Since the effectiveness of the flexible current arc suppression method heavily relies on the accurate measurement of the distribution line-to-ground parame-ters,the suppression of single line-to-ground(SLG)fault curre...Since the effectiveness of the flexible current arc suppression method heavily relies on the accurate measurement of the distribution line-to-ground parame-ters,the suppression of single line-to-ground(SLG)fault current may deteriorate due to factors such as line switching and other disturbances during SLG fault arc suppression.Additionally,during SLG fault arc suppres-sion,promptly identifying the fault type and rapidly de-activating the flexible arc suppression device(FASD)can reduce the overvoltage risk in non-faulted phase devices.To address these issues,this paper presents a parameter identification method based on recursive least squares(RLS)while a variable forgetting factor strategy is in-troduces to enhance the RLS algorithm’s disturbance rejection capability.Simulations verify that the variable forgetting factor recursive least squares(VFF-RLS)algo-rithm can accurately identify distribution line-to-ground parameters in real time and effectively suppress SLG fault current.The online identification of grounding transition conductance is simultaneously used to deter-mine the fault type and quickly detect when the SLG fault has been cleared.展开更多
The catalogs of ground motion parameters for earthquake-prone regions of Kazakhstan used for modeling seismic effects in seismic hazard assessment and microzonation are presented.
This study examines the feasibility of using a machine learning approach for rapid damage assessment of rein-forced concrete(RC)buildings after the earthquake.Since the real-world damaged datasets are lacking,have lim...This study examines the feasibility of using a machine learning approach for rapid damage assessment of rein-forced concrete(RC)buildings after the earthquake.Since the real-world damaged datasets are lacking,have limited access,or are imbalanced,a simulation dataset is prepared by conducting a nonlinear time history analy-sis.Different machine learning(ML)models are trained considering the structural parameters and ground motion characteristics to predict the RC building damage into five categories:null,slight,moderate,heavy,and collapse.The random forest classifier(RFC)has achieved a higher prediction accuracy on testing and real-world damaged datasets.The structural parameters can be extracted using different means such as Google Earth,Open Street Map,unmanned aerial vehicles,etc.However,recording the ground motion at a closer distance requires the installation of a dense array of sensors which requires a higher cost.For places with no earthquake recording station/device,it is difficult to have ground motion characteristics.For that different ML-based regressor models are developed utilizing past-earthquake information to predict ground motion parameters such as peak ground acceleration and peak ground velocity.The random forest regressor(RFR)achieved better results than other regression models on testing and validation datasets.Furthermore,compared with the results of similar research works,a better result is obtained using RFC and RFR on validation datasets.In the end,these models are uti-lized to predict the damage categories of RC buildings at Saitama University and Okubo Danchi,Saitama,Japan after an earthquake.This damage information is crucial for government agencies or decision-makers to respond systematically in post-disaster situations.展开更多
Peak ground acceleration (PGA), frequency content and time duration are three fundamental parameters of seismic loading. This study focuses on the seismic load frequency and its effect on the underground structures. E...Peak ground acceleration (PGA), frequency content and time duration are three fundamental parameters of seismic loading. This study focuses on the seismic load frequency and its effect on the underground structures. Eight accelerograms regarding different occurred earthquakes that are scaled to an identical PGA and variation of ground motion parameters with ratio of peak ground velocity (PGV) to PGA, as a parameter related to the load frequency, are considered. Then, concrete lining response of a circular tunnel under various seismic conditions is evaluated analytically. In the next, seismic response of underground structure is assessed numerically using two different time histories. Finally, effects of incident load frequency and frequency ratio on the dynamic damping of geotechnical materials are discussed. Result of analyses show that specific energy of seismic loading with identical PGA is related to the seismic load frequency. Furthermore, incident load frequency and natural frequency of a system have influence on the wave attenuation and dynamic damping of the system.展开更多
Strong ground motion parameters for Shillong plateau of northeastern India are examined. Empirical relations are obtained for main parameters of ground motions as a function of earthquake magnitude, fault type, source...Strong ground motion parameters for Shillong plateau of northeastern India are examined. Empirical relations are obtained for main parameters of ground motions as a function of earthquake magnitude, fault type, source depth, velocity characterization of medium and distance. Correlation between ground motion parameters and characteristics of seismogenic zones are established. A new attenuation relation for peak ground acceleration is developed, which predicts higher expected PGA in the region. Parameters of strong motions, particularly the predominant periods and duration of vibrations, depend on the morphology of the studied area. The study measures low estimates of logarithmic width in Shillong plateau. The attenuation relation estimated for pulse width critically indicates increased pulse width dependence on the logarithmic distance which accounts for geometrical spreading and anelastic attenuation.展开更多
Based on the calculation of the bedrock effective peak acceleration (EPA) zoning map in the Panxi area, the ratios of EPA with exceedance probabilities of 63%, 5%, 3%, 2% and 1% over 50 years to that of 10% in 50 year...Based on the calculation of the bedrock effective peak acceleration (EPA) zoning map in the Panxi area, the ratios of EPA with exceedance probabilities of 63%, 5%, 3%, 2% and 1% over 50 years to that of 10% in 50 years are 0.302, 1.30, 1.55, 1.76 and 2.14, respectively. The seismic effect will be conservative and safe if taking this zoning map as the earthquake resistant fortification level and following the relevant rules of the Code for Seismic Design of Buildings (GBJ11 89) to calculate the seismic effect. Furthermore, the main factors that influence the A10/A63 ratios have been found to be the attenuation relationship of seismic ground motion, the division of seismic potential source regions and the seismicity parameters. These achievements are helpful to the spreading and applying of the zoning map.展开更多
Domestic nuclear power plants are basically located in the seaside, plant site according to the planning requirements, through the site level to meet the nuclear power unit and supporting engineering layout requiremen...Domestic nuclear power plants are basically located in the seaside, plant site according to the planning requirements, through the site level to meet the nuclear power unit and supporting engineering layout requirements, different regions of the site and the gay love situation is different. There are a variety of buildings in the plant, different buildings, according to their importance, their seismic requirements are different. Therefore, although the buildings in the factory are located in the same area, the seismic requirements of different buildings and the ground foundation conditions of the site are different. The designed ground motion parameters cannot be determined directly according to the Chinese ground motion parameter zoning map of GB18306-2015 and the provisions of the building seismic design code of GB50011-2010, but need to be re-calculated.展开更多
Based on the image theory,the analytical solutions of tunneling-induced ground displacement were derived in conjunction with the nonuniform convergence model.The reasonable value of Poisson ratio in the analytical sol...Based on the image theory,the analytical solutions of tunneling-induced ground displacement were derived in conjunction with the nonuniform convergence model.The reasonable value of Poisson ratio in the analytical solution was discussed.The ground settlement width parameter which could reflect the ground condition was introduced to modify the analytical solutions proposed above,and new analytical solutions were presented.To evaluate the validity of the present solutions using the nonuniform convergence model,the results were compared with the observed values for four engineering projects,including 38 measured data of ground settlement.The agreement shows that the present solutions using the nonuniform convergence model are effective for evaluating the tunneling-induced ground displacements.展开更多
Currently available earthquake attenuation equations are locally applicable,and methods based on observation data are not applicable in areas without available observation data.To solve the above problems and further ...Currently available earthquake attenuation equations are locally applicable,and methods based on observation data are not applicable in areas without available observation data.To solve the above problems and further improve the prediction accuracy of ground motion parameters,we present a prediction model referred to as a light gradient boosting machine with feature selection(LGB-FS).It is based on a light gradient boosting machine(LightGBM)constructed using historical strong motion data from the NGA-west2 database and can quickly simulate the distribution of strong motion near the epicenter after an earthquake.Cases study shows that compared with GMPE methods and those based on real-time observation data,the model has a better prediction effect in areas without available observation data and can be applied to Yangbi Earthquake and Maduo Earthquake.The feature importance evaluation based on both information gains and partial dependence plots(PDPs)reveals the complex relationships between multiple factors and ground motion parameters,allowing us to better understand their mechanisms and connections.展开更多
In displacement-based seismic design, inelastic displacement ratio spectra （IDRS） are particularly useful for estimating the maximum lateral inelastic displacement demand of a nonlinear SDOF system from the maximum ...In displacement-based seismic design, inelastic displacement ratio spectra （IDRS） are particularly useful for estimating the maximum lateral inelastic displacement demand of a nonlinear SDOF system from the maximum elastic displacement demand of its counterpart linear elastic SDOF system. In this study, the characteristics of IDRS for near-fault pulse-type ground motions are investigated based on a great number of earthquake ground motions. The influence of site conditions, ratio of peak ground velocity （PGV） to peak ground acceleration （PGA）, the PGV, and the maximum incremental velocity （MIV） on IDRS are also evaluated. The results indicate that the effect of near-fault ground motions on IDRS are significant only at periods between 0.2 s - 1.5 s, where the amplification can approach 20%. The PGV/PGA ratio has the most significant influence on IDRS among the parameters considered. It is also found that site conditions only slightly affect the IDRS.展开更多
How to select the adequate real strong earthquake ground motion for seismic analysis and design of structures is an essential problem in earthquake engineering research and practice. In the paper the concept of the se...How to select the adequate real strong earthquake ground motion for seismic analysis and design of structures is an essential problem in earthquake engineering research and practice. In the paper the concept of the severest design ground motion is proposed and a method is developed for comparing the severity of the recorded strong ground motions. By using this method the severest earthquake ground motions are selected out as seismic inputs to the structures to be designed from a database that consists of more than five thousand significant strong ground motion records collected over the world. The selected severest ground motions are very likely to be able to drive the structures to their critical response and thereby result in the highest damage potential. It is noted that for different structures with different predominant natural periods and at different sites where structures are located the severest design ground motions are usually different. Finally, two examples are illustrated to demonstrate the rationality of the concept and the reliability of the selected design motion.展开更多
Estimating cross-range velocity is a challenging task for space-borne synthetic aperture radar（SAR）, which is important for ground moving target indication（GMTI）. Because the velocity of a target is very small com...Estimating cross-range velocity is a challenging task for space-borne synthetic aperture radar（SAR）, which is important for ground moving target indication（GMTI）. Because the velocity of a target is very small compared with that of the satellite, it is difficult to correctly estimate it using a conventional monostatic platform algorithm. To overcome this problem, a novel method employing multistatic SAR is presented in this letter. The proposed hybrid method, which is based on an extended space-time model（ESTIM） of the azimuth signal, has two steps： first, a set of finite impulse response（FIR） filter banks based on a fractional Fourier transform（FrFT） is used to separate multiple targets within a range gate; second, a cross-correlation spectrum weighted subspace fitting（CSWSF） algorithm is applied to each of the separated signals in order to estimate their respective parameters. As verified through computer simulation with the constellations of Cartwheel, Pendulum and Helix, this proposed time-frequency-subspace method effectively improves the estimation precision of the cross-range velocities of multiple targets.展开更多
Through the systematic analysis of the ground settlement generated by the process of shield tunneling,the relationships between ground deformation and construction parameters are studied in this paper.Based on the ass...Through the systematic analysis of the ground settlement generated by the process of shield tunneling,the relationships between ground deformation and construction parameters are studied in this paper.Based on the assumption of linear small deformation,a mathematical model of the relationship between ground deformation and construction parameters is set up.The principle and method of optimization for estimating ground deformation is studied.The actual measured data are compared with the results of theoretical analysis in a case.Considering different ground formations in different construction sites with different adverse effects on surface and underground structures,the ground surface deformations caused by shield tunneling is an aimed topic in this paper.The contributions and research implications are the revealed relationships between the ground deformation and the shield tunneling parameters during construction.展开更多
The probabilistic seismic hazard analysis (PSHA) method used in existing seismic ground motion parameters zonation map of China (the traditional PSHA-CN method) is based on a two-dimensional area seismic source framew...The probabilistic seismic hazard analysis (PSHA) method used in existing seismic ground motion parameters zonation map of China (the traditional PSHA-CN method) is based on a two-dimensional area seismic source framework and does not account for the rupture dimension of large earthquakes,which may lead to underestimation of seismic hazard at near-fault sites.By employing stochastic sampling to integrate three-dimensional fault sources and two-dimensional area seismic sources,a new PSHA-CN method was developed in recent years,but it faces limitations in accuracy and computational ef ciency due to sampling constraints,particularly for low probability of exceedance scenarios or large earthquakes with long return periods.To enhance the computational ef ciency of the new PSHA-CN method,this study developed a novel spatial integration algorithm for PSHA.The algorithm considers rupture dimension,enables ef cient fault geometry modeling using the Frankel Fault Surface (FFS) and Stirling Fault Surface (SFS) models,and maintains compatibility with the traditional PSHA-CN framework.Validation against test cases from the Pacific Earthquake Engineering Research Center (PEER) demonstrated the algorithm’s reliability.Furthermore,the algorithm was applied to assess seismic hazard in the Changsha-Zhuzhou-Xiangtan metropolitan region in Hunan Province to validate its performance in regions with moderate seismic activity in China.A comparative analysis of the new algorithm results with those of the traditional PSHA-CN method revealed that the PSHA-CN method underestimates near-fault seismic hazards.The proposed algorithm will be implemented in next-generation seismic ground motion parameters zonation map in China.展开更多
Türkey is located in a seismically active region where the Anatolia,Africa,and Arabia tectonic plates converge.The high seismic hazard causes the region to be repeatedly struck by major earthquakes.On February 06...Türkey is located in a seismically active region where the Anatolia,Africa,and Arabia tectonic plates converge.The high seismic hazard causes the region to be repeatedly struck by major earthquakes.On February 06,2023,a devastating Mw 7.7 earthquake struck Türkey at 04:17 a.m.local time(01:17 UTC).Around 9 h later at 10:24 a.m.local time,another destructive Mw 7.6 earthquake struck at a distance of 95 km towards the north of the first earthquake(www.tadas.afad.gov.tr).The strong ground motion from the Mw 7.7 event shows peak ground accelerations exceeding 1 g in the near-field region and affected 11 cities.The effect of the complex fault geometry on the observed high PGAs needs to be examined to understand the associated structural damage.The present study investigates the key characteristics of strong ground motions recorded from 40 stations located in the vicinity of 100 km which are commonly used intensity parameters for vulnerability and risk analysis.The complex interaction between fault segments significantly influenced the overall rupture process and the distribution of ground shaking and generated significant pulse-like ground motions in the near-fault region.These ground motions exhibited directivity effects,characterized by pulse-like velocities,high peak ground accelerations,and spectral accelerations.The response spectra are derived for ground motions from several stations for the present destructive/major earthquake and are observed to exceed code prescribed spectra corresponding to the 475-year and 2475-year return periods.展开更多
The study on seismic intensity can be traced prior to the time that modern seismology was established. In its early stage the seismic intensity was designed to serve as a measure in scaling the severity of earthquake ...The study on seismic intensity can be traced prior to the time that modern seismology was established. In its early stage the seismic intensity was designed to serve as a measure in scaling the severity of earthquake damage to civil engineering and environmental structures. Also the seismic intensity is usually assigned by engineers and seismologists with one or two characteristic parameters of earthquake ground motions to reflect earthquake damage potential so as to be able to serve as an input earthquake load for seismic design of structures. So choosing a proper parameter to reflect the action of seismic intensity is the main objective of the research on physical measure of seismic intensity. However, since various kinds of structures have quite different damage mechanisms, there will exist great differences in damages to different structures located at the same area during the same earthquake. Particularly, in some cases, quite different damages have happened even to the structures of same kind due to many other factors such as different construction materials, different configurations or on the different types of sites where structures located. In addition, the ground motion parameters, which result in damage to structures, are not the single peak value of ground motion. Hence, this paper emphasizes that the research on new physical measure of seismic intensity should not only consider the structural characteristics but also take into account other parameters such as duration, energy of ground motion and so on. In particular, as the physical measures of intensity, different ground motion parameter should be adopted for different structures.展开更多
The continuous collision of the Eurasian plate and the Indian plate has resulted in several earthquakes in the Himalayan region.The 6.9 Mw 2011 Sikkim earthquake,which caused immense damage to the built environment in...The continuous collision of the Eurasian plate and the Indian plate has resulted in several earthquakes in the Himalayan region.The 6.9 Mw 2011 Sikkim earthquake,which caused immense damage to the built environment in Sikkim,was triggered by an intraplate source on the overriding Eurasian plate.Strong ground motions from the earthquake were recorded at stations established by IIT Roorkee as part of the PESMOS program.In this paper,near-field and far-field ground motions from this earthquake were analyzed to evaluate their key characteristics and examine their time-frequency features by employing Fast Fourier Transforms(FFTs)and Continuous Wavelet Transforms(CWTs).A comparison between the ground motion parameters of near-field and far-field seismic waves highlights the distinct characteristics of near-field ground motions.Additionally,the impact of near-field and far-field ground motions on the seismic response of a code-compliant RC building is investigated.The results from the non-linear time history analyses indicate that the roof displacements,drift ratio and strain induced in the frame elements are less than the code-prescribed maximum limits.Further,the demand and capacity levels for the RC frame elements were evaluated to compute the performance ratios.The results indicate that the extensive damage to reinforced concrete buildings in the 2011 Sikkim quake was primarily due to the nonengineered nature of the structures and also due to the non-compliance of the built structures to the seismic design code provisions.展开更多
Macroseismic investigation is presented with a new potential means of investigation in the "digital age". In this paper we studied several cases in the May 12, 2008, Wenchuan M_S8.0 earthquake with a view to...Macroseismic investigation is presented with a new potential means of investigation in the "digital age". In this paper we studied several cases in the May 12, 2008, Wenchuan M_S8.0 earthquake with a view to exploring the feasibility of retrieving intensity, or even strong ground motion parameters, from public monitoring video which was originally deployed for security purposes. We used public monitoring video records from 44 sites across the meizoseismal region and its surroundings to estimate the intensity. By using the video from a bank in Dujiangyan, Sichuan Province and making the simple assumption that ground vibration is in the form of a propagating harmonic wave, we estimated that the local ground motion acceleration was 0.14g.展开更多
基金supported in part by the National Natural Science Foundation of China(No.51677030)in part by the Natural Science Foundation of Fujian Province,China(No.2023J05106).
文摘Since the effectiveness of the flexible current arc suppression method heavily relies on the accurate measurement of the distribution line-to-ground parame-ters,the suppression of single line-to-ground(SLG)fault current may deteriorate due to factors such as line switching and other disturbances during SLG fault arc suppression.Additionally,during SLG fault arc suppres-sion,promptly identifying the fault type and rapidly de-activating the flexible arc suppression device(FASD)can reduce the overvoltage risk in non-faulted phase devices.To address these issues,this paper presents a parameter identification method based on recursive least squares(RLS)while a variable forgetting factor strategy is in-troduces to enhance the RLS algorithm’s disturbance rejection capability.Simulations verify that the variable forgetting factor recursive least squares(VFF-RLS)algo-rithm can accurately identify distribution line-to-ground parameters in real time and effectively suppress SLG fault current.The online identification of grounding transition conductance is simultaneously used to deter-mine the fault type and quickly detect when the SLG fault has been cleared.
文摘The catalogs of ground motion parameters for earthquake-prone regions of Kazakhstan used for modeling seismic effects in seismic hazard assessment and microzonation are presented.
文摘This study examines the feasibility of using a machine learning approach for rapid damage assessment of rein-forced concrete(RC)buildings after the earthquake.Since the real-world damaged datasets are lacking,have limited access,or are imbalanced,a simulation dataset is prepared by conducting a nonlinear time history analy-sis.Different machine learning(ML)models are trained considering the structural parameters and ground motion characteristics to predict the RC building damage into five categories:null,slight,moderate,heavy,and collapse.The random forest classifier(RFC)has achieved a higher prediction accuracy on testing and real-world damaged datasets.The structural parameters can be extracted using different means such as Google Earth,Open Street Map,unmanned aerial vehicles,etc.However,recording the ground motion at a closer distance requires the installation of a dense array of sensors which requires a higher cost.For places with no earthquake recording station/device,it is difficult to have ground motion characteristics.For that different ML-based regressor models are developed utilizing past-earthquake information to predict ground motion parameters such as peak ground acceleration and peak ground velocity.The random forest regressor(RFR)achieved better results than other regression models on testing and validation datasets.Furthermore,compared with the results of similar research works,a better result is obtained using RFC and RFR on validation datasets.In the end,these models are uti-lized to predict the damage categories of RC buildings at Saitama University and Okubo Danchi,Saitama,Japan after an earthquake.This damage information is crucial for government agencies or decision-makers to respond systematically in post-disaster situations.
文摘Peak ground acceleration (PGA), frequency content and time duration are three fundamental parameters of seismic loading. This study focuses on the seismic load frequency and its effect on the underground structures. Eight accelerograms regarding different occurred earthquakes that are scaled to an identical PGA and variation of ground motion parameters with ratio of peak ground velocity (PGV) to PGA, as a parameter related to the load frequency, are considered. Then, concrete lining response of a circular tunnel under various seismic conditions is evaluated analytically. In the next, seismic response of underground structure is assessed numerically using two different time histories. Finally, effects of incident load frequency and frequency ratio on the dynamic damping of geotechnical materials are discussed. Result of analyses show that specific energy of seismic loading with identical PGA is related to the seismic load frequency. Furthermore, incident load frequency and natural frequency of a system have influence on the wave attenuation and dynamic damping of the system.
基金ILTP (Integrated Long Term Project) Scheme towards Indo-Russian Collaborative Project
文摘Strong ground motion parameters for Shillong plateau of northeastern India are examined. Empirical relations are obtained for main parameters of ground motions as a function of earthquake magnitude, fault type, source depth, velocity characterization of medium and distance. Correlation between ground motion parameters and characteristics of seismogenic zones are established. A new attenuation relation for peak ground acceleration is developed, which predicts higher expected PGA in the region. Parameters of strong motions, particularly the predominant periods and duration of vibrations, depend on the morphology of the studied area. The study measures low estimates of logarithmic width in Shillong plateau. The attenuation relation estimated for pulse width critically indicates increased pulse width dependence on the logarithmic distance which accounts for geometrical spreading and anelastic attenuation.
文摘Based on the calculation of the bedrock effective peak acceleration (EPA) zoning map in the Panxi area, the ratios of EPA with exceedance probabilities of 63%, 5%, 3%, 2% and 1% over 50 years to that of 10% in 50 years are 0.302, 1.30, 1.55, 1.76 and 2.14, respectively. The seismic effect will be conservative and safe if taking this zoning map as the earthquake resistant fortification level and following the relevant rules of the Code for Seismic Design of Buildings (GBJ11 89) to calculate the seismic effect. Furthermore, the main factors that influence the A10/A63 ratios have been found to be the attenuation relationship of seismic ground motion, the division of seismic potential source regions and the seismicity parameters. These achievements are helpful to the spreading and applying of the zoning map.
文摘Domestic nuclear power plants are basically located in the seaside, plant site according to the planning requirements, through the site level to meet the nuclear power unit and supporting engineering layout requirements, different regions of the site and the gay love situation is different. There are a variety of buildings in the plant, different buildings, according to their importance, their seismic requirements are different. Therefore, although the buildings in the factory are located in the same area, the seismic requirements of different buildings and the ground foundation conditions of the site are different. The designed ground motion parameters cannot be determined directly according to the Chinese ground motion parameter zoning map of GB18306-2015 and the provisions of the building seismic design code of GB50011-2010, but need to be re-calculated.
基金Project(09JJ1008) supported by Hunan Provincial Science Foundation of China
文摘Based on the image theory,the analytical solutions of tunneling-induced ground displacement were derived in conjunction with the nonuniform convergence model.The reasonable value of Poisson ratio in the analytical solution was discussed.The ground settlement width parameter which could reflect the ground condition was introduced to modify the analytical solutions proposed above,and new analytical solutions were presented.To evaluate the validity of the present solutions using the nonuniform convergence model,the results were compared with the observed values for four engineering projects,including 38 measured data of ground settlement.The agreement shows that the present solutions using the nonuniform convergence model are effective for evaluating the tunneling-induced ground displacements.
基金supported by the National Key R&D Program of China(No.2017YFB0504104)the National Natural Science Foundation of China(No.41971280)。
文摘Currently available earthquake attenuation equations are locally applicable,and methods based on observation data are not applicable in areas without available observation data.To solve the above problems and further improve the prediction accuracy of ground motion parameters,we present a prediction model referred to as a light gradient boosting machine with feature selection(LGB-FS).It is based on a light gradient boosting machine(LightGBM)constructed using historical strong motion data from the NGA-west2 database and can quickly simulate the distribution of strong motion near the epicenter after an earthquake.Cases study shows that compared with GMPE methods and those based on real-time observation data,the model has a better prediction effect in areas without available observation data and can be applied to Yangbi Earthquake and Maduo Earthquake.The feature importance evaluation based on both information gains and partial dependence plots(PDPs)reveals the complex relationships between multiple factors and ground motion parameters,allowing us to better understand their mechanisms and connections.
基金National Natural Science Foundation of China Under Grants No. 50608024 andNo.50538050Opening Laboratory of Earthquake Engineering and Engineering Vibration Foundation Under Grant No.2007001
文摘In displacement-based seismic design, inelastic displacement ratio spectra （IDRS） are particularly useful for estimating the maximum lateral inelastic displacement demand of a nonlinear SDOF system from the maximum elastic displacement demand of its counterpart linear elastic SDOF system. In this study, the characteristics of IDRS for near-fault pulse-type ground motions are investigated based on a great number of earthquake ground motions. The influence of site conditions, ratio of peak ground velocity （PGV） to peak ground acceleration （PGA）, the PGV, and the maximum incremental velocity （MIV） on IDRS are also evaluated. The results indicate that the effect of near-fault ground motions on IDRS are significant only at periods between 0.2 s - 1.5 s, where the amplification can approach 20%. The PGV/PGA ratio has the most significant influence on IDRS among the parameters considered. It is also found that site conditions only slightly affect the IDRS.
基金National Natural Science Foundation of China (59895410)Natural Science Foundation of Heilongjiang Province (E0228) Joint Seismological Foundation of China (95-07-444).
文摘How to select the adequate real strong earthquake ground motion for seismic analysis and design of structures is an essential problem in earthquake engineering research and practice. In the paper the concept of the severest design ground motion is proposed and a method is developed for comparing the severity of the recorded strong ground motions. By using this method the severest earthquake ground motions are selected out as seismic inputs to the structures to be designed from a database that consists of more than five thousand significant strong ground motion records collected over the world. The selected severest ground motions are very likely to be able to drive the structures to their critical response and thereby result in the highest damage potential. It is noted that for different structures with different predominant natural periods and at different sites where structures are located the severest design ground motions are usually different. Finally, two examples are illustrated to demonstrate the rationality of the concept and the reliability of the selected design motion.
基金supported by the National Natural Science Foundation of China (No. 61271343)the Research Fund for the Doctoral Program of Higher Education of China (No. 20122302110012)the 2014 Innovation of Science and Technology Program of China Aerospace Science and Technology Corporation
文摘Estimating cross-range velocity is a challenging task for space-borne synthetic aperture radar（SAR）, which is important for ground moving target indication（GMTI）. Because the velocity of a target is very small compared with that of the satellite, it is difficult to correctly estimate it using a conventional monostatic platform algorithm. To overcome this problem, a novel method employing multistatic SAR is presented in this letter. The proposed hybrid method, which is based on an extended space-time model（ESTIM） of the azimuth signal, has two steps： first, a set of finite impulse response（FIR） filter banks based on a fractional Fourier transform（FrFT） is used to separate multiple targets within a range gate; second, a cross-correlation spectrum weighted subspace fitting（CSWSF） algorithm is applied to each of the separated signals in order to estimate their respective parameters. As verified through computer simulation with the constellations of Cartwheel, Pendulum and Helix, this proposed time-frequency-subspace method effectively improves the estimation precision of the cross-range velocities of multiple targets.
文摘Through the systematic analysis of the ground settlement generated by the process of shield tunneling,the relationships between ground deformation and construction parameters are studied in this paper.Based on the assumption of linear small deformation,a mathematical model of the relationship between ground deformation and construction parameters is set up.The principle and method of optimization for estimating ground deformation is studied.The actual measured data are compared with the results of theoretical analysis in a case.Considering different ground formations in different construction sites with different adverse effects on surface and underground structures,the ground surface deformations caused by shield tunneling is an aimed topic in this paper.The contributions and research implications are the revealed relationships between the ground deformation and the shield tunneling parameters during construction.
基金Funding for this research was provided by the National Key R&D Program of China(Grant No.2022YFC3003505)This research was also funded by the National Natural Science Foundation of China(Grant No.41974065)the Special Fund of the Institute of Geophysics,China Earthquake Administration(Grant No.DQJB23Y32).
文摘The probabilistic seismic hazard analysis (PSHA) method used in existing seismic ground motion parameters zonation map of China (the traditional PSHA-CN method) is based on a two-dimensional area seismic source framework and does not account for the rupture dimension of large earthquakes,which may lead to underestimation of seismic hazard at near-fault sites.By employing stochastic sampling to integrate three-dimensional fault sources and two-dimensional area seismic sources,a new PSHA-CN method was developed in recent years,but it faces limitations in accuracy and computational ef ciency due to sampling constraints,particularly for low probability of exceedance scenarios or large earthquakes with long return periods.To enhance the computational ef ciency of the new PSHA-CN method,this study developed a novel spatial integration algorithm for PSHA.The algorithm considers rupture dimension,enables ef cient fault geometry modeling using the Frankel Fault Surface (FFS) and Stirling Fault Surface (SFS) models,and maintains compatibility with the traditional PSHA-CN framework.Validation against test cases from the Pacific Earthquake Engineering Research Center (PEER) demonstrated the algorithm’s reliability.Furthermore,the algorithm was applied to assess seismic hazard in the Changsha-Zhuzhou-Xiangtan metropolitan region in Hunan Province to validate its performance in regions with moderate seismic activity in China.A comparative analysis of the new algorithm results with those of the traditional PSHA-CN method revealed that the PSHA-CN method underestimates near-fault seismic hazards.The proposed algorithm will be implemented in next-generation seismic ground motion parameters zonation map in China.
文摘Türkey is located in a seismically active region where the Anatolia,Africa,and Arabia tectonic plates converge.The high seismic hazard causes the region to be repeatedly struck by major earthquakes.On February 06,2023,a devastating Mw 7.7 earthquake struck Türkey at 04:17 a.m.local time(01:17 UTC).Around 9 h later at 10:24 a.m.local time,another destructive Mw 7.6 earthquake struck at a distance of 95 km towards the north of the first earthquake(www.tadas.afad.gov.tr).The strong ground motion from the Mw 7.7 event shows peak ground accelerations exceeding 1 g in the near-field region and affected 11 cities.The effect of the complex fault geometry on the observed high PGAs needs to be examined to understand the associated structural damage.The present study investigates the key characteristics of strong ground motions recorded from 40 stations located in the vicinity of 100 km which are commonly used intensity parameters for vulnerability and risk analysis.The complex interaction between fault segments significantly influenced the overall rupture process and the distribution of ground shaking and generated significant pulse-like ground motions in the near-fault region.These ground motions exhibited directivity effects,characterized by pulse-like velocities,high peak ground accelerations,and spectral accelerations.The response spectra are derived for ground motions from several stations for the present destructive/major earthquake and are observed to exceed code prescribed spectra corresponding to the 475-year and 2475-year return periods.
基金Specialized Research Fund for the Doctoral Program of Higher Education (20030213042) and Natural Science Foundation of Heilongjiang Province (ZJG03-03).
文摘The study on seismic intensity can be traced prior to the time that modern seismology was established. In its early stage the seismic intensity was designed to serve as a measure in scaling the severity of earthquake damage to civil engineering and environmental structures. Also the seismic intensity is usually assigned by engineers and seismologists with one or two characteristic parameters of earthquake ground motions to reflect earthquake damage potential so as to be able to serve as an input earthquake load for seismic design of structures. So choosing a proper parameter to reflect the action of seismic intensity is the main objective of the research on physical measure of seismic intensity. However, since various kinds of structures have quite different damage mechanisms, there will exist great differences in damages to different structures located at the same area during the same earthquake. Particularly, in some cases, quite different damages have happened even to the structures of same kind due to many other factors such as different construction materials, different configurations or on the different types of sites where structures located. In addition, the ground motion parameters, which result in damage to structures, are not the single peak value of ground motion. Hence, this paper emphasizes that the research on new physical measure of seismic intensity should not only consider the structural characteristics but also take into account other parameters such as duration, energy of ground motion and so on. In particular, as the physical measures of intensity, different ground motion parameter should be adopted for different structures.
文摘The continuous collision of the Eurasian plate and the Indian plate has resulted in several earthquakes in the Himalayan region.The 6.9 Mw 2011 Sikkim earthquake,which caused immense damage to the built environment in Sikkim,was triggered by an intraplate source on the overriding Eurasian plate.Strong ground motions from the earthquake were recorded at stations established by IIT Roorkee as part of the PESMOS program.In this paper,near-field and far-field ground motions from this earthquake were analyzed to evaluate their key characteristics and examine their time-frequency features by employing Fast Fourier Transforms(FFTs)and Continuous Wavelet Transforms(CWTs).A comparison between the ground motion parameters of near-field and far-field seismic waves highlights the distinct characteristics of near-field ground motions.Additionally,the impact of near-field and far-field ground motions on the seismic response of a code-compliant RC building is investigated.The results from the non-linear time history analyses indicate that the roof displacements,drift ratio and strain induced in the frame elements are less than the code-prescribed maximum limits.Further,the demand and capacity levels for the RC frame elements were evaluated to compute the performance ratios.The results indicate that the extensive damage to reinforced concrete buildings in the 2011 Sikkim quake was primarily due to the nonengineered nature of the structures and also due to the non-compliance of the built structures to the seismic design code provisions.
文摘Macroseismic investigation is presented with a new potential means of investigation in the "digital age". In this paper we studied several cases in the May 12, 2008, Wenchuan M_S8.0 earthquake with a view to exploring the feasibility of retrieving intensity, or even strong ground motion parameters, from public monitoring video which was originally deployed for security purposes. We used public monitoring video records from 44 sites across the meizoseismal region and its surroundings to estimate the intensity. By using the video from a bank in Dujiangyan, Sichuan Province and making the simple assumption that ground vibration is in the form of a propagating harmonic wave, we estimated that the local ground motion acceleration was 0.14g.
