Shake Table Research Articles

Experimental Study on Transverse Seismic Behavior of Long-Span Cable-Stayed Bridge with Two Inverted Y-Shaped Reinforced Concrete Towers

ABSTRACT The transverse seismic behavior of a long-span cable-stayed bridge with two inverted Y-shaped reinforced concrete towers is investigated in this study. To accomplish this, a 1/35-scale model of a cable-stayed bridge with a span of 1088 m was designed, constructed, and tested until failure on four shake tables; the test was conducted at Tongji University, China. A site-specific artificial wave was applied in the transverse direction. Moreover, the input peak ground acceleration was increased from 0.1 g to 1.3 g until the test model failed. The transverse displacement, force, rebar strain, and curvature responses of the bridge model are obtained and studied. The test results showed that the transverse displacement response of the tower was significantly affected by high-order modes. This resulted in the maximum seismic displacement of the tower at the middle – upper level of the middle column except for the tower top. The ratio of the transverse seismic forces acting on the towers significantly exceeded that of the forces acting on the piers. In the final test case, severe damage, including concrete crushing and rebar exposure, occurred at the bottom of the middle column – the most critical part of the tower – leading to the inclination of the tower. Damage to the cables or deck was not observed. The finite element model captured the elastic transverse seismic behavior of the test model.

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

Shaking table tests and numerical analysis of RC coupled shear wall structure with hybrid replaceable coupling beams

AbstractA variety of innovative structural solutions have been recently introduced to mitigate damage and expedite the repair of buildings subjected to extreme seismic events, hence contributing to the urgent need for resilient societies. In this context, the present study experimentally and numerically investigates an innovative reinforced concrete (RC) shear wall (SW) structure with replaceable coupling beams (CBs) equipped with hybrid devices. These hybrid devices couple metallic and viscoelastic dampers and aim at satisfying multiple lateral load performances effectively. To assess the seismic performance of the proposed coupled SW system and verify the design principle, comparative shaking table tests were performed on two 1/4‐scale seven‐story SW structure specimens, including a conventional RC coupled SW and the proposed coupled SW with hybrid devices. The tests results indicate the improved performance of the proposed compared with the conventional system in terms of: (1) reduced interstory drifts and story accelerations demand under a wide range of seismic intensities, (2) concentrated damage in the hybrid device and minimal damage to the other components contributing to the reparability of the structure. Furthermore, 3D finite element models for the shaking table test specimens were established in OpenSees and validated against experimental response. Successively, a numerical parametric study was conducted by performing non‐linear response history analyses under a set of 22 ground motions to investigate the influence of different design configurations of the hybrid device on the peak interstory drifts and peak story accelerations.

Modal characterization of a three‐story buckling‐restrained braced frame steel building by non‐destructive field testing

AbstractA full‐scale, reconfigurable, three‐story steel building was constructed and its modal properties identified prior to shake table testing on the UC San Diego Large High Performance Outdoor Shake Table (LHPOST6). The aim of this pre‐shake table test erection was to demonstrate the rapid constructability of the building and identify construction fit issues prior to its assembly on LHPOST6. This posed a unique opportunity to characterize the building's modal properties using a variety of non‐destructive, low‐amplitude techniques. To this end, two novel, non‐destructive methods were used, namely: (1) impact tests conducted by swinging a tire from a crane to impact strategically selected locations, and (2) dynamic base vibration tests, induced by driving heavy machinery in the vicinity of the base of the structure. A system of accelerometers located throughout the structure captured waves propagating from each test to characterize the as‐built dynamic properties of the building. Results from various system identification methods are presented and compared to theoretical and numerical analysis. Comparisons indicate that the theoretical, numerical, and experimentally determined periods are nominally within 15% of each other. The erection of the structure was complete over the course of 3 days and construction fit‐up issues were addressed. The structure was then rapidly deconstructed and stored prior to erection for full‐scale shake table testing. This pre‐shake table test exercise demonstrated the viability of two, simple, low‐amplitude excitation approaches for use in the dynamic characterization of full‐scale buildings, with results consistent with theoretical and numerical models.

Experimental investigation of sliding-based isolation system with re-centering functions for seismic protection of masonry structures

A sliding-based isolation system is an efficient strategy to enhance the seismic performance of low-rise brick masonry buildings, a common type of construction across the globe. The previously developed isolation systems lack a proper re-centering mechanism. Therefore, in this study, a low-cost isolation system, termed reinforced cut wall (RCW) with an appropriate re-centering mechanism, is designed and tested experimentally using a shake table, which hasn’t been tested previously. Two unconfined reduced scale (1:3) brick masonry buildings were subjected to frequency-based seismic excitation, and the model's corresponding acceleration and displacement response were captured. Compared to the fixed base model, considerable reductions were observed in the acceleration and displacement response in the case of the isolated model. Similarly, the inter-story drift and floor relative displacement response was also reduced in the isolated model. Furthermore, the rebars used for the re-centering mechanism remained within the linear viscoelastic range. Based on the experimental validation, the proposed low-cost RCW isolator was found to be an efficient isolation strategy for low-rise masonry buildings in high seismic regions.

Shaking Table Testing of an Unstrengthened and Strengthened with Textile Reinforced Mortar (TRM) Full-Scale Masonry Cross Vault

ABSTRACT This article presents the results of the LNEC-3D shaking table tests on a full-scale masonry cross vault without and with the textile reinforced mortar used as strengthening solution. The specimen has been tested in the scope of the European project SERA. TA 07 “Seismic Response of Masonry Cross Vaults: Shaking table tests and numerical validations”. The specimen replicates a generic cross-section of a central bay located in a lateral nave of a three-nave church, derived from the intersection of two semi-circular barrel vaults with low rise. It is representative of a generic monumental church in Central Italy, generated by a squared base groin vault with a net span of 3.13 m and 1.13 m rise at full scale. A unidirectional seismic action is applied to develop shear damage in the shell of the vault. A detailed description of the two tests and the conclusions are presented. The response is evaluated based on the displacements, damage, and collapse mechanisms developed as a function of an increasing intensity earthquake testing protocol, in which a pre-processed strong ground motion component of the L’Aquila (Italy) earthquake (April 6, 2009) was used.

Dynamic plastic hinge rotation measurement for RC columns under seismic loads using MEMS inclinometers

Plastic hinge rotation is an efficient and essential response parameter for post-disaster damage assessment on RC structures. In this paper, a micro-electronic mechanical system (MEMS) inclinometer-based approach is developed to dynamically measure the plastic hinge rotation of RC columns under earthquake loads. The plastic hinge rotation is regarded as the relative angle of rotation, measured by inclinometers, between cross-sections such that influence from the absolute rotation of floors can be eliminated. Meanwhile, since the inclinometers are densely installed near the bottom, translational acceleration-induced error can be compensated by subtracting the lowest sensor’s output from others’. However, issues caused by rotational and translational vibration are considered as the major challenges in real applications. The contribution of external vibration to the sensor’s overall output is revealed via analysis on a simplified inclinometer model. A numerical study utilizing typical RC column’s deformation characteristics and dimensions is conducted to analyze the influence of major factors: vibrational frequency, sensor position and damage extent. A method for static and dynamic inclinometer calibration is presented. The related calibration experiments are carried out to quantify the sensor’s sensitivity as well as the relationship between rotational frequency and error. The calibration method is validated with a set of vibration tests that use three seismic waves as input. Finally, performance of the proposed approach in full scale structures is investigated through a shake table test.

The analysis of seismic induced progressive instability and failure mechanisms: A case study

The 2008 Wenchuan Ms8.0 earthquake triggered a catastrophic landslide, i.e., the Daguangbao (DGB) landslide (1.2 ✕ 109 m3). Its shear failure occurred within a deep-seated (average depth of 400 m) saturated carbonate bedding fault in the Paleozoic Formation. The frequent seismic events in the tectonic belt make the landslide initiation mechanism more complex. Shake table tests were conducted on the DGB landslide to understand the coupling effect of multiple earthquakes, geology and hydrology. The results showed that the multiple earthquakes weakened the friction coefficient as the Boltzmann function on the sliding surface of the landslide. The friction law of the basal surface related to seismic energy was established and incorporated into the Newmark analysis. And the seismic energy consumed in the steep scarp surface release of landslide during an earthquake is also considered. It found that the traditional Newmark model overestimates the time for earthquake-induced landslides due to ignoring the steep scarp surface release stage. It proposed that evaluating pre-earthquake induced slope damage, and critical seismic energy for triggering co-seismic landslides are important for predicting post-seismic landslides.

A novel data-driven sensor placement optimization method for unsupervised damage detection using noise-assisted neural networks with attention mechanism

Optimization of sensor placement (OSP) is one of the important steps in structural health monitoring to reduce the instrumentation cost, and improve damage detection. Although modal analysis is an optional intermediate process in terms of damage detection, conventional OSP methods for damage detection are mostly dependent on mode shapes. In this case, the sensor placement and damage detection are highly relying on the accuracy of modal analysis, and the results may not be adapted to different type of excitations. In this article, a novel noise-assisted neural network with attention mechanism is proposed based on the above challenges. This method which can be used to optimize sensor placement in an unsupervised and data-driven manner, is verified using a dataset simulated from the ASCE benchmark and an experimental dataset obtained from shake table tests. The results from the simulated dataset show that the percentage of the sensors that could be removed are higher than the conventional effective independence (EFI) method, with a highest of 62.5% for cases with low noise levels. In the meantime, the occurrence and the level of damage can still be well detected with a reduced number of sensors. Most importantly, in the proposed approach the optimal sensor placement configurations can be determined adaptively to account for different forms of excitations and noise levels, which is impossible for conventional model-driven methods. The results obtained from the experimental dataset show that the proposed method is also effective for real-world applications. As a result, the proposed data-driven OSP method skips the conventional model analysis process and directly focuses on the sensor arrangement that enables accurate detection of damage. It also has the potential for application in related fields, such as the monitoring of aerospace and mechanical infrastructures.

Shake table test and seismic fragility analysis of transmission tower-line system considering duration effect

Although extensive attention has been devoted to the influence of ground motion duration on the seismic performance of various structures, the integration of the duration effect into the seismic analysis of transmission tower-line systems (TTLSs) has been rarely studied, leading to a lack of understanding regarding the relationship between the ground motion duration and the seismic response of TTLSs. This paper aims to quantify the duration effect on the structural performance and seismic fragility of a TTLS through shake table tests and numerical simulations. To achieve this goal, a reduced-scale experimental model of a TTLS is carefully designed and fabricated, and a group of ground motions with contrasting durations is chosen using a spectral matching method. Subsequently, shake table tests are conducted to examine the duration effect on the seismic responses of the TTLS. The recorded data indicates that long-duration ground motions (LDGMs) significantly amplify the seismic responses and have the potential to degrade the structural performance. Furthermore, a validated finite element model of the TTLS is employed to compute its nonlinear responses from elastic behavior to complete plasticity utilizing incremental dynamic analysis. Probabilistic assessments are also conducted to investigate the seismic fragility and loss of the TTLS. The findings reveal higher damage probabilities and more severe losses caused by LDGMs, emphasizing the importance of considering the duration effect in the seismic performance assessment of TTLSs. This investigation contributes to a meaningful exploration for reliably assessing the seismic capacity of TTLSs while accounting for the duration effects.

Experimental study on a cable-stayed bridge isolated with the combination of elastoplastic cables and fluid viscous dampers in the transverse direction

It is usually challenging to design an effective transverse isolation strategy that needs both large restoring force and large deformation capacity for cable-stayed bridges to meet the requirements under regular operation and earthquakes. The authors proposed a novel transverse isolation device that combines elastoplastic cables and fluid viscous dampers (FVDs) to address this challenge. The elastoplastic cables are adopted to control the relative displacements at the girder-pylon connections in the transverse direction under both regular operation and earthquakes. FVDs are responsible for dissipating input seismic energy. To further validate the effectiveness of the proposed isolation system under both far and near-fault ground motions, shake table tests were conducted for a cable-stayed bridge with a scale ratio of 1/20. Details of the scaled model for the isolated and fixed systems, including dimensions of the components, additional mass arrangement, instrumentations, and boundary conditions, are briefly described. Seismic responses are recorded for each test case, such as accelerations and displacements of the pylons and girder, hysteretic responses of the combined devices, and strain responses of the pylon rebars. The experimental results indicate that the transverse boundary conditions have significant effects on the seismic responses of the girder, and the high-mode content of ground motions mainly dominates the seismic responses of the pylons. In addition, the isolated system effectively reduces the seismic responses at the bottom of the pylons, and the effectiveness of the isolation is becoming more evident with an increase in the PGA of the ground motions.

Shaking table tests of sliding‐prone blocks subjected to unidirectional and bidirectional ground and floor motions

AbstractFreestanding museum collections with low friction coefficients and high aspect ratios may be damaged due to excessive sliding displacements during earthquakes. However, several key issues have not been adequately addressed, such as the friction and sliding behavior of museum collections under actual conditions. Unidirectional and bidirectional shaking table tests were conducted to determine the maximum sliding displacements (MSDs) of a freestanding glass block on sandpaper, which had the lowest friction coefficient among forty‐two contact interfaces in slow‐pull tests. Fourteen far‐field and fourteen near‐fault pulse‐like ground motion records were applied with peak ground accelerations (PGAs) of the major components scaled from 0.05 to 0.6 g. Shaking table tests of a full‐scale three‐story reinforced concrete frame structure containing glass blocks were carried out. Seismic fragility curves corresponding to the sliding failure of the glass block were generated based on the experimental results considering the friction coefficient uncertainty. The results show that the influence of the bidirectional interaction on the MSD is more significant for near‐fault pulse‐like ground motions than far‐field ground motions. For a specific ground motion record, the sliding displacement of the glass block may not increase with the increase of the PGA or peak floor acceleration due to the friction coefficient uncertainty, but this has a negligible influence on the fragility. A clearance around sliding‐prone museum collections with friction coefficients larger than 0.20 is recommended to ensure that the probability of exceedance is lower than 5%.

Experimental-based numerical simulation of interacting suspended ceiling-sprinkler piping systems

Suspended ceiling and fire sprinkler piping (CP) systems are two of the most common interacting nonstructural elements inside the buildings. While each of these elements individually is prone to losses during the earthquakes, their interaction can even more intensify their associated damage. This article aims to integrate system-level modeling methodology by using existing subsystem-level models in OpenSees platform to simulate the interacting behavior of CP systems. To do so, the numerical model of the CP systems is developed by using a series of previously developed component-level nonlinear models. Experimental results from a shake table study of CP systems installed in a five-story building (fully scaled) are used for the validation of the proposed methodology. Experimental acceleration and displacement responses of CP systems at different locations as well as the damage-progression pattern in the suspended ceiling system are predicted well through the use of the proposed modeling technique.

Centrifuge shake table tests on damage process and failure mode of embankments with different slope gradient

Centrifuge shake table tests on damage process and failure mode of embankments with different slope gradient

Experimental analysis of a shake table test of strip footing on two layered reinforced soil

Experimental analysis of a shake table test of strip footing on two layered reinforced soil

Data‐Driven Structural Health Monitoring on Shaking Table Tests of a 3‐Story Steel Building with Sliding Slabs

Data‐driven structural health monitoring (SHM) is an approach which relies on the information contained in the data and through signal analysis techniques captures the features, variations, and uncertainties that data contain. This paper presents the response of shaking table tests of a full‐scale, 3‐story building with sliding slabs connected by horizontal buckling‐restrained braces for energy dissipation. First, the global dynamic characteristics of the structure were identified from a series of the building response data under different intensity level of base excitations. The variation of the identified modal parameters, such as the mode frequencies and modal shapes, was discovered. The influence of sliding slabs on the dynamic characteristics of the frame was also investigated through the measured response and the equation of motion with six degree of freedom systems. Comparison on the achieved interstory stiffness due to the implementation of sliding slabs and the fixed (locked up) slab was examined. The mechanism and dynamic characteristics of sliding slabs, including energy dissipation of the friction force, BRB hysteresis behavior, and unintended damping force during strong base excitation were analyzed directly using the ARX/recursive model. The extracted unintended damping force performed like a friction hysteretic response, which needs to be considered for frame modeling in shaking table tests. The findings through the data analysis have clarified the important aspects of sliding slabs and demonstrated the benefits and applicability of sliding slabs on reducing the frame response.

Shake table tests on levees deteriorated by seepage-induced internal erosion in geotechnical centrifuge

Shake table tests on levees deteriorated by seepage-induced internal erosion in geotechnical centrifuge

Rocking foundations on geosynthetic-improved sand

This study focuses on the load-deformation response of a heavily loaded rocking footing on geogrid-reinforced sand via centrifuge-model scale shake table tests. To mitigate issues observed with overturning failure and excessive settlement of shallow footings on unimproved ground, geogrid reinforcement can help control footing kinematics while maintaining the enhanced energy dissipation of a rocking footing. The scalemodel geogrid evaluated in this study was manufactured with 3D printing and placed at a depth equal to the footing width. Shake sequences induced controlled yielding, and the geogrid was observed to reduce settlement during rocking and preserved recentering under strong shaking.

Analysis of Seismic Earth Pressure Acting on Basement Walls of Buildings Using 1g Shaking Table Model Test

Analysis of Seismic Earth Pressure Acting on Basement Walls of Buildings Using 1g Shaking Table Model Test

Shake Table Tests on the Bending Moment Distribution of Monopile-Supported Offshore Wind Turbines Subjected to Seismic Motion

Shake Table Tests on the Bending Moment Distribution of Monopile-Supported Offshore Wind Turbines Subjected to Seismic Motion