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.

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 Evaluation on the Soil Flexibility of the Largest HEP Dam Area in East Malaysia using 1-D Equivalent Linear Analysis

2021 ◽  
Vol 11 (4) ◽  
pp. 1535
Author(s):  
Raudhah Ahmadi ◽  
Muhammad Haniz Azahari Muhamad Suhaili ◽  
Imtiyaz Akbar Najar ◽  
Muhammad Azmi Ladi ◽  
Nisa Aqila Bakie ◽  
...  
Keyword(s):  
Linear Analysis ◽  
Equivalent Linear ◽  
East Malaysia ◽  
Soil Flexibility ◽  
Equivalent Linear Analysis

Conditional Ground-Motion Model for Damaging Characteristics of Near-Fault Ground Motions Based on Instantaneous Power

2020 ◽  
Vol 110 (6) ◽  
pp. 2828-2842
Author(s):  
Esra Zengin ◽  
Norman Abrahamson
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Accurate Estimation ◽  
Spectral Acceleration ◽  
Motion Model ◽  
Velocity Pulse ◽  
Near Fault ◽  
Instantaneous Power ◽  
Ground Motion Model ◽  
Short Time

ABSTRACT The velocity pulse in near-fault ground motions has been used as a key characteristic of damaging ground motions. Characterization of the velocity pulse involves three parameters: presence of the pulse, period of the pulse, and amplitude of the pulse. The basic concept behind the velocity pulse is that a large amount of seismic energy is packed into a short time, leading to larger demands on the structure. An intensity measure for near-fault ground motions, which is a direct measure of the amount of energy arriving in short time, called instantaneous power (IP (T1)), is defined as the maximum power of the bandpass-filtered velocity time series measured over a time interval of 0.5T1, in which T1 is the fundamental period of the structure. The records are bandpass filtered in the period band (0.2T1−3T1) to remove the frequencies that are not expected to excite the structure. Zengin and Abrahamson (2020) showed that the drift is better correlated with the IP (T1) than with the velocity pulse parameters for records scaled to the same spectral acceleration at T1. A conditional ground-motion model (GMM) for the IP is developed based on the 5%-damped spectral acceleration at T1, the earthquake magnitude, and the rupture distance. This conditional GMM can be used for record selection for near-fault ground motions that captures the key features of velocity pulses and can lead to a better representation of the median and variability of the maximum interstory drift. The conditional GMM can also be used in a vector hazard analysis for spectral acceleration (T1) and IP (T1) that can be used for more accurate estimation of drift hazard and seismic risk.

Sign in / Sign up

Export Citation Format

Share Document