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development of the shaking table and array system technology in china

development of the shaking table and array system technology in china

Chun-hua Gao, Xiao-bo Yuan, "Development of the Shaking Table and Array System Technology in China", Advances in Civil Engineering, vol. 2019, Article ID 8167684, 10 pages, 2019. https://doi.org/10.1155/2019/8167684

Shaking table is important experimental equipment to carry out antiseismic research. Research, conclusion, comparison, and analysis concerning the developmental history, constructional situation, performance index, control algorithm, and experimental technique of the internal shaking table were reviewed and compared. Such functional parameters as internal shaking tables table-board size, bearing capacity, working frequency, and maximum acceleration were given. Shaking tables constructional status quo and developmental trend were concluded. The advantages and disadvantages of different control algorithms were contrastively analyzed. Typical shaking table test, array system tests, and experimental simulation materials were induced and contrasted. Internal existing shaking table and array system tests structural type, reduced scale, and model-material selection were provided. Analysis and exposition about the developmental tendency of shaking tables enlargement, multiple shaking tables array, full digitalization, and network control were made. The developmental direction, comparison of technical features, and relevant research status quo of shaking table with high-performance were offered. The result can be reference for domestic or overseas shaking tables design and type selection, control technique, and research on experimental technique.

At present, the structural seismic research methods include the pseudostatic test, pseudodynamic test, and shaking table test. The test method of the shaking table test can recreate the structural response and seismic oscillation in the lab accurately and reproduce the whole process of seismic oscillation effect or artificial effect in real time. The development of shaking table provides an accurate and effective way to study structural elastic-plastic seismic response [13].

Japan and the United States are the first two countries to establish shaking tables in the world. And, China initially built a shaking table in 1960 [1] when Institute of Engineering Mechanics, Chinese Academy of Sciences, built one-way horizontal vibration [47] with a specimen size of 12m3.3m. So far in China, there are a lot of shaking tables [1]; some were made in China, some were systematically remodeled from imported parts, and some were totally imported. In recent years, many scholars [8, 9] and Wang et al. [2] conducted abundant research on the development and control technology of Chinas shaking tables and also got some research achievements. However, such results are mostly summaries of the test technologies or control technologies of shaking table [10], while there are few summaries concerning the construction history and usage of domestic shaking tables. This paper makes a comprehensive summary of the development and application of domestic shaking tables and array test technologies in terms of the development, control technology, test application, and development trend of shaking table and array system based on current collected information, so as to provide some reference and basis for the construction and development of domestic shaking table.

The development of shaking table in China came relatively late [1, 3, 1114]. It can be roughly divided into four stages. In 1960s, the mechanical shaking table was the main stream with a working frequency of 1Hz40Hz, of which the characteristics of the specimens in low segment are difficult to be controlled [2, 10, 11]. Electrohydraulic shaking table was then rapidly developed with its high frequency. In 1966, departments of machinery and electronics collaborated with each other to build Chinas first exclusive shaking table for national system of defense in three years [2, 10, 13]. Thereafter, many domestic colleges and universities as well as scientific research institutes also begun to conduct researches. For example, Tongji University brought in the 4m4m two-horizontal dimensional identically dynamic electrohydraulic shaking table developed by American MTS, which has been transformed into three- to six-degree-of-freedom identically dynamic shaking table [1]. At the beginning of the 70s, the research on shaking table in China was continuously carried out and quickly developed. Our country also started to develop one-way electrohydraulic servo shaking table but rarely hooked into multiaxis shaking table [1520]. And, foreign shaking tables were introduced only when the test was demanding, so the introduction quantity of shaking tables was sharply decreased. Domestic institutes that conduct researches on shaking table mainly include China Academy of Building Research, Xian Jiaotong University, HIT (Harbin Institute of Technology), Institute of Engineering Mechanics, and Tianshui Hongshan Testing Machine Co., Ltd. [21, 22]. The shaking table construction situation in China is shown in Table 1.

The work frequency of electrohydraulic shaking table in the early stage of our country was about 50Hz. At present, at home and abroad, the work frequency of high-thrust shaking table with over 50t can reach more than 1000Hz. For instance, the work frequency of Y2T.10c shaking table developed by 303 Research Institute of China Aviation Industry Corporation is as high as 1000Hz, and the wide band random vibration control precision is 2.0dB [23] within the frequency range of 20Hz1000Hz.

In 2006, Beijing University of Technology built a nine-sub-building block array system with a size of 1m1m, which along with the original 3m3m single-array system composed the 10-subarray system, which can be used to constitute testing systems with any several subarray systems and many optional positions; at the end of 2006, Institute of Electro-Hydraulic Servo Simulation and Test System of Harbin Institute of Technology (HIT) developed successfully the first domestic multiaxis independent intellectual property rights (the hydraulic vibration test system with shaking table system is shown in Figure 1) and got identification, which changed the history of depending on importing shaking tables [24]. In 2012, Jiangsu Suzhou Dongling Vibration Test Instrument Co., Ltd. successfully developed the worlds largest single electromagnetic shaking table test system (http://www.cnki.net/kcms/detail/11.2068.TU.20130124.1608.001.html) with a thrust of 50 tons.

With the 9-subarray system of Beijing University of Technology as an example, this paper introduces the construction situation of shaking table array system. In 2003, The State University of New York built the first set of two-subarray systems. In the same year, the University of Nevada-Reno built the three-subarray system with three movable two-direction shaking tables. The size of the table and the maximum bearing capacity of the shaking table are introduced. The array system (shown in Figure 3) is suitable for experimental research on spindly space structure.

In 2004, Chongqing Jiaotong Institute of our country completed the constitution of the two-subarray system with a specimen size of 6m3m, of which one is fixed and the other is movable (shown in Figure 4). And, in 2008, National Key Laboratory of Bridge Dynamics was established.

In 2011, Beijing University of Technology began to prepare to construct nine-subarray system (shown in Figure 5) and has built 12 sets of actuator building block array systems till 2006, which was increased to 16 sets in 2009 and is now the array system with the largest number of single-array system in the world. Each single shaking table is composed by mesa, 5 connecting rods, a vibrator, and a base. The array system can be made into various combinations by 16 sets of vibrators and connecting rods to conduct varied shaking table array tests with different layouts and forms. The performance indicators of nine-subarray system are shown in Table 2. The system uses four piston pumps to offer oil. The rated oil supply pressure of the seismic simulated shaking table system is the same as the maximum oil supply pressure. In addition to 4 oil pumps, the system also has energy storage to supplement the oil supply when the oil supply of the oil supply pump is insufficient.

There are two main types of traditional shaking table control technology: one is PID control based on displacement control and the other is three-parameter feedback control (also known as the three-state feedback control) synthesized by the displacement, velocity, and acceleration [25]. It is essential for feedback theory to adjust the system after making the right measurement and comparison. In 1950, the PID control method mainly composed of unit P proportion, integral unit I, and differential unit D was developed. The traditional PID control method is simple in control algorithm, good in stability, and high in reliability and thus has been widely applied in the practical engineering. The PID control method is especially suitable for deterministic control system. Yet, as the target signal of shaking table is acceleration signal, high-frequency control performance is poorer when the displacement PID control is adopted, while the mesa cannot be located if acceleration PID is used. Meanwhile, in the process of control, nonlinear behavior exists in every specimen; thus, the effect of traditional PID control is not ideal due to the large waveform distortion [24, 2629]. As the structure sets higher requirement for control accuracy, three-parameter feedback control synthesized by the displacement, velocity, and acceleration was put forward in 1970s (the control principle is shown in Figure 6), which makes up for the narrow frequency band and the inability to realize acceleration control of single displacement control. Acceleration feedback can improve the system damping, and velocity feedback can improve the oil column resonance frequency. Adopting the displacement to control low frequency, speed to control midfrequency, and acceleration to control high frequency plays an important role in improving the dynamic behavior and bandwidth of the system. The introduction of three-parameter control technology greatly improved the playback accuracy of seismic time history, but due to the complexity of transfer function in the system, the correlation of input and output waveform is still not high. Power spectrum emersion control algorithm modifies drive spectrum utilizing system impedance and the deviation of the reference spectrum and the control spectrum, so as to get a relative high consistency of response spectrum and reference spectrum of the system [30, 31]. Power spectrum retrieval principle diagram is shown in Figure 7. This method belongs to the nonparametric method, which has nothing to do with any model parameters. But the matching degree of estimated power spectral density and real power spectral density is very low, so it is an estimation method with low resolution.

Another kind of the parametric estimation method, using the parameterized model, can give a much higher frequency resolution than period gram methods. The power spectrum control method based on the parameter model has high resolution and can improve the system control convergence speed and power spectrum estimation precision, yet it is sensitive to noise with higher computation requirements. Therefore, in the vibration test control, it has not reached practical stage [32].

The traditional control algorithm is based on the linear model of vibration table and specimen [33], and the parameters in the process of test are assumed unchanged, but the actual test object is very complex. The components experience elastic-plastic phase and then the failure stage in the process of the test, and the parameters that were assumed to be unchanged turn out to have been changed in the process of test. The change of the parameters influences the accuracy of the input seismic signal, which is the biggest defect in the traditional control technology. From the 1970s to 80s, intelligent control is a new theory and technology with strong control ability and great fault tolerance. The introduction of the adaptive control improved the robustness and control precision of the system, such as adaptive harmonic control theory (AHC), adaptive inverse function control theory (AIC), and the minimum control algorithm (MCS) [34]. At present, the fuzzy control algorithm of the structure control attracted the attention of more and more scholars with its advantages of powerful knowledge expression ability, simple operational method, and the adoption of fuzzy language to describe the dynamic characteristics of the system. As early as 1996, some scholars abroad has carried out the induction and comparison of structural seismic control methods and summarized the advantages and disadvantages of various control methods, particularly expounding that the fuzzy control and neural network control algorithm could better solve the problem of nonlinear. The application of domestic intelligent control algorithm in the engineering structure control is relatively late. In 2000, Ou [29] and other scholars proposed the control algorithm which can realize fuzzy control according to the control rules and fuzzy subset, which greatly improved the practicability and efficiency of fuzzy control algorithm.

Most of the fuzzy control rules are established based on experience, leading to great difficulty in structure control. In view of this, Wang and Ou [35], in 2001, put forward the method of extraction, optimization, and generation of fuzzy control rules with the basis of structural vibration fuzzy modeling and genetic algorithm. Qu and Qiu [36] came up with a kind of active feed forward control method based on adaptive fuzzy logic system method, which better solved the nonlinear control problems of reference signal and external interference in the feedforward control. Wang [30] for flexible structure completed the application of the fuzzy PID control method in the structural vibration and conducted the active control experimental verification of beam vibration.

The efficiency of fuzzy control depends on the selection of function parameters and the establishment of the fuzzy control rules. Therefore, the adaptive fuzzy control is of great research significance for the nonlinear structure system. Because of the functions of self-adaptation and self-study of artificial neural network, the application of neural network in seismic control in civil engineering began in the 60s, which adopts a simple neural network controller to control the movement of the inverted pendulum, and achieved good effect. In 2003, Mo and Sun [31] implemented numerical simulation of active vibration control on the beam vibration control model by using genetic algorithm with the minimum energy storage structure as the goal, compared with the exhaustive method, and achieved good control effect. Chen and Gu [37] carried out simulation research on the application of frequency adaptive control algorithm based on the least square method in the domain of vibration control, and the simulation got the damping effect of about 50db. Li and Mao [38] achieved evolutionary adaptive filtering algorithm with strong instantaneity and applied it into the vibration control of structures to conduct simulation calculation based on genetic algorithm and moving least mean square algorithm of transient step, and the simulation obtained the damping effect of about 30db.

To solve the limit bearing capacity of shaking table for large structure test, scholars from all over the world conducted a wide variety of researches. The combination of substructure technique and shaking table test is an effective way to solve this problem [39]. Hybrid vibration test divides the structure into test substructure and numerical substructure. Test substructure is the complex part in experiment on shaking table, while numerical substructure is the simple part to carry out numerically simulation. Test substructure can carry out full-scale or large-scale model test, avoiding the influence of the size limit of shaking table with large-scale structure, and thus was widely used in the study of the engineering seismic test. The domestic researchers Chen and Bai [33] implemented preliminary exploration into structural seismic hybrid test technique on account of the condensation technology. In 2008, Chen and Bai [33] also embarked on the hybrid vibration test on the hybrid structural system of commercial and residential buildings, of which the bottom commercial district was put into a full-scale experiment on shaking table and other parts were involved in numerical simulation.

In 2007, Mr. Wu Bin from Harbin Institute of Technology applied the center difference method into the change of the acceleration calculation formula in hybrid real-time test which takes consideration of the quality of test substructure and analyzed the stability of the algorithm. The test results show that the stability of the center difference method in real-time substructure application is poorer than that of the standardized center difference method. Such scholars as Yang [40] in the same year made the numerical simulation analysis on the shaking test substructure test, and the analysis results show that the integral step change is sensitive to the influence of experimental stability. At the same time, he verified the validity of the theoretical research results.

In recent years, the structural styles of shaking table test research were developed from masonry structure, frame structure, tube structure to bridge structure, structures with the consideration of some isolation and damping measures, and structural foundation interaction experiment. The application of shaking table tests on the structure seismic resistance made it possible to establish structure nonlinear model with various structural styles [2]. Many shaking table tests have been carried out in recent years in China, which, according to the testing purpose, can be roughly divided into three categories: the first type is to determine structural earthquake-resistance performance as the test purpose; the second type is to determine the dynamic characteristics of structure, obtain such dynamic parameters as the natural vibration period and damping of structure, seek for weak parts of the structure damage, and provide the basis for super high-rise and supergage designs; the third type is to verify the applicability of certain measure or design theory in the structure. This paper drew a conclusion of typical shaking table tests in recent years in terms of building types, model dimensions, and so on (shown in Table 3).

Shaking table experiment diversifies the structural styles in experiment, makes it possible to establish the nonlinear damage model, and provides a reliable basis for all kinds of structures to establish the corresponding destruction specification. But large span structure tests on bridges, pipes, aqueduct, transmission lines, and so on may produce traveling wave effect under the action of earthquake due to large span, and a single shaking table will not be able to simulate the real response of the whole structure under seismic action. Array system can better solve these problems. For example, the State University of New York-Buffalo did damper damping effect research on Greek Antiliweng Bridge using 2-subarray system; conducted shaking table array test research on two continuous steel plate girder bridge and concrete girder bridge by using the 3-subarray system of University of Nevada. Many domestic scholars also carried out shaking table array test research on different structures of array systems. For instance, in 2008, Gao Wenjun made shaking table array test research of organic glass model on Chongqing Chaotianmen Bridge with the 2-subarray system of Chongqing Traffic Academy; conducted a multipoint shaking table array test research on concrete-filled steel tubes arch bridge with the 9-subarray system in Beijing University of Technology.

According to the size of mesa, shaking tables can be divided into large, medium, and small ones; in general, specimen size less than 2m2m for the small, 6m6m for the medium, and over 10m10m for the large. Due to the size limitation of a small seismic simulation vibration table, it can only do small-scale tests, and there is a certain gap with the prototype test. In the seismic simulation vibration table test of scale model, all parameters are required to meet the similarity principle, but it is difficult to do in practical engineering. For some important structures, especially the important parts of large structures, to accurately reflect the dynamic characteristics of the structure, within the permitted scope of the condition of capital, it is necessary to increase the specimen size and the maximum load as much as possible to eliminate the size effect of the model, so the large full-scale test must be the development trend of shaking table. China Academy of Building Research developed a shaking table with a mesa dimension of 6.1m6.1m and the maximum model load of 80t.

Due to the great investment, high maintenance cost, and test fees as well as long production cycle of large-scale shaking table, infinite increase in size of shaking table is obviously unreasonable, and likewise, it is not possible to fully meet the actual requirements only by increasing the size of shaking table. For large-span structure tests on bridges, pipes, aqueduct, transmission line, and so on array systems composed of many sets of small shaking table can be adopted. Shaking table array can either conduct a single test or make seismic resistance test on the structure of large-scale, multidimensional, multipoint ground motion input with varied combinations according to various needs. Therefore, the array system composed of many sets of small shaking tables must be the development trend of shaking table.

In terms of control mode, power spectral density control was mostly adopted before 1975. After 1975, Huang Haohua and other scholars used the time-history playback control to finish the seismic wave control research in a broad band. In the mid-1990s, digital control and analog control are widely used in the shaking table control, of which digital control is mainly applied in the system signal and compensation and the analog control is the basis for the control, whose control mode is complicated in operation with too much manual adjustment. After 1990s, Fang Zhong and other scholars developed a full digital control technology which has been widely used in the hydraulic servo control system with the rapid development of digital technology. Other than the valve control device and feedback sensor which adopt analog circuits, the rest utilize digital software to fulfill implementation. This control method can make up for some flaws in the analog control with simple test operation, being able to improve the accuracy, reliability, and stability of the system. Full digital control is the inevitable development trend of hydraulic servo system control.

With the appearance of slender and shaped structures and the application of new materials in building engineering, the seismic test methods of structures are put forward with higher and higher requirements. To meet the requirements of actual engineering and seismic research, scholars from all over the world are active in exploration and attempt and put forward some new testing methods. In recent years, countries around the world greatly invest in seismic research. From 2000 to 2004, the United States Science Foundation Committee spent eighty million dollars of research funding on the NEES plan; Europe established a collaborative research system European Network to Reduce Earthquake Risk (ENSRM); South Korea established a virtual structure laboratory using grid technology, which includes the wind tunnel, the shaking table, and other scientific research equipment. Furthermore, Internet ISEE Earthquake Engineering Simulation System in Taiwan of China was the earthquake engineering research platform developed by National Earthquake Engineering Research Center of Taiwan, China, with the Internet. The platform not only allows several laboratories to interconnect each other to implement large-scale shaking table test but also permits different laboratory researchers around the world to observe the test simultaneously and synchronously.

In China, Hunan University firstly put forward the structure network synergy test research and cooperated with Vision Technology Co., Ltd in 2000 to develop the network structure laboratory (NetSLab is shown in Figure 8). The main module and interface are shown in Figure 8. Thereafter, Hunan University cooperated with Harbin Institute of Technology to accomplish secondary development to establish the network collaborative hybrid test system and conducted a structure remote collaborative test along with Tsinghua University, Harbin Institute of Technology. Three domestic universities firstly completed remote collaboration pseudodynamic test, which is shown in Figure 9.

This paper drew a conclusion of the construction, history, and status quo as well as application and research of shaking table and array. The main conclusions are as follows:(i)On account of factors of actual application demand and economy, the size of the shaking table is between 1m and Xm, among which 3m6m are the majority. For large span structures such as bridges and pipes many sets of small array mode of vibration table can be used.(ii)Shaking table mesa acceleration and speed are about and 80cm/s, respectively. Through statistics, the remarkable frequency of previous ground motion records is mainly within 0.1Hz30Hz, and the frequency range of medium shaking table should be in 0Hz50Hz according to the requirements of the similar rule. Moreover, tests with special requirements need to be above 100Hz.(iii)With the appearance of slender and shaped structures and the application of new materials in building engineering, the seismic test methods of structures are put forward with higher and higher requirements.

The authors acknowledge the support from the Science and Technology Breakthrough Project of the Science and Technology Department of Henan Province ( 9), the Key Scientific Research Projects in He Nan Province (No. 18B560009), and Nanhu Scholars Program for Young Scholars of XYNU in China. The authors thank Xin Yang Normal University School of Architecture and Civil Engineering Laboratory and would also like to thank teachers and students of the team for collecting data.

Copyright 2019 Chun-hua Gao and Xiao-bo Yuan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

shaking table tests on deformation and failure mechanisms of seismic slope | jve journals

shaking table tests on deformation and failure mechanisms of seismic slope | jve journals

Journal of Vibroengineering, Vol. 17, Issue 1, 2015, p. 382-392. Received 20 October 2014; received in revised form 5 December 2014; accepted 14 January 2015; published 15 February 2015

Zhao Mingsheng, Huang Dong, Cao Maosen, Qiao Jianping Shaking table tests on deformation and failure mechanisms of seismic slope. Journal of Vibroengineering, Vol. 17, Issue 1, 2015, p. 382-392.

The 2008 Wenchuan earthquake in China induced many landslides. Gigantic slope failures have attracted serious concerns in engineering practice; however, small slope failures should also be investigated as they are more common. In particular, the detailed characteristics of slope failures during earthquakes remain unknown. Therefore, the present study carried out 1-G shaking table tests on a straight shape slope model with different shaking intensities and frequencies. The test results showed the amplification of motion, the initiation of failure, and final failure mode of the straight shape slope. Also, the experimental results can be used to investigate the response and amplification behavior of some prototype slopes. The results are helpful to demonstrate the detailed collapsing behavior of the slope under earthquake excitation, and provide useful data to analyze the failure mechanism of landslides and valuable references for seismic design of landslide engineering.

Seismic landslide is one of the main disasters caused by earthquakes [1-4]. The 2008 Wenchuan earthquake (Ms=8.0) in Sichuan Province of China induced approximately 20,000 slope failures [5], among which the large earthquakes have drawn engineering attention because they killed many people and formed natural dams, further leading to the risk of breaching and flooding [6-8].

At present, analysis and prediction of seismic landslide basically include three aspects, namely remote sensing techniques, analog methods, theoretical analysis and experimental modeling. The remote sensing technique is used to study an area before and after the occurrence of earthquake using panchromatic sharpened linear imaging self scanning images, in which landslide inventories are first produced. Thus the remote sensing technique is an appraisal procedure, rather than predicting the probability of a landslide occurrence. The analog method is used mainly to predict the occurrence probability of a landslide under potential earthquake by comparing with previous landslides in typical earthquakes. Therefore, the analog methods is only an empirical method. The method of theoretical analysis focuses on the mechanical behaviors under earthquake using analytical or numerical methods. However, it is difficult to describe the complex behaviors in the process of a landslide, and the parameters of rock mass, which are needed in numerical simulation, can only be determined approximately. Experimental modeling can well reflect the occurrence mechanism and process of a landslide under earthquake at the model scale and the manner of exerting seismic loading is suitable.

In this regard, the present paper focuses on failures of relatively small scale slopes which occur much more often than the large ones. The present study determines the initiation of the earthquake-induced landslide with approaches based on either the acceleration of the sliding body or the development of displacement. Further, the effects of nonlinear stress-strain characteristics of soils are considered. This is because the shallow part of mountain slopes is often subjected to weathering and hence is composed of fragmentary rocks. As a result, an elastic dynamic analysis is merely an oversimplified approach for design, and nonlinear dynamic response and failure behavior of mountain slopes should be further studied. It is noteworthy that many mountain slopes once subjected to strong earthquakes became instable in later earthquakes, with features such as debris flow [9-13]. This confirms the importance of considering mountain slopes as consisting of soils rather than intact rocks.

To more realistically demonstrate the behavior of small scale slopes, the present study was undertaken by performing 1-G shaking table tests on models of mountain slopes undergoing different intensities and frequencies of shaking.

Fig.1 illustrates a slope failure of relatively small size that occurred at Tazhiping in Dujiangyan City at the location (103.375_E, 31.629_N) in the Hongse village, Hongkou Town. It is evident that the slip plane is rather straight, suggesting that the weak materials at the surface fell under seismic excitation. There were many similar events associated with straight slip planes in the Wenchuan earthquake-hit region. The Tazhiping landslide was triggered by the main shock of Wenchuan earthquake and caused at least 1 fatality. The elevation of the landslide ranged from 1107m to 1370m. Its length was about 530m, and the width was about 145m. The landslide lithology was fragmentary rocks and the surface was covered by silty clay and gravel. The space distribution of slippery bodies was thick in the center and thin near the perimeter, and the estimated thickness of the sliding mass was 20m to 25m. The estimated volume of the landslide was about 116104 m3. The landslide angle was around 32 degrees.

To investigate the deformations and failure mechanisms of straight slopes, a series of tests was performed with different input amplitudes and frequencies of sinusoidal waves. Based on the measurements of the acceleration and displacement of different points in the slope model, the dynamic characteristics and responses of the straight model slope under earthquake, as well as the influence of ground motion parameters, are discussed.

The shaking table at the Geotechnical Engineering Laboratory, University of Tokyo, is 2m wide and 3m long, and is capable of applying bi-directional horizontal accelerations. The bearing capacity of the shaking table is 7 tons, and the maximum applied acceleration is 1,000 Gal (1g) frequencies up to 50 Hz. Soil slope models were prepared in a soil container with 3 m in length, 0.4 m in width and 0.6 m in depth. This container was tightly fixed onto the shaking table so that there was no slippage between them. A total number of 14 accelerometers and 4 displacement gauges were installed to measure horizontal dynamic responses during the experiments (inclinometers were prepared by making a column of accelerometers) [14-16]. Fig.2 shows that the accelerometers were installed in vertical arrays below the crest and the shoulder as well as along the slope to measure the distribution of accelerations inside the slope model. It is also seen that square grids with color were installed in the vertical glass wall to demonstrate visually the dynamically-induced deformation of the model.

Slope models consisted of uniform Toyoura sand with the mean grain size of 0.174 mm and the void ratio between emin= 0.605 and emax= 0.974. In the preparation of the slope models, the relative density of 32%, the void ratio of 0.857, and the moisture content of 1% were used. The effective stress in the small-scale 1-G model tests was around 1/500 of the prototype, and thus the density of sand was reduced so that similitude of dilatancy was maintained [17-19]. In line with this, the time scale in the model tests was made shorter than the prototype event in consideration of the reduced size of models by shaking all the models at, for example, 10 Hz, which was higher than the real earthquake events. Shaking at lower frequencies of 2 and 5 Hz was run as well. The duration of shaking was 30 seconds. The moisture content of 1% was employed to provide a certain apparent cohesion to the sand to avoid failure at the very surface of the slope. The intensity of base shaking in the horizontal and longitudinal direction of models varied from 100 to 700 Gal.

Fig.4 shows detailed acceleration time histories. Fig.5 plots the ratio of maximum acceleration (amplitude) along the vertical array in the slope (A1 to A5 in Fig.2) to the shaking table acceleration. The case of 500Gal shaking under frequency of 10Hz exhibits more remarkable amplification than others, as shown in Fig.5(a). This is most probably due to the nonlinear stress-strain behavior of sand in that the elastic modulus decreases as the dynamic stress and shear strain increase, leading to varying natural periods in the model. This point is examined in more detail in Fig.5(b), in which the variation of amplification with shaking frequency is plotted for base acceleration with input seismic wave of 500Gal. Fig. 5(b) shows that the case of 10Hz is probably closer to the resonance frequency of the model, exhibiting more remarkable amplification than the other cases.

Fig.6(a) shows the ratio of the maximum acceleration (i.e. amplitude) at the surface of the slope (AC1 to AC4 in Fig. 3) to that applied the base with amplitude up to 500 Gal. This allows study of the effects of nonlinearity of soils in greater detail. Actually, shaking at 700 Gal caused slope failure and thus the corresponding results are not included in Fig. 6. AC4 at the crest shows more significant amplification than the other cases. The amplification at the slope shoulder (AC3) is large as well but smaller than that at the crest (AC3

Fig. 8 illustrates the failed shape after 700-Gal shaking at 10Hz frequency. The square grids in the photo clearly indicate that shear failure or slippage took place at some depth below the surface, as expected by using 1% moisture content. The linear shape of the shear plane was similar to the failure of the prototype slope as shown in Fig.1.

Fig.9 compares the shape of the slope before and after shaking. The model slope, nearly intact under 500Gal shaking, suddenly developed cracks and then slid at shallow depth below the slope under 700Gal shaking. In the same figure, the time histories of horizontal acceleration along the slope surface are shown. The bias from zero is due to tilting of the transducer after slope failure. From the amplitude of acceleration at the slope surface, it is found that the shaking was weaker in the lower part of the slope (AC1 and AC2), and stronger in the upper half (AC3 and AC4). The increasing acceleration towards the top was caused by energy concentration at the narrower slope, as observed in reality. Moreover, the acceleration in the slope shoulder (C1) became less than that at the surface.

The recorded acceleration was integrated twice and the effects of tilting and other baseline errors from the acceleration were removed to obtain the time history of displacement, as shown in Fig.10. Clearly, the displacement amplitude, which was closely related to the local shear strain amplitude, increased from the bottom (AC1) to the shoulder (AC3) and the crest of the slope (AC4), indicating more nonlinearity and extent of yielding of soils at higher elevations. The significant shear strain induced large deformation. The failure was initiated at AC4 at the crest and then proceeded to AC1 at the bottom of the slope. Fig.11 traces the development of slope failure with time. The displacements in this photo are consistent with the findings in Fig.10.

The deformation of the slope subjected to seismic loads was further studied by the particle image velocimetry (PIV) [18]. Fig.12 presents a digital cross-correlation analysis of double frame/single exposure records, in which the cross-correlation between two interrogation windows sampled from the image records is calculated [20] and the displacement of sand grains between photographs at two time points is detected. The PIV technology was applied to large-scale shaking table model tests of slope stability, and Fig.13 indicates that the displacement and the velocity were greater above a plane known as the slip plane.

The results show that the PIV technology could effectively measure the displacement of any point at any time with accuracy within the observation region. Furthermore, more information about the process of deformation development could be obtained, such as the formation of strain localization and the whole failure process of slopes under earthquake.

To compare the dynamic failure of slope model in shaking table tests, a finite-element dynamic analysis was performed. The total number of elements was 804 with 886 nodes, as shown in Fig.14. For this analysis, an elastic-perfectly plastic constitutive model with the Mohr-Coulomb failure criterion was adopted for soils. The input parameters for slightly wet Toyoura sand are shown in Table 1 [21]. The sand parameters will be discussed later. 300 Gal (10 Hz) and 700Gal (10 Hz) seismic wave inputs were applied at the bottom of the numerical model, which was consistent with the shaking model tests (see Fig.2). The duration of shaking was 30 seconds.

Fig.15 shows the peak acceleration within the slope and at its surface (corresponding to AC1-AC4 and A1-A5 in Fig.1), respectively. Compared with the model tests (Fig.5(a)), the calculated accelerations under this relatively weak shaking are similar to the experimental findings. Therefore, the FEM approach is suitable for calculating the acceleration in the slope when the whole slope is intact.

The time histories of the displacement of AC4 and AC3 (as indicated in Fig.3) are shown in Fig.16, and correspond to the maximum shear strain in the slope. The displacement at the shoulder of the slope (AC3) is nearly consistent with that from the experiment result (Fig.11). However, at the crest of the slope (AC4), the calculated displacement is smaller than the experiment result. This implies that the simulation is not suitable for evaluating the failed shape of a slope, because conventional FEM cannot properly deal with large deformation.

A series of shaking table tests was conducted in 1-G environment to study the effects of shallow slope instability during earthquakes. The effects of reduced confining pressure and the small model size as compared with the prototype were taken into account by employing reduced sand density and shortened time scale. The major findings from this study are summarized as follows:

1)Model tests show that greater acceleration developed near the top of the slope, suggesting the amplification of motion. The displacement amplitude, which was closely related to the local strain amplitude, increased from the bottom to the top of the slope, indicating greater nonlinearity and extent of yielding of sand soils at higher elevations.

2)The acceleration near the shoulder of the slope (AC3) was greater than that at the crest of the slope (AC4) when the slope angle was small. This suggests that failure is initiated from the shoulder.

3)The PIV technology was able to effectively measure the displacement of any point at any time with reasonable accuracy within the observation region. Furthermore, more information can be obtained about the process of deformation development, the formation of strain localization and the whole failure process of slope under earthquakes.

The present study was conducted within a framework of an international collaboration project between Institute of Mountain Hazard and Environment Chinese Academy of Science and University of Tokyo. This work was supported by National Natural Science Foundation of China (Grant No.41301009) and the International Cooperation Program of the Ministry of Science and Technology of China (Grant No.2013DFA21720), the National Science and Technology Support Program during the Twelfth Five-Year Plan Period (Grant No.2011BAK12B01) and the Guizhou Province Outstanding Young Scientific Talents Training Program Funded Projects (No.(2013)30). The authors express their gratitude for those aids and assistances.

shaking table | gravity separator - mineral processing

shaking table | gravity separator - mineral processing

Shaking tables are one of the oldest gravity separators in the mineral processing industry, capable of handling minerals and coal of 0-2mm.Shaking tables are rectangular-shaped tables with riffled decks across which a film of water flows. The mechanical drive imparts motion along the long axis of the table, perpendicular to the flow of the water. The water carries the particles of the feed in slurry across the riffles in a fluid film. This causes the fine, high density particles to fall into beds behind the riffles as the coarse, low-density particles are carried in the quickly-moving film. The action of the table is such that particles move with the bed towards the discharge end until the end of the table stroke, at which point the table rapidly moves backwards and the particles momentum propels them still forward.

The capacity of the shaking table is about 0.5 t/h. 1.5-2TPH depending on the particle size of the process. In chromite processing and dressing industry, it is usually dozens of shaking table series or parallel installation to deal with excess tons. Therefore, the required installation space, equipment control difficulties due to the increased number of installations and the need for more automated processes have brought new challenges to the process design.

1. Big channel frame, very strong steel base structure( other companies use small channel frame)2. Polypropylene materials feeding chute and collection chute.(other companies dont have )3. Heighten steel stand,making it more convenient when feeding materials.4. Add cover for belt wheel5. Use top quality fiberglass deck,more wear-resisting6. Has various grooves on the table for your choice. We will recommend the best grooves to you according to your gold size.

a benchmark 1g shaking table test of shallow segmental mini-tunnel in sand | springerlink

a benchmark 1g shaking table test of shallow segmental mini-tunnel in sand | springerlink

A 1g shaking table test of a shallow segmental mini-tunnel in sand is performed to investigate its dynamic responses. The properties of sand, the materials and design of the segmental tunnel, the construction process of testing models and the instrumentation scheme are introduced in full detail. Two levels of intensity and three typical central frequencies of idealized Ricker wavelets, making six cases of excitations, are applied to both the free-field model and the soil-tunnel model. Two white noise cases before and after the design-level cases are also performed to verify the dynamic characteristics of the models. Comprehensive results, including the acceleration responses of the two models, deformations at radial joints and in the diametral directions of the tunnel, bolt tensions between segments as well as strains of segments, are presented. The minutiae of the test are clarified to reduce uncertainties, and experimental results are carefully verified. It could be a benchmark test of segmental tunnels in dry sand ground by means of 1g shaking table.

Chen G, Chen S, Qi C, Du X, Wang Z, Chen W (2015) Shaking table tests on a three-arch type subway station structure in a liquefiable soil. Bull Earthq Eng 13:16751701. https://doi.org/10.1007/s10518-014-9675-0

Chen Z, Liang S, Shen H, He C (2018) Dynamic centrifuge tests on effects of isolation layer and cross-section dimensions on shield tunnels. Soil Dyn Earthq Eng 109:173187. https://doi.org/10.1016/j.soildyn.2018.03.002

Gazetas G, Psarropoulos PN, Anastasopoulos I, Gerolymos N (2004) Seismic behaviour of flexible retaining systems subjected to short-duration moderately strong excitation. Soil Dyn Earthq Eng 24:537550. https://doi.org/10.1016/j.soildyn.2004.02.005

Kawamata Y, Nakayama M, Towhata I, Yasuda S (2016) Dynamic behaviors of underground structures in E-Defense shaking experiments. Soil Dyn Earthq Eng 82:2439. https://doi.org/10.1016/j.soildyn.2015.11.008

Lanzano G, Bilotta E, Russo G, Silvestri F (2015) Experimental and numerical study on circular tunnels under seismic loading. Eur J Environ Civ Eng 19:539563. https://doi.org/10.1080/19648189.2014.893211

Liu X, Bai Y, Yuan Y, Mang HA (2016) Experimental investigation of the ultimate bearing capacity of continuously jointed segmental tunnel linings. Struct Infrastruct Eng 12:13641379. https://doi.org/10.1080/15732479.2015.1117115

Madabhushi GSP, Madabhushi SSC, Haigh SK (2018) LEAP-GWU-2015: centrifuge and numerical modelling of slope liquefaction at the University of Cambridge. Soil Dyn Earthq Eng 113:671681. https://doi.org/10.1016/j.soildyn.2016.11.009

Pitilakis K, Tsinidis G (2014) Performance and seismic design of underground structures. In: Maugeri M, Soccodato C (eds) Earthquake geotechnical engineering design. Springer, Cham. https://doi.org/10.1007/978-3-319-03182-8-11

Rabeti Moghadam M, Baziar MH (2016) Seismic ground motion amplification pattern induced by a subway tunnel: shaking table testing and numerical simulation. Soil Dyn Earthq Eng 83:8197. https://doi.org/10.1016/j.soildyn.2016.01.002

Rgnier J et al (2016) International benchmark on numerical simulations for 1D, nonlinear site response (PRENOLIN): verification phase based on canonical cases. Bull Seismol Soc Am 106:21122135. https://doi.org/10.1785/0120150284

Tobita T, Ashino T, Ren J, Iai S (2018) Kyoto University LEAP-GWU-2015 tests and the importance of curving the ground surface in centrifuge modelling. Soil Dyn Earthq Eng 113:650662. https://doi.org/10.1016/j.soildyn.2017.10.012

Tsai C, Lin W, Chiou J (2016) Identification of dynamic soil properties through shaking table tests on a large saturated sand specimen in a laminar shear box. Soil Dyn Earthq Eng 83:5968. https://doi.org/10.1016/j.soildyn.2016.01.007

Tsinidis G, Pitilakis K, Trikalioti AD (2014) Numerical simulation of round robin numerical test on tunnels using a simplified kinematic hardening model. Acta Geotech 9:641659. https://doi.org/10.1007/s11440-013-0293-9

Wang G, Yuan M, Miao Y, Wu J, Wang Y (2018) Experimental study on seismic response of underground tunnel-soil-surface structure interaction system. Tunn Undergr Sp Tech 76:145159. https://doi.org/10.1016/j.tust.2018.03.015

Yu H, Yuan Y, Xu G, Su Q, Yan X, Li C (2018) Multi-point shaking table test for long tunnels subjected to non-uniform seismic loadingspart II: application to the HZM immersed tunnel. Soil Dyn Earthq Eng 108:187195. https://doi.org/10.1016/j.soildyn.2016.08.018

Yuan Y, Yuan J, Yu H, Li C, Yan X (2018) Multi-point shaking table test for long tunnels subjected to non-uniform seismic loadingspart I: theory and validation. Soil Dyn Earthq Eng 108:177186. https://doi.org/10.1016/j.soildyn.2016.08.017

Zhou Y, Sun Z, Chen Y (2018) Zhejiang University benchmark centrifuge test for LEAP-GWU-2015 and liquefaction responses of a sloping ground. Soil Dyn Earthq Eng 113:698713. https://doi.org/10.1016/j.soildyn.2017.03.010

The research has been supported by the National Key Research and Development Plan of China (2018YFC0809600,2018YFC0809602 and2017YFC1500703), the National Natural Science Foundation of China (41922059, 51678438 and 51778487) and the China Scholarship Council (201806260218).

Yuan, Y., Yang, Y., Zhang, S. et al. A benchmark 1g shaking table test of shallow segmental mini-tunnel in sand. Bull Earthquake Eng 18, 53835412 (2020). https://doi.org/10.1007/s10518-020-00909-w

shaking table test of a multi-story subway station under pulse-like ground motions - sciencedirect

shaking table test of a multi-story subway station under pulse-like ground motions - sciencedirect

Shaking table tests were conducted on a four-story subway structure.Effects of pulse-like motions on seismic responses of underground structures were discussed.Rich low-frequency components of pulse-like motions result in severe responses.Lateral displacements of the side wall manifest as racking deformation.Central columns are vulnerable structures subjected to pulse-like ground motion.

A series of shaking table tests were conducted to investigate the effect of pulse-like ground motion on a multi-story subway station. Dynamic response data, including internal forces, column drift, and settlement and deformation of the soil were obtained and analyzed. Results show that the pulse-like ground motion increases dynamic responses of the subway station and surrounding soils mainly owing to its inherent rich low-frequency component and high energy. In terms of the structure, central columns, especially central columns on a floor with large story height, are vulnerable components of a multi-story subway station. Both the dynamic earth pressure and the deformation mode of the side wall were analyzed.

6s shaking table - gold shaker table for sale

6s shaking table - gold shaker table for sale

The decks are built of 16 mm zircon-reinforced fiberglass with fabricated steel frames at the bottom and are easy to clean, requiring little maintenance. The specific gravity of fiberglass made into decks is one third of that of steel, while its strength reaches as high as 70% that of steel. This fiberglass desks also has the characteristic of water-resistance and corrosion-resistance and can hold the shape unchangeable at 50.

At Hengcheng, we provide more than just processing equipment, but constantly strive to assist you in achieving overall business excellence. This is why when you partner with Hengcheng, you dont just get a diversified product offering, but form a relationship based on product refinement.etc

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