Consideration of Three Seismic Isolation Performances as Design Objectives for Equivalent Linear Analysis of Bilinear Hysteretic Isolation Systems

2021 ◽  
pp. 2250001
Author(s):  
Shiang-Jung Wang ◽  
Yin-Nan Huang ◽  
Hsueh-Wen Lee ◽  
Yu-Wen Chang
Keyword(s):  
Seismic Isolation ◽  
Ground Motions ◽  
Linear Analysis ◽  
Analysis Procedure ◽  
Numerical Comparison ◽  
Near Fault ◽  
Equivalent Linear ◽  
Isolation Systems ◽  
Seismic Isolation Systems ◽  
Equivalent Linear Analysis

The design displacement, its corresponding acceleration performance, and the re-centering performance of bilinear hysteretic isolation systems are adopted as previously determined design objectives for equivalent linear analysis. To demonstrate the applicability and generalization of the analysis procedure, two sets of values for damping modification factors are employed in the analysis: those provided by ASCE/SEI 7-16, and those estimated for different ranges of the ratios of effective periods of seismic isolation systems to pulse periods of ground motions. To investigate a broad range of seismic responses of base-isolated structures, 15 pulse-like near-fault ground motions are used for numerical demonstration. The analysis procedure is numerically verified to be practically feasible. A numerical comparison also shows that the three design objectives previously determined in the analysis procedure are sufficiently conservative compared with analysis results from nonlinear dynamic response history, even when subjected to pulse-like near-fault ground motions. Regarding the approximation to maximum inelastic acceleration and displacement responses, it is particularly more conservative for the former when the design displacement is greater and when adopting values of the damping modification factors provided in ASCE/SEI 7-16. For the approximation to dynamic residual displacement responses, the influences of pulse-like near-fault ground motions and different design objectives on the re-centering performance of bilinear hysteretic isolation systems still need further study.

scholarly journals Evaluating the Accuracy of an Equivalent Linear Model in Predicting Peak Displacement of Seismic Isolation Systems using Single Friction Pendulum Bearings

2021 ◽  
Author(s):  
Thanh-Truc Nguyen ◽  
Nhan Dinh Dao
Keyword(s):  
Linear Model ◽  
Seismic Isolation ◽  
Peak Displacement ◽  
Equivalent Linear ◽  
Linear And Nonlinear ◽  
Isolation Systems ◽  
Seismic Isolation Systems ◽  
Friction Pendulum ◽  
Equivalent Linear Model ◽  
Motion Types

This study evaluates the accuracy of an equivalent linear model in predicting peak nonlinear time-history displacement of seismic isolation systems with single friction pendulum bearings. To perform this evaluation, dynamic response of numerical models of 120 isolation systems subjected to 390 strong earthquake ground motions, including motions with pulse and motions without pulse, was analyzed and statistically processed. The results show that the equivalent linear model can partly predict the peak displacement of its counterpart nonlinear model. However, the equivalent model can also underestimate or overestimate the peak displacement. On average sense, the equivalent linear model underestimates small peak displacement and overestimates large peak displacement. It is also observed that the relationship between linear and nonlinear peak displacements depends on ground motion types. Based on the analysis data, equations representing relationship between linear and nonlinear peak displacements at different reliable levels for different ground motion types were proposed. These equations can be used in practice.

Improved Effective Damping Equation for Equivalent Linear Analysis of Seismic-Isolated Bridges

2006 ◽  
Vol 22 (1) ◽  
pp. 29-46 ◽  
Author(s):  
Murat Dicleli ◽  
Srikanth Buddaram
Keyword(s):  
Ground Motion ◽  
Nonlinear Response ◽  
Ground Motions ◽  
Linear Analysis ◽  
Frequency Characteristics ◽  
Accurate Estimation ◽  
Effective Period ◽  
Equivalent Linear ◽  
Isolated Bridges ◽  
Equivalent Linear Analysis

In this study, an improved effective damping (ED) equation is proposed to obtain more reasonable estimates of the actual nonlinear response of seismic-isolated bridges (SIB) using equivalent linear (EL) analysis procedure. For this purpose, first the EL analysis results using AASHTO's ED equation is evaluated using harmonic and seismic ground motions. The effect of several parameters such as substructure stiffness, isolator properties, and the intensity and frequency characteristics of the ground motion are considered in the evaluation. Next, the effect of the superstructure mass on the ED ratio is studied. It is found that the accuracy of the EL analysis results is affected by the frequency characteristics and intensity of the ground motion. It is also demonstrated that AASHTO's ED equation should incorporate the effective period of the SIB and isolator properties for a more accurate estimation of the seismic response quantities. A new ED equation that includes such parameters is formulated and found to improve the accuracy of the EL analysis.

Optimal seismic isolation characteristics for bridges in moderate and high seismicity areas

2020 ◽  
Author(s):  
Xuan-Dai NGUYEN ◽  
Lotfi Guizani
Keyword(s):  
Seismic Isolation ◽  
Ground Motions ◽  
Elastic Stiffness ◽  
Spectral Parameters ◽  
Moderate Seismicity ◽  
Isolation Systems ◽  
Seismic Isolation Systems ◽  
Seismic Forces ◽  
Seismic Area ◽  
High Seismicity

This paper aims to identify the optimal properties of Seismic Isolation Systems (SISs) for bridges in moderate seismicity areas (MSAs) and high seismicity areas (HSAs). Amplitude and spectral parameters of ground motions are proposed to identify these areas. A parametric study, with varying SIS properties, is carried out, and the seismic isolation performance is evaluated for several locations within MSAs and HSAs in North America and Europe. The optimal characteristic strength, Qd, and post-elastic stiffness, Kd, of SISs are determined for each seismic area class to minimize seismic forces and displacement demands. Results indicate that ground motions for MSAs have a rich high frequency content, causing seismic spectra to vanish more rapidly with the elongation of the structure period. SISs with low-to-moderate energy dissipation capacities show the best performance for MSAs, while HSAs require SISs with higher damping capacities. Ranges for optimal Qd and Kd of SISs for bridges in MSAs and HSAs are proposed.

scholarly journals Seismic Behavior of RNC-Isolated Bridges: A Comparative Study under Near-Fault, Long-Period, and Pulse-Like Ground Motions

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
Mohammed Ismail ◽  
José Rodellar ◽  
Joan R. Casas
Keyword(s):  
Prestressed Concrete ◽  
Seismic Isolation ◽  
Ground Motions ◽  
Great Majority ◽  
Performance Measure ◽  
Isolation System ◽  
Near Fault ◽  
Long Period ◽  
Prestressed Concrete Bridge ◽  
Isolation Systems

This paper introduces a recent seismic isolation system, named Roll-in-Cage (RNC) isolator, for efficient protection of bridges against destructive earthquakes. The RNC isolator is a rolling-based isolation system with several integrated features in a single unit providing all the necessary functions of vertical rigid support, horizontal flexibility, full stability, hysteretic energy dissipation, and resistance to minor vibration loads. Besides, it is distinguished by a self-stopping (buffer) mechanism to limit the peak bearing displacement under abrupt severe excitations, a linear gravity-based self-recentering mechanism to prevent permanent dislocations after excitations, and a notable resistance to axial tension. A three-span box-girder prestressed concrete bridge is investigated under a set of different destructive real and synthetic earthquakes including near-fault, long-period, and pulse-like ground motions. As a performance measure, the responses of isolated and nonisolated cases are compared. In addition, the RNC isolator’s behavior is then compared with those of other isolation systems including HDB, FPS, and LRB. The results confirmed that the RNC isolator has a superior behavior in achieving a balance between the peak displacements and accelerations of the isolated deck, relative other isolation systems, besides being the most (relatively) efficient isolator in the great majority of studies performed.

Development of Mechanism for Preventing Derailing of Material Handling Equipment

2016 ◽  
Author(s):  
Kosuke Iwamoto ◽  
Yuji Sato ◽  
Teruyoshi Otoyo ◽  
Munenori Horiuchi ◽  
Hidetoshi Sakai ◽  
...  
Keyword(s):  
Seismic Isolation ◽  
Material Handling ◽  
Ground Motions ◽  
Element Model ◽  
Material Handling Equipment ◽  
Strong Ground Motions ◽  
Isolation Systems ◽  
Vibration Tests ◽  
Seismic Isolation Systems ◽  
Strong Ground

All of the traveling cranes at the port of Kobe were damaged by the strong ground motion of the Southern Hyogo Prefecture Earthquake in 1995. Seismic isolation systems for traveling cranes were developed to increase earthquake resistance against strong ground motions. In general, the isolation systems for traveling cranes for strong ground motions are very large. Quays which are not reinforced have a risk of being damaged by strong ground motions, and require traveling cranes to prevent derailing during middle strong motions, because derailing leads to collapse of the traveling cranes. A mechanism for preventing derailing of material handling equipment was developed for middle strong ground motions. A middle rocker beam of the new mechanism is divided into two beams, and uplift motion of a leg of a crane can be absorbed by rotating motions of the two beams. This allows the mechanism for preventing derailing to be easily installed into the established equipment. Seismic analyses using an finite element model of the traveling crane and vibration tests were conducted to verify the validity of the design and derailing prevention performance. The results of analyses and vibration tests showed that the mechanism for preventing derailing can prevent wheels from derailing during middle strong earthquakes. The configuration of the mechanism and the results of the analyses and vibration tests are presented in this paper.

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