scholarly journals Seismic Response and Vibration Reduction Analysis of Suspended Structure under Wave Passage Excitation

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Wenhua Cai ◽  
Bujun Yu ◽  
Fajong Wu ◽  
Jianhua Shao
Keyword(s):  
Seismic Response ◽  
Wave Velocity ◽  
Vibration Reduction ◽  
Shaking Table ◽  
Dynamic Responses ◽  
Uniform Motion ◽  
Acceleration Response ◽  
Maximum Acceleration ◽  
Damping Effect ◽  
Suspended Structure

In order to study the influence of traveling wave effect on the seismic response and damping effect of suspended structure, a series of shaking table tests of the 1 : 20 suspended structure have been carried out to compare and analyze the dynamic responses of suspended structures under two points and a consistent input. The vibration damping effect and vibration reduction law of suspended structure are discussed at different apparent wave velocity and in the different connection. The research shows that the damping suspended structure has a good damping effect, and the amplitude reduction of the top displacement peak response is up to 15%, which corresponds to smaller apparent velocities. Moreover, the upper bound of the maximum acceleration response at the structures’ top under nonuniform input motions equals that of the uniform motion. However, there is a hysteresis in the acceleration response under wave travelling excitations, and the smaller the apparent wave velocity, the more obvious the hysteresis.

scholarly journals Shaking Table Tests for Seismic Response of Orthogonal Overlapped Tunnel under Horizontal Seismic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Honggang Wu ◽  
Hao Lei ◽  
Tianwen Lai
Keyword(s):  
Dynamic Response ◽  
Seismic Response ◽  
Seismic Wave ◽  
Shaking Table Test ◽  
Shaking Table ◽  
Shaking Table Tests ◽  
Acceleration Response ◽  
Test Device ◽  
Deformation Stages ◽  
Superposition Effect

This paper presents the seismic dynamic response and spectrum characteristics of an orthogonal overlapped tunnel by shaking table tests. First, a prototype of the engineering and shaking table test device, which was used to design details of the experiment, was developed. Then, the sensors used in the test were selected, and the measurement points were arranged. Subsequently, the Wenchuan seismic wave with horizontal direction in different peak ground accelerations was inputted into the model, followed by a short analysis of the seismic response of the overlapped tunnel in the shaking table test as well as the distribution of the peak acceleration. Throughout the studies, the model exhibited obvious deformation stages during the seismic wave loading process, which can be divided into elastic, plastic, plastic enhancement, and failure stage. In particular, the time- and frequency-domain characteristics of the key parts of the tunnel were discussed in detail by using the continuous wavelet transform (CWT) based on the Morlet wavelet as the basis function. We found that the acceleration response was more intense within 25–60 s after the seismic wave was inputted. Furthermore, owing to “the superposition effect,” the seismic response at the crown of the under-crossing tunnel was stronger than that at the invert of the upper-span tunnel. The low and medium frequencies in the transformation of small scales (5–20) significantly affected the overlapped tunnel. These results elucidate the seismic dynamic response of the overlapped tunnel and provide guidance for the design of stabilizing structures for reinforcing tunnels against earthquakes.

scholarly journals Dynamic Response of a Combined Isolation Based Mega-Substructure under Bidirectional Near-Fault Ground Motions

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Xueyuan Yan ◽  
Weihong Chen ◽  
Shen Shi ◽  
Xuan Wang
Keyword(s):  
Seismic Response ◽  
Seismic Isolation ◽  
Control Method ◽  
Ground Motions ◽  
Vibration Reduction ◽  
Shaking Table ◽  
Main Body ◽  
Isolation Layer ◽  
Near Fault ◽  
Model Structures

A typical megaframe structure has a high lateral stiffness and is excellent for high-rise structures. However, this high stiffness can lead to poor seismic response of a structure. Seismic isolation technology is a mature and cheap vibration control method that is used for vibration reduction in megaframes. This paper introduces a megaframe structure based on substructure combined isolation. The structure consists of two parts. The main body is a megaframe, and the substructure is the subframe with the combined isolation layer arranged at the bottom of the subframe. The seismic performance of this structure system was evaluated by performing shaking table tests of two megaframe model structures. The responses of the deformation, acceleration, and shear of the structure were measured. The dynamic behaviors of the structure with or without the combined isolation layer when exposed to single and bidirectional near-fault and far-fault ground motions with different peak values were investigated. The results showed that the combined isolation layer can reduce the bidirectional seismic response of the main frame and subframe. The acceleration, base shear, and displacement responses had similar vibration reduction trends for the two model structures, and the structural responses under bidirectional earthquake were generally greater than that under a single directional earthquake. The near-fault pulse effect increased the seismic response of the structure. The increase of the predominant period of ground motion also increased the seismic response of the structure.

scholarly journals Shaking Table Tests for Seismic Response of Oblique Overlapped Tunnel

2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
Hao Lei ◽  
Honggang Wu ◽  
Tianwen Lai
Keyword(s):  
Seismic Response ◽  
Cross Section ◽  
Slope Failure ◽  
Response Spectrum ◽  
Shaking Table ◽  
Dynamic Responses ◽  
Dynamic Strain ◽  
Seismic Load ◽  
Shaking Table Tests ◽  
The Cross

To study the dynamic response and spectrum characteristics of the three-dimensional crossing tunnel under the action of seismic load, we established a 1/50 downscale model based on a typical of the oblique overlapped tunnel and conducted a series of shaking table tests. Through examining the recorded dynamic responses (acceleration and dynamic strain measured at different locations in model tunnels), we found that the seismic response of the crown was the largest at the central section, and the invert of the tunnels was exactly opposite to the crown, which presented a “parabolic” distribution, and we inferred that the damage within the model may be mainly concentrated on the crown of the tunnels. Additionally, the dynamic strain showed obvious nonlinear and nonstationary characteristics under the action of different degrees of seismic intensities. Different from a single tunnel, the acceleration superposition effect appears in the cross section of two tunnels because of the spatial effect of overlapping tunnels, resulting in the obvious seismic response in the cross section. Meanwhile, we also found that the 1st dominant frequency (0.1–6.26 Hz) seismic wave played a leading role in the process of tunnel slope failure. Furthermore, the analysis of the acceleration response spectrum also showed that the surrounding rock mass has an amplification effect on low-frequency seismic waves. These results help us better understand the features of the dynamic responses and also provide evidence to reinforce the overlapped tunnels against earthquakes.

scholarly journals Seismic Response of a Tunnel Embedded in Compacted Clay through Large-Scale Shake Table Testing

2018 ◽  
Vol 2018 ◽  
pp. 1-17
Author(s):  
Hao Zhou ◽  
Xinghua Wang ◽  
Changdi He ◽  
Changxi Huang
Keyword(s):  
Seismic Response ◽  
Large Scale ◽  
Clay Soil ◽  
Shaking Table ◽  
Compacted Clay ◽  
Soil Pressure ◽  
Hoop Strain ◽  
Maximum Acceleration ◽  
Cross Sectional ◽  
Absorbing Layer

To investigate the seismic response of large-scale tunnel in compacted clay and effect of shock absorbing layer to the tunnel, a series of three dimensional (3D) shaking table model tests were carried out. The similarity ratio of the model is 1 : 8 and the size of the model container is 9.3 m (length) × 3.7 m (width) × 2.5 m (height). The cross-sectional diameter of the model tunnel is 0.9 m, and the thickness of the tunnel lining is 0.06 m. To simulate the clay soil surrounding condition, the container was filled with clay soil. During the tests, the concrete strain, acceleration, and dynamic soil pressure on the surface of the model tunnel were measured. The results show the existence of tunnel can decrease the maximum acceleration of the model in the X direction; the shock absorbing layer can further decrease the maximum acceleration, however, cannot change the dominant frequency of the ground motion. The longitudinal and hoop strain of the model tunnel with excitation of the input motion is mainly in tension state and the maximum hoop deformation of the model tunnel is located at the conjugate 45°. In addition, the shock absorbing layer has an effect on the strain and dynamic earth pressure of the model tunnel.

scholarly journals Design analysis and experimental verification of vibration reduction of spatial composite damping truss structure

2018 ◽  
Vol 10 (12) ◽  
pp. 168781401881934 ◽  
Author(s):  
Haitao Luo ◽  
Jia Fu ◽  
Peng Wang ◽  
Haonan Wang
Keyword(s):  
Vibration Reduction ◽  
Truss Structure ◽  
Space Structures ◽  
Original Structure ◽  
Test Results ◽  
Acceleration Response ◽  
Damping Effect ◽  
Space Truss ◽  
Constrained Damping ◽  
Tube Structure

In order to solve the problem that the photoelectric instrument may fail when the vibration response of the truss composite structure is too large, the method of applying the viscoelastic-constrained damping layer on the truss wall and the box panel is used to reduce the vibration of the whole structure. In this article, a broken long tube with viscoelastic-constrained damping layer is introduced. The long tube of the original structure is broken into two identical short tubes, and a tube with free damping layer is added to the junction of the two short pipes, which is connected by adhesive and broken long pipe. By analyzing the frequency response of the traditional space truss and spaceflight load structure, and a broken long tube structure, the acceleration response cloud diagram and the acceleration response curve of the fixed measuring node are obtained. Experiments were carried out to verify the feasibility of the structure. The test results show that the method of broken long pipe with viscoelastic-constrained damping layer can achieve better damping effect than the traditional truss structure, and it can effectively reduce the vibration level of the space load at the end of the truss, and has important reference significant for the vibration reduction design of other space structures.

Seismic response characteristics of multi-story subway station through shaking table test

2021 ◽  
pp. 136943322199329
Author(s):  
Zhiyi Chen ◽  
Pengfei Huang ◽  
Wei Chen
Keyword(s):  
Seismic Response ◽  
Shaking Table Test ◽  
Earth Pressure ◽  
Frequency Component ◽  
Shaking Table ◽  
Dynamic Responses ◽  
High Frequency Component ◽  
Subway Station ◽  
Response Characteristics ◽  
Dynamic Earth Pressure

A series of shaking table tests were carried out to investigate the seismic response characteristics of a multi-story subway station. Dynamic responses, including accelerations of the soils and the underground structure, layer drift, dynamic earth pressure, and lateral deformation of soils were recorded and analyzed. Several seismic characteristics of multi-story subway station structures are figured out. It is found that in addition to the racking deformation, the rotation vibration is observed for the multi-story subway station subjected to acceleration waves. From the viewpoint of frequency, the low-frequency component and high-frequency component of the acceleration response of the subway station represent the translation and rotation component of the multi-story subway structure, respectively. In addition, the rotation vibration of the deep-depth structure leads to the local squeezing and detachment from the surrounding soils alternately at both top and bottom ends of the sidewalls. This results in the hump-shaped distribution of dynamic earth pressure. The racking deformation of the multi-story subway station has a linear relationship with the dynamic earth pressure at a certain area along the sidewall, where the top of hump-shaped distribution of dynamic earth pressure is.

scholarly journals Shaking Table Tests of Suspended Structures Equipped with Viscous Dampers

2019 ◽  
Vol 9 (13) ◽  
pp. 2616 ◽  
Author(s):  
Wenhua Cai ◽  
Bujun Yu ◽  
Sakdirat Kaewunruen
Keyword(s):  
Primary Structure ◽  
Damping Ratio ◽  
Seismic Energy ◽  
Shaking Table ◽  
Dynamic Responses ◽  
Strain Response ◽  
Peak Acceleration ◽  
Shaking Table Tests ◽  
Viscous Dampers ◽  
Suspended Structure

In this study, a series of shaking table tests of a ten storey concrete suspended structure equipped with viscous dampers were carried out to evaluate the dynamic responses and vibration damping performance of suspended structures. The effects of link types between the primary structure and suspended floors and different seismic excitations on the response of suspended structure models was verified. The responses include the damping ratio, the frequency, maximum relative displacements, accelerations and maximum strains of the suspended structures. Test results showed that the damping ratio and the frequency of suspended structures installed with dampers (called damping suspended structure) are adjusted compared with a conventional suspended structure with rigid-bar links (conventional suspended structure). Maximum relative displacements of the primary structure of the damping suspended structure were distinctly smaller than those of the conventional suspended structure. However, the maximum relative displacement between the primary structure and the suspended floors of the damping suspended structure was significantly larger than that of the conventional structure, indicating that the swing of the suspended floor can help dissipate seismic energy. The peak acceleration and acceleration amplification factors of the damping suspended structure were less than the conventional suspended structure. Moreover, the peak acceleration response of the damping suspended structure was slightly behind the conventional suspended structure. The damping suspended structure certainly had a considerable and stable reduction for strain response, and the maximum strain response was decreased by 42.3%–72.7% for the damping suspended structure compared with the conventional suspended structure.

scholarly journals Shaking Table Test on the Seismic Response of Buried Oil and Gas Pipelines under the Bidirectional Nonuniform Seismic Excitation

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jianbo Dai ◽  
Chengtao Hu ◽  
Li Wang ◽  
Guidi Zhang
Keyword(s):  
Seismic Response ◽  
Oil And Gas ◽  
Axial Direction ◽  
Shaking Table ◽  
Seismic Excitation ◽  
Acceleration Response ◽  
Peak Displacement ◽  
Loading Level ◽  
Oil And Gas Pipelines ◽  
Laminar Shear

This paper studies the seismic response of buried oil and gas pipelines under the bidirectional nonuniform excitation. Based on the bidirectional shaking table array test, the loading and testing scheme is designed and developed, analyzing the strain response of the buried oil and gas pipeline under the bidirectional uniform and nonuniform seismic excitation, as well as the acceleration response and displacement response characteristics of the pipeline and the surrounding soil body and their change rule by the test. The test proves to show that the developed bidirectional laminar shear continuum model soil box can meet the requirements of the bidirectional nonuniform seismic excitation and continuous laminar shear deformation of the soil. The peak strains of the pipeline in axial and bending caused by nonuniform excitation are larger than those of the pipeline under uniform excitation, the degree of unevenness in the distribution along the axial direction is greater, and the strain curves are large in the middle and small at both ends along the axial direction of the pipe. The acceleration responses of the pipeline and the soil body under the bidirectional nonuniform excitation are larger than those under the uniform excitation. The acceleration response of both the pipe and the soil under the nonuniform excitation is larger than that under the uniform excitation, and the differences are shown in the transverse and axial directions, the peak acceleration response of the soil body under the nonuniform excitation is about three times that of the transverse direction, and more peak points appear in the axial and transverse acceleration responses of the pipe under the nonuniform excitation as the loading level increases, the peak displacement response of the soil body increases gradually with the height, but the fluctuation range of the peak displacement of the soil body nearby the pipe is larger. The soil displacement curve starts to smooth out when the loading level reaches 1.0 g, and the axial displacement decreases, which indicates that the interaction between the pipe and soil is more intense and the relative motion between the pipe and soil is more obvious under the nonuniform excitation, and the soil is more likely to be damaged and enter the nonlinear stage. Therefore, it is necessary to analyze and design the seismic performance of buried pipes considering the nonuniform seismic excitation.

Seismic Response of Pile Groups Improved with Deep Cement mixing Columns in Liquefiable Sand: Shaking Table Tests

2021 ◽  
Author(s):  
Dingwen Zhang ◽  
Anhui Wang ◽  
Xuanming Ding
Keyword(s):  
Seismic Behavior ◽  
Lateral Displacement ◽  
Bending Moment ◽  
Pile Group ◽  
Shaking Table ◽  
Excess Pore Pressure ◽  
Shaking Table Tests ◽  
Pile Groups ◽  
Acceleration Response ◽  
Table Model

A series of shaking table model tests were performed to examine the effects of deep cement mixing (DCM) columns with different reinforcement depths on the seismic behavior of a pile group in liquefiable sand. Due to the DCM column reinforcement, the fundamental natural frequency of the model ground increases noticeably. The excess pore pressure of soils reduces with the increase of reinforcement depths of the DCM columns. Before liquefaction, the acceleration response of soils in the improved cases is obviously lower than that in the unimproved case, but the acceleration attenuation is greater after liquefaction in the unimproved case. Moreover, the lateral displacement of the superstructure, the settlement of the raft, and the bending moment of the piles in the improved cases are significantly reduced compared to those in the unimproved case, and the reduction ratios rise with the increase of reinforcement depth of the DCM columns. However, reinforcement by the DCM columns may result in the variation of the location of the maximum moment that occurs in the pile.

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