Taken the Dalian lake region as the study area,which represents the typical agriculture production mode and agricultural non-point source pollution (ANSP) in Dianshan lake area in Shanghai City,basis on the characte...Taken the Dalian lake region as the study area,which represents the typical agriculture production mode and agricultural non-point source pollution (ANSP) in Dianshan lake area in Shanghai City,basis on the characteristics of regional ANSP and combing with the seasonal water quality monitoring of Dalian Lake and reaches of its main influents,the laws of seasonal impact on the water environment were investigated.The results showed that,the seasonal change of TN and COD concentration of regional water had no significant correlation with the local ANSP emissions,while the seasonal changes of TP was consistent with seasonal emissions of regional TP pollution,and it had a significant correlation with Chl.a in four seasons,indicating that regional TP pollutant was the constriction factor influenced the eutrophication degree of Dalian lake.Because more than 80% of TP emissions came from the drainage of intensive pounds in winter,summer and fall,TP pollutant control should be adopted as the control target of regional ANSP control.展开更多
With Hongli Feicheng Peach as the test material, the effects of bagging with 4 kinds of paper bags and 3 kinds of non-woven bags on the soluble sugar, organic acids and aroma compounds in peach fruits were investigate...With Hongli Feicheng Peach as the test material, the effects of bagging with 4 kinds of paper bags and 3 kinds of non-woven bags on the soluble sugar, organic acids and aroma compounds in peach fruits were investigated using headspace solid-phase microextraction (HS-SPME) combined with gas chromatogra- phy-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). The results showed that there were significant differences in sugar and acids contents of peach fruits between different bagging treatments. The sugar con- tent of peach fruits was increased when bagged with single-layer inner-black outer- yellow paper bags and double-layer inner-white outer-yellow paper bags. The organ- ic acid content in peach fruits bagged with all the types of bags except the single- layer inner-black outer-yellow paper bag was increased greatly. The count and rela- tive content of aroma compounds were all decreased after bagging. Combined with the detection results of soluble sugar, organic acids and aroma compounds, the sin- gle-layer inner-black outer-yellow paper bag was suitable for bagging of Hongli Fe- icheng peach.展开更多
Ezra Pound is one of the founders of the American Imagist poetry, and Chinese Classic Poetry happened to be a great stimulus as the Renaissance from the Greeks to this poetry movement. Pound, who was deeply fascinated...Ezra Pound is one of the founders of the American Imagist poetry, and Chinese Classic Poetry happened to be a great stimulus as the Renaissance from the Greeks to this poetry movement. Pound, who was deeply fascinated by Chinese poetry, has rendered many into English. Yet due to cultural differences, Pound’s translation has a lot of mistakes. And this paper aims at a cultural analysis of the mistranslation on a certain text to display its influence upon the Imagist Movement in the history of American Poetry.展开更多
Cathay by Ezra Pound is the masterpiece in modern poetry in the West,and it contains nineteen Chinese poems.Based on literary stylistic theory,Pound’s translation style in Cathay is analyzed from lexical categories,a...Cathay by Ezra Pound is the masterpiece in modern poetry in the West,and it contains nineteen Chinese poems.Based on literary stylistic theory,Pound’s translation style in Cathay is analyzed from lexical categories,aspects of syntax and figures of speech etc.It is found that the vocabulary and sentences in Cathay are very simple and brief,and the language is rich of images,which is the exact reflection of Pound’s idea of Imagism.展开更多
Base isolation can effectively reduce the seismic forces on a superstructure, particularly in lowto medium-rise buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level bet...Base isolation can effectively reduce the seismic forces on a superstructure, particularly in lowto medium-rise buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level between the baseisolated building (BIB) and its surrounding retaining walls. To effectively investigate the behavior of the BIB pounding with adjacent structures, after assessing some commonly used impact models, a modified Kelvin impact model is proposed in this paper. Relevant parameters in the modified Kelvin model are theoretically derived and numerically verified through a simple pounding case. At the same time, inelasticity of the isolated superstructure is introduced in order to accurately evaluate the potential damage to the superstructure caused by the pounding of the BIB with adjacent structures. The reliability of the modified Kelvin impact model is validated through numerical comparisons with other impact models. However, the difference between the numerical results from the various impact analytical models is not significant. Many numerical simulations of BIBs are conducted to investigate the influence of various design parameters and conditions on the peak inter-story drifts and floor accelerations during pounding. It is shown that pounding can substantially increase floor accelerations, especially at the ground floor where impacts occur. Higher modes of vibration are excited during poundings, increasing the inter-story drifts instead of keeping a nearly rigid-body motion of the superstructure. Furthermore, higher ductility demands can be imposed on lower floors of the superstructure. Moreover, impact stiffness seems to play a significant role in the acceleration response at the isolation level and the inter-story drifts of lower floors of the superstructure. Finally, the numerical results show that excessive flexibility of the isolation system used to minimize the floor accelerations may cause the BIB to be more susceptible to pounding under a limited seismic gap.展开更多
This paper presents an experimental study to investigate the performance of shape memory alloy(SMA) restrainers for mitigating the pounding and unseating of highway bridges when subjected to seismic excitations.Mechan...This paper presents an experimental study to investigate the performance of shape memory alloy(SMA) restrainers for mitigating the pounding and unseating of highway bridges when subjected to seismic excitations.Mechanical property tests of the SMA wire used in the restrainers are conducted first to understand the pseudo-elastic characteristics of the material.Then,a series of shaking table tests are carried out on a highway bridge model.The structural responses of the highway bridge model equipped with SMA restrainers,installed in the form of deck-deck and deck-pile connections,are analyzed and compared with the uncontrolled structures.The test results of this study indicate that the SMA restrainers are not only effective in preventing unseating but also in suppressing the seismic-induced pounding of the highway bridge model used in this study.展开更多
Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes.The consequences of pounding include d...Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes.The consequences of pounding include damage to piers,abutments,shear keys,bearings and restrainers,and possible collapse of deck spans.This paper investigates pounding in bridges from an analytical perspective.A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior,to study the seismic response to longitudinal ground motion.Pounding is implemented using the contact force-based Kelvin model,as well as the momentum-based stereomechanical approach.Parameter studies are conducted to determine the effects of frame period ratio,column hysteretic behavior,energy dissipation during impact and near source ground motions on the pounding response of the bridge.The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7.Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact,especially for elastic behavior of the frames.Representation of stiffness degradation in bridge columns is essential in capturing the accurate response of pounding frames subjected to far field ground motion.Finally,it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records.展开更多
Many closely located adjacent buildings have suffered from pounding during past earthquakes because they vibrated out of phase. Furthermore, buildings are usually constructed on soil; hence, there are interactions bet...Many closely located adjacent buildings have suffered from pounding during past earthquakes because they vibrated out of phase. Furthermore, buildings are usually constructed on soil; hence, there are interactions between the buildings and the underlying soil that should also be considered. This paper examines both the interaction between adjacent buildings due to pounding and the interaction between the buildings through the soil as they affect the buildings' seismic responses. The developed model consists of adjacent shear buildings resting on a discrete soil model and a linear visco- elastic contact force model that connects the buildings during pounding. The seismic responses of' adjacent buildings due to ground accelerations are obtained for two conditions: fixed-based (FB) and structure-soil-structure interaction (SSSI). The results indicate that pounding worsens the buildings' condition because their seismic responses are amplified after pounding. Moreover, the underlying soil negatively impacts the buildings' seismic responses during pounding because the ratio of their seismic response under SSSI conditions with pounding to those without pounding is greater than that of the FB condition.展开更多
In this study the seismic pounding response of adjacent multi-degree-of-freedom(MDOF) buildings with bilinear inter-story resistance characteristics is investigated through dimensional analysis. The application of dim...In this study the seismic pounding response of adjacent multi-degree-of-freedom(MDOF) buildings with bilinear inter-story resistance characteristics is investigated through dimensional analysis. The application of dimensional analysis leads to a condensed presentation of the response, and the remarkable self-similarity property for bilinear MDOF buildings with inelastic collision is uncovered. It is shown that when the response is expressed in the appropriate dimensionless form, response spectra for any intensity of the excitation collapse to a single master curve. The reduced Π set explicitly describes the interaction between the colliding structures. The effect of pounding on the MDOF building’s response is illustrated using three well-divided spectral regions(amplifi ed, de-amplifi ed and unaffected regions). Parametric studies are conducted to investigate the effects of the story stiffness of structures, the story stiffness ratio and mass ratio of adjacent buildings, the structural inelastic characteristics and the gap size values. Results show that(i) the infl uence of system stiffness ratio to the lighter and more fl exible building is more signifi cant in the fi rst spectral region, where the maximum response of the building is amplifi ed because of pounding; and(ii) the velocity and pounding force of the heavier and stiffer building is unexpectedly sensitive to the mass ratio of adjacent buildings.展开更多
The paper aims to explore Pound's early discovery of Confucianism and his conversion to Confucianism. Pound's interest in Confucianism coincided with the time when Christianity, already "contaminated" by "histori...The paper aims to explore Pound's early discovery of Confucianism and his conversion to Confucianism. Pound's interest in Confucianism coincided with the time when Christianity, already "contaminated" by "historical diseases" in Pound's view, could not offer a valid vision by which to guide the spiritual life, resulting in losing self in a modem society. Pound discovers three main deficiencies of Christianity: lack of respect for individuality, the decline of ethics, and open attack upon nature, which could not provide solutions to Western problems. Pound turned to Confucianism to search the existence of modem man in the face of society, and nature, which results in Pound's Confucian medicine to cure Western moral obtuseness.展开更多
Pound's poem In a Station of a Metro is a masterpiece of imagism. Pound once talked about the energy in language, and American scholar Allen Tate told us that the meaning of poetry is its tension. Based on those t...Pound's poem In a Station of a Metro is a masterpiece of imagism. Pound once talked about the energy in language, and American scholar Allen Tate told us that the meaning of poetry is its tension. Based on those two notions, this essay focuses on that how the tension in In a Station of a Metro presented and those tensions form harmony, fully releasing the energy in language in Pound's hand, enabling readers being fascinated for generations in that way.展开更多
The prominent features of Li Bai's "The Jewel Stairs'Grievance" are precise diction;implicit meaning;an absent narrator;and a seamless unity of images and feelings.Pound's translation of it in Ca...The prominent features of Li Bai's "The Jewel Stairs'Grievance" are precise diction;implicit meaning;an absent narrator;and a seamless unity of images and feelings.Pound's translation of it in Cathay reveals some kind of connections between some Chinese poetic principals and Pound's individual poetics.展开更多
This paper is to explore the function of colour in Ezra Pound's Imagist poetry.As the position of image in poetry is raised,colour,as a part making up image,play a much more positive role in Pound's Imagist po...This paper is to explore the function of colour in Ezra Pound's Imagist poetry.As the position of image in poetry is raised,colour,as a part making up image,play a much more positive role in Pound's Imagist poems by defining the image to be more concrete and definite and reinforcing the theme directly.Pound's Imagist poetry includes his typical short Imagist poems and his poems in Cathay.展开更多
In the present study,actual three-dimensional structures are converted into a stick model of multi degree of-freedom(MDOF)systems for understanding the macro-behavior of structures.The study investigates the performan...In the present study,actual three-dimensional structures are converted into a stick model of multi degree of-freedom(MDOF)systems for understanding the macro-behavior of structures.The study investigates the performance of three closely spaced,adjacent G+10,fixed-base MDOF systems with the mass aligned at the same levels and subjected to accidental underground blast loading.The acceleration time history of underground blast loading is generated based on past empirical relationships.The blast charge weight varies from 10 to 75 t while keeping the charge distance constant(R=100 m).The entire formulation is solved with the MATLAB solver,using the state space form solution.Three cases are considered,based on changing the position of the three stick systems.The first case considered left building rigid,middle building moderate rigid,and right building flexible.The second assumed left building flexible,middle building rigid,and right building moderate rigid.The third examined the left building as moderate rigid,the middle building as flexible,and the right building rigid.An analysis of the results shows that the arrangement with low stiffness,high stiffness,and moderately stiff buildings placed to the left,middle,and right side,respectively,yields minimum structural response when compared to the other two combinations.展开更多
Based on Hertz contact theory, a method to determine the parameters of Kelvin impact model for seismic pounding analysis of bridges is proposed. The impact stiffness of Kelvin model is determined by the ratio of maxim...Based on Hertz contact theory, a method to determine the parameters of Kelvin impact model for seismic pounding analysis of bridges is proposed. The impact stiffness of Kelvin model is determined by the ratio of maximum impact force to maximum contact deformation, which is calculated based on Hertz contact theory with considering the vibration effect. The restitution coefficient which has great influence on the damping coefficient of Kelvin impact model is investigated by numerical analysis. Numerical results indicate that the impact stiffness of Kelvin impact model increases with the increment of the Hertz contact stiffness, approaching velocity or the length ratio of short to long girders. Vibration effect has remarkable influence on the impact stiffness and cannot be neglected. The restitution coefficient decreases when approaching velocity increases or the length ratio of short girder to long girder decreasing. The practical ranges of impact stiffness and restitution coefficient are obtained as 3 × 10^8--6 × 10^8 N/m and 0.6-3.95 respectively.展开更多
The nonlinear analysis of pounding between bridge deck segments subjected to multi-support excitations and multi-dimensional earthquake motion was performed.A novel bottom rigid element(BRE)method of the current displ...The nonlinear analysis of pounding between bridge deck segments subjected to multi-support excitations and multi-dimensional earthquake motion was performed.A novel bottom rigid element(BRE)method of the current displacement input model for structural seismic analysis under the multi-support excitations was used to calculate structural dynamic response.In the analysis,pounding between adjacent deck segments was considered.The seismic response of a multi-span bridge subjected to the multi-support excitation,considering not only the traveling-wave effect and partial coherence effect,but also the seismic non-stationary characteristics of multi-support earthquake motion,was simulated using finite element method(FEM).Meanwhile,the seismic response of the bridge under uniform earthquake was also analyzed.Finally,comparative analysis was conducted and some calculation results were shown for pounding effect,under multi-dimensional and multi-support earthquake motion,when performing seismic response analysis of multi-span bridge.Compared with the case of uniform/multi-support/multi-support and multi-dimensional earthquake input,the maximum values of pounding force in the case of multi-support and multi-dimensional earthquake input increase by about 5 8 times;the absolute value of bottom moment and shear force of piers increase by about50%600%and 23.1%900%,respectively.A conclusion can be given that it is very necessary to consider the pounding effect under multi-dimensional and multi-support earthquake motion while performing seismic response analysis of multi-span bridge.展开更多
Precast segmental column bridges exhibit various construction advantages in comparison to traditional monolithic column bridges.However,the lack of cognitions on seismic behaviors has seriously restricted their applic...Precast segmental column bridges exhibit various construction advantages in comparison to traditional monolithic column bridges.However,the lack of cognitions on seismic behaviors has seriously restricted their applications and developments.In this paper,comprehensive investigations are conducted to analyze the dynamic characteristics of precast segmental column bridges under near-fault,forward-directivity ground motions.First,the finite-element models of two comparable bridges with precast segmental columns and monolithic columns are constructed by using OpenSees software,and the nonlinearities of the bridges are considered.Next,three different earthquake loadings are meticulously set up to handle engineering problems,namely recorded near-and far-field ground motions,parameterized pulses,and pulse and residual components extracted from real records.Finally,based on the models and earthquake sets,extensive explorations are carried out.The results show that near-fault forward-directivity ground motions are more threatening than far-field ones;precast segmental column bridges may suffer more pounding impacts than monolithic bridges;the“narrow band”effect caused by near-fault,forward-directivity ground motions may occur in bridges with shorter periods than pulse periods;and pulse and residual components play different roles in seismic responses.展开更多
The damage to the masonry-infilled reinforced concrete( RC) frame buildings in Charikot,the capital city of Dolakha district in Nepal,during the 2015 April-to-May Nepal earthquake sequence is reported. Most of these b...The damage to the masonry-infilled reinforced concrete( RC) frame buildings in Charikot,the capital city of Dolakha district in Nepal,during the 2015 April-to-May Nepal earthquake sequence is reported. Most of these buildings were built by the owners with little governmental inspections regarding their structural design or constructional quality. Although they generally performed better than other structural systems such as stone-masonry houses,the RC frames sustained extensive damage ranging from cracking of infill to complete collapse. In particular,eight of the 72 inspected RC frames alongside an uphill street collapsed in different ways. In addition to the un-engineered nature of these RC frames,their collapse could also be attributed to multiple technical reasons including the effect of terrain, the pounding between adjacent buildings and the accumulative damage in the earthquake sequence.展开更多
A new compound K6Ti0.67Nb15.33O42 was prepared for the first time by solid state reaction in K2O-Ni2O3-Nb2O5 ternary system. The new compound was characterized by electron probe, X-ray powder diffraction and DTA. The ...A new compound K6Ti0.67Nb15.33O42 was prepared for the first time by solid state reaction in K2O-Ni2O3-Nb2O5 ternary system. The new compound was characterized by electron probe, X-ray powder diffraction and DTA. The result of X-ray powder diffraction shows that K6Ti0.67Nb15.33O42 crystallizes the hexagonal system with unit cell parameters a = 9. 1341(5) A ,c=12. 090(1)A . and space group P62/mcm(193 ).展开更多
Seismic pounding phenomena, particularly the collision of neighboring buildings under long-period ground motion, are becoming a significant issue in Japan. We focused on a specific apartment structure called the Nuevo...Seismic pounding phenomena, particularly the collision of neighboring buildings under long-period ground motion, are becoming a significant issue in Japan. We focused on a specific apartment structure called the Nuevo Leon buildings in the Tlatelolco district of Mexico City, which consisted of three similar buildings built consecutively with narrow expansion joints between the buildings. Two out of the three buildings collapsed completely in the 1985 Mexican earthquake. Using a finite element code based on the adaptively shifted integration (ASI)-Gauss technique, a seismic pounding analysis is performed on a simulated model of the Nuevo Leon buildings to understand the impact and collapse behavior of structures built near each other. The numerical code used in the analysis provides a higher computational efficiency than the conventional code for this type of problem and enables us to address dynamic behavior with strong nonlinearities, including phenomena such as member fracture and elemental contact. Contact release and recontact algorithms are developed and implemented in the code to understand the complex behaviors of structural members during seismic pounding and the collapse sequence. According to the numerical results, the collision of the buildings may be a result of the difference of natural periods between the neighboring buildings. This difference was detected in similar buildings from the damages caused by previous earthquakes. By setting the natural period of the north building to be 25% longer than the other periods, the ground motion, which hada relatively long period of 2 s, first caused the collision between the north and the center buildings. This collision eventually led to the collapse of the centerbuilding, followed by the destruction of the north building.展开更多
基金Supported by Science and Technology Support Program in Shanghai Science and Technology Committee (08DZ1203200, 08DZ1203205)~~
文摘Taken the Dalian lake region as the study area,which represents the typical agriculture production mode and agricultural non-point source pollution (ANSP) in Dianshan lake area in Shanghai City,basis on the characteristics of regional ANSP and combing with the seasonal water quality monitoring of Dalian Lake and reaches of its main influents,the laws of seasonal impact on the water environment were investigated.The results showed that,the seasonal change of TN and COD concentration of regional water had no significant correlation with the local ANSP emissions,while the seasonal changes of TP was consistent with seasonal emissions of regional TP pollution,and it had a significant correlation with Chl.a in four seasons,indicating that regional TP pollutant was the constriction factor influenced the eutrophication degree of Dalian lake.Because more than 80% of TP emissions came from the drainage of intensive pounds in winter,summer and fall,TP pollutant control should be adopted as the control target of regional ANSP control.
基金Supported by National Peach Industrial Technology System(CARS-31-Z-09)Project for Research on Quality and Efficiency Improvement and Standardized Key Production Technology of Excellent and Special Fruit in Shandong Province(2014CXZ04-1)+1 种基金National Rural Areas Project Application in the 12~(th) Five-Year Period(2013BAD02B03)Key Science and Technology Innovation Project of Shandong Academy of Agricultura Sciences(2014CXZ11-4)~~
文摘With Hongli Feicheng Peach as the test material, the effects of bagging with 4 kinds of paper bags and 3 kinds of non-woven bags on the soluble sugar, organic acids and aroma compounds in peach fruits were investigated using headspace solid-phase microextraction (HS-SPME) combined with gas chromatogra- phy-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC). The results showed that there were significant differences in sugar and acids contents of peach fruits between different bagging treatments. The sugar con- tent of peach fruits was increased when bagged with single-layer inner-black outer- yellow paper bags and double-layer inner-white outer-yellow paper bags. The organ- ic acid content in peach fruits bagged with all the types of bags except the single- layer inner-black outer-yellow paper bag was increased greatly. The count and rela- tive content of aroma compounds were all decreased after bagging. Combined with the detection results of soluble sugar, organic acids and aroma compounds, the sin- gle-layer inner-black outer-yellow paper bag was suitable for bagging of Hongli Fe- icheng peach.
文摘Ezra Pound is one of the founders of the American Imagist poetry, and Chinese Classic Poetry happened to be a great stimulus as the Renaissance from the Greeks to this poetry movement. Pound, who was deeply fascinated by Chinese poetry, has rendered many into English. Yet due to cultural differences, Pound’s translation has a lot of mistakes. And this paper aims at a cultural analysis of the mistranslation on a certain text to display its influence upon the Imagist Movement in the history of American Poetry.
文摘Cathay by Ezra Pound is the masterpiece in modern poetry in the West,and it contains nineteen Chinese poems.Based on literary stylistic theory,Pound’s translation style in Cathay is analyzed from lexical categories,aspects of syntax and figures of speech etc.It is found that the vocabulary and sentences in Cathay are very simple and brief,and the language is rich of images,which is the exact reflection of Pound’s idea of Imagism.
基金National Natural Science Foundation of China Under Grant No.50778077 and 50878093
文摘Base isolation can effectively reduce the seismic forces on a superstructure, particularly in lowto medium-rise buildings. However, under strong near-fault ground motions, pounding may occur at the isolation level between the baseisolated building (BIB) and its surrounding retaining walls. To effectively investigate the behavior of the BIB pounding with adjacent structures, after assessing some commonly used impact models, a modified Kelvin impact model is proposed in this paper. Relevant parameters in the modified Kelvin model are theoretically derived and numerically verified through a simple pounding case. At the same time, inelasticity of the isolated superstructure is introduced in order to accurately evaluate the potential damage to the superstructure caused by the pounding of the BIB with adjacent structures. The reliability of the modified Kelvin impact model is validated through numerical comparisons with other impact models. However, the difference between the numerical results from the various impact analytical models is not significant. Many numerical simulations of BIBs are conducted to investigate the influence of various design parameters and conditions on the peak inter-story drifts and floor accelerations during pounding. It is shown that pounding can substantially increase floor accelerations, especially at the ground floor where impacts occur. Higher modes of vibration are excited during poundings, increasing the inter-story drifts instead of keeping a nearly rigid-body motion of the superstructure. Furthermore, higher ductility demands can be imposed on lower floors of the superstructure. Moreover, impact stiffness seems to play a significant role in the acceleration response at the isolation level and the inter-story drifts of lower floors of the superstructure. Finally, the numerical results show that excessive flexibility of the isolation system used to minimize the floor accelerations may cause the BIB to be more susceptible to pounding under a limited seismic gap.
基金Earthquake Engineering and Engineering Vibration Laboratory Foundation,Institute of Engineering Mechanics, China Earthquake Administration Under Grant No.2009a1the National Natural Science Foundation of China under Grant No.50878071
文摘This paper presents an experimental study to investigate the performance of shape memory alloy(SMA) restrainers for mitigating the pounding and unseating of highway bridges when subjected to seismic excitations.Mechanical property tests of the SMA wire used in the restrainers are conducted first to understand the pseudo-elastic characteristics of the material.Then,a series of shaking table tests are carried out on a highway bridge model.The structural responses of the highway bridge model equipped with SMA restrainers,installed in the form of deck-deck and deck-pile connections,are analyzed and compared with the uncontrolled structures.The test results of this study indicate that the SMA restrainers are not only effective in preventing unseating but also in suppressing the seismic-induced pounding of the highway bridge model used in this study.
基金Earthquake Engineering Research Centers Program of the National Science Foundation Under Award Number EEC-9701785(Mid-America Earthquake Center)
文摘Seismic pounding between adjacent frames in multiple-frame bridges and girder ends in multi-span simply supported bridges has been commonly observed in several recent earthquakes.The consequences of pounding include damage to piers,abutments,shear keys,bearings and restrainers,and possible collapse of deck spans.This paper investigates pounding in bridges from an analytical perspective.A simplified nonlinear model of a multiple-frame bridge is developed including the effects of inelastic frame action and nonlinear hinge behavior,to study the seismic response to longitudinal ground motion.Pounding is implemented using the contact force-based Kelvin model,as well as the momentum-based stereomechanical approach.Parameter studies are conducted to determine the effects of frame period ratio,column hysteretic behavior,energy dissipation during impact and near source ground motions on the pounding response of the bridge.The results indicate that pounding is most critical for highly out-of-phase frames and is not significant for frame period ratios greater than 0.7.Impact models without energy dissipation overestimate the displacement and acceleration amplifications due to impact,especially for elastic behavior of the frames.Representation of stiffness degradation in bridge columns is essential in capturing the accurate response of pounding frames subjected to far field ground motion.Finally,it is shown that strength degradation and pounding can result in significant damage to the stiffer frames of the bridge when subjected to large acceleration pulses from near field ground motion records.
文摘Many closely located adjacent buildings have suffered from pounding during past earthquakes because they vibrated out of phase. Furthermore, buildings are usually constructed on soil; hence, there are interactions between the buildings and the underlying soil that should also be considered. This paper examines both the interaction between adjacent buildings due to pounding and the interaction between the buildings through the soil as they affect the buildings' seismic responses. The developed model consists of adjacent shear buildings resting on a discrete soil model and a linear visco- elastic contact force model that connects the buildings during pounding. The seismic responses of' adjacent buildings due to ground accelerations are obtained for two conditions: fixed-based (FB) and structure-soil-structure interaction (SSSI). The results indicate that pounding worsens the buildings' condition because their seismic responses are amplified after pounding. Moreover, the underlying soil negatively impacts the buildings' seismic responses during pounding because the ratio of their seismic response under SSSI conditions with pounding to those without pounding is greater than that of the FB condition.
基金the National Natural Science Foundation of China under Grant Nos.51322801,51238012 and 91215301)the Program for International Science and Technology Cooperation Projects of China under Grant No.2012DFA70810+1 种基金the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No.NCET-11-08the National Science and Technology Major Project under Grant 2013zx06002001-09
文摘In this study the seismic pounding response of adjacent multi-degree-of-freedom(MDOF) buildings with bilinear inter-story resistance characteristics is investigated through dimensional analysis. The application of dimensional analysis leads to a condensed presentation of the response, and the remarkable self-similarity property for bilinear MDOF buildings with inelastic collision is uncovered. It is shown that when the response is expressed in the appropriate dimensionless form, response spectra for any intensity of the excitation collapse to a single master curve. The reduced Π set explicitly describes the interaction between the colliding structures. The effect of pounding on the MDOF building’s response is illustrated using three well-divided spectral regions(amplifi ed, de-amplifi ed and unaffected regions). Parametric studies are conducted to investigate the effects of the story stiffness of structures, the story stiffness ratio and mass ratio of adjacent buildings, the structural inelastic characteristics and the gap size values. Results show that(i) the infl uence of system stiffness ratio to the lighter and more fl exible building is more signifi cant in the fi rst spectral region, where the maximum response of the building is amplifi ed because of pounding; and(ii) the velocity and pounding force of the heavier and stiffer building is unexpectedly sensitive to the mass ratio of adjacent buildings.
文摘The paper aims to explore Pound's early discovery of Confucianism and his conversion to Confucianism. Pound's interest in Confucianism coincided with the time when Christianity, already "contaminated" by "historical diseases" in Pound's view, could not offer a valid vision by which to guide the spiritual life, resulting in losing self in a modem society. Pound discovers three main deficiencies of Christianity: lack of respect for individuality, the decline of ethics, and open attack upon nature, which could not provide solutions to Western problems. Pound turned to Confucianism to search the existence of modem man in the face of society, and nature, which results in Pound's Confucian medicine to cure Western moral obtuseness.
文摘Pound's poem In a Station of a Metro is a masterpiece of imagism. Pound once talked about the energy in language, and American scholar Allen Tate told us that the meaning of poetry is its tension. Based on those two notions, this essay focuses on that how the tension in In a Station of a Metro presented and those tensions form harmony, fully releasing the energy in language in Pound's hand, enabling readers being fascinated for generations in that way.
文摘The prominent features of Li Bai's "The Jewel Stairs'Grievance" are precise diction;implicit meaning;an absent narrator;and a seamless unity of images and feelings.Pound's translation of it in Cathay reveals some kind of connections between some Chinese poetic principals and Pound's individual poetics.
文摘This paper is to explore the function of colour in Ezra Pound's Imagist poetry.As the position of image in poetry is raised,colour,as a part making up image,play a much more positive role in Pound's Imagist poems by defining the image to be more concrete and definite and reinforcing the theme directly.Pound's Imagist poetry includes his typical short Imagist poems and his poems in Cathay.
文摘In the present study,actual three-dimensional structures are converted into a stick model of multi degree of-freedom(MDOF)systems for understanding the macro-behavior of structures.The study investigates the performance of three closely spaced,adjacent G+10,fixed-base MDOF systems with the mass aligned at the same levels and subjected to accidental underground blast loading.The acceleration time history of underground blast loading is generated based on past empirical relationships.The blast charge weight varies from 10 to 75 t while keeping the charge distance constant(R=100 m).The entire formulation is solved with the MATLAB solver,using the state space form solution.Three cases are considered,based on changing the position of the three stick systems.The first case considered left building rigid,middle building moderate rigid,and right building flexible.The second assumed left building flexible,middle building rigid,and right building moderate rigid.The third examined the left building as moderate rigid,the middle building as flexible,and the right building rigid.An analysis of the results shows that the arrangement with low stiffness,high stiffness,and moderately stiff buildings placed to the left,middle,and right side,respectively,yields minimum structural response when compared to the other two combinations.
基金Supported by National Natural Science Foundation of China (No. 50578109)Tianjin Municipal Natural Science Foundation of China(No. 05YFGMGC10900)
文摘Based on Hertz contact theory, a method to determine the parameters of Kelvin impact model for seismic pounding analysis of bridges is proposed. The impact stiffness of Kelvin model is determined by the ratio of maximum impact force to maximum contact deformation, which is calculated based on Hertz contact theory with considering the vibration effect. The restitution coefficient which has great influence on the damping coefficient of Kelvin impact model is investigated by numerical analysis. Numerical results indicate that the impact stiffness of Kelvin impact model increases with the increment of the Hertz contact stiffness, approaching velocity or the length ratio of short to long girders. Vibration effect has remarkable influence on the impact stiffness and cannot be neglected. The restitution coefficient decreases when approaching velocity increases or the length ratio of short girder to long girder decreasing. The practical ranges of impact stiffness and restitution coefficient are obtained as 3 × 10^8--6 × 10^8 N/m and 0.6-3.95 respectively.
基金Project(51078242)supported by the National Natural Science Foundation of China
文摘The nonlinear analysis of pounding between bridge deck segments subjected to multi-support excitations and multi-dimensional earthquake motion was performed.A novel bottom rigid element(BRE)method of the current displacement input model for structural seismic analysis under the multi-support excitations was used to calculate structural dynamic response.In the analysis,pounding between adjacent deck segments was considered.The seismic response of a multi-span bridge subjected to the multi-support excitation,considering not only the traveling-wave effect and partial coherence effect,but also the seismic non-stationary characteristics of multi-support earthquake motion,was simulated using finite element method(FEM).Meanwhile,the seismic response of the bridge under uniform earthquake was also analyzed.Finally,comparative analysis was conducted and some calculation results were shown for pounding effect,under multi-dimensional and multi-support earthquake motion,when performing seismic response analysis of multi-span bridge.Compared with the case of uniform/multi-support/multi-support and multi-dimensional earthquake input,the maximum values of pounding force in the case of multi-support and multi-dimensional earthquake input increase by about 5 8 times;the absolute value of bottom moment and shear force of piers increase by about50%600%and 23.1%900%,respectively.A conclusion can be given that it is very necessary to consider the pounding effect under multi-dimensional and multi-support earthquake motion while performing seismic response analysis of multi-span bridge.
基金National Natural Science Foundation of China under Grant Nos.U1434205 and 51678490the Major Research Plan of China National Railway Ministry of China under Grant Nos.2015G002-B and P2018G007the National Key R&D Program of China under Grant No.2017YFC1500803。
文摘Precast segmental column bridges exhibit various construction advantages in comparison to traditional monolithic column bridges.However,the lack of cognitions on seismic behaviors has seriously restricted their applications and developments.In this paper,comprehensive investigations are conducted to analyze the dynamic characteristics of precast segmental column bridges under near-fault,forward-directivity ground motions.First,the finite-element models of two comparable bridges with precast segmental columns and monolithic columns are constructed by using OpenSees software,and the nonlinearities of the bridges are considered.Next,three different earthquake loadings are meticulously set up to handle engineering problems,namely recorded near-and far-field ground motions,parameterized pulses,and pulse and residual components extracted from real records.Finally,based on the models and earthquake sets,extensive explorations are carried out.The results show that near-fault forward-directivity ground motions are more threatening than far-field ones;precast segmental column bridges may suffer more pounding impacts than monolithic bridges;the“narrow band”effect caused by near-fault,forward-directivity ground motions may occur in bridges with shorter periods than pulse periods;and pulse and residual components play different roles in seismic responses.
基金jointly sponsored by the Scientific Research Fund of Engineering Mechanics,China Earthquake Administration(2016A05)the grant from the National Natural Science Foundation of China(51478441)
文摘The damage to the masonry-infilled reinforced concrete( RC) frame buildings in Charikot,the capital city of Dolakha district in Nepal,during the 2015 April-to-May Nepal earthquake sequence is reported. Most of these buildings were built by the owners with little governmental inspections regarding their structural design or constructional quality. Although they generally performed better than other structural systems such as stone-masonry houses,the RC frames sustained extensive damage ranging from cracking of infill to complete collapse. In particular,eight of the 72 inspected RC frames alongside an uphill street collapsed in different ways. In addition to the un-engineered nature of these RC frames,their collapse could also be attributed to multiple technical reasons including the effect of terrain, the pounding between adjacent buildings and the accumulative damage in the earthquake sequence.
基金Funded by International Centre for Diffraction Data.
文摘A new compound K6Ti0.67Nb15.33O42 was prepared for the first time by solid state reaction in K2O-Ni2O3-Nb2O5 ternary system. The new compound was characterized by electron probe, X-ray powder diffraction and DTA. The result of X-ray powder diffraction shows that K6Ti0.67Nb15.33O42 crystallizes the hexagonal system with unit cell parameters a = 9. 1341(5) A ,c=12. 090(1)A . and space group P62/mcm(193 ).
文摘Seismic pounding phenomena, particularly the collision of neighboring buildings under long-period ground motion, are becoming a significant issue in Japan. We focused on a specific apartment structure called the Nuevo Leon buildings in the Tlatelolco district of Mexico City, which consisted of three similar buildings built consecutively with narrow expansion joints between the buildings. Two out of the three buildings collapsed completely in the 1985 Mexican earthquake. Using a finite element code based on the adaptively shifted integration (ASI)-Gauss technique, a seismic pounding analysis is performed on a simulated model of the Nuevo Leon buildings to understand the impact and collapse behavior of structures built near each other. The numerical code used in the analysis provides a higher computational efficiency than the conventional code for this type of problem and enables us to address dynamic behavior with strong nonlinearities, including phenomena such as member fracture and elemental contact. Contact release and recontact algorithms are developed and implemented in the code to understand the complex behaviors of structural members during seismic pounding and the collapse sequence. According to the numerical results, the collision of the buildings may be a result of the difference of natural periods between the neighboring buildings. This difference was detected in similar buildings from the damages caused by previous earthquakes. By setting the natural period of the north building to be 25% longer than the other periods, the ground motion, which hada relatively long period of 2 s, first caused the collision between the north and the center buildings. This collision eventually led to the collapse of the centerbuilding, followed by the destruction of the north building.