Shake Table Studies on Viscous Dampers in Seismic Control of a Single-Tower Cable-Stayed Bridge Model under Near-Field Ground Motions

2018 ◽  
Vol 12 (05) ◽  
pp. 1850011 ◽  
Author(s):  
Jiang Yi ◽  
Jianzhong Li ◽  
Zhongguo Guan
Keyword(s):  
Ground Motions ◽  
Near Field ◽  
Far Field ◽  
Viscous Damper ◽  
Viscous Dampers ◽  
Damping Force ◽  
Seismic Control ◽  
Cable Stayed Bridge ◽  
Bridge Model ◽  
Cable Stayed Bridges

To investigate the effectiveness of viscous damper on seismic control of single-tower cable-stayed bridges subjected to near-field ground motions, a 1/20-scale full cable-stayed bridge model was designed, constructed and tested on shake tables. A typical far-field ground motion and a near-field one were used to excite the bridge model from low to high intensity. The seismic responses of the bridge model with and without viscous dampers were analyzed and compared. Both numerical and test results revealed that viscous dampers are quite effective in controlling deck displacement of cable-stayed bridges subjected to near-field ground motions. However, due to near-field effects, viscous damper dissipated most energy through one large hysteresis loop, extensively increasing the deformation and damping force demand of the damper. Further study based on numerical analysis reveals that to optimize deck displacement of cable-stayed bridges during an earthquake, a viscous damper with relatively larger damping coefficient should be introduced under near-field ground motions than far-field ones.

Effect of Frame-Restoring Force Characteristics on the Pounding Response of Multiple-Frame Bridges

2005 ◽  
Vol 21 (4) ◽  
pp. 1113-1135 ◽  
Author(s):  
Susendar Muthukumar ◽  
Reginald DesRoches
Keyword(s):  
Ground Motions ◽  
Near Field ◽  
Hysteretic Behavior ◽  
Impact Response ◽  
Far Field ◽  
Restoring Force ◽  
Bridge Model ◽  
Multiple Frame ◽  
The Impact ◽  
Force Characteristics

This study examines the effect of column hysteretic behavior on the impact response of adjacent frames in multiple-frame bridges. A simplified planar analytical bridge model is developed including inelastic frame action, nonlinear hinge behavior, and abutment effects. Pounding is simulated using a stereomechanical approach. The frame hysteretic models considered include the elasto-plastic and bilinear (traditional), Q-Hyst (stiffness-degrading), and pivot hysteresis (strength-degrading) models. Analytical studies conducted on adjacent bridge frames reveal that the traditional models underestimate the stiff frame displacement amplification due to pounding, and overestimate the flexible frame displacement amplification, when compared with other hysteretic models. A stiffness-degrading model is recommended to accurately estimate the pounding response of bridge frames subjected to far-field ground motion. The use of a strength-degrading model increases the stiff frame displacement amplification by 125% when compared to the stiffness-degrading model for highly out-of-phase frames, and is recommended in the presence of near-field ground motions.

scholarly journals Seismic Fragility Analysis of Mid-Story Isolation Buildings

2021 ◽  
Keyword(s):  
Fragility Curves ◽  
Ground Motions ◽  
Near Field ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Plastic State ◽  
Far Field ◽  
Analysis Method ◽  
Isolation System ◽  
Isolation Layer

Abstract. Seismic fragility analysis is essential for seismic risk assessment of structures. This study focuses on the damage probability assessment of the mid-story isolation buildings with different locations of the isolation system. To this end, the performance-based fragility analysis method of the mid-story isolation system is proposed, adopting the maximum story drifts of structures above and below the isolation layer and displacement of the isolation layer as performance indicators. Then, the entire process of the mid-story isolation system, from the initial elastic state to the elastic-plastic state, then to the limit state, is simulated on the basis of the incremental dynamic analysis method. Seismic fragility curves are obtained for mid-story isolation buildings with different locations of the isolation layer, each with fragility curves for near-field and far-field ground motions, respectively. The results indicate that the seismic fragility probability subjected to the near-field ground motions is much greater than those subjected to the far-field ground motions. In addition, with the increase of the location of the isolation layer, the dominant components for the failure of mid-story isolated structures change from superstructure and isolation system to substructure and isolation system.

Experimental study on seismic control of towers in cable-supported bridges by incorporating fluid viscous dampers between sub-towers

2020 ◽  
Vol 23 (10) ◽  
pp. 2086-2096
Author(s):  
Peng Zhou ◽  
Min Liu ◽  
Suchao Li ◽  
Hui Li ◽  
Gangbing Song
Keyword(s):  
Control Strategies ◽  
Experimental Tests ◽  
Shaking Table ◽  
Viscous Dampers ◽  
Damping Force ◽  
Alternative Scheme ◽  
Seismic Control ◽  
Fluid Viscous Dampers ◽  
Seismic Loadings ◽  
Energy Dissipation Devices

In this article, the seismic control of towers incorporated with fluid viscous dampers between sub-towers is investigated experimentally. To replace one entire tower, an alternative scheme consisting of four separate sub-towers is first proposed. Fluid viscous dampers are utilized as energy dissipation devices to be installed between sub-towers. Experimental tests are conducted to study the damping force characteristics. Three control strategies with various distributions of these dampers between sub-towers are developed. Then, a series of shaking table tests are carried out to evaluate the control performance of the proposed control strategies. Different earthquake records are adopted as seismic loadings. Experimental results clearly show a remarkable reduction in the towers seismic responses, including the accelerations, relative displacements, and strains. Rather than attaching dampers in concentrated ways, the strategy of distributing dampers uniformly behaves better.

Seismic Hazard Assessment in the Southeastern United States

1995 ◽  
Vol 11 (1) ◽  
pp. 129-160 ◽  
Author(s):  
Paul C. Rizzo ◽  
N. R. Vaidya ◽  
E. Bazan ◽  
C. F. Heberling
Keyword(s):  
North American ◽  
Peak Ground Acceleration ◽  
Ground Motions ◽  
Near Field ◽  
Southeastern United States ◽  
Seismic Hazard Assessment ◽  
Response Spectra ◽  
Seismic Hazards ◽  
Far Field ◽  
Ground Acceleration

Comparisons of response spectra from near and far-field records to those estimated by attenuation functions commonly used in evaluating seismic hazards show that these functions provide reasonable results for near-field western North American sites. However, they estimate relatively small motions for far-field eastern North American sites, which is contrary to the empirical evidence of the 1886 Charleston and 1988 Saguenay Earthquakes. Using the 1988 Saguenay records scaled for magnitude, and several western North American records scaled to account for the slower attenuation in the east, we have developed deterministic median and 84th percentile, 5 percent damped response spectra to represent ground motions from a recurrence of the 1886 Charleston Earthquake at a distance between 85 to 120 km. The resulting 84th percentile spectrum has a shape similar to, but is less severe than, the USNRC Regulatory Guide 1.60 5 percent damped spectrum tied to a peak ground acceleration of 0.2g.

Seismic Displacements Reduction for a Long-Span Cable-Stayed Bridge

2011 ◽  
Vol 255-260 ◽  
pp. 840-845
Author(s):  
Xi Wen Yang ◽  
Zi Bao Lian
Keyword(s):  
Inertial Force ◽  
Center Of Gravity ◽  
Shear Forces ◽  
Viscous Dampers ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Seismic Shear ◽  
Seismic Displacements ◽  
Floating Systems ◽  
Cable Stayed Bridges

Floating or semi-floating systems are usually employed for long-span cable-stayed bridges to lengthen their fundamental periods, and accordingly, to reduce their seismic inertial force, but the structures’ seismic displacements could be increased by utilizing these systems. Taking Yong-jiang railway cable-stayed bridge which has a low center of gravity as engineering background, the function of viscous dampers in controlling seismic displacements is studied. Firstly, the rational parameters of dampers are determined by parametric analysis, and then the seismic displacements and forces of the bridge, utilizing and un-utilizing viscous dampers, are compared. The results show that: viscous dampers are efficient in controlling seismic displacements of the bridge; the seismic shear forces at the bottom of towers are reduced slightly and the corresponding moments are reduced in a larger extent for cable-stayed bridge with low center of gravity.

scholarly journals Seismic Response Mitigation of a Long-Span Tower Bridge with Two Types of Constraint System

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Li Xu ◽  
Qingfei Gao ◽  
Junhao Zheng ◽  
Chuanhui Ding ◽  
Kang Liu
Keyword(s):  
Element Model ◽  
Main Beam ◽  
Seismic Load ◽  
Viscous Damper ◽  
Viscous Dampers ◽  
Damping Effect ◽  
Cable Stayed Bridge ◽  
Long Span ◽  
Drift Frequency ◽  
Nonlinear Finite Element Model

The stress of the main tower of a cable-stayed bridge depends on the connection type between the tower and deck. In order to study the most suitable longitudinal damping mode for a long-span cable-stayed bridge. In this article, a nonlinear finite element model is established based on a large span concrete cable-stayed bridge with a main span of 680 m. Without considering the influence of the transverse constraint, the damping effect of the elastic connection device and the viscous damper is simulated when the longitudinal seismic load is input. The results show that the stiffness of the main beam is increased by installing the elastic connection device, so the longitudinal drift frequency of the main beam is increased, but the stiffness of the structure is not changed by installing the viscous damper. Both viscous dampers and elastic connection structures can reduce the longitudinal displacement of the beam end, but viscous dampers are more favorable for the stress of the main tower. In terms of damping effect, viscous dampers are more suitable for long-span cable-stayed bridges, but, in terms of economy and parameter control, elastic connection devices have more advantages.

Simplified Method of Isolated Structure Collapse Capacity Part, (I): Ground Motion Intensity Measure

2013 ◽  
Vol 275-277 ◽  
pp. 1466-1470
Author(s):  
Yang Liu ◽  
Wen Guang Liu ◽  
Wen Fu He ◽  
Qiao Rong Yang
Keyword(s):  
Correlation Coefficient ◽  
Ground Motion ◽  
Ground Motions ◽  
Near Field ◽  
Far Field ◽  
Intensity Measure ◽  
Maximum Deformation ◽  
Average Value ◽  
Short Period ◽  
Ground Motion Intensity Measure

The equivalent velocity spectrum as a new ground motion intensity measure (IM) characterization parameter is proposed in this paper. 44 far field ground motions and 20 near-field high-speed pulse seismic waves were used for single-degree-freedom (SDOF) nonlinear time history analysis, respectively. The correlations between five IMs and maximum deformation for SDOF at various periods and different yield coefficients were analyzed. The results show that for the structures with medium-to-long period, the correlation coefficient average value of the proposed equivalent speed and maximum deformation is more than 0.6, and maximum of those is more than 0.9. The correlation coefficient average value by using the proposed equivalent speed under far field ground motions is more than those under near field ground motions. The P-delta effect on the correlation coefficients between proposed IM for the structures with medium-to-short period is significant

scholarly journals Assessing Seismic Performance of Gantry Crane Subjected to Near-Field Ground Motions Using Incremental Dynamic and Endurance Time Analysis Methods

2022 ◽  
Vol 2022 ◽  
pp. 1-14
Author(s):  
Qihui Peng ◽  
Wen-ming Cheng ◽  
Peng Guo ◽  
Hongyu Jia
Keyword(s):  
Seismic Performance ◽  
Incident Angle ◽  
Ground Motions ◽  
Near Field ◽  
Maxwell Model ◽  
Element Model ◽  
Gantry Crane ◽  
Time Analysis ◽  
Viscous Dampers ◽  
Endurance Time

Assessing the seismic performance of the gantry crane is significant since the structure is more vulnerable to earthquakes with the increase in size and lifting weight capacity. This paper aims to investigate the seismic response of the gantry crane incorporating near-field ground motions using incremental dynamic and endurance time analysis (IDA and ETA) methods. To model the structure accurately, a nonlinear finite element model of the gantry crane considering the viscoelastic effect is developed in the OpenSees platform. Then, the IDA method is also carried out for a comparison with the ETA method. The results of the two methods are consistent with a correlation of 93.9% while the computational demand of the ETA method is much less than those of the IDA method. To study further, both the seismic incident angle and the application of viscous dampers using the Maxwell model are analyzed and discussed in detail. The results show that seismic incident angle has a distinct influence on the maximum seismic displacement and viscous dampers can significantly reduce the seismic demand of the gantry crane. These findings support the seismic design of gantry cranes and evaluate the structural seismic performance efficiently.

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