Bedding parallel stepped rock slopes exist widely in nature and are used in slope engineering.They are characterized by complex topography and geological structure and are vulnerable to shattering under strong earthqu...Bedding parallel stepped rock slopes exist widely in nature and are used in slope engineering.They are characterized by complex topography and geological structure and are vulnerable to shattering under strong earthquakes.However,no previous studies have assessed the mechanisms underlying seismic failure in rock slopes.In this study,large-scale shaking table tests and numerical simulations were conducted to delineate the seismic failure mechanism in terms of acceleration,displacement,and earth pressure responses combined with shattering failure phenomena.The results reveal that acceleration response mutations usually occur within weak interlayers owing to their inferior performance,and these mutations may transform into potential sliding surfaces,thereby intensifying the nonlinear seismic response characteristics.Cumulative permanent displacements at the internal corners of the berms can induce quasi-rigid displacements at the external corners,leading to greater permanent displacements at the internal corners.Therefore,the internal corners are identified as the most susceptible parts of the slope.In addition,the concept of baseline offset was utilized to explain the mechanism of earth pressure responses,and the result indicates that residual earth pressures at the internal corners play a dominant role in causing deformation or shattering damage.Four evolutionary deformation phases characterize the processes of seismic responses and shattering failure of the bedding parallel stepped rock slope,i.e.the formation of tensile cracks at the internal corners of the berm,expansion of tensile cracks and bedding surface dislocation,development of vertical tensile cracks at the rear edge,and rock mass slipping leading to slope instability.Overall,this study provides a scientific basis for the seismic design of engineering slopes and offers valuable insights for further studies on preventing seismic disasters in bedding parallel stepped rock slopes.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
When an underground structure passes through a liquefiable soil layer,the soil liquefaction may pose a significant threat to the structure.A centrifuge shaking table test was performed to research the seismic response...When an underground structure passes through a liquefiable soil layer,the soil liquefaction may pose a significant threat to the structure.A centrifuge shaking table test was performed to research the seismic response of underground structures in liquefiable interlayer sites,and a valid numerical model was obtained through simulation model test.Finally,the calibrated numerical model was used to perform further research on the influence of various distribution characteristics of liquefiable interlayers on the seismic reaction of underground structures.The key findings are as follows.The structure faces the most unfavorable condition once a liquefiable layer is located in the middle of the underground structure.When a liquefiable layer exists in the middle of the structure,the seismic reactions of both the underground structure and model site will increase with the rise of the thickness of the liquefiable interlayer.The inter-story drift of the structure in the non-liquefiable site is much smaller than that in the liquefiable interlayer site.The inter-story drift of the structure is not only associated with the site displacement and the soil-structure stiffness ratio but also closely associated with the slippage of the soil-structure contact interface under the condition of large deformation of the site.展开更多
The seismic safety of the reinforcement dam slope is studied through shaking table test and numerical simulation.The dynamic characteristics of dam slopes,failure mechanism,seismic stability,as well as the effect of r...The seismic safety of the reinforcement dam slope is studied through shaking table test and numerical simulation.The dynamic characteristics of dam slopes,failure mechanism,seismic stability,as well as the effect of reinforcement during earthquakes are discussed.An elasto-plastic analysis method (FLAC) is used to simulate the dynamic failure process of the reinforcement dam slope.The change law of permanent displacement of dam slope is studied.The effect of the length and the space of reinforcement on the depth of slip surface and the slope stability are investigated.Good agreement is obtained between the numerical results and those from shaking table tests.The results show that the dynamic failure is a gradual process not at a particular time.With the increase of the reinforcement length or the decreasing reinforcement spacing,the slip surface becomes deeper and thus the slope stability is improved.The reinforcement can obviously enhance the overall stability of slope dam.It can also effectively control the shallow sliding of slope.These researches provide basic data for reinforcement measures design of earth-rockfill dam.展开更多
In order to study the infl uence of the ground motion spatial eff ect on the seismic response of large span spatial structures with isolation bearings, a single-layer cylindrical latticed shell scale model with a simi...In order to study the infl uence of the ground motion spatial eff ect on the seismic response of large span spatial structures with isolation bearings, a single-layer cylindrical latticed shell scale model with a similarity ratio of 1/10 was constructed. An earthquake simulation shaking table test on the response under multiple-support excitations was performed with the high-position seismic isolation method using high damping rubber (HDR) bearings. Small-amplitude sinusoidal waves and seismic wave records with various spectral characteristics were applied to the model. The dynamic characteristics of the model and the seismic isolation eff ect on it were analyzed at varying apparent wave velocities, namely infi nitely great, 1000 m/s, 500 m/s and 250 m/s. Besides, numerical simulations were carried out by Matlab software. According to the comparison results, the numerical results agreed well with the experimental data. Moreover, the results showed that the latticed shell roof exhibited a translational motion as a rigid body after the installation of the HDR bearings with a much lower natural frequency, higher damping ratio and only 1/2~1/8 of the acceleration response peak values. Meanwhile, the structural responses and the bearing deformations at the output end of the seismic waves were greatly increased under multiple-support excitations.展开更多
Studies on landslides by the 2008 Wenchuan earthquake showed that topography was of great importance in amplifying the seismic shaking, and among other factors, lithology and slope structure controlled the spatial occ...Studies on landslides by the 2008 Wenchuan earthquake showed that topography was of great importance in amplifying the seismic shaking, and among other factors, lithology and slope structure controlled the spatial occurrence of slope failures. The present study carried out experiments on four rock slopes with steep angle of 60° by means of a shaking table. The recorded Wenchuan earthquake waves were scaled to excite the model slopes. Measurements from accelerometers installed on free surface of the model slope were analyzed, with much effort on timedomain acceleration responses to horizontal components of seismic shaking. It was found that the amplification factor of peak horizontal acceleration, RPHA, was increasing with elevation of each model slope, though the upper and lower halves of the slope exhibited different increasing patterns. As excitation intensity was increased, the drastic deterioration of the inner structure of each slope caused the sudden increase of RPHA in the upper slope part. In addition, the model simulating the soft rock slope produced the larger RPHA than the model simulating the hard rock slope by a maximum factor of 2.6. The layered model slope also produced the larger RPHA than the homogeneous model slope by a maximum factor of 2.7. The upper half of a slope was influenced more seriously by the effect of lithology, while the lower half was influenced more seriously by the effect of slope structure.展开更多
To investigate the seismic response of the steel-strip reinforced soil retaining wall with fullheight rigid facing in terms of the acceleration in the backfill, dynamic earth pressure in the backfill, the displacement...To investigate the seismic response of the steel-strip reinforced soil retaining wall with fullheight rigid facing in terms of the acceleration in the backfill, dynamic earth pressure in the backfill, the displacements on the facing and the dynamic reinforcement strain distribution under different peak acceleration, a large 1-g shaking table test was performed on a reduced-scale reinforced-earth retaining wall model. It was observed that the acceleration response in non-strip region is greater than that in potential fracture region which is similar with the stability region under small earthquake,while the acceleration response in potential fracture region is greater than that in stability region in middle-upper of the wall under moderately strong earthquakes. The potential failure model of the rigid wall is rotating around the wall toe. It also was discovered that the Fourier spectra produced by the inputting white noises after seismic wave presents double peaks, rather than original single peak, and the frequency of the second peak trends to increase with increasing the PGA(peak ground amplitude) of the excitation which is greater than 0.4 g. Additionally,the non-liner distribution of strip strain along the strips was observed, and the distribution trend was not constant in different row. Soil pressure peak value in stability region is larger than that in potential fracture region. The wall was effective under 0.1 g-0.3 g seismic wave according to the analyses of the facing displacement and relative density. Also, it was discovered that the potential failure surface is corresponds to that in design code, but the area is larger. The results from the study can provide guidance for a more rational design of reinforced earth retaining walls with full-height rigid facing in the earthquake zone.展开更多
The seismic response characteristics of three-bucket jacket foundations for offshore wind turbines(OWTs)and the liquefaction of the surrounding soil are particularly important for the development and application of th...The seismic response characteristics of three-bucket jacket foundations for offshore wind turbines(OWTs)and the liquefaction of the surrounding soil are particularly important for the development and application of this type of structure for offshore use.Using the shaking table test and three-dimensional finite element analysis,different magnitudes of simulated earthquake waves were used as inputs to the shaking table to model seismic excitations.The resulting changes in the excess pore water pressure and acceleration response of the soil under horizontal earthquake are compared in this paper.Calculations of the anti-liquefaction shear stress and equivalent shearing stress during the earthquake,determination of the areas prone to liquefaction,and identification of the effect of the three-bucket jacket foundation on the soil liquefaction resistance were conducted by developing a soil-structure finite element model.The development law of the soil’s amplification effect on seismic acceleration and the seismic response of the foundation soil under various magnitude earthquake waves were also discussed.Results indicate that liquefying the soil inside the bucket of the foundation is more difficult than that outside the bucket during the excitation of seismic waves due to the large upper load and the restraint of the surrounding hoop.This finding confirms the advantages of the three-bucket jacket foundations in improving the liquefaction resistance of the soil inside the bucket.However,the confinement has a barely noticeable impact on the nearby soil outside the skirt.The phenomenon of soil liquefaction at the bottom of the skirt occurred earlier than that in other positions during the seismic excitation,and the excess pore water pressure slowly dissipated.The acceleration amplification coefficient of the sand outside the bucket increases with depth,but that of the sand inside the bucket is substantially inhibited in the height range of the bucket foundation.This result proves the inhibition effects of the three-bucket jacket foundations on the seismic responses of soils.The liquefied soil layer has a significant effect in absorbing a certain amount of seismic wave energy and reducing the amplification effect.The numerical simulation results are consistent with the phenomenon and data measured during the shaking table test.The current study also verifies the feasibility of the excess pore water pressure ratio and the anti-liquefaction shear stress method for judging soil liquefaction.展开更多
Based on the the large shaking table test results on irregular section subway station structure in soft soil,an overall time-history numerical simulation is conducted to study the nonlinear dynamic interaction of the ...Based on the the large shaking table test results on irregular section subway station structure in soft soil,an overall time-history numerical simulation is conducted to study the nonlinear dynamic interaction of the soilirregular underground structure.Typical test results,including the acceleration of the soil,acceleration,and deformation of the structure,were analyzed.Satisfactory consistency between the simulation and test results is verified,and the difference between these results was discussed in detail.The maximum inter-story drift ratio was approximately 1/472 under input PGA=0.54 g.The strain responses of columns were significantly larger than those of the side walls and slabs.The components in the lower layers of the irregular subway station structure,particularly in the central columns,underwent cumulative damage.The research results could provide a simplified analysis method to quantitatively evaluate the damage of irregular underground structures in soft soil.展开更多
It is considered thai the damage of the underground structures caused by earthquakes is minor for a long time. However, the catastrophic damages induced by several recent earthquakes （e. g. Kobe earthquake in 1995 ）...It is considered thai the damage of the underground structures caused by earthquakes is minor for a long time. However, the catastrophic damages induced by several recent earthquakes （e. g. Kobe earthquake in 1995 ） revealed that the study on the dynamic properties of the underground structures is indispensable. The dynamic behavior and damage mechanism of underground structure are analyzed by using shaking table tests （ both shallow-and deep-buried） and numerical simulation （3D FEM） including horizontal and vertical input motions, individually and simultaneously. From the results, the underground structure collapsed due to strong horizontal forces although vertical deformation is not negligible. The vertical excitation increases the response of structure, especially the stress and shear stress at the upper section; the soil influenced the property of soilstructure system. In the same excitation, the response in shallow-buried test is larger than deep case. Both overburden and vertical earthquake play important roles in the response of structure and those are two critical aspects in the design of the large-span underground structures, such as subway stations.展开更多
Seismic-induced liquefaction of sandy soils can fail foundations in the vicinity of buildings.To investigate the effect of a non-free field subsurface seismic history on the ability of saturated sandy soils to resist ...Seismic-induced liquefaction of sandy soils can fail foundations in the vicinity of buildings.To investigate the effect of a non-free field subsurface seismic history on the ability of saturated sandy soils to resist liquefaction,four shaking events with different accelerations were input to the sandy soils in the non-free-field.The results of the study revealed that:(1)Shallow soils that are not free-field undergo acceleration amplification effects after being subjected to seismic loading.(2)Building overburden pressure reduces the sensitivity of the shallow soils directly below in small and moderate earthquakes,which are more prone to rearranging and forming unstable structures under strong seismic effects.The excess pore pressure response on the load side resembles that of a free site,with the depth range of the liquefaction strength of soils affected by the seismic history,increasing progressively as input seismic intensity increases.(3)After experiencing earthquakes of different intensities,the excess pore pressure directly below the building overburden pressure at 0.1 m and 0.2 m is greater than that at the side.At the same time,the side of the building structure is more prone to liquefaction than the soil directly below it.展开更多
This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical ...This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical main factory building of a large thermal power plant. In order to investigate the seismic performance of this type of structure, several ground motion accelerations with different levels for seismic intensity Ⅷ, based on the Chinese Code for Seismic Design of Buildings, were selected to excite the model. The results show that the design methods of the members and the connections are adequate and that the structural system will perform well in regions of high seismicity. In addition to the tests, numerical simulations were also conducted and the results showed good agreement with the test results. Thus, the numerical model is shown to be accurate and the beam element can be used to model this structural system.展开更多
Structures behave multi-directionally when subjected to earthquake excitation. Thus, it is essential to evaluate the effect of multidirectional loading on the dynamic response and seismic performance of reinforced con...Structures behave multi-directionally when subjected to earthquake excitation. Thus, it is essential to evaluate the effect of multidirectional loading on the dynamic response and seismic performance of reinforced concrete bridge columns in order to develop more advanced and reliable design procedures. To investigate such effects, a 1/4 scaled circular reinforced concrete bridge column specimen was tested under two horizontal and one vertical components of a strong motion that has long duration with several strong pulses. Damage progress of reinforced concrete columns subjected to strong excitation was evaluated from the test. The test results demonstrate that the lateral force response in the principal directions become smaller than computed flexural capacity due to the bilateral flexural loading effects, and that the lateral response is not significantly affected by the fluctuation of the axial force because the horizontal response and axial force barely reached the maximum simultaneously due to difference of the predominant natural periods between the vertical and the horizontal directions. Accuracy of fiber analyses is discussed using the test results.展开更多
This paper describes shaking table tests of three eight-story building models： all are masonry structures in the upper stories, with or without frame-shear walls of one- or two- stories at the bottom. The test result...This paper describes shaking table tests of three eight-story building models： all are masonry structures in the upper stories, with or without frame-shear walls of one- or two- stories at the bottom. The test results of damage characteristics and seismic responses are provided and compared. Then, nonlinear response analyses are conducted to examine the reliability of the dynamic analysis. Finally, many nonlinear response analyses are performed and it is concluded that for relatively hard sites under a certain lateral stiffness ratio （i.e., the ratio of the stiffness of the lowest upper masonry story to that of the frame- shear wall story）, the masonry structure with one-story frame-shear wall at the bottom performs better than a structure built entirely of masonry, and a masonry structure with frame-shear wall of two stories performs better than with one-story frame- shear wall. In relatively soft soil conditions, all three structures have similar performane. In addition, some suggestions that could be helpful for design of masonry structures with ground story of frame-shear wall structure in seismic intensity region VII, such as the appropriate lateral stiffness ratio, shear force increase factor of the frame-shear wall story, and permissible maximum height of the building, are proposed.展开更多
Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure o...Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure on soft site,and analyze its isolation effect.Test results show that the test can reflect the earthquake response characteristics of isolated structure on soft site.It is on soft site that the dynamic characteristics of isolated structure,acceleration magnification factor(AMF)of isolated structure and isolation efficiency of the isolation layer differ from those on rigid foundation with an soil-structure interaction(SSI)effect,represented by the reduction in fundamental vibration frequency of isolated structure and the increase of damping ratio with changes of the SSI effect.SSI can either increase or decrease AMF of isolated structure on soft site,depending on the characteristics of earthquake motion input.Furthermore,the isolation efficiency of isolation layer on soft site is decreased with the SSI effect,which is related to the peak ground acceleration(PGA)and the characteristics of earthquake motion input.展开更多
As the offshore wind turbine foundation,the four-bucket jacket foundation has a large stiffness and the structure is difficult to be damaged under seismic load.Nevertheless,the saturated subsoil of the four-bucket jac...As the offshore wind turbine foundation,the four-bucket jacket foundation has a large stiffness and the structure is difficult to be damaged under seismic load.Nevertheless,the saturated subsoil of the four-bucket jacket foundation tends to be liquefied under earthquake,which greatly affects the safety of offshore wind turbine.Therefore,the seismic performance of four-bucket jacket foundation is mainly reflected in the anti-liquefaction capacity of foundation soil.In this paper,the liquefaction resistance of sandy soil of four-bucket jacket foundation for offshore wind turbine is studied.The liquefaction and dynamic response of sandy soil foundation of four-bucket jacket foundation under seismic load are obtained by carrying out the shaking table test,and the influence mechanism of four-bucket jacket foundation on the liquefaction resistance of sandy soil foundation is analyzed.展开更多
This paper aims to investigate the seismic motion characteristics of bedrock and overburden layer slope with the prototype model taken from slopes in the Zheduo Mountain in Northwest Plateau of Sichuan Province,China....This paper aims to investigate the seismic motion characteristics of bedrock and overburden layer slope with the prototype model taken from slopes in the Zheduo Mountain in Northwest Plateau of Sichuan Province,China.Based on dimensional analysis and similarity principle,two model tests with different slope angles were carried out.A transfer function analysis method was proposed to interpret the results from shaking table tests.After eliminating trend terms and signal filtering,the time-domain acceleration was transformed into frequency domain.Then the transfer function was calculated by an average periodic chart.The variation of transfer function from different positions was analyzed by Pearson correlation coefficient,and the least square iteration method was used for modal analysis.The effect of seismic intensity on the dynamic response was highlighted.It is found that the transfer function obviously changes when the slopes are destroyed.Results from modal analysis show that the natural frequency decreases with the increase of the excitation intensity,and the damping ratio increases due to slope damage.展开更多
Experimental data taken from free-field soil in 1-g shaking table tests are valuable for seismic studies on soil-structure interaction.But the available data from medium-to large-scale shaking table tests were not abu...Experimental data taken from free-field soil in 1-g shaking table tests are valuable for seismic studies on soil-structure interaction.But the available data from medium-to large-scale shaking table tests were not abundant enough to cover a large variety of types and conditions of the soil.In the study,1-g shaking table tests of a 3-m-height sand column were conducted to provide seismic experimental data about sand.The sand was directly collected in-situ,with the largest grain diameter being 2 cm and containing a water content of 6.3%.Properties of the sand were estimated under the influence of white noise plus pulse and earthquake motions,including the settlement,the dynamic properties of the sand column,and the three soil layers′shear modulus degradation relationships.The estimated properties were then indirectly verified by means of finite element analysis.Results show that the estimated parameters were effective and could be used in numerical modeling to reproduce approximate seismic responses of the sand column.展开更多
The model test of seismic simulation shaking table is an important method to study the seismic design of bridge structure. In order to evaluate the seismic response and dynamic characteristics of pile-water-pier syste...The model test of seismic simulation shaking table is an important method to study the seismic design of bridge structure. In order to evaluate the seismic response and dynamic characteristics of pile-water-pier system for developing more reliable design procedures, shaking table model tests of a submerged bridge pier system, including pile groups-cap-pier and inertia mass, were conducted. Since different similitude laws corresponding to different test objectives affected the validity of test results, the similitude law with the aim to consider the effect of hydrodynamic pressure was proposed and confirmed through an actual example. Based on the test results, the effect of water around model on seismic response under seismic excitation input was analyzed and the failure level was judged by observing the variation of basic frequency. The test results indicate that the transfer function of analytical model with water is different from that without water, the natural frequency without water is always higher than that with water, and the first modal shapes are various. It is also concluded that the similitude law is suitable for practical application and the dynamic characteristics and seismic response of the structure system can be changed because of the existence of the surrounding water, which should be paid much attention in the further investigation.展开更多
To explore the cumulative deformation effect of the dynamic response of a tunnel crossing the hauling sliding surface under earthquakes,the shaking table test was conducted in this study.Combined with the numerical ca...To explore the cumulative deformation effect of the dynamic response of a tunnel crossing the hauling sliding surface under earthquakes,the shaking table test was conducted in this study.Combined with the numerical calculations,this study proposed magnification of the Arias intensity(MIa)to characterize the overall local deformation damage of the tunnel lining in terms of the deformation characteristics,frequency domain,and energy.Using the time‐domain analysis method,the plastic effect coefficient(PEC)was proposed to characterize the degree of plastic deformation,and the applicability of the seismic cumulative failure effect(SCFE)was discussed.The results show that the low‐frequency component(f1 and f2≤10 Hz)and the high‐frequency component(f3 and f4>10 Hz)acceleration mainly cause global and local deformation of the tunnel lining.The local deformation caused by the high‐frequency wave has an important effect on the seismic damage of the lining.The physical meaning of PEC is more clearly defined than that of the residual strain,and the SCFE of the tunnel lining can also be defined.The SCFE of the tunnel lining includes the elastic deformation effect stage(<0.15g),the elastic–plastic deformation effect stage(0.15g–0.30g),and the plastic deformation effect stage(0.30g–0.40g).This study can provide valuable theoretical and technical support for the construction of traffic tunnels in high‐intensity earthquake areas.展开更多
基金supported by the National Natural Science Foundation of China (Grant No.52108361)the Sichuan Science and Technology Program of China (Grant No.2023YFS0436)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project (Grant No.SKLGP2022Z015).
文摘Bedding parallel stepped rock slopes exist widely in nature and are used in slope engineering.They are characterized by complex topography and geological structure and are vulnerable to shattering under strong earthquakes.However,no previous studies have assessed the mechanisms underlying seismic failure in rock slopes.In this study,large-scale shaking table tests and numerical simulations were conducted to delineate the seismic failure mechanism in terms of acceleration,displacement,and earth pressure responses combined with shattering failure phenomena.The results reveal that acceleration response mutations usually occur within weak interlayers owing to their inferior performance,and these mutations may transform into potential sliding surfaces,thereby intensifying the nonlinear seismic response characteristics.Cumulative permanent displacements at the internal corners of the berms can induce quasi-rigid displacements at the external corners,leading to greater permanent displacements at the internal corners.Therefore,the internal corners are identified as the most susceptible parts of the slope.In addition,the concept of baseline offset was utilized to explain the mechanism of earth pressure responses,and the result indicates that residual earth pressures at the internal corners play a dominant role in causing deformation or shattering damage.Four evolutionary deformation phases characterize the processes of seismic responses and shattering failure of the bedding parallel stepped rock slope,i.e.the formation of tensile cracks at the internal corners of the berm,expansion of tensile cracks and bedding surface dislocation,development of vertical tensile cracks at the rear edge,and rock mass slipping leading to slope instability.Overall,this study provides a scientific basis for the seismic design of engineering slopes and offers valuable insights for further studies on preventing seismic disasters in bedding parallel stepped rock slopes.
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National Natural Science Foundation of China under Grant No.52078020。
文摘When an underground structure passes through a liquefiable soil layer,the soil liquefaction may pose a significant threat to the structure.A centrifuge shaking table test was performed to research the seismic response of underground structures in liquefiable interlayer sites,and a valid numerical model was obtained through simulation model test.Finally,the calibrated numerical model was used to perform further research on the influence of various distribution characteristics of liquefiable interlayers on the seismic reaction of underground structures.The key findings are as follows.The structure faces the most unfavorable condition once a liquefiable layer is located in the middle of the underground structure.When a liquefiable layer exists in the middle of the structure,the seismic reactions of both the underground structure and model site will increase with the rise of the thickness of the liquefiable interlayer.The inter-story drift of the structure in the non-liquefiable site is much smaller than that in the liquefiable interlayer site.The inter-story drift of the structure is not only associated with the site displacement and the soil-structure stiffness ratio but also closely associated with the slippage of the soil-structure contact interface under the condition of large deformation of the site.
基金Sponsored by the National Natural Science Fund for Distinguished Young Scholars (Grant No. 50808032 )the National Key Basic Research Program(Grant No. 2008CB425801)+2 种基金the National Natural Science Fund for Hydropower Development of Yalongjiang Project (Grant No. 50679093)the National Mega-project of Natural Science Foundation Program (Grant No. 90815024)the Innovative Research Team in Universities Program Funded by Ministry of Education,China (Grant No. IRT0518)
文摘The seismic safety of the reinforcement dam slope is studied through shaking table test and numerical simulation.The dynamic characteristics of dam slopes,failure mechanism,seismic stability,as well as the effect of reinforcement during earthquakes are discussed.An elasto-plastic analysis method (FLAC) is used to simulate the dynamic failure process of the reinforcement dam slope.The change law of permanent displacement of dam slope is studied.The effect of the length and the space of reinforcement on the depth of slip surface and the slope stability are investigated.Good agreement is obtained between the numerical results and those from shaking table tests.The results show that the dynamic failure is a gradual process not at a particular time.With the increase of the reinforcement length or the decreasing reinforcement spacing,the slip surface becomes deeper and thus the slope stability is improved.The reinforcement can obviously enhance the overall stability of slope dam.It can also effectively control the shallow sliding of slope.These researches provide basic data for reinforcement measures design of earth-rockfill dam.
基金National Natural Science Foundation of China under Grant No.51278008the National Key Research and Development Plan of China under Grant No.2016YFC0701103
文摘In order to study the infl uence of the ground motion spatial eff ect on the seismic response of large span spatial structures with isolation bearings, a single-layer cylindrical latticed shell scale model with a similarity ratio of 1/10 was constructed. An earthquake simulation shaking table test on the response under multiple-support excitations was performed with the high-position seismic isolation method using high damping rubber (HDR) bearings. Small-amplitude sinusoidal waves and seismic wave records with various spectral characteristics were applied to the model. The dynamic characteristics of the model and the seismic isolation eff ect on it were analyzed at varying apparent wave velocities, namely infi nitely great, 1000 m/s, 500 m/s and 250 m/s. Besides, numerical simulations were carried out by Matlab software. According to the comparison results, the numerical results agreed well with the experimental data. Moreover, the results showed that the latticed shell roof exhibited a translational motion as a rigid body after the installation of the HDR bearings with a much lower natural frequency, higher damping ratio and only 1/2~1/8 of the acceleration response peak values. Meanwhile, the structural responses and the bearing deformations at the output end of the seismic waves were greatly increased under multiple-support excitations.
基金financially supported by the National Basic Research Program "973" Project of the Ministry of Science and Technology of the People’s Republic of China (Grant No. 2013CB733200)the National Science Found for Distinguished Young Scholars of China (Grant No. 41225011)the Chang Jiang Scholars Program of China and the open fund on "Research on largescale landslides triggered by the Wenchuan earthquake" provided by the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection
文摘Studies on landslides by the 2008 Wenchuan earthquake showed that topography was of great importance in amplifying the seismic shaking, and among other factors, lithology and slope structure controlled the spatial occurrence of slope failures. The present study carried out experiments on four rock slopes with steep angle of 60° by means of a shaking table. The recorded Wenchuan earthquake waves were scaled to excite the model slopes. Measurements from accelerometers installed on free surface of the model slope were analyzed, with much effort on timedomain acceleration responses to horizontal components of seismic shaking. It was found that the amplification factor of peak horizontal acceleration, RPHA, was increasing with elevation of each model slope, though the upper and lower halves of the slope exhibited different increasing patterns. As excitation intensity was increased, the drastic deterioration of the inner structure of each slope caused the sudden increase of RPHA in the upper slope part. In addition, the model simulating the soft rock slope produced the larger RPHA than the model simulating the hard rock slope by a maximum factor of 2.6. The layered model slope also produced the larger RPHA than the homogeneous model slope by a maximum factor of 2.7. The upper half of a slope was influenced more seriously by the effect of lithology, while the lower half was influenced more seriously by the effect of slope structure.
基金founded by the National Natural Science Foundation of China(Grant No.51708163)Research Program of the Ministry of Transport of the People’s Republic of China(Grant No.2013318800020)Doctoral Innovation Fund Program of Southwest Jiaotong University(Grant No.D-CX201703)
文摘To investigate the seismic response of the steel-strip reinforced soil retaining wall with fullheight rigid facing in terms of the acceleration in the backfill, dynamic earth pressure in the backfill, the displacements on the facing and the dynamic reinforcement strain distribution under different peak acceleration, a large 1-g shaking table test was performed on a reduced-scale reinforced-earth retaining wall model. It was observed that the acceleration response in non-strip region is greater than that in potential fracture region which is similar with the stability region under small earthquake,while the acceleration response in potential fracture region is greater than that in stability region in middle-upper of the wall under moderately strong earthquakes. The potential failure model of the rigid wall is rotating around the wall toe. It also was discovered that the Fourier spectra produced by the inputting white noises after seismic wave presents double peaks, rather than original single peak, and the frequency of the second peak trends to increase with increasing the PGA(peak ground amplitude) of the excitation which is greater than 0.4 g. Additionally,the non-liner distribution of strip strain along the strips was observed, and the distribution trend was not constant in different row. Soil pressure peak value in stability region is larger than that in potential fracture region. The wall was effective under 0.1 g-0.3 g seismic wave according to the analyses of the facing displacement and relative density. Also, it was discovered that the potential failure surface is corresponds to that in design code, but the area is larger. The results from the study can provide guidance for a more rational design of reinforced earth retaining walls with full-height rigid facing in the earthquake zone.
基金the National Natural Science Foundation of China(No.52171274)。
文摘The seismic response characteristics of three-bucket jacket foundations for offshore wind turbines(OWTs)and the liquefaction of the surrounding soil are particularly important for the development and application of this type of structure for offshore use.Using the shaking table test and three-dimensional finite element analysis,different magnitudes of simulated earthquake waves were used as inputs to the shaking table to model seismic excitations.The resulting changes in the excess pore water pressure and acceleration response of the soil under horizontal earthquake are compared in this paper.Calculations of the anti-liquefaction shear stress and equivalent shearing stress during the earthquake,determination of the areas prone to liquefaction,and identification of the effect of the three-bucket jacket foundation on the soil liquefaction resistance were conducted by developing a soil-structure finite element model.The development law of the soil’s amplification effect on seismic acceleration and the seismic response of the foundation soil under various magnitude earthquake waves were also discussed.Results indicate that liquefying the soil inside the bucket of the foundation is more difficult than that outside the bucket during the excitation of seismic waves due to the large upper load and the restraint of the surrounding hoop.This finding confirms the advantages of the three-bucket jacket foundations in improving the liquefaction resistance of the soil inside the bucket.However,the confinement has a barely noticeable impact on the nearby soil outside the skirt.The phenomenon of soil liquefaction at the bottom of the skirt occurred earlier than that in other positions during the seismic excitation,and the excess pore water pressure slowly dissipated.The acceleration amplification coefficient of the sand outside the bucket increases with depth,but that of the sand inside the bucket is substantially inhibited in the height range of the bucket foundation.This result proves the inhibition effects of the three-bucket jacket foundations on the seismic responses of soils.The liquefied soil layer has a significant effect in absorbing a certain amount of seismic wave energy and reducing the amplification effect.The numerical simulation results are consistent with the phenomenon and data measured during the shaking table test.The current study also verifies the feasibility of the excess pore water pressure ratio and the anti-liquefaction shear stress method for judging soil liquefaction.
基金funding support provided by the National Natural Science Foundation of China(Grant No.51908216)the Program of Major Disciplines,Academic and Technical Leaders of Jiangxi Province(Grant No.20204BCJL23032)+1 种基金Scientific Research Fund of the Institute of Engineering Mechanics,China Earthquake Administration(Grant No.2020D18)Natural Science Foundation of Jiangxi Province(Grant No.S2020QNJJB1234)。
文摘Based on the the large shaking table test results on irregular section subway station structure in soft soil,an overall time-history numerical simulation is conducted to study the nonlinear dynamic interaction of the soilirregular underground structure.Typical test results,including the acceleration of the soil,acceleration,and deformation of the structure,were analyzed.Satisfactory consistency between the simulation and test results is verified,and the difference between these results was discussed in detail.The maximum inter-story drift ratio was approximately 1/472 under input PGA=0.54 g.The strain responses of columns were significantly larger than those of the side walls and slabs.The components in the lower layers of the irregular subway station structure,particularly in the central columns,underwent cumulative damage.The research results could provide a simplified analysis method to quantitatively evaluate the damage of irregular underground structures in soft soil.
文摘It is considered thai the damage of the underground structures caused by earthquakes is minor for a long time. However, the catastrophic damages induced by several recent earthquakes （e. g. Kobe earthquake in 1995 ） revealed that the study on the dynamic properties of the underground structures is indispensable. The dynamic behavior and damage mechanism of underground structure are analyzed by using shaking table tests （ both shallow-and deep-buried） and numerical simulation （3D FEM） including horizontal and vertical input motions, individually and simultaneously. From the results, the underground structure collapsed due to strong horizontal forces although vertical deformation is not negligible. The vertical excitation increases the response of structure, especially the stress and shear stress at the upper section; the soil influenced the property of soilstructure system. In the same excitation, the response in shallow-buried test is larger than deep case. Both overburden and vertical earthquake play important roles in the response of structure and those are two critical aspects in the design of the large-span underground structures, such as subway stations.
基金National Natural Science Foundation of China under Grant No.U21A20164National Science Fund for Distinguished Young Scholars of China under Grant No.51825904。
文摘Seismic-induced liquefaction of sandy soils can fail foundations in the vicinity of buildings.To investigate the effect of a non-free field subsurface seismic history on the ability of saturated sandy soils to resist liquefaction,four shaking events with different accelerations were input to the sandy soils in the non-free-field.The results of the study revealed that:(1)Shallow soils that are not free-field undergo acceleration amplification effects after being subjected to seismic loading.(2)Building overburden pressure reduces the sensitivity of the shallow soils directly below in small and moderate earthquakes,which are more prone to rearranging and forming unstable structures under strong seismic effects.The excess pore pressure response on the load side resembles that of a free site,with the depth range of the liquefaction strength of soils affected by the seismic history,increasing progressively as input seismic intensity increases.(3)After experiencing earthquakes of different intensities,the excess pore pressure directly below the building overburden pressure at 0.1 m and 0.2 m is greater than that at the side.At the same time,the side of the building structure is more prone to liquefaction than the soil directly below it.
基金Northeast Electric Power Design Institute of China Under Grant No.K07-T716
文摘This paper describes shaking table tests of a 1：12 scale model of a special concentrically braced steel frame with pinned connections, which was fabricated according to a one-bay braced frame selected from a typical main factory building of a large thermal power plant. In order to investigate the seismic performance of this type of structure, several ground motion accelerations with different levels for seismic intensity Ⅷ, based on the Chinese Code for Seismic Design of Buildings, were selected to excite the model. The results show that the design methods of the members and the connections are adequate and that the structural system will perform well in regions of high seismicity. In addition to the tests, numerical simulations were also conducted and the results showed good agreement with the test results. Thus, the numerical model is shown to be accurate and the beam element can be used to model this structural system.
基金NEES/E-Defense Collaboration ResearchProjects for Bridges of the National Research Institute forEarth Science and Disaster Prevention (NIED), Japan.
文摘Structures behave multi-directionally when subjected to earthquake excitation. Thus, it is essential to evaluate the effect of multidirectional loading on the dynamic response and seismic performance of reinforced concrete bridge columns in order to develop more advanced and reliable design procedures. To investigate such effects, a 1/4 scaled circular reinforced concrete bridge column specimen was tested under two horizontal and one vertical components of a strong motion that has long duration with several strong pulses. Damage progress of reinforced concrete columns subjected to strong excitation was evaluated from the test. The test results demonstrate that the lateral force response in the principal directions become smaller than computed flexural capacity due to the bilateral flexural loading effects, and that the lateral response is not significantly affected by the fluctuation of the axial force because the horizontal response and axial force barely reached the maximum simultaneously due to difference of the predominant natural periods between the vertical and the horizontal directions. Accuracy of fiber analyses is discussed using the test results.
基金China Joint Earthquake Science Foundation Under Grant No. 95034National Science Foundation of China Under Grant No. 5067816
文摘This paper describes shaking table tests of three eight-story building models： all are masonry structures in the upper stories, with or without frame-shear walls of one- or two- stories at the bottom. The test results of damage characteristics and seismic responses are provided and compared. Then, nonlinear response analyses are conducted to examine the reliability of the dynamic analysis. Finally, many nonlinear response analyses are performed and it is concluded that for relatively hard sites under a certain lateral stiffness ratio （i.e., the ratio of the stiffness of the lowest upper masonry story to that of the frame- shear wall story）, the masonry structure with one-story frame-shear wall at the bottom performs better than a structure built entirely of masonry, and a masonry structure with frame-shear wall of two stories performs better than with one-story frame- shear wall. In relatively soft soil conditions, all three structures have similar performane. In addition, some suggestions that could be helpful for design of masonry structures with ground story of frame-shear wall structure in seismic intensity region VII, such as the appropriate lateral stiffness ratio, shear force increase factor of the frame-shear wall story, and permissible maximum height of the building, are proposed.
基金supported by the Jiangsu Natural Science Foundation of China(Grant No.BK2012477)the Science Research Foundation of Nanjing Institute of Technology(CKJA201505,JCYJ201618)
文摘Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure on soft site,and analyze its isolation effect.Test results show that the test can reflect the earthquake response characteristics of isolated structure on soft site.It is on soft site that the dynamic characteristics of isolated structure,acceleration magnification factor(AMF)of isolated structure and isolation efficiency of the isolation layer differ from those on rigid foundation with an soil-structure interaction(SSI)effect,represented by the reduction in fundamental vibration frequency of isolated structure and the increase of damping ratio with changes of the SSI effect.SSI can either increase or decrease AMF of isolated structure on soft site,depending on the characteristics of earthquake motion input.Furthermore,the isolation efficiency of isolation layer on soft site is decreased with the SSI effect,which is related to the peak ground acceleration(PGA)and the characteristics of earthquake motion input.
基金financially supported by the National Natural Science Foundation of China(Grant No.52171274).
文摘As the offshore wind turbine foundation,the four-bucket jacket foundation has a large stiffness and the structure is difficult to be damaged under seismic load.Nevertheless,the saturated subsoil of the four-bucket jacket foundation tends to be liquefied under earthquake,which greatly affects the safety of offshore wind turbine.Therefore,the seismic performance of four-bucket jacket foundation is mainly reflected in the anti-liquefaction capacity of foundation soil.In this paper,the liquefaction resistance of sandy soil of four-bucket jacket foundation for offshore wind turbine is studied.The liquefaction and dynamic response of sandy soil foundation of four-bucket jacket foundation under seismic load are obtained by carrying out the shaking table test,and the influence mechanism of four-bucket jacket foundation on the liquefaction resistance of sandy soil foundation is analyzed.
基金financially supported by National Natural Science Foundation of China(No.52078426)National Key Research and Development Plan(Grant No.2018YFE0207100)Sichuan Provincial Science and Technology Support Project(Grant No.2020YJ0253,c)。
文摘This paper aims to investigate the seismic motion characteristics of bedrock and overburden layer slope with the prototype model taken from slopes in the Zheduo Mountain in Northwest Plateau of Sichuan Province,China.Based on dimensional analysis and similarity principle,two model tests with different slope angles were carried out.A transfer function analysis method was proposed to interpret the results from shaking table tests.After eliminating trend terms and signal filtering,the time-domain acceleration was transformed into frequency domain.Then the transfer function was calculated by an average periodic chart.The variation of transfer function from different positions was analyzed by Pearson correlation coefficient,and the least square iteration method was used for modal analysis.The effect of seismic intensity on the dynamic response was highlighted.It is found that the transfer function obviously changes when the slopes are destroyed.Results from modal analysis show that the natural frequency decreases with the increase of the excitation intensity,and the damping ratio increases due to slope damage.
基金Supported by:National Natural Science Foundation of China under Grant Nos.52008233 and U1839201the National Key Research and Development Program of China under Grant No.2018YFC1504305the Innovative Research Groups of the National Natural Science Foundation of China under Grant No.51421005。
文摘Experimental data taken from free-field soil in 1-g shaking table tests are valuable for seismic studies on soil-structure interaction.But the available data from medium-to large-scale shaking table tests were not abundant enough to cover a large variety of types and conditions of the soil.In the study,1-g shaking table tests of a 3-m-height sand column were conducted to provide seismic experimental data about sand.The sand was directly collected in-situ,with the largest grain diameter being 2 cm and containing a water content of 6.3%.Properties of the sand were estimated under the influence of white noise plus pulse and earthquake motions,including the settlement,the dynamic properties of the sand column,and the three soil layers′shear modulus degradation relationships.The estimated properties were then indirectly verified by means of finite element analysis.Results show that the estimated parameters were effective and could be used in numerical modeling to reproduce approximate seismic responses of the sand column.
基金National Basic Research Program of China ("973" Program,No.2011CB013605-4)National Natural Science Foundation of China(No.51178079)Major Program of National Natural Science Foundation of China (No.90915011)
文摘The model test of seismic simulation shaking table is an important method to study the seismic design of bridge structure. In order to evaluate the seismic response and dynamic characteristics of pile-water-pier system for developing more reliable design procedures, shaking table model tests of a submerged bridge pier system, including pile groups-cap-pier and inertia mass, were conducted. Since different similitude laws corresponding to different test objectives affected the validity of test results, the similitude law with the aim to consider the effect of hydrodynamic pressure was proposed and confirmed through an actual example. Based on the test results, the effect of water around model on seismic response under seismic excitation input was analyzed and the failure level was judged by observing the variation of basic frequency. The test results indicate that the transfer function of analytical model with water is different from that without water, the natural frequency without water is always higher than that with water, and the first modal shapes are various. It is also concluded that the similitude law is suitable for practical application and the dynamic characteristics and seismic response of the structure system can be changed because of the existence of the surrounding water, which should be paid much attention in the further investigation.
基金National Key R&D Program of China,Grant/Award Number:2018YFC1504901Science and technology program of Gansu Province,Grant/Award Numbers:21JR7RA738,21JR7RA739+1 种基金Science and Technology Development Project of China Railway Research Institute Co.Ltd,Grant/Award Number:2017‐KJ008‐Z008‐XBNatural Science Foundation of Gansu Province,Grant/Award Number:145RJZA068。
文摘To explore the cumulative deformation effect of the dynamic response of a tunnel crossing the hauling sliding surface under earthquakes,the shaking table test was conducted in this study.Combined with the numerical calculations,this study proposed magnification of the Arias intensity(MIa)to characterize the overall local deformation damage of the tunnel lining in terms of the deformation characteristics,frequency domain,and energy.Using the time‐domain analysis method,the plastic effect coefficient(PEC)was proposed to characterize the degree of plastic deformation,and the applicability of the seismic cumulative failure effect(SCFE)was discussed.The results show that the low‐frequency component(f1 and f2≤10 Hz)and the high‐frequency component(f3 and f4>10 Hz)acceleration mainly cause global and local deformation of the tunnel lining.The local deformation caused by the high‐frequency wave has an important effect on the seismic damage of the lining.The physical meaning of PEC is more clearly defined than that of the residual strain,and the SCFE of the tunnel lining can also be defined.The SCFE of the tunnel lining includes the elastic deformation effect stage(<0.15g),the elastic–plastic deformation effect stage(0.15g–0.30g),and the plastic deformation effect stage(0.30g–0.40g).This study can provide valuable theoretical and technical support for the construction of traffic tunnels in high‐intensity earthquake areas.
