Soil nonlinear behavior displays noticeable effects on the site seismic response.This study proposes a new functional expression of the skeleton curve to replace the hyperbolic skeleton curve.By integrating shear modu...Soil nonlinear behavior displays noticeable effects on the site seismic response.This study proposes a new functional expression of the skeleton curve to replace the hyperbolic skeleton curve.By integrating shear modulus and combining the dynamic skeleton curve and the damping degradation coefficient,the constitutive equation of the logarithmic dynamic skeleton can be obtained,which considers the damping effect in a soil dynamics problem.Based on the finite difference method and the multi-transmitting boundary condition,a 1D site seismic response analysis program called Soilresp1D has been developed herein and used to analyze the time-domain seismic response in three types of sites.At the same time,this study also provides numerical simulation results based on the hyperbolic constitutive model and the equivalent linear method.The results verify the rationality of the new soil dynamic constitutive model.It can analyze the mucky soil site nonlinear seismic response,reflecting the deformation characteristics and damping effect of the silty soil.The hysteresis loop area is more extensive,and the residual strain is evident.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
Case history investigations have shown that pile foundations are more critically damaged in liquefiable soils than non-liquefiable soils.This study examines the differences in seismic response of pile foundations in l...Case history investigations have shown that pile foundations are more critically damaged in liquefiable soils than non-liquefiable soils.This study examines the differences in seismic response of pile foundations in liquefiable and non-liquefiable soils and their sensitivity to numerical model parameters.A two-dimensional finite element(FE)model is developed to simulate the experiment of a single pile foundation centrifuge in liquefiable soil subjected to earthquake motions and is validated against real-world test results.The differences in soil-pile seismic response of liquefiable and non-liquefiable soils are explored.Specifically,the first-order second-moment method(FOSM)is used for sensitivity analysis of the seismic response.The results show significant differences in seismic response for a soil-pile system between liquefiable and non-liquefiable soil.The seismic responses are found to be significantly larger in liquefiable soil than in non-liquefiable soil.Moreover,the pile bending moment was mainly affected by the kinematic effect in liquefiable soil,while the inertial effect was more significant in non-liquefiable soil.The controlling parameters of seismic response were PGA,soil density,and friction angle in liquefiable soil,while the pile bending moment was mainly controlled by PGA,the friction angle of soil,and shear modulus of loose sand in non-liquefiable soil.展开更多
Monitoring the change in horizontal stress from the geophysical data is a tough challenge, and it has a crucial impact on broad practical scenarios which involve reservoir exploration and development, carbon dioxide (...Monitoring the change in horizontal stress from the geophysical data is a tough challenge, and it has a crucial impact on broad practical scenarios which involve reservoir exploration and development, carbon dioxide (CO_(2)) injection and storage, shallow surface prospecting and deep-earth structure description. The change in in-situ stress induced by hydrocarbon production and localized tectonic movements causes the changes in rock mechanic properties (e.g. wave velocities, density and anisotropy) and further causes the changes in seismic amplitudes, phases and travel times. In this study, the nonlinear elasticity theory that regards the rock skeleton (solid phase) and pore fluid as an effective whole is used to characterize the effect of horizontal principal stress on rock overall elastic properties and the stress-dependent anisotropy parameters are therefore formulated. Then the approximate P-wave, SV-wave and SH-wave angle-dependent reflection coefficient equations for the horizontal-stress-induced anisotropic media are proposed. It is shown that, on the different reflectors, the stress-induced relative changes in reflectivities (i.e., relative difference) of elastic parameters (i.e., P- and S-wave velocities and density) are much less than the changes in contrasts of anisotropy parameters. Therefore, the effects of stress change on the reflectivities of three elastic parameters are reasonably neglected to further propose an AVO inversion approach incorporating P-, SH- and SV-wave information to estimate the change in horizontal principal stress from the corresponding time-lapse seismic data. Compared with the existing methods, our method eliminates the need for man-made rock-physical or fitting parameters, providing more stable predictive power. 1D test illustrates that the estimated result from time-lapse P-wave reflection data shows the most reasonable agreement with the real model, while the estimated result from SH-wave reflection data shows the largest bias. 2D test illustrates the feasibility of the proposed inversion method for estimating the change in horizontal stress from P-wave time-lapse seismic data.展开更多
We presented a boundary element method using the approximate analytical Green's function given by Sánchez-Sesma et al.Coordinate transform is introduced to extend the method to deal with the model with consta...We presented a boundary element method using the approximate analytical Green's function given by Sánchez-Sesma et al.Coordinate transform is introduced to extend the method to deal with the model with constant-gradient velocity along oblique direction.The method is validated by comparing the numerical results with other independent methods.This method provides a useful tool for analyzing local site effects.We computed seismic response for two series of models.The results in both frequency and time domains are analyzed and show complex amplification patterns.The fundamental mode of resonance is dependent not only on the velocity at the free surface but also on the velocity distribution of the whole basin.For the higher modes of vibration the heterogeneous basin also has its own characteristic.展开更多
Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its de...Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its design and operation processes all depend on finite element method.However,in engineering practice,there is always deviations between the theoretical and the measured responses due to the inaccurate value of the structural parameters in the model.The structure parameters identification of VPS within NPP is still an unexplored domain to a large extent.In this paper,the initial 2D-finite element model(FEM)for VPS with a DN80 gate valve was updated by utilizing seismic response.The objective function used in the model updating procedure is the vibration control equation error of the VPS.The experimental results show that the updated 2D-FEM can accurately predict the original dynamic characteristic of the VPS.It was also found the Rayleigh damping coefficients corresponding to the VPS vary slightly with the change in seismic excitation amplitude.The research displayed the complete procedure of updating the complex structured initial FEM by utilizing seismic response,and the results show that the parameters can be accurately identified even if the seismic response used for updating merely contained the fundamental frequency information of the structure.展开更多
The optimal design and effectiveness of three control systems,tuned viscous mass damper(TVMD),tuned inerter damper(TID)and tuned mass damper(TMD),on mitigating the seismic responses of base isolated structures,were sy...The optimal design and effectiveness of three control systems,tuned viscous mass damper(TVMD),tuned inerter damper(TID)and tuned mass damper(TMD),on mitigating the seismic responses of base isolated structures,were systematically studied.First,the seismic responses of the base isolated structure with each control system under white noise excitation were obtained.Then,the structural parameter optimizations of the TVMD,TID and TMD were conducted by using three different objectives.The results show that the three control systems were all effective in minimizing the root mean square value of seismic responses,including the base shear of the BIS,the absolute acceleration of structural SDOF,and the relative displacement between the base isolation floor and the foundation.Finally,considering the superstructure as a structural MDOF,a series of time history analyses were performed to investigate the effectiveness and activation sensitivity of the three control systems under far field and near fault seismic excitations.The results show that the effectiveness of TID and TMD with optimized parameters on mitigating the seismic responses of base isolated structures increased as the mass ratio increases,and the effectiveness of TID was always better than TMD with the same mass ratio.The TVMD with a lower mass ratio was more efficient in reducing the seismic response than the TID and TMD.Furthermore,the TVMD,when compared with TMD and TID,had better activation sensitivity and a smaller stroke.展开更多
The purpose is to study the seismic reduction effect of an isolated structure,with wind-resistant bearings( WRBs) setting on its isolation layer to withstand great wind load,and the working mechanism of the WRB. In th...The purpose is to study the seismic reduction effect of an isolated structure,with wind-resistant bearings( WRBs) setting on its isolation layer to withstand great wind load,and the working mechanism of the WRB. In this paper,two isolation models with /without WRBs,taking an actual engineering as the background,are established in the finite element software ETABS. The one with WRBs has horizontal damping coefficient less than 0. 40 while the other between 0. 40 and 0. 53. WRBs are simulated by Plastic 1element and the collaborative work between them and isolation layer is described by a mechanical model. Time history analysis is conducted on the models to compare their responses under earthquake excitations. Results show that the one with WRBs,but less lead-rubber bearings( LRBs),has better damping effect than the other,although they both can meet wind requirements. It is also shown that under normal conditions and small earthquakes,WRBs function well and the isolation layer will not yield; under moderate earthquakes,WRBs will yield and be destroyed to stop functioning but without affecting the damping effect of the upper structure.Additionally, the total yield shear force provided by LRBs is proposed to be close to the standard value of wind load.展开更多
This paper investigates the seismic responses of slopes in coral sand taken from a reef island in the South China Sea.A series of shaking table model tests were conducted to explore the responses of soil acceleration,...This paper investigates the seismic responses of slopes in coral sand taken from a reef island in the South China Sea.A series of shaking table model tests were conducted to explore the responses of soil acceleration,excess pore pressure,and slope displacement for three slope angles(5°,10°,and 15°).The results show that the excess pore pressure ratio of the slope decreases due to an increase in the initial shear stress when the slope angle increases.The acceleration response of the soil increases with the increase of the slope angle.The slope displacement presents substantial increments as the excess pore pressure ratio increases.In addition,the lateral movement,and slope settlement present substantial increments as the slope angle increases.No liquefaction is observed under a dynamic excitation of 0.2 g in the coral sand site.Under a dynamic excitation of 0.4 g,the site liquefies quickly,the acceleration amplification factor decreases,and the lateral movement and the settlement of the slope surface both increase compared with that under 0.2 g excitation.For the slope with an angle of 15°at 0.4 g,the flow distance of the sand strip increase by 289.47%compared with that in the 5°case.The lateral movement of the slope surface near the water level line is substantially larger than that away from the water line.The largest settlement is observed near the middle section of the slope(below the water level)under a dynamic excitation of 0.2 g.In contrast,the largest settlement under a dynamic excitation of 0.4 g occurs at the top of the slope.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
In recent years,special attention has been given to the effects of underground spaces and structures on the seismic response of adjacent ground.Nevertheless,to the best of the authors′knowledge,no method has yet been...In recent years,special attention has been given to the effects of underground spaces and structures on the seismic response of adjacent ground.Nevertheless,to the best of the authors′knowledge,no method has yet been considered to reduce these effects in technical literature.The present study aims to investigate the role of geofoam as the cover material in cut and cover tunnels on the seismic response of the ground surface.For this purpose,a numerical study was performed using FLAC 2D,a finite difference software,and verified against previous studies.The effects of parameters such as the geofoam type,thickness of the geofoam blocks and interfaces between the blocks,on the ground surface amplification pattern were investigated.Parametric studies demonstrate that the geofoam has a strong potential to attenuate the seismic horizontal movements of the ground surface.As the thickness of the geofoam blocks is decreased,its attenuation ability is increased.It was also determined that the interface between the geofoam blocks plays a key role in the attenuation of the aboveground seismic responses.Based on the results,it was concluded that geofoam is a proper material to attenuate seismic amplifications at the ground surface,induced by underground tunnels.展开更多
Research to reliably predict the seismic response of nuclear power stations with a pile-raft foundation is needed to meet the high safety requirements of nuclear power stations.In this study,a scaled superstructure wi...Research to reliably predict the seismic response of nuclear power stations with a pile-raft foundation is needed to meet the high safety requirements of nuclear power stations.In this study,a scaled superstructure with a 4×3 pile-raft foundation,which is constructed in Shanxi kaolin clay,is modelled.Accordingly,the characteristics of seismic response for nuclear power stations with a pile-raft foundation are analyzed using dynamic centrifuge tests.In particular,multiple earthquake motions with different magnitudes and frequency properties are utilized to map the relationship between structural response and properties of earthquake motions.The results show that the seismic response of the soil,raft,and structure are significantly affected by the natural frequency and magnitude of the earthquake motion.The soil surface acceleration is lower than the raft acceleration.The results provide a reliable reference to better understand the seismic response of nuclear power stations.展开更多
To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly ...To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.展开更多
An industrial building is a non-classically damped system due to the different damping properties of the primary structure and equipment.The objective of this paper is to quantify the range of applicability of the rea...An industrial building is a non-classically damped system due to the different damping properties of the primary structure and equipment.The objective of this paper is to quantify the range of applicability of the real model superposition approximation method to the seismic response calculation of industrial buildings.The analysis using lumped mass-and-shear spring models indicates that for the equipment-to-structure frequency ratiosγf>1.1 orγf<0.9,the non-classical damping effect is limited,and the real mode superposition approximation method provides accurate estimates.For 0.9<γf<1.1,the system may have a pair of closely spaced frequency modes,and the non-zero off-diagonal damping terms have a non-negligible effect on the damping ratios and mode shape vectors of these modes.For 0.9<γf<1.1 and the equipment-to-structure mass ratiosγm<0.07,the real mode superposition approximation method results in large errors,while the approximation method can provide an accurate estimation for 0.9<γf<1.1 andγm>0.07.Furthermore,extensive parametric analyses are conducted,where both steel structures and reinforced concrete structures with equipment with various damping ratios are considered.Finally,the finite element analysis of a five-story industrial building is adopted to validate the proposed range of applicability.展开更多
Bedding rock slopes are common geological features in nature that are prone to failure under strong earthquakes. Their failures induce catastrophic landslides and form barrier lakes, posing severe threats to people’s...Bedding rock slopes are common geological features in nature that are prone to failure under strong earthquakes. Their failures induce catastrophic landslides and form barrier lakes, posing severe threats to people’s lives and property. Based on the similarity criteria, a bedding rock slope model with a length of3 m, a width of 0.8 m, and a height of 1.6 m was constructed to facilitate large-scale shaking table tests.The results showed that with the increase of vibration time, the natural frequency of the model slope decreased, but the damping ratio increased. Damage to the rock mass structure altered the dynamic characteristics of the slope;therefore, amplification of the acceleration was found to be nonlinear and uneven. Furthermore, the acceleration was amplified nonlinearly with the increase of slope elevation along the slope surface and the vertical section, and the maximum acceleration amplification factor(AAF) occurred at the slope crest. Before visible deformation, the AAF increased with increasing shaking intensity;however, it decreased with increasing shaking intensity after obvious deformation. The slope was likely to slide along the bedding planes at a shallow depth below the slope surface. The upper part of the slope mainly experienced a tensile-shear effect, whereas the lower part suffered a compressive-shear force. The progressive failure process of the model slope can be divided into four stages, and the dislocated rock mass can be summarized into three zones. The testing data provide a good explanation of the dynamic behavior of the rock slope when subjected to an earthquake and may serve as a helpful reference in implementing antiseismic measures for earthquake-induced landslides.展开更多
In this study,A time-domain seismic response analysis method and a calculation model of the underground structure that can realize the input of seismic P,SV and Rayleigh waves are established,based on the viscoelastic...In this study,A time-domain seismic response analysis method and a calculation model of the underground structure that can realize the input of seismic P,SV and Rayleigh waves are established,based on the viscoelastic artificial boundary elements and the boundary substructure method for seismic wave input.After verifying the calculation accuracy,a comparative study on seismic response of a shallow-buried,double-deck,double-span subway station structure under incident P,SV and Rayleigh waves is conducted.The research results show that there are certain differences in the cross-sectional internal force distribution characteristics of underground structures under different types of seismic waves.The research results show that there are certain differences in the internal force distribution characteristics of underground structures under different types of seismic waves.At the bottom of the side wall,the top and bottom of the center pillar of the underground structure,the section bending moments of the underground structure under the incidences of SV wave and Rayleigh wave are relatively close,and are significantly larger than the calculation result under the incidence of P wave.At the center of the side wall and the top floor of the structure,the peak value of the cross-sectional internal force under the incident Rayleigh wave is larger than the calculation result under SV wave.In addition,the floor of the underground structure under Rayleigh waves vibrates in both the horizontal and vertical directions,and the magnification effect in the vertical direction is more significant.Considering that the current seismic research of underground structures mainly considers the effect of body waves such as the shear waves,sufficient attention should be paid to the incidence of Rayleigh waves in the future seismic design of shallow underground structures.展开更多
The treatment of soft soil foundation under nuclear safety grade corridors with graded sand and gravel materials has a good development prospect.It is of great engineering value to explore the influence of constructio...The treatment of soft soil foundation under nuclear safety grade corridors with graded sand and gravel materials has a good development prospect.It is of great engineering value to explore the influence of construction parameters of graded sand and gravel foundation on the seismic response of gallery structures.Taking the safety grade underground corridor of a nuclear power plant as the engineering background,the equivalent linear method is used to consider the nonlinear dynamic characteristics of graded sand and gravel.The energy transfer boundary is applied at the truncation boundary to simulate the dissipation effect of scattered wave fluctuation energy and the ground motion input.The thicknessless contact element is introduced to consider the contact effect between the corridor structure and the graded sand and gravel foundation,so as to establish the calculation model of the dynamic interaction between the graded sand and gravel foundation and the corridor structure.Furthermore,the influence of the relative compactness and the foundation treatment depth on the seismic response of the corridor structure is studied,and the calculation results of the acceleration response spectrum and relative displacement of the corridor structure are analyzed.The calculation results show that the two construction parameters have different degrees of influence on the seismic response of corridor structure.The research results can provide reference for the engineering design and construction of underground corridors,and provide technical support for the application of graded gravel materials in soft soil foundation treatment.展开更多
Long-period structures(e.g.Isolated structures)tend to produce pseudo-resonance with low frequency compo-nents of long-period ground motions,resulting in the increase in damage.Stiffness mutation occurs due to the set...Long-period structures(e.g.Isolated structures)tend to produce pseudo-resonance with low frequency compo-nents of long-period ground motions,resulting in the increase in damage.Stiffness mutation occurs due to the set-back in the upper body of the large chassis structure.In the parts with stiffness mutation,the torsion effect caused by the tower is far greater than that of the chassis itself.In this study,a total of 273 ground motions are collected and then filtered into four types,including the near-field ordinary,near-field pulse,far-field ordinary,and far-field harmonic.An 8-degree(0.2 g)fortified large chassis base-isolated structure is established.Furthermore,ETABS program software is used to conduct nonlinear time history analysis on the isolation and seismic model under bi-directional earthquake ground motions.The comparison results show that the seismic isolation effect of the base-isolated structure under long-period ground motions is worse than that associated with ordinary ground motions when the seismic response reduction rate of the large base floor significantly decreases compared with that of the tower.When the inter-story displacement angle and the displacement of isolation layer of the chassis exceeds the limit of Code for Seismic Design of Buildings(GB 50011-2010),it is recommended to adopt composite seismic isolation technology or add limit devices.Under the condition of long-period ground motions,the base-isolated structure reduces the lateral-torsional coupling effect of the large chassis structure,while the torsion response of large chassis’top layer increases.Under long-period ground motions with the same acceleration peak,the response of the base-isolated structure increases much more than that of the seismic structure and the consideration of this impact is suggested to be added to the Code.展开更多
Purpose–Under different ground motion excitation modes,the spatial coupling effect of seismic response for the arch bridge with thrust,seismic weak parts and the internal force components of the control section of ma...Purpose–Under different ground motion excitation modes,the spatial coupling effect of seismic response for the arch bridge with thrust,seismic weak parts and the internal force components of the control section of main arch ribs are analyzed.Design/methodology/approach–Taking a 490 m deck type railway steel truss arch bridge as the background,the dynamic calculation model of the whole bridge was established by SAP2000 software.The seismic response analyses under one-,two-and three-dimension(1D,2D and 3D)uniform ground motion excitations were carried out.Findings–For the steel truss arch bridge composed of multiple arch ribs,any single direction ground motion excitation will cause large axial force in the chord of arch rib.The axial force caused by transverse and vertical ground motion excitation in the chord of arch crown area is 1.4–3.6 times of the corresponding axial force under longitudinal seismic excitation.The in-plane bending moment caused by the lower chord at the vault is 4.2–5.5 times of the corresponding bending moment under the longitudinal seismic excitation.For the bottom chord of arch rib,the arch foot is the weak part of earthquake resistance,but for the upper chord of arch rib,the arch foot,arch crown and the intersection of column and upper chord can all be the potential earthquake-resistant weak parts.The normal stress of the bottom chord of the arch rib under multidimensional excitation is mainly caused by the axial force,but the normal stress of the upper chord of the arch rib is caused by the axial force,in-plane and out of plane bending moment.Originality/value–The research provides specific suggestions for ground motion excitation mode and also provides reference information for the earthquake-resistant weak part and seismic design of long-span deck type railway steel truss arch bridges.展开更多
This study explored the seismic response of a house supporting base sides with a polymeric displacement control material and by magnetically levitating the foundation base. In this paper, we explore the possibility an...This study explored the seismic response of a house supporting base sides with a polymeric displacement control material and by magnetically levitating the foundation base. In this paper, we explore the possibility and efficacy of a seismic-isolated detached house as described above from both a shaking table experiment of model and three-dimensional finite element analysis. The seismic-isolated model showed stable response and its acceleration response was significantly reduced compared to the base-fixed model in the shaking table test. Three-dimensional finite element analysis was possible to simulate the experimental results. In the seismic response analysis of a full-scale detached house, the seismic-isolated model showed response reduction and its residual displacement was smaller than that of the sliding-base isolation model.展开更多
基金Major Program of the National Natural Science Foundation of China under Grant No.52192675 and the 111 Project of China under Grant No.D21001。
文摘Soil nonlinear behavior displays noticeable effects on the site seismic response.This study proposes a new functional expression of the skeleton curve to replace the hyperbolic skeleton curve.By integrating shear modulus and combining the dynamic skeleton curve and the damping degradation coefficient,the constitutive equation of the logarithmic dynamic skeleton can be obtained,which considers the damping effect in a soil dynamics problem.Based on the finite difference method and the multi-transmitting boundary condition,a 1D site seismic response analysis program called Soilresp1D has been developed herein and used to analyze the time-domain seismic response in three types of sites.At the same time,this study also provides numerical simulation results based on the hyperbolic constitutive model and the equivalent linear method.The results verify the rationality of the new soil dynamic constitutive model.It can analyze the mucky soil site nonlinear seismic response,reflecting the deformation characteristics and damping effect of the silty soil.The hysteresis loop area is more extensive,and the residual strain is evident.
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National Science Foundation for Excellent Young Scholars of China under Grant No.51722801National Natural Science Foundation of China under Grant Nos.51808006 and 52078016。
文摘Case history investigations have shown that pile foundations are more critically damaged in liquefiable soils than non-liquefiable soils.This study examines the differences in seismic response of pile foundations in liquefiable and non-liquefiable soils and their sensitivity to numerical model parameters.A two-dimensional finite element(FE)model is developed to simulate the experiment of a single pile foundation centrifuge in liquefiable soil subjected to earthquake motions and is validated against real-world test results.The differences in soil-pile seismic response of liquefiable and non-liquefiable soils are explored.Specifically,the first-order second-moment method(FOSM)is used for sensitivity analysis of the seismic response.The results show significant differences in seismic response for a soil-pile system between liquefiable and non-liquefiable soil.The seismic responses are found to be significantly larger in liquefiable soil than in non-liquefiable soil.Moreover,the pile bending moment was mainly affected by the kinematic effect in liquefiable soil,while the inertial effect was more significant in non-liquefiable soil.The controlling parameters of seismic response were PGA,soil density,and friction angle in liquefiable soil,while the pile bending moment was mainly controlled by PGA,the friction angle of soil,and shear modulus of loose sand in non-liquefiable soil.
基金National Natural Science Foundation of China(42174139,41974119,42030103)Laoshan Laboratory Science and Technology Innovation Program(LSKJ202203406)Science Foundation from Innovation and Technology Support Program for Young Scientists in Colleges of Shandong Province and Ministry of Science and Technology of China(2019RA2136).
文摘Monitoring the change in horizontal stress from the geophysical data is a tough challenge, and it has a crucial impact on broad practical scenarios which involve reservoir exploration and development, carbon dioxide (CO_(2)) injection and storage, shallow surface prospecting and deep-earth structure description. The change in in-situ stress induced by hydrocarbon production and localized tectonic movements causes the changes in rock mechanic properties (e.g. wave velocities, density and anisotropy) and further causes the changes in seismic amplitudes, phases and travel times. In this study, the nonlinear elasticity theory that regards the rock skeleton (solid phase) and pore fluid as an effective whole is used to characterize the effect of horizontal principal stress on rock overall elastic properties and the stress-dependent anisotropy parameters are therefore formulated. Then the approximate P-wave, SV-wave and SH-wave angle-dependent reflection coefficient equations for the horizontal-stress-induced anisotropic media are proposed. It is shown that, on the different reflectors, the stress-induced relative changes in reflectivities (i.e., relative difference) of elastic parameters (i.e., P- and S-wave velocities and density) are much less than the changes in contrasts of anisotropy parameters. Therefore, the effects of stress change on the reflectivities of three elastic parameters are reasonably neglected to further propose an AVO inversion approach incorporating P-, SH- and SV-wave information to estimate the change in horizontal principal stress from the corresponding time-lapse seismic data. Compared with the existing methods, our method eliminates the need for man-made rock-physical or fitting parameters, providing more stable predictive power. 1D test illustrates that the estimated result from time-lapse P-wave reflection data shows the most reasonable agreement with the real model, while the estimated result from SH-wave reflection data shows the largest bias. 2D test illustrates the feasibility of the proposed inversion method for estimating the change in horizontal stress from P-wave time-lapse seismic data.
基金supported by the National Science Foundation of China(Nos. D40444002 and D40521002)National Key Basic Research Program(No.2006CB705803)
文摘We presented a boundary element method using the approximate analytical Green's function given by Sánchez-Sesma et al.Coordinate transform is introduced to extend the method to deal with the model with constant-gradient velocity along oblique direction.The method is validated by comparing the numerical results with other independent methods.This method provides a useful tool for analyzing local site effects.We computed seismic response for two series of models.The results in both frequency and time domains are analyzed and show complex amplification patterns.The fundamental mode of resonance is dependent not only on the velocity at the free surface but also on the velocity distribution of the whole basin.For the higher modes of vibration the heterogeneous basin also has its own characteristic.
文摘Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its design and operation processes all depend on finite element method.However,in engineering practice,there is always deviations between the theoretical and the measured responses due to the inaccurate value of the structural parameters in the model.The structure parameters identification of VPS within NPP is still an unexplored domain to a large extent.In this paper,the initial 2D-finite element model(FEM)for VPS with a DN80 gate valve was updated by utilizing seismic response.The objective function used in the model updating procedure is the vibration control equation error of the VPS.The experimental results show that the updated 2D-FEM can accurately predict the original dynamic characteristic of the VPS.It was also found the Rayleigh damping coefficients corresponding to the VPS vary slightly with the change in seismic excitation amplitude.The research displayed the complete procedure of updating the complex structured initial FEM by utilizing seismic response,and the results show that the parameters can be accurately identified even if the seismic response used for updating merely contained the fundamental frequency information of the structure.
基金National Key Research and Development Program of China under Grant No.2017YFC0703600 and No.2017YFC0703604。
文摘The optimal design and effectiveness of three control systems,tuned viscous mass damper(TVMD),tuned inerter damper(TID)and tuned mass damper(TMD),on mitigating the seismic responses of base isolated structures,were systematically studied.First,the seismic responses of the base isolated structure with each control system under white noise excitation were obtained.Then,the structural parameter optimizations of the TVMD,TID and TMD were conducted by using three different objectives.The results show that the three control systems were all effective in minimizing the root mean square value of seismic responses,including the base shear of the BIS,the absolute acceleration of structural SDOF,and the relative displacement between the base isolation floor and the foundation.Finally,considering the superstructure as a structural MDOF,a series of time history analyses were performed to investigate the effectiveness and activation sensitivity of the three control systems under far field and near fault seismic excitations.The results show that the effectiveness of TID and TMD with optimized parameters on mitigating the seismic responses of base isolated structures increased as the mass ratio increases,and the effectiveness of TID was always better than TMD with the same mass ratio.The TVMD with a lower mass ratio was more efficient in reducing the seismic response than the TID and TMD.Furthermore,the TVMD,when compared with TMD and TID,had better activation sensitivity and a smaller stroke.
基金National Natural Science Foundation of China(No.51108092)
文摘The purpose is to study the seismic reduction effect of an isolated structure,with wind-resistant bearings( WRBs) setting on its isolation layer to withstand great wind load,and the working mechanism of the WRB. In this paper,two isolation models with /without WRBs,taking an actual engineering as the background,are established in the finite element software ETABS. The one with WRBs has horizontal damping coefficient less than 0. 40 while the other between 0. 40 and 0. 53. WRBs are simulated by Plastic 1element and the collaborative work between them and isolation layer is described by a mechanical model. Time history analysis is conducted on the models to compare their responses under earthquake excitations. Results show that the one with WRBs,but less lead-rubber bearings( LRBs),has better damping effect than the other,although they both can meet wind requirements. It is also shown that under normal conditions and small earthquakes,WRBs function well and the isolation layer will not yield; under moderate earthquakes,WRBs will yield and be destroyed to stop functioning but without affecting the damping effect of the upper structure.Additionally, the total yield shear force provided by LRBs is proposed to be close to the standard value of wind load.
基金supported by the National Natural Science Foundation of China(Grant Nos.41831282,51878103)the Fundamental Research Funds for the Central Universities(Grant No.2021CDJQY-042)the Postdoctoral innovative talents support program,Chongqing。
文摘This paper investigates the seismic responses of slopes in coral sand taken from a reef island in the South China Sea.A series of shaking table model tests were conducted to explore the responses of soil acceleration,excess pore pressure,and slope displacement for three slope angles(5°,10°,and 15°).The results show that the excess pore pressure ratio of the slope decreases due to an increase in the initial shear stress when the slope angle increases.The acceleration response of the soil increases with the increase of the slope angle.The slope displacement presents substantial increments as the excess pore pressure ratio increases.In addition,the lateral movement,and slope settlement present substantial increments as the slope angle increases.No liquefaction is observed under a dynamic excitation of 0.2 g in the coral sand site.Under a dynamic excitation of 0.4 g,the site liquefies quickly,the acceleration amplification factor decreases,and the lateral movement and the settlement of the slope surface both increase compared with that under 0.2 g excitation.For the slope with an angle of 15°at 0.4 g,the flow distance of the sand strip increase by 289.47%compared with that in the 5°case.The lateral movement of the slope surface near the water level line is substantially larger than that away from the water line.The largest settlement is observed near the middle section of the slope(below the water level)under a dynamic excitation of 0.2 g.In contrast,the largest settlement under a dynamic excitation of 0.4 g occurs at the top of the slope.
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.
文摘In recent years,special attention has been given to the effects of underground spaces and structures on the seismic response of adjacent ground.Nevertheless,to the best of the authors′knowledge,no method has yet been considered to reduce these effects in technical literature.The present study aims to investigate the role of geofoam as the cover material in cut and cover tunnels on the seismic response of the ground surface.For this purpose,a numerical study was performed using FLAC 2D,a finite difference software,and verified against previous studies.The effects of parameters such as the geofoam type,thickness of the geofoam blocks and interfaces between the blocks,on the ground surface amplification pattern were investigated.Parametric studies demonstrate that the geofoam has a strong potential to attenuate the seismic horizontal movements of the ground surface.As the thickness of the geofoam blocks is decreased,its attenuation ability is increased.It was also determined that the interface between the geofoam blocks plays a key role in the attenuation of the aboveground seismic responses.Based on the results,it was concluded that geofoam is a proper material to attenuate seismic amplifications at the ground surface,induced by underground tunnels.
基金Supported by:Scientific Research Program of China General Nuclear Power Corporation(CGN)under Grant No.K-A2017.054Postgraduate Research and Practice Innovation Program of Jiangsu Province under Grant No.KYCX19_0093。
文摘Research to reliably predict the seismic response of nuclear power stations with a pile-raft foundation is needed to meet the high safety requirements of nuclear power stations.In this study,a scaled superstructure with a 4×3 pile-raft foundation,which is constructed in Shanxi kaolin clay,is modelled.Accordingly,the characteristics of seismic response for nuclear power stations with a pile-raft foundation are analyzed using dynamic centrifuge tests.In particular,multiple earthquake motions with different magnitudes and frequency properties are utilized to map the relationship between structural response and properties of earthquake motions.The results show that the seismic response of the soil,raft,and structure are significantly affected by the natural frequency and magnitude of the earthquake motion.The soil surface acceleration is lower than the raft acceleration.The results provide a reliable reference to better understand the seismic response of nuclear power stations.
基金National Natural Science Foundation of China under Grant Nos.51738007,51808099the Fundamental Research Funds for the Central Universities under Grant No.DUT20RC(3)005。
文摘To achieve rational and precise seismic response predictions of large span spatial structures(LSSSs),the inherent non-uniformity and multidimensionality characteristics of earthquake ground motions should be properly taken into consideration.However,due to the limitations of available earthquake stations to record seismic rotational components,the effects of rocking and torsional earthquake components are commonly neglected in the seismic analyses of LSSSs.In this study,a newly developed method to extract the rocking and torsion components at any point along the area of a deployed dense array from the translational earthquake recordings is applied to obtain the rotational seismic inputs for a LSSS.The numerical model of an actual LSSS,the Dalian International Conference Center(DICC),is developed to study the influences of multi-support and multidimensional excitations on the seismic responses of LSSSs.The numerical results reveal that the non-uniformity and multidimensionality of ground motion input can considerably affect the dynamic response of the DICC.The specific degree of influence on the overall and local structural displacements,deformations and forces are comprehensively investigated and discussed.
基金Fund of China National Industrial Building Diagnosis and Reconstruction Engineering Technology Research Center under Grant No.YZA2017Ky03the Beijing Natural Science Foundation under Grant No.JQ18029the National Natural Science Foundation of China under Grant No.52078277。
文摘An industrial building is a non-classically damped system due to the different damping properties of the primary structure and equipment.The objective of this paper is to quantify the range of applicability of the real model superposition approximation method to the seismic response calculation of industrial buildings.The analysis using lumped mass-and-shear spring models indicates that for the equipment-to-structure frequency ratiosγf>1.1 orγf<0.9,the non-classical damping effect is limited,and the real mode superposition approximation method provides accurate estimates.For 0.9<γf<1.1,the system may have a pair of closely spaced frequency modes,and the non-zero off-diagonal damping terms have a non-negligible effect on the damping ratios and mode shape vectors of these modes.For 0.9<γf<1.1 and the equipment-to-structure mass ratiosγm<0.07,the real mode superposition approximation method results in large errors,while the approximation method can provide an accurate estimation for 0.9<γf<1.1 andγm>0.07.Furthermore,extensive parametric analyses are conducted,where both steel structures and reinforced concrete structures with equipment with various damping ratios are considered.Finally,the finite element analysis of a five-story industrial building is adopted to validate the proposed range of applicability.
基金funded by the National Natural Science Foundation of China (Grant No. 41825018)the National Key Research and Development Plan of China (Grant No. 2019YFC1509704)the Second Tibetan Plateau Scientific Expedition and Research Program (STEP, Grant No. 2019QZKK0904)。
文摘Bedding rock slopes are common geological features in nature that are prone to failure under strong earthquakes. Their failures induce catastrophic landslides and form barrier lakes, posing severe threats to people’s lives and property. Based on the similarity criteria, a bedding rock slope model with a length of3 m, a width of 0.8 m, and a height of 1.6 m was constructed to facilitate large-scale shaking table tests.The results showed that with the increase of vibration time, the natural frequency of the model slope decreased, but the damping ratio increased. Damage to the rock mass structure altered the dynamic characteristics of the slope;therefore, amplification of the acceleration was found to be nonlinear and uneven. Furthermore, the acceleration was amplified nonlinearly with the increase of slope elevation along the slope surface and the vertical section, and the maximum acceleration amplification factor(AAF) occurred at the slope crest. Before visible deformation, the AAF increased with increasing shaking intensity;however, it decreased with increasing shaking intensity after obvious deformation. The slope was likely to slide along the bedding planes at a shallow depth below the slope surface. The upper part of the slope mainly experienced a tensile-shear effect, whereas the lower part suffered a compressive-shear force. The progressive failure process of the model slope can be divided into four stages, and the dislocated rock mass can be summarized into three zones. The testing data provide a good explanation of the dynamic behavior of the rock slope when subjected to an earthquake and may serve as a helpful reference in implementing antiseismic measures for earthquake-induced landslides.
基金supported by National Natural Science Foundation of China(Grant no.U1839201)China National Postdoctoral Program of Innovative Talents(Grant no.BX20200192)+1 种基金China Postdoctoral Science Foundation,China(2020M680575)Shuimu Tsinghua Scholar Program(Grant no.2020SM005)。
文摘In this study,A time-domain seismic response analysis method and a calculation model of the underground structure that can realize the input of seismic P,SV and Rayleigh waves are established,based on the viscoelastic artificial boundary elements and the boundary substructure method for seismic wave input.After verifying the calculation accuracy,a comparative study on seismic response of a shallow-buried,double-deck,double-span subway station structure under incident P,SV and Rayleigh waves is conducted.The research results show that there are certain differences in the cross-sectional internal force distribution characteristics of underground structures under different types of seismic waves.The research results show that there are certain differences in the internal force distribution characteristics of underground structures under different types of seismic waves.At the bottom of the side wall,the top and bottom of the center pillar of the underground structure,the section bending moments of the underground structure under the incidences of SV wave and Rayleigh wave are relatively close,and are significantly larger than the calculation result under the incidence of P wave.At the center of the side wall and the top floor of the structure,the peak value of the cross-sectional internal force under the incident Rayleigh wave is larger than the calculation result under SV wave.In addition,the floor of the underground structure under Rayleigh waves vibrates in both the horizontal and vertical directions,and the magnification effect in the vertical direction is more significant.Considering that the current seismic research of underground structures mainly considers the effect of body waves such as the shear waves,sufficient attention should be paid to the incidence of Rayleigh waves in the future seismic design of shallow underground structures.
基金supported by National Natural Science Foundation of China(52108437)Dalian Youth Science and Technology Star Project(2020RQ057)。
文摘The treatment of soft soil foundation under nuclear safety grade corridors with graded sand and gravel materials has a good development prospect.It is of great engineering value to explore the influence of construction parameters of graded sand and gravel foundation on the seismic response of gallery structures.Taking the safety grade underground corridor of a nuclear power plant as the engineering background,the equivalent linear method is used to consider the nonlinear dynamic characteristics of graded sand and gravel.The energy transfer boundary is applied at the truncation boundary to simulate the dissipation effect of scattered wave fluctuation energy and the ground motion input.The thicknessless contact element is introduced to consider the contact effect between the corridor structure and the graded sand and gravel foundation,so as to establish the calculation model of the dynamic interaction between the graded sand and gravel foundation and the corridor structure.Furthermore,the influence of the relative compactness and the foundation treatment depth on the seismic response of the corridor structure is studied,and the calculation results of the acceleration response spectrum and relative displacement of the corridor structure are analyzed.The calculation results show that the two construction parameters have different degrees of influence on the seismic response of corridor structure.The research results can provide reference for the engineering design and construction of underground corridors,and provide technical support for the application of graded gravel materials in soft soil foundation treatment.
基金This project is jointly sponsored by Yunnan Youth Earthquake Science Foundation(2020K06)the National Natural Science Foundation of China(51778149)Xiamen University Tan Kah College School-Enterprise Cooperation Foundation(JGH2020034).
文摘Long-period structures(e.g.Isolated structures)tend to produce pseudo-resonance with low frequency compo-nents of long-period ground motions,resulting in the increase in damage.Stiffness mutation occurs due to the set-back in the upper body of the large chassis structure.In the parts with stiffness mutation,the torsion effect caused by the tower is far greater than that of the chassis itself.In this study,a total of 273 ground motions are collected and then filtered into four types,including the near-field ordinary,near-field pulse,far-field ordinary,and far-field harmonic.An 8-degree(0.2 g)fortified large chassis base-isolated structure is established.Furthermore,ETABS program software is used to conduct nonlinear time history analysis on the isolation and seismic model under bi-directional earthquake ground motions.The comparison results show that the seismic isolation effect of the base-isolated structure under long-period ground motions is worse than that associated with ordinary ground motions when the seismic response reduction rate of the large base floor significantly decreases compared with that of the tower.When the inter-story displacement angle and the displacement of isolation layer of the chassis exceeds the limit of Code for Seismic Design of Buildings(GB 50011-2010),it is recommended to adopt composite seismic isolation technology or add limit devices.Under the condition of long-period ground motions,the base-isolated structure reduces the lateral-torsional coupling effect of the large chassis structure,while the torsion response of large chassis’top layer increases.Under long-period ground motions with the same acceleration peak,the response of the base-isolated structure increases much more than that of the seismic structure and the consideration of this impact is suggested to be added to the Code.
基金supported by the National Natural Science Foundation of China(Grant No.51768037)“Foundation of A Hundred Youth Talents Training Program of Lanzhou Jiaotong University.”。
文摘Purpose–Under different ground motion excitation modes,the spatial coupling effect of seismic response for the arch bridge with thrust,seismic weak parts and the internal force components of the control section of main arch ribs are analyzed.Design/methodology/approach–Taking a 490 m deck type railway steel truss arch bridge as the background,the dynamic calculation model of the whole bridge was established by SAP2000 software.The seismic response analyses under one-,two-and three-dimension(1D,2D and 3D)uniform ground motion excitations were carried out.Findings–For the steel truss arch bridge composed of multiple arch ribs,any single direction ground motion excitation will cause large axial force in the chord of arch rib.The axial force caused by transverse and vertical ground motion excitation in the chord of arch crown area is 1.4–3.6 times of the corresponding axial force under longitudinal seismic excitation.The in-plane bending moment caused by the lower chord at the vault is 4.2–5.5 times of the corresponding bending moment under the longitudinal seismic excitation.For the bottom chord of arch rib,the arch foot is the weak part of earthquake resistance,but for the upper chord of arch rib,the arch foot,arch crown and the intersection of column and upper chord can all be the potential earthquake-resistant weak parts.The normal stress of the bottom chord of the arch rib under multidimensional excitation is mainly caused by the axial force,but the normal stress of the upper chord of the arch rib is caused by the axial force,in-plane and out of plane bending moment.Originality/value–The research provides specific suggestions for ground motion excitation mode and also provides reference information for the earthquake-resistant weak part and seismic design of long-span deck type railway steel truss arch bridges.
文摘This study explored the seismic response of a house supporting base sides with a polymeric displacement control material and by magnetically levitating the foundation base. In this paper, we explore the possibility and efficacy of a seismic-isolated detached house as described above from both a shaking table experiment of model and three-dimensional finite element analysis. The seismic-isolated model showed stable response and its acceleration response was significantly reduced compared to the base-fixed model in the shaking table test. Three-dimensional finite element analysis was possible to simulate the experimental results. In the seismic response analysis of a full-scale detached house, the seismic-isolated model showed response reduction and its residual displacement was smaller than that of the sliding-base isolation model.
