Drift Spectrum vs. Modal Analysis of Structural Response to Near-Fault Ground Motions

2001 ◽  
Vol 17 (2) ◽  
pp. 221-234 ◽  
Author(s):  
Anil K. Chopra ◽  
Chatpan Chintanapakdee
Keyword(s):  
Earthquake Engineering ◽  
Response Spectrum ◽  
Ground Motions ◽  
Structural Response ◽  
Response Spectra ◽  
Engineering Practice ◽  
Drift Spectrum ◽  
Combination Rules ◽  
Near Fault ◽  
Far Fault

A new measure of earthquake demand, the drift spectrum has been developed as an adjunct to the response spectrum, a central concept in earthquake engineering, in calculating the internal deformations of a structure due to near-fault ground motions with pronounced coherent pulses in the velocity and displacement histories. Compared in this paper are certain aspects of the elastic structural response to near-fault and far-fault ground motions. It is demonstrated that (1) the difference between drift and response spectra are not unique to near-fault ground motions; these differences simply reflect higher-mode response, which is larger due to near-fault ground motions; (2) response spectrum analysis (RSA) using existing modal combination rules can provide an estimate of structural response that is accurate to a useful degree; (3) these modal combination rules are similarly accurate for near-fault and far-fault ground motions although the underlying assumptions are not satisfied by near-fault excitations; and (4) RSA is preferable over the drift spectrum in computing structural response because it represents standard engineering practice and is applicable to a wide variety of structures.

Use of RVT for Computation of In-Structure Response Spectra and Peak Responses and Comparison to Time History and Response Spectrum Analysis

2018 ◽  
Vol 34 (4) ◽  
pp. 1913-1930 ◽  
Author(s):  
Irmela Zentner
Keyword(s):  
Response Spectrum ◽  
Structural Response ◽  
Time History ◽  
Strong Motion ◽  
Response Spectra ◽  
Combination Rules ◽  
Floor Response Spectra ◽  
Power Spectral ◽  
Time Histories ◽  
Definition Of

The random vibration theory offers a framework for the conversion of response spectra into power spectral densities (PSDs) and vice versa. The PSD is a mathematically more suitable quantity for structural dynamics analysis and can be straightforwardly used to compute structural response in the frequency domain. This allows for the computation of in-structure floor response spectra and peak responses by conducting only one structural analysis. In particular, there is no need to select or generate spectrum-compatible time histories to conduct the analysis. Peak response quantities and confidence intervals can be computed without any further simplifications such as currently used in the response spectrum method, where modal combination rules have to be derived. In contrast to many former studies, the Arias intensity-based definition of strong-motion duration is adopted here. This paper shows that, if the same definitions of strong-motion duration and modeling assumptions are used for time history and RVT computations, then the same result can be expected. This is illustrated by application to a simplified model of a reactor building.

scholarly journals A Computationally Efficient Ground-Motion Selection Algorithm for Matching a Target Response Spectrum Mean and Variance

2011 ◽  
Vol 27 (3) ◽  
pp. 797-815 ◽  
Author(s):  
Nirmal Jayaram ◽  
Ting Lin ◽  
Jack W. Baker
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Ground Motions ◽  
Structural Response ◽  
Response Spectra ◽  
Selection Algorithm ◽  
Target Response ◽  
Computationally Efficient ◽  
Mean And Variance ◽  
The Impact

Dynamic structural analysis often requires the selection of input ground motions with a target mean response spectrum. The variance of the target response spectrum is usually ignored or accounted for in an ad hoc manner, which can bias the structural response estimates. This manuscript proposes a computationally efficient and theoretically consistent algorithm to select ground motions that match the target response spectrum mean and variance. The selection algorithm probabilistically generates multiple response spectra from a target distribution, and then selects recorded ground motions whose response spectra individually match the simulated response spectra. A greedy optimization technique further improves the match between the target and the sample means and variances. The proposed algorithm is used to select ground motions for the analysis of sample structures in order to assess the impact of considering ground-motion variance on the structural response estimates. The implications for code-based design and performance-based earthquake engineering are discussed.

A procedure for matching the near-fault ground motions based on spectral accelerations and instantaneous power

2021 ◽  
pp. 875529302110145
Author(s):  
Esra Zengin ◽  
Norman A Abrahamson
Keyword(s):  
Time Series ◽  
Response Spectrum ◽  
Ground Motions ◽  
Structural Response ◽  
Rate Of Change ◽  
Time Interval ◽  
Short Time Interval ◽  
Pulse Period ◽  
Near Fault ◽  
Instantaneous Power

Selection of ground motions for use in nonlinear dynamic analysis is one of the most critical steps for both code-based design and probabilistic seismic risk assessment of structures. In practice, time-domain spectrum-matching methods, which add wavelet functions to an initial acceleration time series, have been widely used to obtain a record whose response spectrum closely matches the desired target spectrum. Although the spectral shape is known to be a good predictor of structural response, it does not represent the critical aspects of the velocity pulses, such as pulse amplitude and pulse period for near-fault ground motions. The Instantaneous Power ( IP( T1)), defined as the maximum rate of change of energy of the bandpass-filtered velocity time series over a short time interval given by half of the structural period, has been shown to be an effective alternative parameter to capture effects of the presence of a velocity pulse and the pulse period in near-fault record selection. We introduce an approach to modify time series so as to simultaneously match a target response spectrum and IP spectrum over a specified period interval. We demonstrate that the records modified using the proposed approach produce results comparable to those obtained using unscaled records, and prevent potential bias in structural response, relative to results when matching is performed without consideration of IP.

An Empirical Relationship between Fourier and Response Spectra Using Spectrum-Compatible Times Series

2017 ◽  
Vol 33 (1) ◽  
pp. 179-199 ◽  
Author(s):  
Luis A. Montejo ◽  
Aidcer L. Vidot-Vega
Keyword(s):  
Time Series ◽  
Earthquake Engineering ◽  
Response Spectrum ◽  
Ground Motions ◽  
Strong Dependence ◽  
Empirical Relationship ◽  
Amplitude Spectrum ◽  
Strong Motion ◽  
Response Spectra ◽  
Elastic Response

The Fourier amplitude spectrum (FAS) is widely used in seismology and earthquake engineering as it provides valuable information regarding frequency dependent amplitude of the ground motion. However, for structural design and assessment, the preferred representation of seismic hazard continues to be based on the elastic response spectrum. Therefore, conversions between these spectra are often required. In this article, the connection between FAS and the 5% damping pseudo-acceleration response spectrum (5% PSA) is explored using large data sets of spectrum-compatible time series generated from white noise. The strong dependence of the relation between FAS and 5% PSA with strong motion duration is evidenced and a duration dependent empirical relationship between the both spectra is developed. The equation is validated using recorded ground motions and spectrum-compatible time series generated from the modification of these ground motions. The equation allows simpler one-step conversions when compared to iterative approaches based on RVT theory or time-consuming methodologies that require the generation of spectrum-compatible time series.

Effects of Fling Step and Forward Directivity on Seismic Response of Buildings

2006 ◽  
Vol 22 (2) ◽  
pp. 367-390 ◽  
Author(s):  
Erol Kalkan ◽  
Sashi K. Kunnath
Keyword(s):  
Seismic Response ◽  
Ground Motions ◽  
High Amplitude ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Damage Potential ◽  
Near Fault ◽  
Forward Directivity ◽  
Fling Step ◽  
Far Fault

This paper investigates the consequences of well-known characteristics of near-fault ground motions on the seismic response of steel moment frames. Additionally, idealized pulses are utilized in a separate study to gain further insight into the effects of high-amplitude pulses on structural demands. Simple input pulses were also synthesized to simulate artificial fling-step effects in ground motions originally having forward directivity. Findings from the study reveal that median maximum demands and the dispersion in the peak values were higher for near-fault records than far-fault motions. The arrival of the velocity pulse in a near-fault record causes the structure to dissipate considerable input energy in relatively few plastic cycles, whereas cumulative effects from increased cyclic demands are more pronounced in far-fault records. For pulse-type input, the maximum demand is a function of the ratio of the pulse period to the fundamental period of the structure. Records with fling effects were found to excite systems primarily in their fundamental mode while waveforms with forward directivity in the absence of fling caused higher modes to be activated. It is concluded that the acceleration and velocity spectra, when examined collectively, can be utilized to reasonably assess the damage potential of near-fault records.

scholarly journals A Multi-Objective Ground Motion Selection Approach Matching the Acceleration and Displacement Response Spectra

2018 ◽  
Vol 10 (12) ◽  
pp. 4659 ◽  
Author(s):  
Yabin Chen ◽  
Longjun Xu ◽  
Xingji Zhu ◽  
Hao Liu
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Structural Response ◽  
Response Spectra ◽  
Computationally Efficient ◽  
Ground Motion Selection ◽  
Displacement Response ◽  
Rc Frames ◽  
Selection Approach ◽  
Displacement Response Spectra

For seismic resilience-based design (RBD), a selection of recorded time histories for dynamic structural analysis is usually required. In order to make individual structures and communities regain their target functions as promptly as possible, uncertainty of the structural response estimates is in great need of reduction. The ground motion (GM) selection based on a single target response spectrum, such as acceleration or displacement response spectrum, would bias structural response estimates leading significant uncertainty, even though response spectrum variance is taken into account. In addition, resilience of an individual structure is not governed by its own performance, but depends severely on the performance of other systems in the same community. Thus, evaluation of resilience of a community using records matching target spectrum at whole periods would be reasonable because the fundamental periods of systems in the community may be varied. This paper presents a GM selection approach based on a probabilistic framework to find an optimal set of records to match multiple target spectra, including acceleration and displacement response spectra. Two major steps are included in that framework. Generation of multiple sub-spectra from target displacement response spectrum for selecting sets of GMs was proposed as the first step. Likewise, the process as genetic algorithm (GA), evolvement of individuals previously generated, is the second step, rather than using crossover and mutation techniques. A novel technique improving the match between acceleration response spectra of samples and targets is proposed as the second evolvement step. It is proved computationally efficient for the proposed algorithm by comparing with two developed GM selection algorithms. Finally, the proposed algorithm is applied to select GM records according to seismic codes for analysis of four archetype reinforced concrete (RC) frames aiming to evaluate the influence of GM selection considering two design response spectra on structural responses. The implications of design response spectra especially the displacement response spectrum and GM selection algorithm are summarized.

EVALUATION OF SEISMIC DEMANDS IN A CONTINUOUS BRIDGE

2001 ◽  
Vol 01 (02) ◽  
pp. 235-246 ◽  
Author(s):  
CHIN-HSIUNG LOH ◽  
SHIUAN WAN ◽  
YI-WEN CHANG
Keyword(s):  
Earthquake Engineering ◽  
Ground Motions ◽  
Hysteretic Behavior ◽  
Earthquake Ground Motion ◽  
Far Field ◽  
Base Shear ◽  
Near Fault ◽  
Seismic Design Code ◽  
Cyclic Loading Tests ◽  
Earthquake Characteristics

This paper examines the dynamic behavior of a highway RC-bridge subjected to both near-fault and far-field ground motions. The bridge consists of a hinge supported continuous girder with six concrete piers and the bridge is designed according to the Taiwan seismic design code. To investigate the hysteretic behavior of the bridge piers, cyclic loading tests were carried out at the National Center for Research on Earthquake Engineering (NCREE). The Chi-Chi earthquake ground motion record was adopted as the near-fault earthquake characteristics whereas another earthquake record was selected for the far-field earthquake characteristics. The ductility demands and base shear demands due to the near-fault and the far-field earthquake ground motions are compared and conclusions drawn from the study. The stipulation of code limitations and the present calculated demands are discussed.

Evaluation of SCEC CyberShake Ground Motions for Engineering Practice

2019 ◽  
Vol 35 (3) ◽  
pp. 1311-1328 ◽  
Author(s):  
Ganyu Teng ◽  
Jack Baker
Keyword(s):  
Los Angeles ◽  
Ground Motion ◽  
Ground Motions ◽  
Response Spectra ◽  
Building Design ◽  
Empirical Models ◽  
Soil Conditions ◽  
Engineering Practice ◽  
Ground Motion Selection ◽  
Promising Source

This paper evaluates CyberShake (version 15.12) ground motions for potential application to high-rise building design in the Los Angeles region by comparing them against recordings from past earthquakes as well as empirical models. We consider two selected sites in the Los Angeles region with different underlying soil conditions and select comparable suites of ground motion records from CyberShake and the NGA-West2 database according to the ASCE 7-16 requirements. Major observations include (1) selected ground motions from CyberShake and NGA-West2 share similar features, in terms of response spectra and polarization; (2) when selecting records from Cyber-Shake, it is easy to select motions with sources that match the hazard deaggregation; (3) CyberShake durations on soil are consistent with the empirical models considered, whereas durations on rock are slightly shorter; (4) occasional excessive polarization in ground motion is produced by San Andreas fault ruptures, though those records are usually excluded after the ground motion selection. Results from this study suggest that CyberShake ground motions are a suitable and promising source of ground motions for engineering evaluations.

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