Shaking Table Tests Research Articles

Extended‐state‐observer‐based adaptive robust control of a single‐axis hydraulic shaking table

AbstractThe shaking table test has been widely recognized as one of the most reliable methods for assessing the dynamic response of structures and systems when exposed to a range of vibrations. Replicating these vibrations, recorded as acceleration signals, necessitates precise controller designs. However, traditional controller designs primarily rely on linear system assumptions, leading to complications in incorporating parametric uncertainty and uncertain non‐linearity. This paper presents a novel approach to the acceleration trajectory control problem of single‐axis hydraulic shaking table systems from a non‐linear perspective. This strategy employs a controller combined with an extended state observer (ESO) and adaptive control, offering a design that more closely reflects real‐world scenarios and requires less parameter adjustment. The ESO estimates the uncertain non‐linearity using the displacement signal, while the parametric uncertainty is tackled through adaptive control. The proposed controller's effectiveness is validated through theoretical proof using Lyapunov analysis. The analysis demonstrates that asymptotic tracking performance is guaranteed when the uncertain non‐linearity is time‐invariant. Moreover, with time‐variant uncertain non‐linearity, the controller can also ensure both prescribed transient tracking performance and final tracking accuracy. Comparative experiment results underscore the superior performance of the proposed controller.

Experimental study on effect of assembly process on seismic performance of modular precast composite shear wall structures

Modular buildings utilize prefabricated volumetric modules to resist gravity and lateral loads and can achieve a high prefabrication level. Different from cast-on-site reinforced concrete structures, the seismic performance of precast structures is affected by the construction process. This study investigated the effect of assembly process on the seismic performance of an innovative modular precast composite shear wall structure. Contrastive shaking table tests were carried out on two 1/4-scaled modular models, one by the fully modular precast method and the other by the modular cast-on-site method. Test results showed that the bottom vertical joints were the most critical components and dominated the failure patterns for both modular models. The weakening of screw threads induced by the small model size and assembly process decreased the ultimate capacity of the modular precast model. The modular precast model showed up to a 6.7 % lower initial frequency and 17.6 % lower initial damping ratio than the modular cast-on-site model. The assembly process had no essential influence on the displacement and acceleration responses before vertical joint failure but significantly increased the displacements as the joints approached failure in the limit state. The test work highlights the importance of ensuring bolt strength and protecting bolt threads in practical engineering applications.

Effects of kinematic and inertial interaction on seismic responses of pile-structure system in liquefiable and non-liquefiable deposits

Numerical simulation models for pile group-superstructure in liquefiable and non-liquefiable sites were established. The validity and reliability of the numerical model are verified by the shaking table test results. Based on the cross-correlation analysis of superstructure acceleration-pile bending moment and soil displacement-pile bending moment obtained from the tests, the coupling law of kinematic and inertial interaction and its influence on pile failure modes were discussed combined with the numerical simulation results. The results shown that the effect of kinematic interaction on piles were greater than that of inertial interaction in both types of sites, but coupling mechanisms of kinematic and inertial interaction were different. For the liquefiable site scenario, the middle part of piles was prone to bending failure and the kinematic interaction was the main reason for it. For the non-liquefiable site scenario, the inertial interaction had an obvious influence on the pile failure occurred at the pile top. The results of parameter analysis shown that the mass of the superstructure was the most important parameter of inertial interaction in the liquefiable site. Parameters of inertial interaction would affect the vibration of the superstructure in the non-liquefiable site, but the influence on pile bending moments was not obvious.

Experimental and numerical investigations on seismic responses of wind turbine structures with amplifying damping transfer system

Wind turbine (WT) with a long period is a dynamic sensitive but lightly damped structure, which may be prone to earthquakes, especially for the near-fault pulse-like records containing large amplitude of velocity pulse with a period close to WT's period. An efficient and convenient solution to enhance the damping effect of WT, amplifying damping transfer system (ADTS), is applied by transferring the upper rotation of the wind turbine to its bottom with an amplified damping mechanism. The feasibility of the ADTS is experimentally validated through free vibration tests, sinusoidal excitation tests, and shaking table tests for both non-pulse-like earthquakes and pulse-like earthquakes. Test results of free vibration validate that more than 6.2% extra damping ratio is provided by the ADTS to the tested WT model; while the supplemental stiffness of ADTS shifts the frequency of the tested WT model from 2.16 Hz to 2.61 Hz. Sinusoidal tests show ADTS reduces the displacement (acceleration) response of the tested WT by about 73.88% (58.16%) when subjected to resonant frequency. It is also observed that the ADTS is effective in controlling the seismic responses of non-pulse-like earthquakes and pulse-like earthquakes, providing at least 30% of the reduction in displacement and acceleration. Simulations with high accuracy indicate that the pulse signal usually concentrates the majority of the input energy of near-fault pulse-like earthquakes; while the ADTS can absorb most of the input energy (over 90%), protecting the WT away from undergoing excessive vibration.

Research on seismic resilience evaluation index of mid-rise CFS structures

This paper focuses on the deficiencies of Chinese standard GB/T 38591–2020, and combines the mechanical characteristics, post-earthquake damage characteristics, and repair methods of mid-rise cold-formed steel (CFS) structures to define the damage grade of structural components and revise various index parameters in the “Standard”. Based on the calculation results of 120 sets of 6-story CFS composite shear wall structures, the multi-parameter seismic resilience evaluation index and grading criteria applicable to mid-rise CFS structures are fitted, and the index values (R values) for dividing the 5 resilience grades are 0.5, 1.0, 1.25, and 1.7, respectively. By considering different building usage functions and seismic effects, the 5-story CFS structure shaking table test models and the irregular eccentric CFS structure numerical model are used to jointly verify the reasonableness and universality of the seismic resilience evaluation index and grade classification criteria. The multi-parameter resilience evaluation index system lays the foundation for the study of seismic resilience of mid-rise CFS buildings and provides new ideas for establishing quantitative resilience evaluation indexes for different building systems.

Experimental study on the coordinated behavior of the Combined Viscous-Steel Damping System (CVSDS) for multi-level seismic mitigation

Passive energy dissipation devices, such as the viscous fluid damper (VFD) and the steel yielding damper (SYD), are widely adopted to alleviate structural seismic responses. The Combined Viscous-Steel Damping System (CVSDS) is proposed as a hybrid passive damping device for multi-level seismic mitigation. As two components in the CVSDS, VFD, and SYD are adopted to resist frequent and rare earthquakes, respectively. This study aims to investigate and compare the seismic behavior of CVSDS, VFD, and SYD by shake table tests. Seismic excitations with different intensities are applied to a single-degree-of-freedom system. The comparison of displacement and hysteresis behavior is analyzed by time history analysis and Dynamic Time Warping (DTW) method in the time domain. The time-frequency characteristics are explored by the Wavelet Transform (WT) in the frequency domain. The results indicate that the locking function of the CVSDS remains inactive during low-intensity earthquakes, but is triggered during high-intensity ones. Locking depends on the preset locking force and external loads. Both the analyses in the time domain and frequency domain demonstrate that prior to locking, CVSDS and standalone VFD display similar characteristics, but locked CVSDS resembles standalone SYD. CVSDS allows for VFD with smaller tonnage and stronger vibration control capacity. Increased vibration frequency will be observed in the locked CVSDS during strong earthquakes due to the supplementary stiffness of the SYD.

Full-scale shaking table test on seismic performance of a steel frame with translational-type precast-concrete exterior wall panel

In order to investigate the deformation behavior, mechanical characteristics of connections, and failure mode of translational precast concrete wall-panels under earthquake loading, a full-scale two-story steel frame model was designed. This test model consisted of 12 precast concrete wall-panels connected with fixed connections at the bottom end and translational-type connections at the top end. This model passed the shaking table testing, and the results demonstrate that the translational-type precast concrete exterior wall panel can ensure the sufficient relative displacement between the wall panel and the main structure under large earthquake loads. It has sufficient capacity to adapt the deformation between the main structure and the wall panels. During the test, localized cracking was observed on the wall panel, while all connections remained in elastic state. The connections between precast concrete exterior wall panels exhibited good performance, that indicates it is an effective tool to protect frame building hangings with exterior wall panels under strong earthquake events.

Experimental and numerical analyses of seismic behaviors of L-shaped unreinforced masonry walls

This study investigates the seismic behavior of L-shaped unreinforced concrete-block masonry fence walls. Using a large-scale shaking table, the walls are subjected to uniaxially artificial ground motions that gradually increase in intensity, and the out-of-plane response and failure mode are analyzed. The seismic behavior is then simulated by LS-DYNA using a finite element model under identical conditions as the shaking table tests. The validity of the numerical model is evaluated by comparing the linear response and failure mode of the tests with those of the simulations. Practical modeling techniques and calibrated material model parameters that facilitate reliable simulation results are also presented. The numerical model and techniques are useful in determining the geometrical features required for earthquake-resistant fence walls, such as the maximum permissible width and height as well as the appropriate height- and width-to-thickness ratios, depending on wall support conditions.

Seismic performance and failure mechanism of interbedded slopes with steep rock layers

Numerous interbedded rock (IR) slopes fail during the Wenchuan earthquake in the mountainous region of western China. Landslides are also triggered in IR slopes with a 60° layer inclination, which are generally stable in gravity-dominant environments. This study examines the effect of seismic motion on the response characteristics and failure patterns of IR slopes with steep layers to develop a landslide hazard assessment tool for earthquake-prone regions. First, we use a centrifuge shaking table test to model the failure process and acceleration responses of two IR slope models with stratigraphic dips of 60° and 80°, respectively, under different seismic intensities. Next, we adopt the Particle Flow Code to examine the crack propagation features and peak ground acceleration amplification effects for the IR slopes. We find that the seismic failure pattern of IR slopes depends largely on rock layer inclination: buckling failure is triggered when rock layers are parallel or nearly parallel to the slope surface, while toppling failure is triggered when the rock layer inclination is significantly higher than that of the slope surface. Following seismic excitation, the damage is mainly observed in the weak rock layers, creating lateral stress on adjacent strong rocks, which undergoes deformation and ultimate macroscopic failure. Further, displacement of the IR slope is negatively correlated to rock layer inclination. Rock layer thickness has a major influence on the damaged area inside the slope mass, while rock layer stiffness mainly affects the deformation distribution near the slope shoulder.

Seismic Response of Reinforced-Concrete One-Storey Precast Industrial Buildings with Horizontal Cladding Panels

An extensive parametric study of the seismic response of one-storey precast buildings with horizontal cladding panels frequently used in Central Europe was conducted to analyse the panels’ influence on the overall response of buildings and to find out if the panels can be considered non-structural elements when they are attached to the main building with the connections typically used in practice in Central Europe. The studied structural system consisted of reinforced concrete columns and beams connected by dowels. Horizontal cladding panels were attached to columns using one of the most frequently used isostatic fastening systems. The top connections provided out-of-plane stability, and the bottom connections supported the panel in the vertical direction. The parametric study was preceded by extensive experimental research, including cyclic tests on connections and full-scale shaking table tests of whole buildings. The results of experiments were used to reveal the basic response mechanisms of panels and connections and to develop, validate and calibrate numerical models employed in the parametric study presented herein. Fifteen generalised structures with different masses and heights were subjected to 30 accelerograms with two peak ground acceleration (PGA) intensities of 0.3 g and 0.5 g, corresponding to significant damage and near-collapse limit states. The effects of the construction imperfections in connections, the silicon sealant panel-to-panel connections and different types of connections of the bottom panel to the foundation were analysed. The crucial parameter influencing the response was the displacement capacity of the connections, which was considerably affected by the construction imperfections and, consequently, difficult to estimate. It has been observed that in some buildings, particularly in shorter structures with smaller mass, cladding panels can have a somewhat more notable influence on the overall response. However, in general, when the considered types of connections are used, the panels can be considered as non-structural elements, which do not importantly influence the response of the main building. Owing to structural imperfections and relatively short available gaps, the failure of the considered top connections and falling of the panels is very likely in the high seismicity regions. In the most adverse cases, it can occur even in the moderate seismicity regions.

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.

Detection of Structural Damage in a Shaking Table Test Based on an Auto-Regressive Model with Additive Noise

Damage identification plays an important role in enhancing resilience by facilitating precise detection and assessment of structural impairments, thereby strengthening the resilience of critical infrastructure. A current challenge of vibration-based damage detection methods is the difficulty of enhancing the precision of the detection results. This problem can be approached through improving the noise reduction performance of algorithms. A novel method based partially on the errors-in-variables (EIV) model and its total least-squares (LS) algorithm is proposed in this study. Compared with a classical damage detection approach involving adoption of auto-regressive (AR) models and the least-squares (LS) method, the proposed method accounts for all the observation errors as well as the relationships between them, especially in an elevated level of noise, which leads to a better accuracy. Accordingly, a shaking table test and its corresponding finite element simulation of a full-scale web steel structure were conducted. The acceleration time-series output data of the model after suffering from different seismic intensities were used to identify damage using the presented detection method. The response and identification results of the experiment and the finite element analysis are consistent. The finding of this paper indicated that the presented approach is capable of detecting damage with a higher accuracy, especially when the signal noise is high.

Experimental Study on Seismic Response of Underground Tunnel–Soil–Piled Structure Interaction Using Shaking Table in Loose Sand

The seismic response of structures can have a significant impact on adjacent structures’ response. Although several numerical studies have been applied in the field of tunnel–soil–pile interaction systems, there is a lack of experimental research specifically focused on the effects of this interaction on tunnel cross-section deformation and the existence of structure on encircling soil response. In this study, shaking table tests were conducted to examine the seismic response of a tunnel and the surrounding soil when an eight-story structure with piles was located in the vicinity of the tunnel. Four series of physical models were analyzed, including free-field soil (S), tunnel–soil (TS), soil-piled structure (SP), and tunnel–soil-piled structure (TSP), under sinusoidal vibration at three frequencies on loose sand. According to the results, the tunnel significantly impacts the surrounding soil response during seismic excitation with reduced acceleration at the tunnel invert and increased acceleration at the tunnel crown. In the TSP model, applied frequency affects the recorded acceleration amplitude at the tunnel invert. Although acceleration amplitude decreases at 3 Hz frequency excitation compared to the free field model, 8 Hz excitation resulted in bigger values in tunnel invert. Displacements are higher at the tunnel crown, indicating tunnel-induced soil deformation and maximum shear strain concentrated near the tunnel crown. The tunnel cross-section exhibited oval shape changes, with higher forces on the tunnel crown in the presence of piles.

Transverse seismic responses of a shield tunnel considering the influence of segment joints

The segment joints of a shield tunnel are generally the weak components of the structure, and they can be considerably damaged under strong seismic loading, thus influencing the overall seismic behavior. In this study, Finite Element simulation analyses of centrifuge shaking table tests and a shield tunnel project are carried out to investigate the influences of the segment joints on the seismic responses and the associated mechanisms. First, the reliability of the numerical procedure is validated by using the centrifuge shaking table test results. The numerical procedure is then used, together with the refined simulation approach for segment joints, to carry out extensive numerical analyses of the seismic responses of a shield tunnel project under different horizontal earthquake loadings. The research results show that due to the influence of the segment joints, the peak value of the dynamic bending moment of each segment tends to be more uniform. When the stiffness reduction method is used to consider the influence of the segment joints, the peak values of the dynamic bending moments can be too large, while the peak values of the dynamic axial forces may be too small. In addition, the tunnel segment rotates during an earthquake, resulting in relatively large relative displacements of the segment joints.

Shaking Table Testing of Liquefied Soil Layer Located in the Bottom Slab of a Subway Station

In this study, a shaking table test was conducted to investigate the presence of a liquefied soil layer at a subway station bottom plate. The seismic responses to soil and station structure were investigated by inputting seismic waves of different intensities. The following test results were obtained. As the intensity of the seismic response increases, liquefaction occurs in the soils located at the base of the station. The remainder of the soil liquefies to a lesser degree but still results in soil subsidence and damage to the soils on both sides of the station. In seismic loading conditions, the pore water pressure undergoes a process of “rapid growth and slow dissipation”. As the seismic intensity increases, the main frequency of the soil near the structure develops from a high to a low frequency, and the main frequency of the soil far away from the structure does not change significantly, indicating that the presence of the structure has a significant effect on the working conditions of the soil. The peak acceleration, as well as the peak maximum dynamic strain in the center column of the station, occurs at the bottom of the center column at the platform level, and the maximum dynamic strain in the slab occurs at the bottom slab at the concourse level.

Similar Material Proportioning Tests and Mechanical Properties Based on Orthogonal Design.

Shaking table tests serve as an effective method to simulate landslides triggered by seismic activities. These laboratory experiments necessitate the use of materials that mimic those encountered in real-world scenarios. For this investigation, materials analogous to field conditions for the shaking table tests were formulated using quartz sand, barite powder, iron powder, gypsum, rosin, and alcohol. Within the model test compositions, iron powder, barite powder, and quartz sand acted as aggregates; gypsum functioned as an additive, and a solution of rosin and alcohol was employed as a binder. Employing the orthogonal design method, the physical and mechanical parameters of these analogous materials were ascertained through double-sided shear tests, as well as uniaxial compression and splitting tests. Subsequent analyses included extreme difference and regression assessments targeting the determinants influencing the physical and mechanical characteristics of these materials. The ultimate goal was to determine the optimal mixing ratios for the model test materials. The findings revealed that the physical and mechanical properties of analogous materials at varying ratios span a broad spectrum, fulfilling the criteria for distinct rock model experiments. A thorough examination of the factors impacting the physical and mechanical properties of these materials was undertaken, elucidating their respective influences. Based on the relative significance of each determinant on the mechanical attributes of the analogous materials, dominant factors were identified for a multiple regression analysis, from which the regression equations corresponding to the test ratios were derived.

Rocking stiffness of electrical cabinets with tubular base in nuclear power plants

Safe operation of nuclear power plants during an earthquake requires continued operation of safety related electrical equipment as intended. Such equipment are mounted in electrical cabinets and are seismically qualified by using an in-cabinet response spectra (ICRS). Generation of ICRS requires a good understanding of the cabinet’s dynamic characteristics. Past studies have shown that the rotational stiffness associated with the cabinet base and the mounting arrangement plays a primary role in the dynamic behavior of the cabinet. This rotational stiffness is needed to evaluate and characterize the global rocking mode of cabinet vibration. Existing studies have developed formulations to calculate the rocking stiffness for a few mounting arrangements that are typically found in United States and some other western countries. However, existing formulations could not be applied to cabinets in South Korean nuclear plants due to the differences in cabinet mounting type. This study is focused on consideration of tubular mounting arrangement that is typically found in South Korean plants. First, closed-form formulations are developed using fundamental principles of mechanics for two separate cases of this mounting arrangement. Then, detailed nonlinear finite element (FE) analyses are conducted for different mounting arrangements corresponding to different properties and dimensions of the tubular base. The FE models are used to calibrate the proposed closed-form formulations for various different configurations and structural or geometrical properties of tubular members. The proposed formulations provide a simple and accurate estimation of cabinet rocking stiffness which otherwise is difficult to evaluate without a shake table test or a detailed finite element analysis.

Real-time hybrid simulation incorporating machine learning for deep-water bridges subjected to seismic ground motion with fluid-structure dynamic interaction

The investigation of fluid-structure dynamic interaction (FSI) of deep-water structures subjected to seismic events with underwater shaking table testing method has been restricted by similarity problems and limited experimental capabilities. To address this issue, the authors previously proposed a real-time hybrid simulation (RTHS) method for FSI under seismic loading. In this study, the proposed method is applied to a deep-water bridge to demonstrate the low-cost and high-efficiency features of the proposed method. A total of 100 sets of experimental samples were analyzed, providing details and statistical information of the structural responses with FSI effects during seismic events. In the proposed RTHS application, a machine learning surrogate model was established for real-time calculation of the complex numerical substructure, and data exchange for complex physical-numerical boundaries. Additionally, a solution for RTHS when complex physical substructure boundary conditions can only be partially satisfied has been proposed, further contributing to the versatility of the study. Through the utilization of such advanced computational methods, the authors were able to explore the intricate coupled effect between fluid and structure in a deep-water environment. Such efforts hold the promise of enhancing our understanding of this complex phenomenon and may ultimately inform the design and construction of more resilient structures in the future.

Critical issues in nonlinear modeling of reinforced concrete buildings: code-compliant modeling approaches and the 2015 E-defense shake table tests on a full-scale 10-story building

Critical issues in nonlinear modeling of reinforced concrete buildings: code-compliant modeling approaches and the 2015 E-defense shake table tests on a full-scale 10-story building

Force distribution on polymeric geostrip reinforcements in MSE walls under seismic excitation

In this experimental study, the values and distributions of dynamic tensile force along the polymeric geostrip reinforcements were investigated under stepped increasing sinusoidal excitations with a series of shaking table tests on 1500 mm high or 1/3 scale physical mechanically stabilized earth wall (MSE) model. The effects of the peak ground acceleration ([Formula: see text]), slope angle of the cohesionless backfill material ([Formula: see text]), and stiffness of the polymeric geostrip reinforcement were assessed on both the potential failure surface geometry in the backfill soil and dynamic tensile forces along the lengths of polymeric geostrips. Three potential failure surfaces from the results of shaking table tests in the backfill cohesionless soil were detected as for states of quasi-elastic, plastic, and failure. However, neither the current design codes for MSE walls nor the theoretical recommendations truly reflect potential failure surface geometry in the backfill soil. Additionally, the values and distribution geometry of maximum incremental dynamic tensile forces ([Formula: see text]) on the reinforcements along the height of MSE wall recommended by design codes are not compatible with test results; however, the normalized location of total maximum incremental dynamic tensile force ([Formula: see text]) acclaimed by design codes is consistent with the test results. The traditional pseudo-static limit equilibrium methods result in over conservative horizontal dynamic earth pressure coefficient ([Formula: see text]) values generally as compared with the test results. The slope angle of the backfill material and stiffness of reinforcement have a negligible effect on the potential failure surface geometry; however, incremental dynamic tensile forces, total maximum incremental tensile forces, and horizontal dynamic earth pressure coefficient values increase with an increase in the stiffness of reinforcement and inclination angle of the backfill and peak ground acceleration value.