Large-scale Shaking Table Tests Research Articles

Shaking table tests on deformation pattern and failure mechanism of fault-crossing tunnels in non-rupture scenario

Tunnels, as critical underground infrastructures, often intersect with faults. Field investigations have underscored the susceptibility of fault-crossing tunnels to extensive damages during earthquakes. Hence, large-scale shaking table tests are conducted to investigate the deformation pattern and failure mechanism of fault-crossing tunnels under transverse excitation, particularly in non-rupture scenarios. The dynamic behavior of the tunnel, as expected, is dominated by the surrounding strata. Acceleration responses vary notably across different regions of the fault site. The disparity increases with the increments of seismic intensity and input frequency. The tunnel section at the interface between the fault and the hanging wall manifest the strongest acceleration, where the largest strains of the tunnel and most of the lining cracks also occur, highlighting its vulnerability to seismic vibrations. The damage-induced non-linearity of the tunnel is then identified by the decreasing dominant frequency thereof. The fault-crossing tunnel exhibits unique three-dimensional shearing-torsional deformations, elucidated through the test data and an analytical model. This deformation pattern provides a better understanding of the seismic responses of fault-crossing tunnels under seismic vibrations.

Experimental Study and Comparative Analysis of Shake Table Tests on Metro Stations with or without Columns in Soil-Rock Combination Strata

ABSTRACT As a new type of station structure, the seismic research of long-span column-free metro station is relatively weak compared with the traditional column station, and the seismic characteristics and failure phenomena of these two types of structures are quite different. Therefore, it is necessary to compare the seismic performance of the two structures. In this paper, a large-scale shaking table test was carried out on the large-span column-free metro station structure and the two-layer island subway structure for the typical soil-rock combination stratum in Jinan, and the parameters such as soil-structure acceleration, soil pressure distribution and strain were obtained by numerical simulation. The results show that the maximum acceleration difference between the two types of structures at the middle plate is 13.8%, and the maximum tensile stress at the connection between the bottom plate and the side wall is 11.6%. Under the same geological conditions and seismic waves, the difference of soil-structure seismic response is related to the overall stiffness of the structure. The columns station is more affected by high-frequency seismic waves, while the column-free station is the opposite. Both types of structures meet the general seismic response law, but the column station shows stress concentration at the column-plate connection, which has a better inhibitory effect on the lateral displacement of the surrounding soil. In general, the seismic performance of the column station is about 1/10 stronger than that of the column-free station, but the column-free station can also meet the basic seismic requirements.

Shaking Table Testing and Numerical Study on Aseismic Measures of Twin-Tube Tunnel Crossing Fault Zone with Extra-Large Section

As transportation networks continue to expand into mountainous regions with high seismic activity, ensuring the seismic safety of tunnels crossing active faults has become increasingly crucial. This study aimed to enhance our understanding of the impact of fault zones on the seismic behavior of tunnels and to provide optimized seismic design recommendations through a comprehensive experimental and numerical investigation. The focus of this research is the Xiangyangshan Highway Tunnel in China, which intersects a significant longitudinal fault. Large-scale shake table tests were performed on 1:100 scale physical models of the tunnel to analyze the seismic responses under various ground motion excitations. Detailed three-dimensional finite difference models were developed in FLAC3D and calibrated based on the shake table results. The tests indicated that strains, earth pressures, and accelerations experience localized amplification within 10–20 m of the fault interface compared to undisturbed ground sections. Common seismic mitigation measures, such as rock grouting, seismic joints, and shock absorption layers, were observed to effectively reduce the amplified seismic demands. Grouting, in particular, led to an average reduction of up to 56.3% in circumferential strain and 38.5% in earth pressure. It was concluded that 6 m thick grouted zones and 20 cm thick rubber interlayers between tunnel lining shells provide optimal structural reinforcement against the effects of fault zones. This study provides valuable insights for improving the seismic resilience of underground transportation corridors in seismically active regions.

Local Site Effect of Fault Site and Its Impact on Seismic Response of Fault-Crossing Tunnel

ABSTRACT The areas where tunnels crossing faults are especially susceptible to seismic damage. Local site effects associated with fault site notably contribute to the unfavourable impact on the seismic behaviour of tunnels. In this study, large-scale shaking table tests were conducted to investigate the fault site effect and its impact on the seismic response of tunnels. Real earthquake records, synthetic seismic wave, and sinusoidal waves were selected as input motions, excited in both transverse and longitudinal directions of the tunnel. The local site effect of the fault site was evaluated by time-frequency analysis. The test results indicate that the acceleration response within the fault is significantly greater than those on both sides, regardless of excitation direction. Dynamic characteristics of different regions of the fault site exhibit distinct variations under different excitation directions, with the dynamic behaviour of the strata within the fault playing a crucial role. Marked waveform distortion and trapped waves can be observed within the fault, attributed to harmonic distortion, waveform conversion at fault interfaces, and varying seismic wave propagation pathways. The region of maximum seismic response of the fault-crossing tunnel predominantly occurs near the interface between the fault and the hanging wall. The seismic response of the tunnel located in the hanging wall exceeds that in the footwall. The dynamic characteristics of the fault-crossing tunnel are significantly affected by the dynamic characteristics of the strata around the tunnel, highlighting the necessity of comprehending strata dynamics in the seismic design of such tunnels. The aforementioned findings could offer valuable insights for the seismic design of mountain tunnels crossing fault zones.

The Dynamic Response Characteristics of a Water Transmission Pipe Crossing a Loess Fault Using a Large-Scale Shaking Table Test: A Case Study

The Dynamic Response Characteristics of a Water Transmission Pipe Crossing a Loess Fault Using a Large-Scale Shaking Table Test: A Case Study

Experimental investigation of seismic performance of segmental tunnel with secondary lining under strong earthquake

To assess the seismic performance of large-diameter tunnels in soil ground with and without secondary lining, large scale shaking table tests with geometrical ratio of 1:15 were conducted. The model tunnels were grouped as a tunnel only with segmental linings (Single lining), a tunnel liner with additional semi-ring secondary lining (Semi-ring), and a tunnel with additional full-ring secondary lining (Full-ring). Transverse excitations input from shaking-table were designated as Shanghai artificial accelerogram with magnitudes from 0.3 to 1.0 g. Measurements were made mainly on the time histories of acceleration responses, cross-sectional deformation, extension/closure at longitudinal joints of segmental linings, and earth pressure on external surface, of the model tunnels. Comparison the seismic responses of the tested models gives the effects of secondary lining as: 1) the distribution of acceleration responses on segmental linings is significantly different in the case of single lining model; 2) dynamic normal earth pressure on the external surface of the segmental linings increase along depth, but in different patterns; 3) the constraint effects of semi-ring secondary lining on extension/closure of longitudinal joints are not significant in the upper half of segmental lining. Furthermore, with the increase of earthquake intensity, the constraint effects of full-ring secondary lining on both cross-sectional deformation and extension/closure of longitudinal joints become more remarkable, compared with those of the semi-ring secondary lining.

Effect of excitation frequency and joint density on the dynamic amplification effect of slope surface on jointed rock slopes

This paper presents the slope dynamic response of jointed rock slopes containing three groups of typical joints and analyzes the effect of input harmonic frequency and joint density on the peak horizontal acceleration (PGA) of the slope surface under vertically impinging SV wave (shear vertical wave) excitation. First, the dynamic response of the slope surface of the bedding slope was investigated with a large-scale shaking table test, and the reliability of the numerical model was verified by the physical modeling. Then, a series of jointed rock slope models with different joint densities were established based on the three-dimensional discrete element software 3DEC. It is found that the natural frequency fn of the jointed slope decreases with the increase of joint density. The effect of excitation frequency f on the slope surface dynamic response of the jointed slope is stronger than that of joint density. The closer the f is to the fn, the stronger the slope surface and slope crest dynamic response is. Notably, taking fn as the critical value of f, the slope surface dynamic amplification mode of jointed slope can be divided into two types: when f ≤ fn, the acceleration amplification factor of X-direction (AAF-X) of the slope surface amplifies monotonically with increasing elevation; when f >fn, the AAF-X of the slope surface shows a fluctuated amplification pattern with the increase of elevation. The results of this paper show that in the seismic design of slope engineering, the influence of site conditions on the frequency spectrum characteristics of ground motion should be considered, and then the optimal design should be carried out.

Seismic isolation effect of unconnected piles-caisson foundation: Large-scale shake table tests

The seismic response and isolation mechanism of a new unconnected pile-caisson foundation (UPCF) suitable for supporting deep-water large-span bridges under seismic loading were investigated by large shaking table tests. Five scaled models were constructed utilizing different cushion material (aggregate), cushion thickness and piles configuration. Each model was tested under 18 different seismic loading conditions. The tests observations were analyzed to evaluate the seismic response characteristics and isolation mechanism of UPCF. The maximum displacement of UPCF and the peak acceleration of the input ground motion were linearly related. Under strong ground motions, the foundation soil and cushion displayed a significant softening behavior manifested in reduced natural frequencies and prolonged periods, which resulted in lower acceleration amplification. However, the stiffnesses of soil and cushion were largely restored after the ground shaking ended. The cushion model with larger aggregate particles performed better in terms of the caisson residual displacement and displacement restoration rate of the caisson. It was found that the UPCF constructed with a thin cushion layer comprised of large, rounded aggregate particles exhibited acceptable seismic isolation effect and reduced the peak seismic acceleration by up to 26.7%. It was also observed that the front and middle piles experienced larger loads, and accordingly, their peak moment envelopes were greater and the location of peak moment was shallower.

Impact of asymmetrical corrosion of piers on seismic fragility of ageing irregular concrete bridges

This article investigates the seismic fragility of ageing irregular multi-span reinforced concrete (RC) bridges. Different irregularity sources are considered, including: (i) substructure stiffness irregularity arising from the unequal-height piers, (ii) substructure stiffness irregularity arising from the spatially variable (asymmetrical) corrosion damage of piers and (iii) irregular distribution of effective tributary masses on piers of varying heights. To this end, a three-dimensional nonlinear finite element model is developed for multi-span RC bridges and verified against a large-scale shake table test results of a two-span concrete bridge specimen available in the literature. Nonlinear pushover, incremental dynamic and seismic fragility analyses are performed on three groups of two-span RC bridges with different configurations. Moreover, a time-dependent dimensionless local damage index is employed to evaluate the failure sequence and collapse probability of selected bridge layouts. The analysis results of the three studied irregularity sources show the considerable significance of spatially variable corrosion of bridge piers and substructure irregularity on the failure sequence of piers and seismic fragility of multi-span RC bridges. Furthermore, analysis outcomes show that uneven corrosion of piers triggers an unbalanced distribution of seismic ductility demands and irregular seismic response of equal-height multi-span RC bridges.

Dynamic characteristics of deposit slope under coupled action of earthquake and rainfall

Earthquakes and rainfall both have great influence on the stability of slopes. However, their coupled effects on slope stability are rarely investigated in detail. In this paper, large scale shaking table tests were carried out to investigate the dynamic characteristics and instability mechanism of slope subjected to the coupled action of rainfall and earthquakes. Results of the analyses show that rainfall significantly affects the slip surface within the slope subjected to a subsequent earthquake. It is hypothesized that as the soil effective stresses depend on the pore pressures, the suctions within the slope are reduced when rainfall infiltrates the slopes. When the shaking occurred first, cracks due to ground motion promote subsequent rainfall seepage, reducing the suctions and consequent reduction in the slope stability. The results obtained in this study can provide a theoretical basis for the stability evaluation and design of slope in the areas, which are greatly influenced by earthquakes and rainfall.

Dynamic responses and evolution characteristics of bedrock and overburden layer slope with space anchor cable anti-slide piles based on large-scale shaking table test

The study focuses on the anti-slide pile structure with space anchor cable, designing and conducting the large-scale shaking table test of bedrock and overburden layer slope with space anchor cable anti-slide pile system. The dynamic characteristics of bedrock and overburden layer slope with space anchor cable anti-slide piles are systematically explored from aspects of the overall acceleration field of the slope, the interface between overburden layer and bedrock, and the different depths of overburden layer. The results show that in the design of anti-slide pile with space anchor cable, the strength of the bedrock is utilized to resist the sliding force generated by the overburden layer in order to give full play to the role of the strength of bedrock in slope safety protection. The surface of the overburden layer appears a concentrated area of acceleration amplification and as the increase of ground motion intensity, and the concentrated area gradually shifts from the trailing edge of slope to the anchor head segment of anti-slide pile. Under accelerations in different peaks, the peak accelerations in the direction of free face and vertical direction have the asymptotic amplification effect, and the former is stronger. With the increase of ground motion intensity, the peak acceleration magnification decreases exponentially in direction of free face, while the peak acceleration magnification in the vertical direction presents a wavy distribution that first increases and then decreases.

Large-scale shaking table tests of a six-story floor-by-floor assembled CFS frame-framing shear wall structure

To study the seismic performance of a proposed multi-story floor-by-floor assembled structure using cold-formed steel (CFS) frame with square columns and double-channel beams connected by novel joints, and CFS framing walls as shear walls, shake table tests were conducted on a 2:3 scaled six-story CFS frame-framing shear wall structure (CFSF-FSWS) using bidirectional seismic inputs. A prefabricated concrete floor slab was proposed utilizing the channel section beams as the molds during prefabricating processes. The CFS framing shear walls were designed with various configurations researched before: framed or trussed skeleton, single or double side sheathing, flat or corrugated steel sheathing sheet. The observed damages, dynamic properties, seismic responses and failure mechanisms of the CFSF-FSWS under different peak ground accelerations (PGAs) were analyzed. The CFS frame carried gravity load, and the horizontal earthquakes were mainly resisted by CFS framing shear walls. The results indicated a good deformation capacity and seismic performance of the CFSF-FSWS building. The damping ratio of the test model gradually increased with the accumulation of damage, varying between 3.30%∼6.95%. After all seismic loading, the CFS frame remained intact and the damages were concentrated on the CFS framing shear walls, achieving the design objective of “separated gravity and lateral resisting systems”.

Experimental Investigations of the Seismic Response of a Large Underground Structure at a Soft Loess Site

Based on an underground structure located at a soft loess site in Xi’an as the engineering background, this paper investigated a seismic response and damage model of subway stations at a soft loess site using a large-scale shaking table test, considering the different characteristics of ground motions. The quantitative analysis of the acceleration response and the seismic subsidence of the soft loess site were subjected to different earthquake excitations; based on the experimental results and the corresponding analysis, the development and distribution of seismic structural damage were studied, and the damage mechanism of underground structures in a soft loess area under a strong earthquake was explored. The results indicate that the peak accelerations of the site soil first remained unchanged then increased significantly along the soil height, and the amplification effect of the acceleration response was the most significant at the soil surface. The soft loess soil underwent significant subsidence, and the underground structure was raised compared to both sides of the cover soil; the collapsibility of the soft loess soil was sensitive to strong earthquakes with vertical components. The underground structures in soft loess suffered heavy damage, which rapidly entered the elastic–plastic stage. The composite effect of the collapsibility and vertical seismic excitation impaired the load-carrying capacity of the middle columns, and the strong horizontal seismic excitation enlarged the lateral force and accelerated structural damage development; the underground structure reached failure when plastic damage expended most of the middle columns and structural joints. These results are significant for the seismic design of underground structures in adverse soil conditions.

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.