Large numbers of basic transceiver stations,where the telecommunication room is one of the main components,comprise an important part of the telecommunication system.After earthquakes,considerable economic loss from t...Large numbers of basic transceiver stations,where the telecommunication room is one of the main components,comprise an important part of the telecommunication system.After earthquakes,considerable economic loss from telecommunication systems is often associated with seismic damage and functional loss of the telecommunication room.However,research related to this has been limited.In this study,shaking table tests were conducted for a full-scale typical telecommunication room,including a light-steel house and the necessary communication and power supply equipment.The tests not only focused on the seismic damage to all the structures but also considered the functions of the communication and power supply of the equipment.The interactions between these facilities and their effects on communication function were also investigated.Compared with the damage to structures,the interruption of the power supply due to earthquakes is a weak link.Finally,the damage indexes,together with their threshold values of different damage states for the communication and power supply equipment,were derived from the test results.The results of this research can contribute to the literature gaps regarding seismic performance studies of telecommunication rooms,and can serve as a valuable reference for future research on its seismic fragility and economic losses evaluation.展开更多
On February 6,2023,an M_(w)7.8 earthquake hit the south of Kahramanmaras prefecture,Turkey,followed by another M_(w)7.5 earthquake after nine hours in the middle region of the Kahramanmaras prefecture.More than 84,000...On February 6,2023,an M_(w)7.8 earthquake hit the south of Kahramanmaras prefecture,Turkey,followed by another M_(w)7.5 earthquake after nine hours in the middle region of the Kahramanmaras prefecture.More than 84,000 buildings collapsed or were severely damaged,and more than 50,000 lives were lost in Turkey and Syria.Some of the authors,as members of Chinese rescue team,entered Antakya,Hatay prefecture,and investigated the damaged buildings.This paper first summarizes the damage patterns of buildings and provides three reasons for the massive number of collapsed buildings;i.e.,the lack of seismic measures for better ductility,site effects such as liquefaction and surface rupture,and pronounced low-frequency components of the ground motions.Next,the seismic responses of two typical buildings are calculated based on the geometric data estimated by visual inspection.The results imply that the resonance of the whole structure and the poorer ductility of key members resulted in the collapse of buildings.Finally,some conclusions are drawn.Note that although a large number of buildings were seriously damaged to collapse,the majority of buildings in the areas of extreme shaking were lightly or moderately damaged,which implies that well designed and constructed buildings were able to survive and protect human lives even in over-design earthquakes.展开更多
To enable the experimental assessment of the seismic performance of full-scale nonstructural elements with multiple engineering parameters(EDPs),a three-layer testbed named Nonstructural Element Simulator on Shake Tab...To enable the experimental assessment of the seismic performance of full-scale nonstructural elements with multiple engineering parameters(EDPs),a three-layer testbed named Nonstructural Element Simulator on Shake Table(NEST)has been developed.The testbed consists of three consecutive floors of steel structure.The bottom two floors provide a space to accommodate a full-scale room.To fully explore the flexibility of NEST,we propose a novel control strategy to generate the required shake table input time histories for the testbed to track the target floor motions of the buildings of interest with high accuracy.The control strategy contains two parts:an inverse dynamic compensation via simulation of feedback control systems(IDCS)algorithm and an offline iteration procedure based on a refined nonlinear numerical model of the testbed.The key aspects of the control strategy were introduced in this paper.Experimental tests were conducted to simulate the seismic responses of a full-scale office room on the 21^(st)floor of a 42-story high-rise building.The test results show that the proposed control strategy can reproduce the target floor motions of the building of interest with less than 20%errors within the specified frequency range.展开更多
The seismic performance of medical systems is crucial for the seismic resilience of communities.The report summarizes the observed damage to twelve hospital buildings in the area affected by the MW 7.8 and MW 7.5 eart...The seismic performance of medical systems is crucial for the seismic resilience of communities.The report summarizes the observed damage to twelve hospital buildings in the area affected by the MW 7.8 and MW 7.5 earthquakes on February 6,2023 in Turkey.They include five base-isolated buildings and seven fixed-base buildings in southcentral Turkey's seven most heavily affected provinces.By relating the post-quake occupancy statuses of the hospitals with the estimated seismic demands during the earthquake doublet,the report offers the following observations:(1)the base-isolated hospital buildings on friction pendulum bearings generally exhibited superior performance of achieving the goal of immediate occupancy and provided better protection for nonstructural elements than fixed-base counterparts did;(2)the fixed-base hospital buildings of reinforced concrete structures constructed after 2001 successfully achieved the goal of collapse prevention even under very high seismic demands;(3)some fixed-base hospitals also remained operational even if they were very close to the fault rupture and were subjected to higher-than-design-level earthquake ground motions.展开更多
The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province,China.They include base-isolated buildings,multi-story reinforced concrete(RC)fr...The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province,China.They include base-isolated buildings,multi-story reinforced concrete(RC)frame buildings,and masonry buildings.The near-field region is known to be tectonically highly active,and the local intensity level is the highest,that is,0.4g peak ground acceleration(PGA)for the design basis earthquake,in the Chinese zonation of seismic ground motion parameters.The extent of damage ranged from the weak-story collapse that claimed lives to the extensive nonstructural damage that suspended occupancy.The report highlights the first observation of the destruction of rubber bearings and viscous dampers in the isolation layer of Chinese seismically isolated buildings.It also features the rare observation of the brittle shear failure of RC columns in moment-resisting frames in a region of such a high seismic design requirement.Possible reasons that may have attributed to the reported damage are suggested by providing facts observed in the field.However,careful forensic analyses are needed before any conclusive judgment can be made.展开更多
As an important part of nonstructural components,the seismic response of indoor water supply pipes deserves much attention.This paper presents shaking table test research on water supply pipes installed in a full-scal...As an important part of nonstructural components,the seismic response of indoor water supply pipes deserves much attention.This paper presents shaking table test research on water supply pipes installed in a full-scale reinforced concrete(RC)frame structure.Different material pipes and different methods for penetrating the reinforced concrete floors are combined to evaluate the difference in seismic performance.Floor response spectra and pipe acceleration amplification factors based on test data are discussed and compared with code provisions.A seismic fragility study of displacement demand is conducted based on numerical simulation.The acceleration response and displacement response of different combinations are compared.The results show that the combination of different pipe materials and different passing-through methods can cause obvious differences in the seismic response of indoor riser pipes.展开更多
Displacement control algorithms commonly used to evaluate axial force-bending moment(PM)diagrams may lead to incorrect interpretations of the strength envelopes for asymmetric sections.This paper aims to offer valuabl...Displacement control algorithms commonly used to evaluate axial force-bending moment(PM)diagrams may lead to incorrect interpretations of the strength envelopes for asymmetric sections.This paper aims to offer valuable insights by comparing existing displacement control algorithms with a newly proposed force control algorithm.The main focus is on the PM diagrams of three example sections that exhibit varying degrees of asymmetry.The comparative study indicates that conventional displacement control algorithms inevitably introduce non-zero out-of-plane bending moments.The reported PM diagram in such cases erroneously neglects the out-of-plane moment and fails to represent the strength envelope accurately.This oversight results in significant and unconservative errors when verifying the strength of asymmetric sections.展开更多
It is critical to determine whether a site has potential damage in real-time after an earthquake occurs,which is a challenge in earthquake disaster reduction.Here,we propose a real-time Earthquake Potential Damage pre...It is critical to determine whether a site has potential damage in real-time after an earthquake occurs,which is a challenge in earthquake disaster reduction.Here,we propose a real-time Earthquake Potential Damage predictor(EPDor)based on predicting peak ground velocities(PGVs)of sites.The EPDor is composed of three parts:(1)predicting the magnitude of an earthquake and PGVs of triggered stations based on the machine learning prediction models;(2)predicting the PGVs at distant sites based on the empirical ground motion prediction equation;(3)generating the PGV map through predicting the PGV of each grid point based on an interpolation process of weighted average based on the predicted values in(1)and(2).We apply the EPDor to the 2022 M_(S) 6.9 Menyuan earthquake in Qinghai Province,China to predict its potential damage.Within the initial few seconds after the first station is triggered,the EPDor can determine directly whether there is potential damage for some sites to a certain degree.Hence,we infer that the EPDor has potential application for future earthquakes.Meanwhile,it also has potential in Chinese earthquake early warning system.展开更多
Although the classical spectral representation method(SRM)has been widely used in the generation of spatially varying ground motions,there are still challenges in efficient simulation of the non-stationary stochastic ...Although the classical spectral representation method(SRM)has been widely used in the generation of spatially varying ground motions,there are still challenges in efficient simulation of the non-stationary stochastic vector process in practice.The first problem is the inherent limitation and inflexibility of the deterministic time/frequency modulation function.Another difficulty is the estimation of evolutionary power spectral density(EPSD)with quite a few samples.To tackle these problems,the wavelet packet transform(WPT)algorithm is utilized to build a time-varying spectrum of seed recording which describes the energy distribution in the time-frequency domain.The time-varying spectrum is proven to preserve the time and frequency marginal property as theoretical EPSD will do for the stationary process.For the simulation of spatially varying ground motions,the auto-EPSD for all locations is directly estimated using the time-varying spectrum of seed recording rather than matching predefined EPSD models.Then the constructed spectral matrix is incorporated in SRM to simulate spatially varying non-stationary ground motions using efficient Cholesky decomposition techniques.In addition to a good match with the target coherency model,two numerical examples indicate that the generated time histories retain the physical properties of the prescribed seed recording,including waveform,temporal/spectral non-stationarity,normalized energy buildup,and significant duration.展开更多
The 2022 M6.9 Menyuan earthquake caused severe damage to a high-speed railway bridge,which was designed for high-speed trains running at speeds of above 250 km/h and is located right next to the fault.Bridges of this ...The 2022 M6.9 Menyuan earthquake caused severe damage to a high-speed railway bridge,which was designed for high-speed trains running at speeds of above 250 km/h and is located right next to the fault.Bridges of this type have been widely used for rapidly constructing the high-speed railway network,but few bridges have been tested by near-fault devastating earthquakes.The potential severe impact of the earthquake on the high-speed railway is not only the safety of the infrastructure,trains and passengers,but also economic loss due to interrupted railway use.Therefore,a field survey was carried out immediately after the earthquake to collect time-sensitive data.The damage to the bridge was carefully investigated,and quantitative analyses were conducted to better understand the mechanism of the bridge failure.It was found that seismic action perpendicular to the bridge’s longitudinal direction caused severe damage to the girders and rails,while none of the piers showed obvious deformation or cracking.The maximum values of transverse displacement,out-of-plane rotation and twisting angle of girders reached 212.6 cm,3.1 degrees and 19.9 degrees,respectively,causing severe damage to the bearing supports and anti-seismic retaining blocks.These observations provide a basis for improving the seismic design of high-speed railway bridges located in near-fault areas.展开更多
Seismic fragility analysis of three-tower cable-stayed bridges with three different structural systems,including rigid system(RS),floating system(FS),and passive energy dissipation system(PEDS),is conducted to study t...Seismic fragility analysis of three-tower cable-stayed bridges with three different structural systems,including rigid system(RS),floating system(FS),and passive energy dissipation system(PEDS),is conducted to study the effects of connection configurations on seismic responses and fragilities.Finite element models of bridges are established using OpenSees.A new ground motion screening method based on the statistical characteristic of the predominant period is proposed to avoid irregular behavior in the selection process of ground motions,and incremental dynamic analysis(IDA)is performed to develop components and systems fragility curves.The effects of damper failure on calculated results for PEDS are examined in terms of seismic response and fragility analysis.The results show that the bridge tower is the most affected component by different structural systems.For RS,the fragility of the middle tower is significantly higher than other components,and the bridge failure starts from the middle tower,exhibiting a characteristic of local failure.For FS and PEDS,the fragility of the edge tower is higher than the middle tower.The system fragility of RS is higher than FS and PEDS.Taking the failure of dampers into account is necessary to obtain reliable seismic capacity of cable-stayed bridges.展开更多
A coupled numerical calculation method combining smooth particle hydrodynamics(SPH)and the finite element method(FEM)was implemented to investigate the seismic response of horizontal storage tanks.Anumericalmodel of a...A coupled numerical calculation method combining smooth particle hydrodynamics(SPH)and the finite element method(FEM)was implemented to investigate the seismic response of horizontal storage tanks.Anumericalmodel of a horizontal storage tank featuring a free liquid surface under seismic action was constructed using the SPH–FEM coupling method.The stored liquid was discretized using SPH particles,while the tank and supports were discretized using the FEM.The interaction between the stored liquid and the tank was simulated by using the meshless particle contact method.Then,the numerical simulation results were compared and analyzed against seismic simulation shaking table test data to validate the method.Subsequently,a series of numerical models,considering different liquid storage volumes and seismic effects,were constructed to obtain time history data of base shear and top center displacement,which revealed the seismic performance of horizontal storage tanks.Numerical simulation results and experimental data showed good agreement,with an error rate of less than 18.85%.And this conformity signifies the rationality of the SPH-FEM coupling method.The base shear and top center displacement values obtained by the coupled SPH-FEM method were only 53.3% to 69.1% of those calculated by the equivalent mass method employed in the current code.As the stored liquid volume increased,the seismic response of the horizontal storage tank exhibited a gradual upward trend,with the seismic response increasing from 73% to 388% for every 35% increase in stored liquid volume.The maximum von Mises stress of the tank and the supports remained below the steel yield strength during the earthquake.The coupled SPH-FEM method holds certain advantages in studying the seismic problems of tanks with complex structural forms,particularly due to the representation of the flow field distribution during earthquakes by involving reservoir fluid participation.展开更多
When evaluating an area's seismic risk or resilience,it is necessary to use the spatial correlation to analyze the ground motion parameters of multiple sites together in an earthquake.These two large earthquakes i...When evaluating an area's seismic risk or resilience,it is necessary to use the spatial correlation to analyze the ground motion parameters of multiple sites together in an earthquake.These two large earthquakes in Türkiye provided the possibility for spatial correlation analysis of ground motion intensity measurements in this area.Based on the strong motion records provided by The Disaster and Emergency Management Authority of Türkiye(AFAD),this study uses the local ground motion prediction equation in Türkiye to give spatial correlation analysis of Intensity Measurements.This study gives an exponential model based on a semivariogram and compares it with the correlation model obtained from previous studies.展开更多
Due to differences in the properties of composition materials and construction techniques,unreinforced masonry is characterized by low strength,anisotropy,nonuniformity,and low ductility.In order to accurately simulat...Due to differences in the properties of composition materials and construction techniques,unreinforced masonry is characterized by low strength,anisotropy,nonuniformity,and low ductility.In order to accurately simulate the mechanical behavior of unreinforced brick masonry walls under static and dynamic loads,a new elastoplastic damage constitutive model was proposed and the corresponding subroutine was developed based on the concrete material constitutive model.In the proposed constitutive model,the Rankine strength theory and the Drucker-Prager strength theory were used to define the tensile and compressive yield surface function of materials,respectively.Moreover,the stress updating algorithm was modified to consider the tensile plastic permanent deformation of masonry materials.To verify the accuracy of the proposed constitutive model,numerical simulations of the brick masonry under monotonic and cyclic uniaxial tension and compression loads were carried out.Comparisons among the numerical and theoretical and experimental results show that the proposed model can properly reflect the masonry material mechanical properties.Furthermore,the numerical models of four pieces of masonry walls with different mortar strengths were established.Low cyclic loadings were applied and the results show that the proposed constitutive model can properly simulate the wall shear failure characteristics,and the force-displacement hysteretic curves obtained by numerical simulation are in good agreement with the tests.Overall,the proposed elastic-plastic damage constitutive model can simulate the nonlinear behavior of unreinforced brick masonry walls very well,and can be used to predict the structural response of masonry walls.展开更多
Pin-supported(PS)walls have been proven effective in avoiding weak story failure of frame structures by increasing the height-wise continuous stiffness and producing uniform distribution of story drifts.However,little...Pin-supported(PS)walls have been proven effective in avoiding weak story failure of frame structures by increasing the height-wise continuous stiffness and producing uniform distribution of story drifts.However,little attention has been given to the floor velocity or acceleration responses of PS wall-frame structures,which predominate the seismic damage of various nonstructural components that are critical to the immediate occupancy and quick recovery of buildings.This paper presents a numerical evaluation of the floor velocity and acceleration responses of PS wall-frame structures,highlighting the effects of different types of dampers accompanying the PS walls.The results show that the PS walls alone significantly increase the peak floor velocity(PFV)and peak floor acceleration(PFA)responses.PS wall-frame structures with either steel or viscoelastic(VE)dampers are much less effective in reducing the PFV or PFA responses than they are in reducing the peak inter-story drift ratio(PIDR).The impact of this behavior is demonstrated by a seismic fragility analysis that incorporates demand parameters combining the maximum PIDR,average PFV and PFA.The results show that the use of VE dampers rather than hysteretic dampers results in better protection of nonstructural components in PS wall-frame structures.展开更多
Due to the long construction life,improper design methods,brittle material properties and poor construction techniques,most existing masonry structures do not perform well during earthquakes.The retrofitting method us...Due to the long construction life,improper design methods,brittle material properties and poor construction techniques,most existing masonry structures do not perform well during earthquakes.The retrofitting method using an external steel-meshed mortar layer is widely used to retrofit existing masonry buildings.Assessing the seismic performance of masonry walls reinforced by an external steel-meshed mortar layer reasonably and effectively is a difficult subject in the research field of masonry structures.Based on the combined finite-discrete elements method,the numerical models of retrofitted brick walls with four different masonry mortar strengths by an external mortar layer are established.The shear strength of mortar and the contact between the retrofitted mortar layer and the brick blocks are discussed in detail.The failure patterns and load-displacement curves of the retrofitted brick walls were obtained by applying low cycle reciprocating loads to the numerical model,and the bearing capacity and the failure mechanism of the retrofitted walls were obtained by comparing the failure patterns,ultimate bearing capacity,deformability and other aspects with the tests.This study provides a basis for improving the seismic strengthening design method of masonry structures and helps to better assess the seismic performance of masonry structures after retrofitting.展开更多
Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave lin...Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave line source embedded in the solid is presented.During the derivation,the wave fields in the fluid layer and the semi-infinite solid are firstly constructed by using the generalized ray method and the fluid-solid interface reflection and transmission coefficients.Then,the analytical solution in the transformed domain is obtained by superposing these wave fields,and the analytical solution in the time domain by applying the analytical inverse Laplace transform method.The the head wave generation conditions and arrival times at the fluid-solid interface are derived through this solution.Through the use of numerical examples,the analytical solution is proved right and the impacts of the sloping angle on the hydrodynamic pressure in the sea,the seismic wave propagation in the seabed,the head wave,and the Scholte wave at the seawater-seabed interface are also addressed.展开更多
Since masonry structures are prone to collapse in earthquakes,a novel joint reinforcement method with a polypropylene band(PP-band)and cement mortar(CM)has been put forward.Compared with the common reinforcement metho...Since masonry structures are prone to collapse in earthquakes,a novel joint reinforcement method with a polypropylene band(PP-band)and cement mortar(CM)has been put forward.Compared with the common reinforcement methods,this method not only facilitates construction but also ensures lower reinforcement cost.To systematically explore the influence of joint reinforcement on the seismic performance of masonry walls,quasi-static tests were carried out on six specimens with different reinforcement forms.The test results show that the joint action of PP-band and CM can significantly improve the specimen′s brittle failure characteristics and enhance the integrity of the specimen after cracking.Compared with the specimen without reinforcement,each of the seismic performance indexes of the joint reinforced specimen had obvious improvement.The maximum increased rate about peak load and ductility of the joint reinforced specimen is 100.6%and 233.4%,respectively.展开更多
Purpose–Using the strong motion data ofK-net in Japan,the continuous magnitude prediction method based on support vector machine(SVM)was studied.Design/methodology/approach–In the range of 0.5–10.0 s after the P-wa...Purpose–Using the strong motion data ofK-net in Japan,the continuous magnitude prediction method based on support vector machine(SVM)was studied.Design/methodology/approach–In the range of 0.5–10.0 s after the P-wave arrival,the prediction time window was established at an interval of 0.5 s.12 P-wave characteristic parameters were selected as the model input parameters to construct the earthquake early warning(EEW)magnitude prediction model(SVM-HRM)for high-speed railway based on SVM.Findings–The magnitude prediction results of the SVM-HRM model were compared with the traditional magnitude prediction model and the high-speed railway EEW current norm.Results show that at the 3.0 s time window,themagnitude prediction error of the SVM-HRMmodel is obviously smaller than that of the traditionalτc method and Pd method.The overestimation of small earthquakes is obviously improved,and the construction of the model is not affected by epicenter distance,so it has generalization performance.For earthquake events with themagnitude range of 3–5,the single station realization rate of the SVM-HRMmodel reaches 95%at 0.5 s after the arrival of P-wave,which is better than the first alarm realization rate norm required by“The TestMethod of EEW andMonitoring Systemfor High-Speed Railway.”For earthquake eventswithmagnitudes ranging from3 to 5,5 to 7 and 7 to 8,the single station realization rate of the SVM-HRM model is at 0.5 s,1.5 s and 0.5 s after the P-wave arrival,respectively,which is better than the realization rate norm of multiple stations.Originality/value–At the latest,1.5 s after the P-wave arrival,the SVM-HRM model can issue the first earthquake alarm that meets the norm of magnitude prediction realization rate,which meets the accuracy and continuity requirements of high-speed railway EEW magnitude prediction.展开更多
The most important method of understanding liquefaction-induced engineering failures comes from the investigation and analysis of earthquake damage.In May 2021,the Maduo M_(s)7.4 earthquake occurred on the Tibetan Pla...The most important method of understanding liquefaction-induced engineering failures comes from the investigation and analysis of earthquake damage.In May 2021,the Maduo M_(s)7.4 earthquake occurred on the Tibetan Plateau of China.The most representative engineering disaster caused by this earthquake was bridge damage on liquefied sites.In this study,the mutual relationships between the anti-liquefaction pre-design situation,the ground motion intensity,the site liquefaction severity,and the bridge damage state for this earthquake were systematically analyzed for typical bridge damage on the liquefied sites.Using field survey data and the current Chinese industry code,simulations of the liquefaction scenarios at typical bridge sites were performed for the pre-design seismic ground motion before the earthquake and the seismic ground motion during the earthquake.By combining these results with post-earthquake investigation results,the reason for the serious bridge damage resulting from this earthquake is revealed,and the necessary conditions for avoiding serious seismic damage to bridges built in liquefiable sites is presented.展开更多
基金Key Project of the Key Laboratory of Earthquake Engineering and Engineering Vibration,China Earthquake Administration under Grant Nos.2020EEEVL0502 and 2019EEEVL0304。
文摘Large numbers of basic transceiver stations,where the telecommunication room is one of the main components,comprise an important part of the telecommunication system.After earthquakes,considerable economic loss from telecommunication systems is often associated with seismic damage and functional loss of the telecommunication room.However,research related to this has been limited.In this study,shaking table tests were conducted for a full-scale typical telecommunication room,including a light-steel house and the necessary communication and power supply equipment.The tests not only focused on the seismic damage to all the structures but also considered the functions of the communication and power supply of the equipment.The interactions between these facilities and their effects on communication function were also investigated.Compared with the damage to structures,the interruption of the power supply due to earthquakes is a weak link.Finally,the damage indexes,together with their threshold values of different damage states for the communication and power supply equipment,were derived from the test results.The results of this research can contribute to the literature gaps regarding seismic performance studies of telecommunication rooms,and can serve as a valuable reference for future research on its seismic fragility and economic losses evaluation.
基金National Natural Science Foundation of China for Distinguished Young Scholars under Grant No.52125806Heilongjiang Touyan Innovation Team Program under Grant No.3016。
文摘On February 6,2023,an M_(w)7.8 earthquake hit the south of Kahramanmaras prefecture,Turkey,followed by another M_(w)7.5 earthquake after nine hours in the middle region of the Kahramanmaras prefecture.More than 84,000 buildings collapsed or were severely damaged,and more than 50,000 lives were lost in Turkey and Syria.Some of the authors,as members of Chinese rescue team,entered Antakya,Hatay prefecture,and investigated the damaged buildings.This paper first summarizes the damage patterns of buildings and provides three reasons for the massive number of collapsed buildings;i.e.,the lack of seismic measures for better ductility,site effects such as liquefaction and surface rupture,and pronounced low-frequency components of the ground motions.Next,the seismic responses of two typical buildings are calculated based on the geometric data estimated by visual inspection.The results imply that the resonance of the whole structure and the poorer ductility of key members resulted in the collapse of buildings.Finally,some conclusions are drawn.Note that although a large number of buildings were seriously damaged to collapse,the majority of buildings in the areas of extreme shaking were lightly or moderately damaged,which implies that well designed and constructed buildings were able to survive and protect human lives even in over-design earthquakes.
基金supported by the Natural Science Foundation of China(52122811)。
文摘To enable the experimental assessment of the seismic performance of full-scale nonstructural elements with multiple engineering parameters(EDPs),a three-layer testbed named Nonstructural Element Simulator on Shake Table(NEST)has been developed.The testbed consists of three consecutive floors of steel structure.The bottom two floors provide a space to accommodate a full-scale room.To fully explore the flexibility of NEST,we propose a novel control strategy to generate the required shake table input time histories for the testbed to track the target floor motions of the buildings of interest with high accuracy.The control strategy contains two parts:an inverse dynamic compensation via simulation of feedback control systems(IDCS)algorithm and an offline iteration procedure based on a refined nonlinear numerical model of the testbed.The key aspects of the control strategy were introduced in this paper.Experimental tests were conducted to simulate the seismic responses of a full-scale office room on the 21^(st)floor of a 42-story high-rise building.The test results show that the proposed control strategy can reproduce the target floor motions of the building of interest with less than 20%errors within the specified frequency range.
基金jointly sponsored by the Institute of Engineering Mechanicsthe Natural Science Foundation of China(No.52122811)。
文摘The seismic performance of medical systems is crucial for the seismic resilience of communities.The report summarizes the observed damage to twelve hospital buildings in the area affected by the MW 7.8 and MW 7.5 earthquakes on February 6,2023 in Turkey.They include five base-isolated buildings and seven fixed-base buildings in southcentral Turkey's seven most heavily affected provinces.By relating the post-quake occupancy statuses of the hospitals with the estimated seismic demands during the earthquake doublet,the report offers the following observations:(1)the base-isolated hospital buildings on friction pendulum bearings generally exhibited superior performance of achieving the goal of immediate occupancy and provided better protection for nonstructural elements than fixed-base counterparts did;(2)the fixed-base hospital buildings of reinforced concrete structures constructed after 2001 successfully achieved the goal of collapse prevention even under very high seismic demands;(3)some fixed-base hospitals also remained operational even if they were very close to the fault rupture and were subjected to higher-than-design-level earthquake ground motions.
基金the Natural Science Foundation of China(52122811).
文摘The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province,China.They include base-isolated buildings,multi-story reinforced concrete(RC)frame buildings,and masonry buildings.The near-field region is known to be tectonically highly active,and the local intensity level is the highest,that is,0.4g peak ground acceleration(PGA)for the design basis earthquake,in the Chinese zonation of seismic ground motion parameters.The extent of damage ranged from the weak-story collapse that claimed lives to the extensive nonstructural damage that suspended occupancy.The report highlights the first observation of the destruction of rubber bearings and viscous dampers in the isolation layer of Chinese seismically isolated buildings.It also features the rare observation of the brittle shear failure of RC columns in moment-resisting frames in a region of such a high seismic design requirement.Possible reasons that may have attributed to the reported damage are suggested by providing facts observed in the field.However,careful forensic analyses are needed before any conclusive judgment can be made.
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant Nos.2021EEEVL0204 and 2018A02。
文摘As an important part of nonstructural components,the seismic response of indoor water supply pipes deserves much attention.This paper presents shaking table test research on water supply pipes installed in a full-scale reinforced concrete(RC)frame structure.Different material pipes and different methods for penetrating the reinforced concrete floors are combined to evaluate the difference in seismic performance.Floor response spectra and pipe acceleration amplification factors based on test data are discussed and compared with code provisions.A seismic fragility study of displacement demand is conducted based on numerical simulation.The acceleration response and displacement response of different combinations are compared.The results show that the combination of different pipe materials and different passing-through methods can cause obvious differences in the seismic response of indoor riser pipes.
基金supported by the Natural Science Foundation of China(52122811).
文摘Displacement control algorithms commonly used to evaluate axial force-bending moment(PM)diagrams may lead to incorrect interpretations of the strength envelopes for asymmetric sections.This paper aims to offer valuable insights by comparing existing displacement control algorithms with a newly proposed force control algorithm.The main focus is on the PM diagrams of three example sections that exhibit varying degrees of asymmetry.The comparative study indicates that conventional displacement control algorithms inevitably introduce non-zero out-of-plane bending moments.The reported PM diagram in such cases erroneously neglects the out-of-plane moment and fails to represent the strength envelope accurately.This oversight results in significant and unconservative errors when verifying the strength of asymmetric sections.
基金financially supported by the National Natural Science Foundation of China (U2039209, U1839208, and 51408564)the Natural Science Foundation of Heilongjiang Province (LH2021E119)+1 种基金Spark Program of Earthquake Science (XH23027YB)the National Key Research and Development Program of China (2018YFC1504003).
文摘It is critical to determine whether a site has potential damage in real-time after an earthquake occurs,which is a challenge in earthquake disaster reduction.Here,we propose a real-time Earthquake Potential Damage predictor(EPDor)based on predicting peak ground velocities(PGVs)of sites.The EPDor is composed of three parts:(1)predicting the magnitude of an earthquake and PGVs of triggered stations based on the machine learning prediction models;(2)predicting the PGVs at distant sites based on the empirical ground motion prediction equation;(3)generating the PGV map through predicting the PGV of each grid point based on an interpolation process of weighted average based on the predicted values in(1)and(2).We apply the EPDor to the 2022 M_(S) 6.9 Menyuan earthquake in Qinghai Province,China to predict its potential damage.Within the initial few seconds after the first station is triggered,the EPDor can determine directly whether there is potential damage for some sites to a certain degree.Hence,we infer that the EPDor has potential application for future earthquakes.Meanwhile,it also has potential in Chinese earthquake early warning system.
基金National Key Research and Development Program of China under Grant No.2023YFE0102900National Natural Science Foundation of China under Grant Nos.52378506 and 52208164。
文摘Although the classical spectral representation method(SRM)has been widely used in the generation of spatially varying ground motions,there are still challenges in efficient simulation of the non-stationary stochastic vector process in practice.The first problem is the inherent limitation and inflexibility of the deterministic time/frequency modulation function.Another difficulty is the estimation of evolutionary power spectral density(EPSD)with quite a few samples.To tackle these problems,the wavelet packet transform(WPT)algorithm is utilized to build a time-varying spectrum of seed recording which describes the energy distribution in the time-frequency domain.The time-varying spectrum is proven to preserve the time and frequency marginal property as theoretical EPSD will do for the stationary process.For the simulation of spatially varying ground motions,the auto-EPSD for all locations is directly estimated using the time-varying spectrum of seed recording rather than matching predefined EPSD models.Then the constructed spectral matrix is incorporated in SRM to simulate spatially varying non-stationary ground motions using efficient Cholesky decomposition techniques.In addition to a good match with the target coherency model,two numerical examples indicate that the generated time histories retain the physical properties of the prescribed seed recording,including waveform,temporal/spectral non-stationarity,normalized energy buildup,and significant duration.
基金Scientific Research Funding of IEM under Grant No.2021EEEVL0211Natural Science Foundation of Heilongjiang Province under Grant No.JQ2021E006National Natural Science Foundation of China under Grant No.52208185。
文摘The 2022 M6.9 Menyuan earthquake caused severe damage to a high-speed railway bridge,which was designed for high-speed trains running at speeds of above 250 km/h and is located right next to the fault.Bridges of this type have been widely used for rapidly constructing the high-speed railway network,but few bridges have been tested by near-fault devastating earthquakes.The potential severe impact of the earthquake on the high-speed railway is not only the safety of the infrastructure,trains and passengers,but also economic loss due to interrupted railway use.Therefore,a field survey was carried out immediately after the earthquake to collect time-sensitive data.The damage to the bridge was carefully investigated,and quantitative analyses were conducted to better understand the mechanism of the bridge failure.It was found that seismic action perpendicular to the bridge’s longitudinal direction caused severe damage to the girders and rails,while none of the piers showed obvious deformation or cracking.The maximum values of transverse displacement,out-of-plane rotation and twisting angle of girders reached 212.6 cm,3.1 degrees and 19.9 degrees,respectively,causing severe damage to the bearing supports and anti-seismic retaining blocks.These observations provide a basis for improving the seismic design of high-speed railway bridges located in near-fault areas.
基金National Key R&D Program of China under Grant No.2022YFC3003603。
文摘Seismic fragility analysis of three-tower cable-stayed bridges with three different structural systems,including rigid system(RS),floating system(FS),and passive energy dissipation system(PEDS),is conducted to study the effects of connection configurations on seismic responses and fragilities.Finite element models of bridges are established using OpenSees.A new ground motion screening method based on the statistical characteristic of the predominant period is proposed to avoid irregular behavior in the selection process of ground motions,and incremental dynamic analysis(IDA)is performed to develop components and systems fragility curves.The effects of damper failure on calculated results for PEDS are examined in terms of seismic response and fragility analysis.The results show that the bridge tower is the most affected component by different structural systems.For RS,the fragility of the middle tower is significantly higher than other components,and the bridge failure starts from the middle tower,exhibiting a characteristic of local failure.For FS and PEDS,the fragility of the edge tower is higher than the middle tower.The system fragility of RS is higher than FS and PEDS.Taking the failure of dampers into account is necessary to obtain reliable seismic capacity of cable-stayed bridges.
基金supported by Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration(Grant Nos.2021B06,2021C05)Heilongjiang Natural Science Foundation Joint Guidance Project(Grant No.LH2021E122).
文摘A coupled numerical calculation method combining smooth particle hydrodynamics(SPH)and the finite element method(FEM)was implemented to investigate the seismic response of horizontal storage tanks.Anumericalmodel of a horizontal storage tank featuring a free liquid surface under seismic action was constructed using the SPH–FEM coupling method.The stored liquid was discretized using SPH particles,while the tank and supports were discretized using the FEM.The interaction between the stored liquid and the tank was simulated by using the meshless particle contact method.Then,the numerical simulation results were compared and analyzed against seismic simulation shaking table test data to validate the method.Subsequently,a series of numerical models,considering different liquid storage volumes and seismic effects,were constructed to obtain time history data of base shear and top center displacement,which revealed the seismic performance of horizontal storage tanks.Numerical simulation results and experimental data showed good agreement,with an error rate of less than 18.85%.And this conformity signifies the rationality of the SPH-FEM coupling method.The base shear and top center displacement values obtained by the coupled SPH-FEM method were only 53.3% to 69.1% of those calculated by the equivalent mass method employed in the current code.As the stored liquid volume increased,the seismic response of the horizontal storage tank exhibited a gradual upward trend,with the seismic response increasing from 73% to 388% for every 35% increase in stored liquid volume.The maximum von Mises stress of the tank and the supports remained below the steel yield strength during the earthquake.The coupled SPH-FEM method holds certain advantages in studying the seismic problems of tanks with complex structural forms,particularly due to the representation of the flow field distribution during earthquakes by involving reservoir fluid participation.
基金jointly supported by the National Natural Science Foundation of China U1901602,U2239252)the National Key R&D Program of China(No.2019YFE0115700)+1 种基金the Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration(Grant No.2021EEEVL0202)the Natural Science Foundation of Heilongjiang Province(LH2020E021)。
文摘When evaluating an area's seismic risk or resilience,it is necessary to use the spatial correlation to analyze the ground motion parameters of multiple sites together in an earthquake.These two large earthquakes in Türkiye provided the possibility for spatial correlation analysis of ground motion intensity measurements in this area.Based on the strong motion records provided by The Disaster and Emergency Management Authority of Türkiye(AFAD),this study uses the local ground motion prediction equation in Türkiye to give spatial correlation analysis of Intensity Measurements.This study gives an exponential model based on a semivariogram and compares it with the correlation model obtained from previous studies.
基金National Key Research and Development Program of China under Grant Nos.2018YFC1504400 and 2019YFC1509301Natural Science Foundation of China under Grant No.52078471Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2019EEEVL0402。
文摘Due to differences in the properties of composition materials and construction techniques,unreinforced masonry is characterized by low strength,anisotropy,nonuniformity,and low ductility.In order to accurately simulate the mechanical behavior of unreinforced brick masonry walls under static and dynamic loads,a new elastoplastic damage constitutive model was proposed and the corresponding subroutine was developed based on the concrete material constitutive model.In the proposed constitutive model,the Rankine strength theory and the Drucker-Prager strength theory were used to define the tensile and compressive yield surface function of materials,respectively.Moreover,the stress updating algorithm was modified to consider the tensile plastic permanent deformation of masonry materials.To verify the accuracy of the proposed constitutive model,numerical simulations of the brick masonry under monotonic and cyclic uniaxial tension and compression loads were carried out.Comparisons among the numerical and theoretical and experimental results show that the proposed model can properly reflect the masonry material mechanical properties.Furthermore,the numerical models of four pieces of masonry walls with different mortar strengths were established.Low cyclic loadings were applied and the results show that the proposed constitutive model can properly simulate the wall shear failure characteristics,and the force-displacement hysteretic curves obtained by numerical simulation are in good agreement with the tests.Overall,the proposed elastic-plastic damage constitutive model can simulate the nonlinear behavior of unreinforced brick masonry walls very well,and can be used to predict the structural response of masonry walls.
基金National Natural Science Foundation of China under Grant No.51878629。
文摘Pin-supported(PS)walls have been proven effective in avoiding weak story failure of frame structures by increasing the height-wise continuous stiffness and producing uniform distribution of story drifts.However,little attention has been given to the floor velocity or acceleration responses of PS wall-frame structures,which predominate the seismic damage of various nonstructural components that are critical to the immediate occupancy and quick recovery of buildings.This paper presents a numerical evaluation of the floor velocity and acceleration responses of PS wall-frame structures,highlighting the effects of different types of dampers accompanying the PS walls.The results show that the PS walls alone significantly increase the peak floor velocity(PFV)and peak floor acceleration(PFA)responses.PS wall-frame structures with either steel or viscoelastic(VE)dampers are much less effective in reducing the PFV or PFA responses than they are in reducing the peak inter-story drift ratio(PIDR).The impact of this behavior is demonstrated by a seismic fragility analysis that incorporates demand parameters combining the maximum PIDR,average PFV and PFA.The results show that the use of VE dampers rather than hysteretic dampers results in better protection of nonstructural components in PS wall-frame structures.
基金National Key Research and Development Program of China under Grant Nos. 2018YFC1504400 and 2019YFC1509301Natural Science Foundation of China under Grant No. 52078471Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant No. 19EEEVL0402
文摘Due to the long construction life,improper design methods,brittle material properties and poor construction techniques,most existing masonry structures do not perform well during earthquakes.The retrofitting method using an external steel-meshed mortar layer is widely used to retrofit existing masonry buildings.Assessing the seismic performance of masonry walls reinforced by an external steel-meshed mortar layer reasonably and effectively is a difficult subject in the research field of masonry structures.Based on the combined finite-discrete elements method,the numerical models of retrofitted brick walls with four different masonry mortar strengths by an external mortar layer are established.The shear strength of mortar and the contact between the retrofitted mortar layer and the brick blocks are discussed in detail.The failure patterns and load-displacement curves of the retrofitted brick walls were obtained by applying low cycle reciprocating loads to the numerical model,and the bearing capacity and the failure mechanism of the retrofitted walls were obtained by comparing the failure patterns,ultimate bearing capacity,deformability and other aspects with the tests.This study provides a basis for improving the seismic strengthening design method of masonry structures and helps to better assess the seismic performance of masonry structures after retrofitting.
基金financially supported by the National Key R&D Program of China (Grant No.2021YFC3100700)the National Natural Science Foundation of China (Grant Nos.U2039209 and 41874067)the Natural Science Foundation of Heilongjiang Province,China (Grant No.YQ2021D010)。
文摘Many offshore marine structures are built on the seabed that are slightly or considerably sloping.To study the sloping seabed transient response during marine earthquakes,an analytical solution induced by a P-wave line source embedded in the solid is presented.During the derivation,the wave fields in the fluid layer and the semi-infinite solid are firstly constructed by using the generalized ray method and the fluid-solid interface reflection and transmission coefficients.Then,the analytical solution in the transformed domain is obtained by superposing these wave fields,and the analytical solution in the time domain by applying the analytical inverse Laplace transform method.The the head wave generation conditions and arrival times at the fluid-solid interface are derived through this solution.Through the use of numerical examples,the analytical solution is proved right and the impacts of the sloping angle on the hydrodynamic pressure in the sea,the seismic wave propagation in the seabed,the head wave,and the Scholte wave at the seawater-seabed interface are also addressed.
基金National Natural Science Foundation of China under Grant Nos.51968047 and 51608249the Key Research and Development Program of Jiangxi Province under Grant No.20161BBG70058。
文摘Since masonry structures are prone to collapse in earthquakes,a novel joint reinforcement method with a polypropylene band(PP-band)and cement mortar(CM)has been put forward.Compared with the common reinforcement methods,this method not only facilitates construction but also ensures lower reinforcement cost.To systematically explore the influence of joint reinforcement on the seismic performance of masonry walls,quasi-static tests were carried out on six specimens with different reinforcement forms.The test results show that the joint action of PP-band and CM can significantly improve the specimen′s brittle failure characteristics and enhance the integrity of the specimen after cracking.Compared with the specimen without reinforcement,each of the seismic performance indexes of the joint reinforced specimen had obvious improvement.The maximum increased rate about peak load and ductility of the joint reinforced specimen is 100.6%and 233.4%,respectively.
基金supported by the National Natural Science Foundation of China(U2039209,U1534202,51408564)Natural Science Foundation of Heilongjiang Province(LH2021E119)the National Key Research and Development Program of China(2018YFC1504003).
文摘Purpose–Using the strong motion data ofK-net in Japan,the continuous magnitude prediction method based on support vector machine(SVM)was studied.Design/methodology/approach–In the range of 0.5–10.0 s after the P-wave arrival,the prediction time window was established at an interval of 0.5 s.12 P-wave characteristic parameters were selected as the model input parameters to construct the earthquake early warning(EEW)magnitude prediction model(SVM-HRM)for high-speed railway based on SVM.Findings–The magnitude prediction results of the SVM-HRM model were compared with the traditional magnitude prediction model and the high-speed railway EEW current norm.Results show that at the 3.0 s time window,themagnitude prediction error of the SVM-HRMmodel is obviously smaller than that of the traditionalτc method and Pd method.The overestimation of small earthquakes is obviously improved,and the construction of the model is not affected by epicenter distance,so it has generalization performance.For earthquake events with themagnitude range of 3–5,the single station realization rate of the SVM-HRMmodel reaches 95%at 0.5 s after the arrival of P-wave,which is better than the first alarm realization rate norm required by“The TestMethod of EEW andMonitoring Systemfor High-Speed Railway.”For earthquake eventswithmagnitudes ranging from3 to 5,5 to 7 and 7 to 8,the single station realization rate of the SVM-HRM model is at 0.5 s,1.5 s and 0.5 s after the P-wave arrival,respectively,which is better than the realization rate norm of multiple stations.Originality/value–At the latest,1.5 s after the P-wave arrival,the SVM-HRM model can issue the first earthquake alarm that meets the norm of magnitude prediction realization rate,which meets the accuracy and continuity requirements of high-speed railway EEW magnitude prediction.
基金Natural Science Foundation of Heilongjiang Province under Grant No.ZD2019E009Key Project of National Natural Science Foundation of China under Grant No.U1939209。
文摘The most important method of understanding liquefaction-induced engineering failures comes from the investigation and analysis of earthquake damage.In May 2021,the Maduo M_(s)7.4 earthquake occurred on the Tibetan Plateau of China.The most representative engineering disaster caused by this earthquake was bridge damage on liquefied sites.In this study,the mutual relationships between the anti-liquefaction pre-design situation,the ground motion intensity,the site liquefaction severity,and the bridge damage state for this earthquake were systematically analyzed for typical bridge damage on the liquefied sites.Using field survey data and the current Chinese industry code,simulations of the liquefaction scenarios at typical bridge sites were performed for the pre-design seismic ground motion before the earthquake and the seismic ground motion during the earthquake.By combining these results with post-earthquake investigation results,the reason for the serious bridge damage resulting from this earthquake is revealed,and the necessary conditions for avoiding serious seismic damage to bridges built in liquefiable sites is presented.
