Seismic performance evaluation of water supply pipes installed in a full-scale RC frame structure based on a shaking table test

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.

基于SHAKING方法的北斗星基增强系统电离层模型可用性分析

北斗星基增强系统(BeiDou Satellite-Based Augmentation System,BDSBAS)通过境内的监测站为中国及周边地区用户提供电离层改正及电离层完好性监测服务,因此其对电离层算法的可用性要求较高.本文采用附加Kriging估计的调整球谐函数建模方法(adjusted spherical harmonics adding Kriging,SHAKING)解算BDSBAS电离层参数信息.通过对现有星基增强系统(Satellite-Based Augmentation System,SBAS)电离层的性能分析可以发现,部分SBAS播发了标记为未监测点的延迟修正信息.通过对中国区域SBAS格网点需求分析可以发现:在卫星截止高度角为15°时,SHAKING方法提供的电离层可用点为189个、不可用点为3个,满足服务需求;结合BDSBAS提供的钟轨改正信息,SHAKING方法较反距离加权插值(inverse distance weighted,IDW)方法的垂直制导进近可用性范围提高约30%.

Evaluation of the effects of EPS composite soil replacement on the dynamic performance of caisson structure using shaking table tests

The seismic performance of a caisson structure under two types of models with a saturated sandy foundation(CSS)and an expanded polystyrene(EPS)composite soil foundation(CES)are studied using shaking table tests.The macro phenomena of the two different foundation models are described and analyzed.The effects of the replacement of EPS composite soil on seismic-induced liquefaction of backfill and the dynamic performance of a caisson structure are evaluated in detail.The results show that the excess pore water pressure generation in the CES is significantly slower than that in the CSS during the shaking.The dynamic earth pressure acting on the caisson has a triangular shape.The response of horizontal acceleration,displacement,settlement,and rotation angle of the caisson in the CES is smaller than that in the CSS,which means the caisson in the CES has a better seismic performance.Furthermore,the out-of-phase phenomenon between dynamic earth thrust and inertial force in the CES is more obvious than that in the CSS,which is beneficial to reduce the lateral force and improve the stability of the caisson structure.

Numerical analysis on seismic performance of underground structures in liquefiable interlayer sites from centrifuge shaking table test

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.

Exploring Shaking for Cancer Treatment

1.Double-sided role of vibration and shaking Removing vibration and shaking is a pivotal engineering task,which is showcased,for instance,in spacecraft attitude control systems that ensure a precise three-dimensional orientation.Vibration or shaking,such as precession caused by external torque,nutation stemming from off-axis angular momentum,and wobbling due to geometric misalignment,necessitate active and passive damping mechanisms.This principle extends beyond spacecraft to centrifugation techniques,pivotal not only in washing machines but also in a spectrum of biomedical apparatuses used for isolating cells and organelles and separating DNA and proteins.

Experimental studies on liquefaction and reliquefaction potential of saturated ground subjected to repeated incremental acceleration loading with varying shaking duration

Past research has focused on the factors that influence liquefaction under normal shaking conditions.However,studies on parameters that influence the reliquefaction potential of saturated deposits during repeated shaking events are limited.In this study,an attempt has been made to examine the influence of acceleration amplitude and shaking duration on liquefaction and reliquefaction potential under repeated shaking conditions is conducted.1-g uni-axial shaking table experiments were performed on saturated ground prepared with 40%and 60%relative density.The prepared ground was subjected to alternate longer and shorter shaking durations(40 and 20 s)of repeated incremental 0.1 g,0.2 g,0.3 g and 0.4 g acceleration loading,respectively.The variation in density,excess pore water pressure(EPWP),cyclic resistance ratio(CRR)and surface settlement were estimated.The results showed that due to repeated incremental shaking events,reliquefaction was observed on the prepared ground.During longer shaking duration,the post-liquefied soil showed density improvement with improved soil resistance.However,the application of shorter duration loading followed by longer shaking reduced the beneficial effect of density improvement by disturbing the densified ground.Due to this,the ground was found to be more susceptible to reliquefaction in the subsequent incremental longer shaking event.

Seismic response of underground utility tunnels: shaking table testing and FEM analysis

Underground utility tunnels are widely used in urban areas throughout the world for lifeline networks due to their easy maintenance and environmental protection capabilities. However, knowledge about their seismic performance is still quite limited and seismic design procedures are not included in current design codes. This paper describes a series of shaking table tests the authors performed on a scaled utility tunnel model to explore its performance under earthquake excitation. Details of the experimental setup are first presented focusing on aspects such as the design of the soil container, scaled structural model, sensor array arrangement and test procedure. The main observations from the test program, including structural response, soil response, soil-structure interaction and earth pressure, are summarized and discussed. Further, a finite element model （FEM） of the test utility tunnel is established where the nonlinear soil properties are modeled by the Drucker- Prager constitutive model; the master-slave surface mechanism is employed to simulate the soil-structure dynamic interaction; and the confining effect of the laminar shear box to soil is considered by proper boundary modeling. The results from the numerical model are compared with experiment measurements in terms of displacement, acceleration and amplification factor of the structural model and the soil. The comparison shows that the numerical results match the experimental measurements quite well. The validated numerical model can be adopted for further analysis.

Shaking table test and numerical analysis of offshore wind turbine tower systems controlled by TLCD

A wind turbine system equipped with a tuned liquid column damper （TLCD） is comprehensively studied via shaking table tests using a 1/13-scaled model. The effects of wind and wave actions are considered by inputting response- equivalent accelerations on the shaking table. The test results show that the control effect of the TLCD system is significant in reducing the responses under both wind-wave equivalent loads and ground motions, but obviously varies for different inputs, Further, a blade-hub-tower integrated numerical model for the wind turbine system is established. The model is capable of considering the rotational effect of blades by combining Kane＇s equation with the finite element method. The responses of the wind tower equipped with TLCD devices are numerically obtained and compared to the test results, showing that under both controlled and uncontrolled conditions with and without blades＇ rotation, the corresponding responses exhibit good agreement. This demonstrates that the proposed numerical model performs well in capturing the wind-wave coupled response of the offshore wind turbine systems under control. Both numerical and experimental results show that the TLCD system can significantly reduce the structural response and thus improve the safety and serviceability of the offshore wind turbine tower systems. Additional issues that require further study are discussed.

Seismic response of tunnel under normal fault slips by shaking table test technique

Mountain tunnel crossing a normal fault in seismically active zone is easily affected by normal fault slip and earthquake. It is necessary to study tunnel dynamic response under action of normal fault slip and earthquake. In this paper, a three-dimensional normal fault sliding device was designed, and a shaking table test was carried out to study tunnel seismic performance under normal fault slip. The results show that peak acceleration of lining is dominated by an existence of fault and direction of seismic excitation, not normal fault slip. And the incremental strains of lining in critical zone with 1.7 times fault thickness and centered in faults induced by normal fault slip and seismic excitation are larger than ones only by seismic excitation. And the incremental strains in critical zone increase with the increase of normal fault slip magnitude ranging from 0 to 2 mm. And normal fault slip results in a significant reduction of overall tunnel stiffness subjected to an earthquake. These experimental results provide a scientific reference for prevention and control measurement of tunnel damage under earthquake and normal fault slip.

Effect of Lithology and Structure on Seismic Response of Steep Slope in a Shaking Table Test

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.

Shaking table test and numerical simulation of an isolated cylindrical latticed shell under multiple-support excitations

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.

Study on dynamic response of embedded long span corrugated steel culverts using scaled model shaking table tests and numerical analyses

A series of scaled-model shaking table tests and its simulation analyses using dynamic finite element method were performed to clarify the dynamic behaviors and the seismic stability of embedded corrugated steel culverts due to strong earth-quakes like the 1995 Hyogoken-nanbu earthquake. The dynamic strains of the embedded culvert models and the seismic soil pressure acting on the models due to sinusoidal and random strong motions were investigated. This study verified that the cor-rugated culvert model was subjected to dynamic horizontal forces (lateral seismic soil pressure) from the surrounding ground, which caused the large bending strains on the structure; and that the structures do not exceed the allowable plastic deformation and do not collapse completely during strong earthquake like Hyogoken-nanbu earthquake. The results obtained are useful for design and construction of embedded long span corrugated steel culverts in seismic regions.

Large scale shaking table model test and analysis on seismic response of utility tunnel in non-homogeneous soil

Underground utility tunnels are the most fundamental and reliable lifeline network in urban cities,and are widely constructed throughout the world.In urban areas,most utility tunnels usually encounter the non-homogeneity of subsoil condition due to various construction effects.Studies have shown that the damage mechanism of shallow underground structures mainly depends on the inhomogeneity of the subsoil conditions.This would become a considerable factor for the stability of the underground utility tunnel structures.However,this type of research still needs to establish the vulnerable seismic design.In this study,a series of shaking table tests were conducted on non-homogenous soils to investigate the performance of seismic interaction between utility tunnels,surrounding soils and interior pipelines.The dynamic responses measured from the test account for the boundary condition of non-homogeneous soils,the internal forces,displacement of tunnel joints,the dynamic characteristics on interior pipelines and the reasonable spring stiffness with damping in the seismically isolated gas pipeline model inside the tunnel.The vulnerability of underground utility tunnel in non-homogeneous soil zone and the mechanism of the stability of interior facilities are the main topics discussed in this paper.

Shaking table test and numerical analysis of a 1:12 scale model of a special concentrically braced steel frame with pinned connections

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.

Shaking table experimental study of recycled concrete frame-shear wall structures

In this study, four 1/5 scaled shaking table tests were conducted to investigate the seismic performance of recycled concrete frame-shear wall structures with different recycled aggregates replacement rates and concealed bracing detail. The four tested structures included one normal concrete model, one recycled coarse aggregate concrete model, and two recycled coarse and fi ne aggregate concrete models with or without concealed bracings inside the shear walls. The dynamic characteristics, dynamic response and failure mode of each model were compared and analyzed. Finite element models were also developed and nonlinear time-history response analysis was conducted. The test and analysis results show that the seismic performance of the recycled coarse aggregate concrete frame-shear wall structure is slightly worse than the normal concrete structure. The seismic resistance capacity of the recycled concrete frame-shear wall structure can be greatly improved by setting up concealed bracings inside the walls. With appropriate design, the recycled coarse aggregate concrete frame-shear wall structure and recycled concrete structure with concealed bracings inside the walls can be applied in buildings.

Shaking table test for reinforcement of soil slope with multiple sliding surfaces by reinforced double-row anti-slide piles

Despite the continuous advancements of engineering construction in high-intensity areas,many engineering landslides are still manufactured with huge thrust force,and double-row piles are effective to control such large landslides.In this study,large shaking table test were performed to test and obtain multi-attribute seismic data such as feature image,acceleration,and dynamic soil pressure.Through the feature image processing analysis,the deformation characteristics for the slope reinforced by double-row piles were revealed.By analyzing the acceleration and the dynamic soil pressure time domain,the spatial dynamic response characteristics were revealed.Using Fast Fourier Transform and half-power bandwidth,the damping ratio of acceleration and dynamic soil pressure was obtained.Following that,the Seism Signal was used to calculate the spectral displacement of the accelerations to obtain the regional differences of spectral displacement.The results showed that the overall deformation mechanism of the slope originates from tension failure in the soil mass.The platform at the back of the slope was caused by seismic subsidence,and the peak acceleration ratio was positively correlated with the relative pile heights.The dynamic soil pressure of the front row piles showed an inverted"K"-shaped distribution,but that of the back row piles showed an"S"-shaped distribution.The predominant frequency of acceleration was 2.16 Hz,and the main frequency band was 0.7-6.87 Hz;for dynamic soil pressure,the two parameters became 1.15 Hz and 0.5-6.59 Hz,respectively.In conclusion,dynamic soil pressure was more sensitive to dampening effects than acceleration.Besides,compared to acceleration,dynamic soil pressure exhibited larger loss factors and lower resonance peaks.Finally,back row pile heads were highly sensitive to spectral displacement compared to front row pile heads.These findings may be of reference value for future seismic designs of double-row piles.

Artificial ground motion compatible with specified ground shaking peaks and target response spectrum

This article describes a hybrid simulation method to generate artificial ground motion time histories that are compatible with specified peak seismic acceleration, velocity and displacement as well as the target response spectrum of absolute acceleration. First, based on traditional methods that match the target spectrum in the frequency domain, an initial acceleration time history was synthesized to satisfy the specified peak acceleration, target spectral acceleration and intensity envelope. Second, by using the inversion formula of the seismic input to a linear single-degree-of-freedom system and by superimposing a series of narrow-band time histories in the time domain, the initial time history is further modified to allow its peak velocity and displacement to approach the targets and improve its matching precision with the target spectrum. Numerical examples are provided to demonstrate that the proposed method achieves good agreement with the target values.

Seismic responses of the steel-strip reinforced soil retaining wall with full-height rigid facing from shaking table test

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.

Shaking table tests and dynamic analyses of masonry wall buildings with frame-shear walls at lower stories

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.

Chemically induced changes in the geotechnical response of cementing paste backfill in shaking table test

Cemented paste backfill(CPB)is extensively used for underground mine support and/or tailings management.However,CPB behavior under cyclic loadings might be affected by the chemistry of its porewater,which often contains sulphate ions.Till today,no studies have addressed the effect of sulphate on the response of CPB to cyclic loadings by using shaking table technique.This study presents new findings of assessing the effect of the sulphate in the pore water of CPB on its geotechnical response to cyclic loading by using shaking table.CPB mixtures were prepared(with and without sulphate),poured into a flexible laminar shear box,cured to 4 h,and then exposed to cyclic loading using one-dimensional(1D)shaking table.Several parameters(e.g.pore water pressure,settlement,lateral deformation,acceleration,electrical conductivity,effective stress,and liquefaction susceptibility)were monitored or determined before,during,and after shaking.Obtained results indicate that the sulphate-bearing CPB cured to 4 h can be prone to liquefaction under the studied conditions.However,sulphate-free CPB samples are resistant to liquefaction.These results are expected to contribute to a better understanding of the effect of water chemistry on the cyclic behavior of CPB,consequently enhancing the cost-effective design of CPB structures.