DESIGN OF ISOLATED BRIDGES USING POLYNOMIAL FRICTION PENDULUM ISOLATOR

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
T. Y. Lee ◽  
L. Y. Lu ◽  
K. J. Chung
Keyword(s):  
Ground Motions ◽  
Near Field ◽  
Design Procedure ◽  
Design Parameters ◽  
Seismic Responses ◽  
Nonlinear Responses ◽  
Seismic Design Code ◽  
Friction Pendulum ◽  
Isolated Bridges ◽  
Restoring Stiffness

This paper is aimed to develop a design procedure of Polynomial Friction Pendulum Isolator (PFPI), a various-frequency sliding isolator, for decreasing the seismic responses of isolated bridges. Although sliding isolators have been widely used to mitigate seismic hazard, it may be not effective in decreasing the seismic responses of isolated structures subjected to near-field ground motions. The sliding surface of the PFPI is defined by a sixth-order polynomial function to avoid resonance under near-field ground motions. The restoring stiffness of the PFPI possesses softening section as well as hardening section. The structural acceleration response can be decreased by decreasing the restoring stiffness in softening section while the structural displacement response can be decreased by increasing the restoring stiffness in hardening section. However, it is difficult to determine the design parameters of PFPI in practical implementations. This study proposes a design procedure for the PFPI based on the bridge seismic design code in Taiwan. Designers can follow this procedure to easily design the bridge with PFPIs which satisfies the requirements of the code. The bridge with PFPIs designed by using this procedure is analyzed to realize the dynamic nonlinear responses of the bridge under artificial strong earthquake. The results show that the PFPIs effectively decrease the seismic responses of isolated bridges as compared with non-isolated bridges.

Seismic Response of Triple Friction Pendulum Bearing under Near-Fault Ground Motions

2016 ◽  
Vol 16 (06) ◽  
pp. 1550021 ◽  
Author(s):  
Gholamreza Ghodrati Amiri ◽  
Pejman Namiranian ◽  
Mohamad Shamekhi Amiri
Keyword(s):  
Seismic Response ◽  
Spherical Surface ◽  
Ground Motions ◽  
Damping Ratio ◽  
Radius Of Curvature ◽  
Seismic Responses ◽  
Base Shear ◽  
Near Fault ◽  
Inner Surface ◽  
Friction Pendulum

The seismic response of a stiff single-story and a flexible multi-story building isolated with triple friction pendulum bearing (TFPB) are investigated under the pulse-like (near-fault, NF-Pulse) and (NF-No Pulse) NF nonpulse ground motions. By varying the geometric parameters, such as the effective spherical surface radius, or by specifying different friction coefficients for each surface, one can adjust the behavior of the bearing. Consequently, the stiffness and damping ratio of the system can be optimized for multiple performance objectives under multiple levels of hazard. The seismic responses are evaluated under different isolation parameters for the displacement of isolation and the superstructure demand functions of the system, including the base shear, maximum inter-story drift and top floor absolute acceleration of the isolated structure. First, the seismic response of twenty TFPBs with different stiffnesses and damping ratios are investigated under NF motions. A comparison of results suggested that the displacement of the TFPB under the NF-Pulse motion is about twice that of the NF-No Pulse motions. The best performance of the system is found when the TFPB works in its third stage of motion. Next, from the sensitivity analysis, the effect of each parameter of the TFPB on the seismic response of system is investigated and the trends for optimal parameters of TFPB are presented. The criterion selected for optimality is to minimize the performance function that considers all seismic responses simultaneously. The optimum ranges for the related parameters are: (a) 0.02–0.04 for the coefficient of friction of the inner surface; (b) 0.06–0.14 and 0.04–0.12 for the bottom concave plate under the NF-Pulse and NF-No Pulse, respectively; (c) 0.06–0.18 and 0.06–0.16 for the top concave plate under the NF-Pulse and NF-No Pulse, respectively; (d) 200–500 mm for the radius of curvature of the inner surface; and (e) 2500–4500 mm for the outer surface.

A simplified iterative approach for testing the pulse derailment of light rail vehicles across a viaduct to near-fault earthquake scenarios

2021 ◽  
pp. 095440972098741
Author(s):  
Ling-Kun Chen ◽  
Peng Liu ◽  
Li-Ming Zhu ◽  
Jing-Bo Ding ◽  
Yu-Lin Feng ◽  
...  
Keyword(s):  
Ground Motions ◽  
Simulation Software ◽  
Light Rail ◽  
Rail Transit ◽  
Light Rail Transit ◽  
Seismic Responses ◽  
Near Fault ◽  
Rail Vehicle ◽  
Pulse Type ◽  
The Impact

Near-fault (NF) earthquakes cause severe bridge damage, particularly urban bridges subjected to light rail transit (LRT), which could affect the safety of the light rail transit vehicle (“light rail vehicle” or “LRV” for short). Now when a variety of studies on the fault fracture effect on the working protection of LRVs are available for the study of cars subjected to far-reaching soil motion (FFGMs), further examination is appropriate. For the first time, this paper introduced the LRV derailment mechanism caused by pulse-type near-fault ground motions (NFGMs), suggesting the concept of pulse derailment. The effects of near-fault ground motions (NFGMs) are included in an available numerical process developed for the LRV analysis of the VBI system. A simplified iterative algorithm is proposed to assess the stability and nonlinear seismic response of an LRV-reinforced concrete (RC) viaduct (LRVBRCV) system to a long-period NFGMs using the dynamic substructure method (DSM). Furthermore, a computer simulation software was developed to compute the nonlinear seismic responses of the VBI system to pulse-type NFGMs, non-pulse-type NFGMs, and FFGMs named Dynamic Interaction Analysis for Light-Rail-Vehicle Bridge System (DIALRVBS). The nonlinear bridge seismic reaction determines the impact of pulses on lateral peak earth acceleration (Ap) and lateral peak land (Vp) ratios. The analysis results quantify the effects of pulse-type NFGMs seismic responses on the LRV operations' safety. In contrast with the pulse-type non-pulse NFGMs and FFGMs, this article's research shows that pulse-type NFGM derail trains primarily via the transverse velocity pulse effect. Hence, this study's results and the proposed method can improve the LRT bridges' seismic designs.

scholarly journals A Two-Round Optimization Design Method for Aerostatic Spindles Considering the Fluid–Structure Interaction Effect

2021 ◽  
Vol 11 (7) ◽  
pp. 3017
Author(s):  
Qiang Gao ◽  
Siyu Gao ◽  
Lihua Lu ◽  
Min Zhu ◽  
Feihu Zhang
Keyword(s):  
Optimal Design ◽  
Optimization Design ◽  
Design Method ◽  
Fluid Structure Interaction ◽  
Design Procedure ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerostatic Spindle

The fluid–structure interaction (FSI) effect has a significant impact on the static and dynamic performance of aerostatic spindles, which should be fully considered when developing a new product. To enhance the overall performance of aerostatic spindles, a two-round optimization design method for aerostatic spindles considering the FSI effect is proposed in this article. An aerostatic spindle is optimized to elaborate the design procedure of the proposed method. In the first-round design, the geometrical parameters of the aerostatic bearing were optimized to improve its stiffness. Then, the key structural dimension of the aerostatic spindle is optimized in the second-round design to improve the natural frequency of the spindle. Finally, optimal design parameters are acquired and experimentally verified. This research guides the optimal design of aerostatic spindles considering the FSI effect.

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