Past earthquakes have revealed that topographic features have significant impacts on the characteristics of ground motions,which may cause the amplification and de-amplification of input seismic waves.The topographic ...Past earthquakes have revealed that topographic features have significant impacts on the characteristics of ground motions,which may cause the amplification and de-amplification of input seismic waves.The topographic effect with the assumption of plane seismic waves on the seismic responses of bridges has been investigated in the existing literature;however,the influence of near-source topographic effects has not been thoroughly understood.The objective of this study is to numerically explore the near-source topographic effects on the seismic behaviors of an existing railway bridge crossing a symmetrical V-shaped canyon.The influence of the source of incident waves is estimated.Numerical results demonstrate that the topographic effects can noticeably amplify the seismic responses of the bridge.Compared to the bridge without crossing a canyon,the peak displacements of the girder,pier,and bearing in the case of the canyon crossing bridge increase by 15.2%,2.9%−14.5%,and 24.2%−229.6%,respectively.The piers at the illuminated side of the canyon experience larger seismic responses compared to the piers at the shaded side of the canyon due to the unequal motion amplitudes at each support.As the source-to-canyon distance increases,the seismic responses of the piers show an increasing trend.展开更多
Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for...Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.展开更多
The dynamic interaction between tunnel lining and its surrounding soil is a complicated issue as the magnitude of seismic wave from bedrock to the structure can be easily influenced by the geometrical layout and struc...The dynamic interaction between tunnel lining and its surrounding soil is a complicated issue as the magnitude of seismic wave from bedrock to the structure can be easily influenced by the geometrical layout and structural stiffness of the tunnel.A series of numerical analysis was conducted to study the dynamic response of the tunnel lining of side-by-side and vertically stacked double-tube tunnel since the inertia and kinematic interactions between the tunnel lining and the surrounding soil during an earthquake could induce excessive stresses to the lining itself due to the stiffness variation between the lining and the soil.Real earthquake ground acceleration was used as an input motion in the dynamic analysis.The interactive behavior of bending moment and axial forces,and the displacement of the tunnels were used to evaluate the effect of tunnel geometrical layout on the performance of the lining.It is found that the effect of earthquake on the axial thrust of the lining is insignificant,and there is a reduction of the bending moment in the lining due to the redistribution of the surrounding soil after the earthquake.展开更多
Modal analysis and seismic response analysis were carried out for the equatorial diagnostic port plug of international thermonuclear experimental reactor (ITER). The aim of the theoretical analysis is to verify struct...Modal analysis and seismic response analysis were carried out for the equatorial diagnostic port plug of international thermonuclear experimental reactor (ITER). The aim of the theoretical analysis is to verify structural strength and reliability of the device. The working condition includes one-dimensional seismic wave and two-dimensional seismic wave. Modal analysis of the device shows that primary vibration is inclined to occur in low-order modes. The horizontal (X-direction, Y-direction) maximum vibration appears at the first and the fourth eigen modes, with the natural frequency of 70.59 and 215.88 Hz respectively, and the vertical (Z-direction) primary vibration appears at the second eigen mode with the natural frequency of 82.85 Hz. According to the results of the finite element analysis (FEA) program, the weak portions of the device are distributed in the joint of port body with blanket shielding module (BSM) and inner side wall of ribbed plate for lifting flange, the maximum von Mises stress is 14.8 MPa with the Y-direction seismic wave. In accordance with the design criteria, the destructive effect is far below the failure boundary, and the structural reliability of the equatorial diagnostic port plug can meet the requirements of the design specifications.展开更多
In order to analyze the seismic response characteristics of pile-supported structure,a computational model considering pile-soil-structure interaction effect was established by finite element method.Then,numerical imp...In order to analyze the seismic response characteristics of pile-supported structure,a computational model considering pile-soil-structure interaction effect was established by finite element method.Then,numerical implementation was made in time domain.At the same time,a simplified approximation for seismic response analysis of pile-soil-structure system was briefly presented.Furthermore,comparative study was performed for an engineering example.Through comparative analysis,it is shown that the results obtained by the simplified method well agree with those achieved by the finite element method.These results show that spectrum characteristics and intensity of input earthquakes are two important factors that can notablely influence the seismic response characteristics of superstructure.When the input ground motion acceleration amplitude gradually increases from 1 to 4 m/s2,the acceleration of pier top will increase,but it will not be simply proportional to the increase of input acceleration amplitude.展开更多
This work investigates the correlation between a large number of widely used ground motion intensity measures(IMs) and the corresponding liquefaction potential of a soil deposit during earthquake loading. In order to ...This work investigates the correlation between a large number of widely used ground motion intensity measures(IMs) and the corresponding liquefaction potential of a soil deposit during earthquake loading. In order to accomplish this purpose the seismic responses of 32 sloping liquefiable site models consisting of layered cohesionless soil were subjected to 139 earthquake ground motions. Two sets of ground motions, consisting of 80 ordinary records and 59 pulse-like near-fault records are used in the dynamic analyses. The liquefaction potential of the site is expressed in terms of the the mean pore pressure ratio, the maximum ground settlement, the maximum ground horizontal displacement and the maximum ground horizontal acceleration. For each individual accelerogram, the values of the aforementioned liquefaction potential measures are determined. Then, the correlation between the liquefaction potential measures and the IMs is evaluated. The results reveal that the velocity spectrum intensity(VSI) shows the strongest correlation with the liquefaction potential of sloping site. VSI is also proven to be a sufficient intensity measure with respect to earthquake magnitude and source-to-site distance, and has a good predictability, thus making it a prime candidate for the seismic liquefaction hazard evaluation.展开更多
As a new type of structure which has never been built, submerged floating tunnel was studied mainly by numerical simulations. To further study the seismic response of a submerged floating tunnel, the first model exper...As a new type of structure which has never been built, submerged floating tunnel was studied mainly by numerical simulations. To further study the seismic response of a submerged floating tunnel, the first model experiment of submerged floating tunnel （SFT） under the earthquake was carried out on the unique underwater shaking table in China. The experimental results show that vertical excitation induces larger response than horizontal and different inclination degrees of the tether also cause different seismic responses. Subsequently, based on the fluid-structure interaction theory, the corresponding numerical model is established. And comparing the numerical results with the experimental results, those of shaking table test. Numerical model adopted is effective for it is shown that the numerical results are basically identical with dynamic response of SFT.展开更多
Loess is widely distributed in China and the Loess Plateau is one of the major areas where strong earthquakes often take place. The seismic amplification effects were discovered in the Plateau during the Wenchuan Ms8....Loess is widely distributed in China and the Loess Plateau is one of the major areas where strong earthquakes often take place. The seismic amplification effects were discovered in the Plateau during the Wenchuan Ms8.0 earthquake and some other strong events. Based on earth tremor observation, borehole exploration and site seismic response analysis, the site effects of topography of Loess Yuan on ground motion were investigated in details. The earth tremor investigation shows that predominant frequencies at the bottom sites of Loess Yuan are greater than those at the top obviously. The sites seismic response analysis shows that the Loess Yuan may amplify peak ground acceleration (PGA) by 1.44 2.0 times. Therefore, site effects of mountains and loess topography on ground motion should be taken account into in seismic design in loess regions.展开更多
The behavior of viscous fluid damper applied in coupling structures subjected to near-fault earthquake was studied.The structural nonlinearity was characterized by Bouc-Wen model and several near-fault ground motions ...The behavior of viscous fluid damper applied in coupling structures subjected to near-fault earthquake was studied.The structural nonlinearity was characterized by Bouc-Wen model and several near-fault ground motions were simulated by the combination of a recorded earthquake(background ground motion) with equivalent velocity pulses that possess near-fault features.Extensive parametric studies were carried out to find the appropriate damping coefficient.Performances of viscous fluid dampers were demonstrated by the relationship between the force and displacement,the maximal damper force and stroke.The control performances were demonstrated in terms of the response reductions of adjacent structures.The results show that the dynamic responses of adjacent structures are mitigated greatly.Proper damping coefficients of connecting fluid dampers have a small difference,while adjacent structures under different near-fault ground motions with the same peak acceleration.The maximum force of damper is about 0.8 MN,and the maximum damper stroke is about ±550 mm.Satisfied viscous fluid dampers can be produced according to the current manufacturing skills.展开更多
Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were...Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.展开更多
基金Projects(51908123,51678140,U1934205)supported by the National Natural Science Foundation of ChinaProjects(BK20190370,BK20180383) supported by the Natural Science Foundation of Jiangsu Province,China+1 种基金Project(18KJA580005) supported by the Natural Science Foundation of Jiangsu Higher Education Institutions of ChinaProject(KYY2019096(19-21)) supported by the Science and Technology Research Plan of China Railway Eryuan Engineering Group Corporation。
文摘Past earthquakes have revealed that topographic features have significant impacts on the characteristics of ground motions,which may cause the amplification and de-amplification of input seismic waves.The topographic effect with the assumption of plane seismic waves on the seismic responses of bridges has been investigated in the existing literature;however,the influence of near-source topographic effects has not been thoroughly understood.The objective of this study is to numerically explore the near-source topographic effects on the seismic behaviors of an existing railway bridge crossing a symmetrical V-shaped canyon.The influence of the source of incident waves is estimated.Numerical results demonstrate that the topographic effects can noticeably amplify the seismic responses of the bridge.Compared to the bridge without crossing a canyon,the peak displacements of the girder,pier,and bearing in the case of the canyon crossing bridge increase by 15.2%,2.9%−14.5%,and 24.2%−229.6%,respectively.The piers at the illuminated side of the canyon experience larger seismic responses compared to the piers at the shaded side of the canyon due to the unequal motion amplitudes at each support.As the source-to-canyon distance increases,the seismic responses of the piers show an increasing trend.
基金Projects(03JJY3078, 04JJ40032) supported by the Natural Science Foundation of Hunan Province, China project(03A006) supported by Scientific Research Fund of Hunan Provincial Education Department, China
文摘Based on the analysis method for tailings dam in upstream raising method presently used in metallurgy and nonferrous metals tailings depository in the world, an effective stress analysis method of seismic response for high tailings dam was developed according to the results of engineering geological exploration, static and dynamic test and stability analysis on Baizhishan tailing dam 113.5 m high. The law of generation, diffusion and dissipation of seismic pore water pressure during and after earthquake was investigated, and the results of tailings dam’s acceleration, seismic dynamic stress and pore water pressure were obtained. The results show that the seismic stability and liquefaction resistance of high tailings dam are strengthened remarkably, and the scope and depth of liquefaction area at the top of dam are reduced greatly. The interior stress is compressive stress, the stress level of every element is less than 1.0 and the safety coefficient of every element is greater than 1.0. The safety coefficient against liquefaction of every element of tailing dam is greater than 1.5 according to the effective stress analysis of seismic response by finite element method. The calculated results prove that liquefaction is the main reason of seismic failure of high tailing dams, and the effect of seismic inertia forces on high tailing dams’ stability during earthquake is secondary reason.
文摘The dynamic interaction between tunnel lining and its surrounding soil is a complicated issue as the magnitude of seismic wave from bedrock to the structure can be easily influenced by the geometrical layout and structural stiffness of the tunnel.A series of numerical analysis was conducted to study the dynamic response of the tunnel lining of side-by-side and vertically stacked double-tube tunnel since the inertia and kinematic interactions between the tunnel lining and the surrounding soil during an earthquake could induce excessive stresses to the lining itself due to the stiffness variation between the lining and the soil.Real earthquake ground acceleration was used as an input motion in the dynamic analysis.The interactive behavior of bending moment and axial forces,and the displacement of the tunnels were used to evaluate the effect of tunnel geometrical layout on the performance of the lining.It is found that the effect of earthquake on the axial thrust of the lining is insignificant,and there is a reduction of the bending moment in the lining due to the redistribution of the surrounding soil after the earthquake.
基金Project(10405024) supported by the National Natural Science Foundation of ChinaProject supported by International Thermonuclear Experimental Reactor Organization in France
文摘Modal analysis and seismic response analysis were carried out for the equatorial diagnostic port plug of international thermonuclear experimental reactor (ITER). The aim of the theoretical analysis is to verify structural strength and reliability of the device. The working condition includes one-dimensional seismic wave and two-dimensional seismic wave. Modal analysis of the device shows that primary vibration is inclined to occur in low-order modes. The horizontal (X-direction, Y-direction) maximum vibration appears at the first and the fourth eigen modes, with the natural frequency of 70.59 and 215.88 Hz respectively, and the vertical (Z-direction) primary vibration appears at the second eigen mode with the natural frequency of 82.85 Hz. According to the results of the finite element analysis (FEA) program, the weak portions of the device are distributed in the joint of port body with blanket shielding module (BSM) and inner side wall of ribbed plate for lifting flange, the maximum von Mises stress is 14.8 MPa with the Y-direction seismic wave. In accordance with the design criteria, the destructive effect is far below the failure boundary, and the structural reliability of the equatorial diagnostic port plug can meet the requirements of the design specifications.
基金Project(Y2007F48) supported by the Natural Science Foundation of Shandong Province,ChinaProject(SDTS20080422) supported by the Specialized Development Foundation for Taishan Scholars of Shandong Province, China Project(SDVS20090525) supported by the Specialized Foundation for Domestic Visiting Scholars of Shandong Province,China
文摘In order to analyze the seismic response characteristics of pile-supported structure,a computational model considering pile-soil-structure interaction effect was established by finite element method.Then,numerical implementation was made in time domain.At the same time,a simplified approximation for seismic response analysis of pile-soil-structure system was briefly presented.Furthermore,comparative study was performed for an engineering example.Through comparative analysis,it is shown that the results obtained by the simplified method well agree with those achieved by the finite element method.These results show that spectrum characteristics and intensity of input earthquakes are two important factors that can notablely influence the seismic response characteristics of superstructure.When the input ground motion acceleration amplitude gradually increases from 1 to 4 m/s2,the acceleration of pier top will increase,but it will not be simply proportional to the increase of input acceleration amplitude.
基金Project(5141001028)supported by International Cooperation and Exchanges of NSFC,ChinaProjects(51308566,51308565,51409025)supported by the National Natural Science Foundation of ChinaProject(CDJZR12200002)supported by the Fundamental Research Funds for the Central Universities,China
文摘This work investigates the correlation between a large number of widely used ground motion intensity measures(IMs) and the corresponding liquefaction potential of a soil deposit during earthquake loading. In order to accomplish this purpose the seismic responses of 32 sloping liquefiable site models consisting of layered cohesionless soil were subjected to 139 earthquake ground motions. Two sets of ground motions, consisting of 80 ordinary records and 59 pulse-like near-fault records are used in the dynamic analyses. The liquefaction potential of the site is expressed in terms of the the mean pore pressure ratio, the maximum ground settlement, the maximum ground horizontal displacement and the maximum ground horizontal acceleration. For each individual accelerogram, the values of the aforementioned liquefaction potential measures are determined. Then, the correlation between the liquefaction potential measures and the IMs is evaluated. The results reveal that the velocity spectrum intensity(VSI) shows the strongest correlation with the liquefaction potential of sloping site. VSI is also proven to be a sufficient intensity measure with respect to earthquake magnitude and source-to-site distance, and has a good predictability, thus making it a prime candidate for the seismic liquefaction hazard evaluation.
基金Projects(51108224,51179026) supported by the National Natural Science Foundation of China
文摘As a new type of structure which has never been built, submerged floating tunnel was studied mainly by numerical simulations. To further study the seismic response of a submerged floating tunnel, the first model experiment of submerged floating tunnel （SFT） under the earthquake was carried out on the unique underwater shaking table in China. The experimental results show that vertical excitation induces larger response than horizontal and different inclination degrees of the tether also cause different seismic responses. Subsequently, based on the fluid-structure interaction theory, the corresponding numerical model is established. And comparing the numerical results with the experimental results, those of shaking table test. Numerical model adopted is effective for it is shown that the numerical results are basically identical with dynamic response of SFT.
基金Foundation item： Projects（40902094, 50978239） supported by the National Natural Science Foundation of China Project（2012IESLZO1） supported by the Fund of the Institute of Earthquake Prediction, CEA, China
文摘Loess is widely distributed in China and the Loess Plateau is one of the major areas where strong earthquakes often take place. The seismic amplification effects were discovered in the Plateau during the Wenchuan Ms8.0 earthquake and some other strong events. Based on earth tremor observation, borehole exploration and site seismic response analysis, the site effects of topography of Loess Yuan on ground motion were investigated in details. The earth tremor investigation shows that predominant frequencies at the bottom sites of Loess Yuan are greater than those at the top obviously. The sites seismic response analysis shows that the Loess Yuan may amplify peak ground acceleration (PGA) by 1.44 2.0 times. Therefore, site effects of mountains and loess topography on ground motion should be taken account into in seismic design in loess regions.
基金Project(50778077) supported by the National Natural Science Foundation of ChinaProject(50925828) supported by the National Science Foundation for Distinguished Young Scholars of China
文摘The behavior of viscous fluid damper applied in coupling structures subjected to near-fault earthquake was studied.The structural nonlinearity was characterized by Bouc-Wen model and several near-fault ground motions were simulated by the combination of a recorded earthquake(background ground motion) with equivalent velocity pulses that possess near-fault features.Extensive parametric studies were carried out to find the appropriate damping coefficient.Performances of viscous fluid dampers were demonstrated by the relationship between the force and displacement,the maximal damper force and stroke.The control performances were demonstrated in terms of the response reductions of adjacent structures.The results show that the dynamic responses of adjacent structures are mitigated greatly.Proper damping coefficients of connecting fluid dampers have a small difference,while adjacent structures under different near-fault ground motions with the same peak acceleration.The maximum force of damper is about 0.8 MN,and the maximum damper stroke is about ±550 mm.Satisfied viscous fluid dampers can be produced according to the current manufacturing skills.
基金Project(51178203)supported by the National Natural Science Foundation of China
文摘Based on a simplified 3-DOF model of twin-tower structure linked by a sky-bridge,the frequency response functions,the displacement power spectral density(PSD)functions,and the time-averaged total vibration energy were derived,by assuming the white noise as the earthquake excitation.The effects of connecting parameters,such as linking stiffness ratio and linking damping ratio,on the structural vibration responses were then studied,and the optimal connecting parameters were obtained to minimize the vibration energy of either the independent monomer tower or the integral structure.The influences of sky-bridge elevation position on the optimal connecting parameters were also discussed.Finally,the distribution characteristics of the top displacement PSD and the structural responses,excited by El Centro,Taft and artificial waves,were compared in both frequency and time domain.It is found that the connecting parameters at either end of connection interactively affect the responses of the towers.The optimal connecting parameters can greatly improve the damping connections on their seismic reduction effectiveness,but are unable to reduce the seismic responses of the towers to the best extent simultaneously.It is also indicated that the optimal connecting parameters derived from the simplified 3-DOF model are applicable for two multi-story structures linked by a sky-bridge with dampers.The seismic reduction effectiveness obtained varies from 0.3 to 1.0 with different sky-bridge mass ratio.The displacement responses of the example structures are reduced by approximately 22% with sky-bridge connections.
