Large-scale Shaking Table Tests Research Articles

Shaking Table Test for Seismic Response of Nuclear Power Plant on Non-Rock Site

In order to compare and analyze the seismic response characteristics of a safety-related nuclear structure on a non-rock site in the condition of raft and pile group foundations under unidirectional and multidirectional seismic motion input, a large-scale shaking table test of the soil-nuclear structure system was carried out in this paper. In the test, the soil was uniform silted clay, and the shear wave velocity was 213 m/s. Considering the similarity of the superstructure natural frenquency, the actual nuclear power structure was simplified to a three-story frame shear wall structure model. The annular laminated shear model box was used to take the boundary effect of soil into consideration; the seismic motions = were input in only one horizontal direction or three directions at the same time for the shaking table test, and the results were analyzed. The results of the test show that the acceleration response of the safety-related nuclear plant is affected by the directions of input seismic motion and the forms of the foundation. When the seismic motion is input simultaneously in three directions, the acceleration responses of the horizontal motion and vertical rocking of the safety-related plant are larger than those of the single-direction input. The acceleration response of the horizontal motion and vertical rocking of the safety-related structure with the pile group foundation is smaller than that with the raft foundation. The values of most frequency bands in the horizontal acceleration Fourier amplitude spectrum at the top of the pile-foundation structure are smaller than that at the top of the raft-foundation structure, while the displacement is basically the same as that of the raft-foundation structure. This is related to the relation between the frequency component of input seismic motion and the natural frequency of the structure system. Therefore, it is more reasonable to use three-dimensional seismic input in the seismic response analysis of nuclear power plants. The seismic performance of nuclear power plants can be enhanced by using pile group foundations.

Large-scale shaking table test and three-dimensional numerical simulation research on earthquake seismic failure response of laterally spreading site-pile group-superstructure system

Large-scale shaking table test and three-dimensional numerical simulation research on earthquake seismic failure response of laterally spreading site-pile group-superstructure system

Shaking table test on the seismic response and reinforcement measures of double-arch tunnels in mountainous areas

Double-arch tunnels are commonly used in mountainous areas but are more vulnerable to earthquake damage than single-hole tunnels due to their large span and weak joints between the main tunnel and the centre wall. This study aims to understand the seismic response and damage characteristics of double-arch tunnels and provide design advice. A large-scale shaking table test was conducted in a high-intensity seismic zone, using strip reinforcement as seismic measures. Results show that peak accelerations of the inverted arch of tunnels increase as peak accelerations of seismic waves increase. Peak accelerations of the centre wall increase until peak loading accelerations achieve at 0.4 g. Large peak internal forces are mainly concentrated at the bottom of tunnels and near the centre wall. For the centre wall, bending moments are significantly influenced by structural abruptness at the junctions between the centre wall and the main tunnel, whereas axial forces are more evenly distributed in the centre wall. Seismic waves with high energy at low frequencies excite peak responses of strains and bending moments for the centre wall, especially at the wall top. Parts of the main tunnel connecting to the centre wall are in an adverse stress state, with the bottom and vault of tunnels being susceptible to cracking. Penetration cracks are likely to occur in the inverted arch and vault of tunnels as peak accelerations of seismic waves gradually increase. However, after penetration cracks appear in each of these two parts, further cracking is more likely to occur in the inverted arch, especially during strong seismic shaking. The overall forces in double-arch tunnels with strip reinforcement are significantly reduced, but there is little reduction in force for the bottom and outside of the lining.

Seismic performance of U-shaped spillway retaining wall from shake table tests

A series of large-scale shake table tests were performed to evaluate the seismic behavior of a U-shaped spillway retaining wall. Three test model configurations were employed using different backfill conditions in terms of in-place soil density. Two earthquake records were employed as input motion and scaled in terms of time duration and acceleration amplitude to assess various aspects of seismic response. The test results showed that dynamic wall deflection and wall bending moment generally increased with Peak Ground Acceleration (PGA) amplitude. At peak wall deflection, the seismic earth pressure increment coefficient (ΔKAE) was back-calculated from the measured bending moment along each wall. In addition, the location of ΔKAE along the wall height and the resulting base moment were evaluated and discussed. The results suggested that seismic demands were generally lower up to a PGA of about 0.8 g, compared to the classic Seed and Whitman recommendation for seismic lateral earth pressure and seismic bending moment of retaining walls. Beyond PGA of 0.8 g, test results were in general agreement with the Seed and Whitman solution. Finally, two-dimensional finite element analyses were performed, and the computational results showed overall reasonable agreement with the experimental data.

Seismic assessment of free‐standing artifacts: Full‐scale tests on large shake table

AbstractRecent severe earthquakes highlighted the high vulnerability of artistic assets. Thus, the seismic assessment and formulation of preservation strategies of artifacts are key challenges of modern earthquake engineering, which require theoretical and experimental investigations. The present paper discusses the outcomes from large scale shake table tests carried out on full‐scale free‐standing artifacts. The study is also aimed at evaluating the reliability of existing simplified formulations to predict the rocking motion activation. Emphasis is on prototypes of marble busts with solid and hollow pedestals with different geometries. Comprehensive tests were performed within “Seismic Resilience of Museum Contents” (SEREME) project, which was recently funded by H2020 Framework Programme – Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA). Uniaxial and biaxial earthquake natural records with different amplitudes and frequency contents were considered to assess the rocking motion of the sample specimens. Response parameters such as uplift, horizontal and vertical accelerations, angular velocity were measured to assess the rocking response of the sample freestanding busts and pedestals. Coefficients of amplification (CAF) of acceleration were also computed. The value of CAF showed that for solid pedestals they were not significantly influenced by peak ground acceleration (PGA) and earthquake type. Conversely, hollow pedestals, which were characterized by larger values of CAF than solid counterparts, ranging between 1 and 7, were affected by PGA and earthquake characteristics. Finally, the outcomes of the presented shake table tests showed that uplifts and angular velocity are effective measures for assessing rocking occurrence of tested artifacts.

Seismic performance of small and medium-sized homogeneous earthen dams considering valley site effects in large-scale shaking table tests

Many existing small and medium-sized homogenous earthen dams (SMHEDs), which were constructed worldwide before the establishment of seismic design codes, are prone to fail when subjected to earthquakes. The geologic condition and shape of the valley sites where SMHEDs are located have an important role in the seismic performance of the dams. In this paper, large-scale shaking table tests were conducted to analyse the seismic responses of the SMHED considering valley site effects. A geologic model with a ‘stiff’ dam built in a ‘soft’ valley was employed to simulate the inappropriate site selection and insufficient treatment of the soft soil layers of valley sites during the construction of SMHEDs. The effects of the spectral characteristics of the dam and the frequency components of the input motions on the seismic responses of the SMHED are analyzed in combination with frequency-domain analysis. The results indicate that the local dominant frequencies at different positions of the SMHED exhibit differences due to valley site effects. Under the input motion with different predominant frequencies (FP), the local dominant frequency differences along the dam crest lead to different distribution patterns of the acceleration response along the SMHED crest, and consequently, different damage modes. Under input motions with FP lower than the dominant frequency of the SMHED, the combined damage of collapses and cracks at the end of the SMHED crest tends to develop into massive sliding. Furthermore, recommendations for the aseismic and reinforcement design of SMHEDs are given.

Structural finite element model updating considering soil-structure interaction using ls-dyna in loop

In this study, a finite element model updating method which can consider soil-structure interaction was developed to analyze the effect of soil properties on the structural response while considering interaction between the soil and the structure. Additionally, LS-DYNA, a commercial finite element program, was included in the loop of the proposed technique using MATLAB to conveniently utilize the complex structures updated by the model. To validate the performance of the proposed method, a large-scale shake table test was conducted. The objective of the validation test was to seek how accurately the proposed model updating method can detect the change in the stiffness. To compare the result of the proposed method with the conventional method, the model updating procedure was conducted with and without considering soil-structure interaction. The proposed finite element model updating method which considers the soil-structure interaction estimated the stiffness of the structure with maximum accuracy of 91%, while the conventional finite element model updating without considering the soil-structure interaction showed maximum accuracy of 88%. By comparing the proposed method with the conventional method without considering the soil-structure interaction, it was confirmed that the proposed method had an 3% higher accuracy on average.

Experimental evaluation of the seismic isolation effectiveness of friction pendulum bearings in bridges considering transverse poundings

Most previous studies investigating how transverse poundings at shear keys affect the seismic behavior of bridges were conducted numerically. Few laboratory investigations were reported, especially for isolated bridges. This study investigates the effect of transverse poundings on a bridge isolated by friction pendulum bearings (FPB) using 1:6 large-scale shake table tests. To evaluate the seismic isolation effectiveness of FPB in the cases of no pounding and pounding, bridges with ordinary spherical steel bearings (SSB) are also tested and regarded as reference cases. Results indicate that FPB has a better ability to reduce the acceleration of girder and the bending moment at pier base than SSB in the case of no pounding. However, poundings significantly increase the seismic forces developed in the bridge super- and substructure, especially for the bridge using FPB, which would considerably reduce the isolation effectiveness. The findings highlight the importance of considering transverse poundings when designing an isolated bridge.

Study of the dynamic performance of a gabion wall

Due to the wide increase in the usage of gabion-faced retaining walls in seismically active zones, like the Himalayas in India, it has become necessary to analyze the performances of gabion structures under dynamic conditions. In this study, in the absence of any full-scale dynamic test, shake table tests are conducted on a scaled-down (1:6.7) model gabion wall (without backfill) for different base accelerations (0.1 g, 0.2 g, 0.3 g, and 0.4 g) and frequencies (3 Hz, 5 Hz, 7 Hz, and 9 Hz). The performance of the gabion wall with and without bottom embedment is analyzed in terms of percentage displacements and acceleration amplification factors at different elevations. It is observed that the percentage displacements and acceleration amplification factors increase significantly with the increase in the frequency of the base motion. The bottom embedment has reduced the acceleration amplification factor at the top of the wall by a maximum of 8 %. The maximum lateral deformations are 0.9 % and 1 % of the height of the wall, with and without embedment, respectively. No damage to the gabion mesh, and no sliding at the base of the wall, is observed even at higher accelerations and frequencies. A finite element analysis, has been carried out to numerically simulate the observed behavior of the gabion wall in the shake table tests. The natural frequency and the damping of the gabion wall are calculated from the experimental free vibration responses and are utilized to derive Rayleigh damping coefficients. The inclusion of damping and the adoption of appropriate interaction properties between the gabion basket and the gravel fill/sand determined from the shake table tests have helped in achieving a good agreement between the numerical results and the experimental data. A large-scale shake table test on a gabion wall with backfill reported by Nakasawa et al. has been numerically simulated using the developed numerical model. A good match between the large scale experiment and the numerical results shows the validity and efficacy of the proposed model.

Finite-Element Modeling for Seismic Damage Estimation of Suspended Ceiling Systems

The seismic qualification and seismic performance assessment of suspended ceiling systems have been traditionally conducted through large-scale shake table testing. This experimentally-based approach not only involves significant financial and time resources but is also not flexible to evaluate several configurations of suspended ceiling systems. As an alternate approach, this paper discusses the development of a general finite-element (FE) model of suspended ceiling systems that accurately captures the propagation of damage observed during full-scale shake table testing using the commercial finite-element analysis software, Abaqus/Explicit. The results of the large-scale shake table testing on suspended ceiling systems conducted at the University at Buffalo as part of the NEES nonstructural project were used to validate the FE model. The major components of suspended ceiling systems such as grid runners, ceiling tiles, and hanger wires were modeled and assembled with significant detail in the FE model. The properties of the connections between the grid runners, which are vital for capturing the seismic behavior of suspended ceiling systems were derived numerically. A user-defined subroutine was incorporated in the Abaqus/Explicit software framework to capture the multidirectional pinched hysteretic behavior of the connections between grid runners. An illustrative example of the application of the proposed FE model to develop robust numerically generated fragility curves for suspended ceiling systems is presented.

Large-scale shake table testing of shallow tunnel-ground system

Soil-structure interaction (SSI) is of critical importance in evaluating the seismic response of shallow tunnels. Experimental observations are crucial in assessing the influence of the surrounding and overburden soil near the ground surface. Therefore, this paper presents a series of shake table tests to investigate the seismic response of a scaled shallow tunnel with different backfill material properties and thickness of overburden soil (burial depth). A shallow tunnel was tested incorporating ground representative of realistic backfill conditions using the large-scale 1-g outdoor shake table at the University of California, San Diego (UCSD). The tunnel structure was designed at 1/9 scale based on the configuration of an actual recently constructed prototype structure in San Francisco, California. The test results were interpreted in full-scale, which demonstrated that the maximum tunnel deformation generally occurred at the instant of peak ground acceleration (PGA). Relatively large shear strains were developed (up to 6%) and significant reduction of the soil shear modulus were evaluated as the PGA increased during the shaking. The backfill shear strains were lower as the tunnel embedment depth increased because of the increased soil stiffness and strength due to the higher overburden stress. In addition, the tunnel racking deformation became closer to that of the ground as the tunnel embedment increased. At the largest observed soil shear strains, tunnel racking was significantly lower than that of ground deformation due to the decrease in soil. The FHWA simplified solution was used to estimate tunnel racking deformation and wall bending moments. The FHWA solution produced reasonable estimates of ground deformation. However, a discrepancy was noted in estimating the tunnel deformation in the given ground deformation known as racking ratio (Rr). This discrepancy contributed to conservatism in the FHWA racking prediction that was pronounced particularly with the decreased overburden soil stress.

Fusing damage-sensitive features and domain adaptation towards robust damage classification in real buildings

Structural Health Monitoring (SHM) enables the rapid assessment of structural integrity in the immediate aftermath of strong ground motions. Data-driven techniques, often relying on damage-sensitive features (DSFs) derived from vibration monitoring, may be deployed to attribute a specific damage class to a structure. In practical applications, individual features are sensitive to specific levels of damage, and therefore combining multiple DSFs is required to formulate robust damage indicators. However, the combination of DSFs typically involves empirical thresholds that are often structure-specific and hinder generalization to different structural configurations. This work evaluates the predictive performance of a large ensemble of DSFs, computed on an extensive dataset of nonlinear simulations of frame structures with varying geometrical and material configurations. Gradient-boosted decision trees and convolutional neural networks are deployed to fuse multiple DSFs into damage classifiers, improving the predictive accuracy compared to best-practice methods and individual DSFs. A Domain Adversarial Neural Network (DANN) architecture enables the transfer of knowledge obtained from numerical simulations to real data from a large-scale shake-table test. After exposure to limited data, exclusively from the healthy state, the DANN framework yields satisfactory performance in predicting unseen damage states in the experimental data. The results demonstrate the potential of DANN in transferring knowledge from simulations to real-world monitoring applications, where only limited data characterizing exclusively the current, typically healthy, structural state is available. Overall, this work comprises the definition of multiple DSFs, their fusion through ML approaches, and the generalization of the knowledge obtained from simulations to real data through domain adaptation.

Cumulative damage evolution rule of rock slope based on shaking table test using VMD-HT

Cumulative damage can be produced within the slope under multiple earthquakes, including frequent earthquakes in earthquake-prone areas, foreshocks, and aftershocks of an earthquake event, which have great potential to trigger landslides. Consequently, clarifying the cumulative damage evolution rule subject to multiple earthquakes are of significance in identifying landslides. A large-scale shaking-table test was performed on a rock slope to investigate the rule. First, variational mode decomposition and Hilbert transform methods (VMD-HT) were proposed to recognize and extract the natural frequency of the slope. Then, the damage coefficient based on the first natural frequencies of the slope before and after loading were established, and the cumulative damage evolution of the slope during the test were investigated. The results showed that the root mean square (RMS) amplification factor was mainly distributed at the steep structural surfaces and outlet of the weak interlayer, and the factor decreases significantly at first, and then becomes stable with the increase in intensity. In addition, the marginal spectrum exhibited multiple peaks with the increase in elevation. The first peak (IMF1) mainly included the input signal information, which gradually dominates with damage accumulation under multiple earthquakes. Meanwhile, the second and third peaks (IMF2 and IMF3) mainly reflected the first and second natural characteristics of the slope and were amplified significantly with an increase in elevation. Moreover, with damage accumulation, the natural frequency of the slope gradually decreased. A large damage coefficient was mainly distributed at the steep structural plane and outlet of the weak interlayer, and the failure of the slope in the test was a progressive process which increased slightly at first (slow growth stage), then increased greatly (rapid growth stage), and finally remained approximately the same (destruction stages). The proposed method can properly evaluate the damage degree of a slope under earthquakes, which is meaningful for slope stability analysis, landslide monitoring, and early warning works.

Seismic behaviour of sandy cutting slope in large-scale shaking table test

Seismic behaviour of sandy cutting slope in large-scale shaking table test

Seismic response of ultra-large diameter shield tunnel in upper-soft and lower-hard site: Shaking table tests and numerical simulations

The shaking table test study on the ultra-large diameter shield tunnel in upper-soft and lower-hard site was rare, due to the limitations of test technology and equipment performance. This study performed a series of large-scale shaking table tests and numerical simulations, addressing this deficiency on the seismic response of an ultra-large diameter shield tunnel in upper-soft and lower-hard site. In shaking table tests, a modified method of similitude ratio designing developed in our previous study was adopted, which made it possible to conduct the large-scale test on a shaking table with general loading performance. The test and numerical results meet a good agreement, showing that an evident inflection occurs at the soft-hard interface in the curves of peak acceleration amplification factors versus depth. Furthermore, combining numerical simulations on the upper-soft and lower-hard site, pure soft site and pure hard site, the seismic response differences of the tunnel between upper-soft and lower-hard site and pure soft and hard sites are further revealed. The results demonstrate that the largest relative difference of tunnel strains between upper-soft and lower-hard site and pure soft or hard site always appears at haunch, and the haunch strain of the tunnel in upper-soft and lower-hard site keeps being larger than those in pure soft or hard site regardless of excitations. In addition, the deformation mode of the tunnel in upper-soft and lower-hard site is more like the shape of an avocado, while it presents a typical ellipse in pure soft or hard site.

Geotechnical Seismic Isolation System Based on Rubber-Sand Mixtures for Rural Residence Buildings: Shaking Table Test

The anti-seismic problem of rural residential buildings is the weak link of seismic retrofitting in China. Recently, geotechnical seismic isolation (GSI) technology based on rubber-sand mixtures (GSI-RSM) using rubber-sand mixtures (RSM) between the structural foundation and the foundation soil has been proven to have the possibility of potential applications in rural residential buildings. Many theoretical studies exist on the effectiveness of seismic isolation of the GSI-RSM system, but few studies on either the seismic response test of model buildings placed on the RSM layer or the large-scale shaking table test exist. Therefore, this study considers a large shaking table test performed on a 1/4 single-story masonry structure model with and without a GSI-RSM system by selecting a standard input ground motion and varying input acceleration amplitudes. The test results show that the GSI-RSM system can reduce the seismic response of superstructures. The isolation effect of the GSI-RSM system is low in small earthquakes and increases with increasing earthquake magnitude. Overall, the RSM layer can filter part of the high-frequency components of the earthquake to transmit to the superstructure and consume more seismic energy by generating friction slip in the interaction with the structural foundation.

Experimental study on progressive deformation and failure mode of loess fill slopes under freeze-thaw cycles and earthquakes

Earthquakes and freeze-thaw cycles are two important causes of landslides, but knowledge of their combined effect is limited. Therefore, a freeze-thaw test and large-scale shaking table tests were carried out to simulate the progressive deformation and failure mode of loess fill slopes. The process of frost-heaving deformation and seismic deformation was observed, and the failure mode was analyzed by comparing with the accelerations. The results showed that the slope stability decreased after freeze-thaw cycles. Freezing and thawing causes the crest and upper portion melted, and settled to the lower portion, creating frost-heaving zones and irreversible cracks. Comparisons between the freezing-thawing slope and nonfreezing-thawing slope allowed to highlight, through the analysis of seismic responses, the possible and not negligible effect of both frost-heaving spatial distribution of slope surface soil and freeze-thaw interface during the seismic shaking in initiation and development of landslides. The peak ground acceleration (PGA) amplification factors of freezing-thawing slope were higher, especially in the frost-heaving zones. Cracks in freezing-thawing slope developed faster and deformation was greater. The freeze-thaw interface became a potential slip surface and a multistep landslide suddenly occurred under 1.2 g seismic loads, while the nonfreezing-thawing slope was stable. The freezing-thawing slope shows a brittle superficial shear failure, and its failure mode is freeze-thaw cycles - forming potential sliding surface and irreversible cracks - slow expansion of cracks - rapid development and penetration of cracks - superficial shear sliding.

Mitigation of liquefaction-induced hazard using geosynthetics: An experimental study using cyclic triaxial and large-scale shake table tests

Mitigation of liquefaction-induced hazard using geosynthetics: An experimental study using cyclic triaxial and large-scale shake table tests

Experimental study on seismic response and progressive failure characteristics of bedding rock slopes

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 of 3 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.

Large-scale shake table testing of pile group-bridge model in inclined liquefiable soils with overlying crusts

Large scale shaking table tests were performed to investigate the failure mechanism of pile group-bridge system subjected to liquefaction-induced lateral spreading. The tests comprised two cases: Case L which refers to a bridge model supported by a 2 × 2 pile group embedded into the inclined liquefiable soils with crusts; and case R which refers to the same bridge model fixed to a rigid foundation. The experimental details are provided and typical test results are elucidated. The failure mechanism of the pile group-bridge system under strong earthquakes is revealed. The results indicate that the lateral peak soil displacement profile has a linear distribution, while the lateral permanent displacement profile has a cosine distribution pattern. It was also found that the pile is prone to damage and bending failure both at its head and at the bottom of saturated sand where it is fixed into bearing stratum. For the pile group-bridge system, the liquefaction-induced lateral spreading causes the failure position to move from the pier bottom to the pile head. In addition, the pier bottom is more likely to experience damage under strong earthquakes in case R than in case L, while the opposite is true during weak earthquake excitation.