensional effective stress space is studied in detail for the purpose of its practical use.
文摘A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom（MDOF） system is approximated by using the modal energy-decomposition. Energybased base shear coefficients are verified by means of both pushover analysis and nonlinear time history（NLTH） analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation.
文摘In this paper, a formulation for shakedown analysis of elastic-plastic offshore structures under cyclic wave loading is presented. In this formulation, a fast numerical solution method is used, suitable for the Finite Element Method (FEM) analysis of large offshore structures on which shear effects in addition to bending and axial effects are taken into account. The Morison equation is adopted for converting the velocity and acceleration terms into resultant forces and it is extended to consider arbitrary orientations of the structural members. The theoretical methods of the shakedown analysis are discussed in detail and the formulation is applied to an offshore structure to verify the concept employed and its analytical capabilities.
文摘The project of Xiaoxihu Yellow River Bridge in Lanzhou is chosen as partial cable-stayed bridge. To get the shear lag effect and anti-earthquake performance of the actual bridge under various loading conditions, organic glass scaled model was adopted to have an experiment and a theory research at one time. The experiment result is the basically same as the theory calculation which proves the FEA method can well calculate shear lag effect and dynamical performance. As a result, because the bridge is located in a seismic area of 8 degree, an elasto-plastic seismic checking is performed by customized FEA program in this paper.
文摘To investigate the effects of mechanical factors on matrix metalloproteinase9(MMP-9) expressions in rat bone marrow-derived mesenchymal stem cells(MSCs) and possible mechanism signal.Rat bone marrow MSCs were isolated and cultured,then,exposed to laminar shear stress
文摘Classical bending theories for beams and plates can not be used for short, stubby beams and thick plates since transverse shearing effect is excluded, and ordinary theories with multiple generalized displacements can not be used for long, slender beams and thin plates since the innate relation between rotation angle and deflection is ignored. These two types of theories are not consistent due to the contradiction of dependence and independence of the rotation angle. Based on several basic assumptions, a new type of theories which not only include the transverse shearing effect is presented, but also the relation between potation angle and deflection is obtained. Analytical solutions of several simple beams are given. It has been testified by numerical examples that the new theories can be used for either long, slender beams and thin plates or short, stubby beams and thick plates.
基金Projects(51078355,50938008)supported by the National Natural Science Foundation of ChinaProject(094801020)supported by the Academic Scholarship for Doctoral Candidates of the Ministry of Education,China+1 种基金Project(CX2011B093)supported by the Doctoral Candidate Research Innovation Project of Hunan Province,ChinaProject(20117Q008)supported by the Central University Basic Scientific Research Business Expenses Special Fund of China
文摘Based on Hamilton principle,the governing differential equations and the corresponding boundary conditions of steel-concrete composite box girder with consideration of the shear lag effect meeting self equilibrated stress,shear deformation,slip,as well as rotational inertia were induced.Therefore,natural frequency equations were obtained for the boundary types,such as simple support,cantilever,continuous girder and fixed support at two ends.The ANSYS finite element solutions were compared with the analytical solutions by calculation examples and the validity of the proposed approach was verified,which also shows the correctness of longitudinal warping displacement functions.Some meaningful conclusions for engineering design were obtained.The decrease extent of each order natural frequency of the steel-concrete composite box-girder is great under action of the shear lag effect.The shear-lag effect of steel-concrete composite box girder increases when frequency order rises,and increases while span-width ratio decreases.The proposed approach provides theoretical basis for further research of free vibration characteristics of steel-concrete composite box-girder.
基金Supported by the National Natural Science Foundation of China (No. 20076011, No. 20236040 and No. 20225619).
文摘By investigating the shear effect on submerged cultivation of a traditional Chinese medicinal herb Ganoderma lucidum, a relatively high cell concentration of 13.8 g·L-1 by dry mass was obtained in bioreactor at an impeller tip speed (ITS) of 0.51m·s-1. At an ITS of 0.51,1.02 and 1.53m·s-1, a maximal production titer of intracellular polysaccharide was 2.64, 2.20 and 2.28g·L-1 and that of ganoderic acid was 306, 299 and 273g·L-1, respectively. Under these ITSs, the maximal mean projected area of dispersed hyphae was 3.70, 2.54 and 2.13×104μm2, and that of pellets was 0.91, 0.67 and 0.55mm2, respectively. The information obtained is useful for efficient submerged cultivation of mushrooms on a large scale.
基金Projects(51205171,51376081)supported by the National Natural Science Foundation of ChinaProject(1201026B)supported by the Postdoctoral Science Foundation of Jiangsu Province,China
文摘At jet pressures ranging from 80 to 120 MPa, submerged water jets are investigated by numerical simulation and experiment. Numerical simulation enables a systematic analysis of major flow parameters such as jet velocity, turbulent kinetic energy as well as void fraction of cavitation. Experiments facilitate an objective assessment of surface morphology, micro hardness and surface roughness of the impinged samples. A comparison is implemented between submerged and non-submerged water jets. The results show that submerged water jet is characterized by low velocity magnitudes relative to non-submerged water jet at the same jet pressure. Shear effect serves as a key factor underlying the inception of cavitation in submerged water jet stream. Predicted annular shape of cavity zone is substantiated by local height distributions associated with experimentally obtained footprints. As jet pressure increases, joint contribution of jet kinetic energy and cavitation is demonstrated. While for non-submerged water jet, impingement force stems exclusively from flow velocity.
基金Key Research Project of National Natural Science Foundation of China Under Grant No.90715018National Basic Research Program of China Under Grant No.2007CB714200the Special Fund for the Commonweal Industry of China Under Grant No.200808022
文摘Three groups of dynamic triaxial tests were performed for saturated Nanjing fine sand subjected to uniform cyclic loading. The tested curves of the excess pore water pressure （EPWP） ratio variation with the ratio of the number of cycles are provided. The concept of the EPWP increment ratio is introduced and two new concepts of the effective dynamic shear stress ratio and the log decrement of effective stress are defined. It is found that the development of the EPWP increment ratio can be divided into three stages： descending, stable and ascending. Furthermore, at the stable and ascending stages, a satisfactory linear relationship is obtained between the accumulative EPWP increment ratio and natural logarithm of the effective dynamic shear stress ratio. Accordingly, the EPWP increment ratio at the number of cycles N has been deduced that is proportional to the log decrement of effective stress at the cycle number N-l, but is independent of the cyclic stress amplitude. Based on the analysis, a new EPWP increment model for saturated Nanjing fine sand is developed from tested data fitting, which provides a better prediction of the curves of EPWP generation, the number of cycles required for initial liquefaction and the liquefaction resistance.
文摘Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. To analyze the elastic-plastic response of a short-leg shear wall structure during an earthquake, this study modified the multiple-vertical-rod element model of the shear wall, considered the shear lag effect and proposed a multiple-vertical-rod element coupling beam model with a new local stiffness domain. Based on the principle of minimum potential energy and the variational principle, the stiffness matrixes of a short-leg shear wall and a coupling beam are derived in this study. Furthermore, the bending shear correlation for the analysis of different parameters to describe the structure, such as the beam height to span ratio, short-leg shear wall height to thickness ratio, and steel ratio are introduced. The results show that the height to span ratio directly affects the structural integrity; and the short-leg shear wall height to thickness ratio should be limited to a range of approximately 6.0 to 7.0. The design of short-leg shear walls should be in accordance with the ＂strong wall and weak beam＂ principle.
基金funded by the Major Basic Research and Development Program of China(No.2014CB046905)the Ph.D.Programs Foundation of Ministry of Education of China(No.20130095110018)
文摘Based on the stress field distribution rule of the mining floor under abutment pressure, we have established a simplified mechanical model, which contains multiple factors relating to activation and evolution of insidious water-conductive faults. The influence of normal and shear stresses on fault activation and effective shear stress distribution in the fault plane was acquired under mining conditions.Using fracture mechanics theory to calculate the stress intensity factor of an insidious fault front, we have derived the criterion for main fault activation. Results indicate that during the whole working face advance, transpressions are exerted on fault planes twice successively in opposite directions. In most cases, the second transpression is more likely to lead to fault activation. Activation is influenced by many factors, predominant among which are: burial depth of the insidious fault, friction angle of the fault plane, face advance direction and pore water pressure. Steep fault planes are more easily activated to induce a sustained water inrush in the face.
