Seismic Time History Data Precision and Time Interval Requirement

2020 ◽  
Author(s):  
Dali Li
Keyword(s):  
Response Spectrum ◽  
Total Duration ◽  
Time History ◽  
Response Spectra ◽  
Design Parameters ◽  
Time Interval ◽  
Nyquist Frequency ◽  
Frequency Range ◽  
History Data ◽  
Data Points

Abstract This paper provides the seismic time history data precision and time interval requirement for seismic dynamic analysis. U.S.NRC SRP 3.7.1 “Seismic Design Parameters” Acceptance Criteria for Design Time Histories specifies the power spectral density Nyquist Frequency, time interval, and total duration; however, it does not have the requirement for Response Spectra. The response spectrum bandwidth is inverse-proportional to time interval of the time history. For the time interval of 0.005 seconds, the bandwidth for the response spectrum is between 0.194 Hz and 80.5 Hz; the PSD Nyquist frequency is 100 Hz. For 20.48 seconds time history, 4096 data points are required. The response spectrum between 1.28 Hz and 13.6 Hz has the peak flat magnitude value; the magnitude drops to 0.707 of the peak value from 1.28 Hz to 0.194 Hz and from 13.6 Hz to 80.5 Hz. This paper also provides the time interval requirement for various response spectrum peak flat magnitude value; i.e., the response spectrum highest flat magnitude of 27.2 Hz requires a time interval of 0.0025 seconds time history. For 20.48 seconds time history, 8192 data points are required. For CSDRS, the time interval of 0.005 seconds is adequate for the frequency range of interest between 0.36 Hz and 57.2 Hz. For HRHF, the time interval of 0.0025 seconds is required to analyze the frequency range of interest between 0.36 Hz and 114.4 Hz.

Response spectral matching of horizontal ground motion components to an orientation-independent spectrum (RotDnn)

2020 ◽  
pp. 875529302097098
Author(s):  
Luis A Montejo
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Time History ◽  
Response Spectra ◽  
Major Axis ◽  
Component Level ◽  
Nonlinear Characteristics ◽  
Target Spectrum ◽  
Horizontal Ground Motion ◽  
Median Spectrum

This article presents a methodology to spectrally match two horizontal ground motion components to an orientation-independent target spectrum (RotDnn). The algorithm is based on the continuous wavelet transform decomposition and iterative manipulation of the two horizontal components of a seed record. The numerical examples presented follow current ASCE/SEI 7 specifications and therefore maximum-direction spectra (RotD100) are used as target for the match. However, the proposed methodology can be used to match other RotDnn spectra, like the median spectrum (RotD50). It is shown that with the proposed methodology the resulting RotDnn from the modified horizontal components closely match the smooth target RotDnn spectrum, while the response spectrum for each horizontal component continue to exhibit a realistic jagged behavior. The response spectra variability at the component level within suites of spectrally matched motions was found to be of the same order than the variability measured in suites composed of amplitude scaled records. Moreover, the spectrally matched records generated preserved most of the characteristics of the seed records, including the nonlinear characteristics of the time history traces and the period-dependent major axis orientations.

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 Unique Method for Generating Design Earthquake Time Histories

2008 ◽  
Author(s):  
R. E. Spears
Keyword(s):  
Response Spectrum ◽  
Low Frequency ◽  
Time History ◽  
Response Spectra ◽  
Cumulative Energy ◽  
Time Histories ◽  
Displacement Response Spectra ◽  
Unique Method ◽  
Design Earthquake ◽  
Velocity Response Spectrum

A method has been developed which takes a seed earthquake time history and modifies it to produce given design response spectra. It is a multi-step process with an initial scaling step and then multiple refinement steps. It is unique in the fact that both the acceleration and displacement response spectra are considered when performing the fit (which primarily improves the low frequency acceleration response spectrum accuracy). Additionally, no matrix inversion is needed. The features include encouraging the code acceleration, velocity, and displacement ratios and attempting to fit the pseudo velocity response spectrum. Also, “smoothing” is done to transition the modified time history to the seed time history at its start and end. This is done in the time history regions below a cumulative energy of 5% and above a cumulative energy of 95%. Finally, the modified acceleration, velocity, and displacement time histories are adjusted to start and end with an amplitude of zero (using Fourier transform techniques for integration).

scholarly journals High voltage circuit breaker supported on a base isolating tripod for earthquake protection

1989 ◽  
Vol 22 (3) ◽  
pp. 145-154
Author(s):  
B. F. Safi ◽  
L. T. Pham ◽  
M. J. Busby
Keyword(s):  
Response Spectrum ◽  
Circuit Breaker ◽  
Time History ◽  
Degree Of Freedom ◽  
Design Parameters ◽  
Circuit Breakers ◽  
Helical Springs ◽  
Safe Level ◽  
Induced Motion ◽  
Earthquake Protection

The 1987 Bay of Plenty earthquake caused the total destruction of a 220 kV circuit breaker. Failures occurred in the porcelain columns supporting the Interrupter Heads. There are many other circuit breakers of the same type in the national grid. To protect these circuit breakers from earthquake damage, a proposal is made to replace the existing support stand with a base isolating tripod. On the tripod, Helical Springs and oil filled dampers are used to control the earthquake induced motion of the circuit breaker. By controlling this motion the forces on the porcelain support column are reduced to a safe level. The design is modelled using a multi degree of freedom system subjected to Response Spectrum and Time History analyses. The model produces results which are consistent with tests, and confirms the design parameters selected by a single degree of freedom approximation. The result is an economical tripod stand design which is expected to protect the circuit breaker from earthquake ground accelerations up to twice the level of the 1940 El Centro earthquake. This level of earthquake is considerably stronger than the 1987 Bay of Plenty earthquake.

scholarly journals Site-Specific Response Spectra: Guidelines for Engineering Practice

CivilEng ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 712-735
Author(s):  
Yiwei Hu ◽  
Nelson Lam ◽  
Prashidha Khatiwada ◽  
Scott Joseph Menegon ◽  
Daniel T. W. Looi
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Time History ◽  
Response Spectra ◽  
Engineering Practice ◽  
Site Classification ◽  
Specific Response ◽  
Potential Cost ◽  
Site Specific ◽  
Real Behavior

Code response spectrum models, which are used widely in the earthquake-resistant design of buildings, are simple to apply but they do not necessarily represent the real behavior of an earthquake. A code response spectrum model typically incorporates ground motion behavior in a diversity of earthquake scenarios affecting the site and does not represent any specific earthquake scenario. The soil amplification phenomenon is also poorly represented, as the current site classification scheme contains little information over the potential dynamic response behavior of the soil sediments. Site-specific response spectra have the merit of much more accurately representing real behavior. The improvement in accuracy can be translated into significant potential cost savings. Despite all the potential merits of adopting site-specific response spectra, few design engineers make use of these code provisions that have been around for a long time. This lack of uptake of the procedure by structural designers is related to the absence of a coherent set of detailed guidelines to facilitate practical applications. To fill in this knowledge gap, this paper aims at explaining the procedure in detail for generating site-specific response spectra for the seismic design or assessment of buildings. Surface ground motion accelerograms generated from the procedure can also be employed for nonlinear time-history analyses where necessary. A case study is presented to illustrate the procedure in a step-by-step manner.

Study on Piping Response Under Multiple Excitation: Part 2 — Validation for Multiple Excitation Analysis of Piping

2013 ◽  
Author(s):  
Satoru Kai ◽  
Tomoyoshi Watakabe ◽  
Naoaki Kaneko ◽  
Kunihiro Tochiki ◽  
Makoto Moriizumi ◽  
...  
Keyword(s):  
Seismic Response ◽  
Seismic Design ◽  
Nuclear Power ◽  
Response Spectrum ◽  
Time History ◽  
Response Spectra ◽  
Shaking Table ◽  
Response Analysis ◽  
Multiple Time ◽  
Floor Response Spectra

The piping in a nuclear power plant is laid across multiple floors of a single building or two buildings, which are supported at many points. As the piping is excited by multiple-inputs from the supporting points during an earthquake, seismic response analysis by multiple excitations is needed to obtain the exact seismic response of the piping. However, few experiments involving such multiple excitation have been performed to verify the validity of multiple excitation analysis. Therefore, analysis of the seismic design of piping in Japan is performed by the enveloped Floor Response Spectrum (FRS), which covers all floor response spectra at all supporting points. The piping response estimated by enveloped FRS is conservative in most cases compared with the actual seismic response by multiple excitations. To perform rational seismic design and evaluation, it is important to investigate the seismic response by multiple excitations and to verify the validity of the analytical method by multiple excitation test. This paper reports the validation results of the multiple-excitation analysis of piping compared with the results of the multiple excitations shaking test using triple uni-axial shaking table and a 3-dimensional piping model (89.1mm diameter and 5.5mm thickness). Three directional moments from the analysis and the shaking test were compared on the validation. As the result, it is confirmed that the analysis by multiple time history excitation corresponds with the test result.

Seismic design of base-isolated highway bridges utilizing lead–rubber bearings

1990 ◽  
Vol 17 (3) ◽  
pp. 413-422 ◽  
Author(s):  
A. Ghobarah ◽  
H. M. Ali
Keyword(s):  
Seismic Design ◽  
Base Isolation ◽  
Time History ◽  
Highway Bridges ◽  
Response Spectra ◽  
Design Guidelines ◽  
Design Parameters ◽  
Seismic Behaviour ◽  
Isolation System ◽  
Design Procedures

A study is made of the seismic behaviour of base-isolated highway bridges with the objective of developing design procedures in the form of code-type approach. The recommendations of current codes concerning the use of energy dissipation mechanisms for the seismic design of bridges are reviewed. A model representing the bridge deck, piers, and the base-isolation system is used to evaluate the response of the bridge to a selected earthquake time history record and to evaluate the effects of various design parameters on the dynamic response. The results of this analysis are used in the development of design guidelines for the isolated bridge system. It was found that base isolation affects the design forces on piers and abutments as well as the deck displacements. An optimum design should provide a reasonable balance between the shear forces on supports and tolerable displacements. Two design procedures are proposed based on the time history and inelastic response spectra approaches. Simplified charts are presented which aid in the seismic design of new bridges as well as in the upgrading of existing ones. Key words: dynamic, seismic, design, highway, bridges, earthquake, base isolation.

scholarly journals Linear Stochastic Models in Discrete and Continuous Time

Econometrics ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 35
Author(s):  
D. Stephen G. Pollock
Keyword(s):  
Moving Average ◽  
Limited Range ◽  
Autoregressive Moving Average ◽  
Nyquist Frequency ◽  
Frequency Range ◽  
White Noise Process ◽  
Moving Average Models ◽  
Data Points ◽  
Underlying Processes ◽  
Autoregressive Moving Average Models

The econometric data to which autoregressive moving-average models are commonly applied are liable to contain elements from a limited range of frequencies. If the data do not cover the full Nyquist frequency range of [0,π] radians, then severe biases can occur in estimating their parameters. The recourse should be to reconstitute the underlying continuous data trajectory and to resample it at an appropriate lesser rate. The trajectory can be derived by associating sinc fuction kernels to the data points. This suggests a model for the underlying processes. The paper describes frequency-limited linear stochastic differential equations that conform to such a model, and it compares them with equations of a model that is assumed to be driven by a white-noise process of unbounded frequencies. The means of estimating models of both varieties are described.

Vehicle Structure Optimization for Crash Pulse

2004 ◽  
Author(s):  
Lei Gu ◽  
T. Tyan ◽  
G. Li ◽  
R. J. Yang
Keyword(s):  
Design Optimization ◽  
Response Surface ◽  
Time History ◽  
Structure Design ◽  
Time Interval ◽  
Vehicle Structure ◽  
Occupant Injury ◽  
Data Points ◽  
Vehicle Motion ◽  
Occupant Kinematics

In vehicle safety engineering, it is important to determine the severity of occupant injury during a crash. Computer simulations are widely used to study how occupants move in a crash, what they collide during the crash and thus how they are injured. The vehicle motion is typically defined for the occupant simulation by specifying a crash pulse. Many computer models used to analyze occupant kinematics do not calculate both vehicle motion and occupant motion at the same time. This paper presents a framework of response surface methodology for the crash pulse prediction and vehicle structure design optimization. The process is composed of running simulation at DOE sampling data points, generating surrogate models (response surface models), performing sensitivity analysis and structure design optimization for time history data (e.g., crash pulse). Within this framework, the engineer can perform DOE sampling, surrogate modeling, main effect plot within any time interval, and design optimization. Some recent applications are presented to demonstrate how these approaches are employed for a vehicle structure design.

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