Generating ground motion by two new techniques of adding harmonic wave in the time domain and approximating to response spectrum as a whole

1997 ◽  
Vol 10 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Chang-Qing Cai ◽  
Jian-Wen Sheng
Keyword(s):  
Ground Motion ◽  
Time Domain ◽  
Response Spectrum ◽  
Harmonic Wave ◽  
New Techniques ◽  
The Time Domain

Selection of random vibration theory procedures for the NGA-East project and ground-motion modeling

2021 ◽  
Vol 37 (1_suppl) ◽  
pp. 1420-1439
Author(s):  
Albert R Kottke ◽  
Norman A Abrahamson ◽  
David M Boore ◽  
Yousef Bozorgnia ◽  
Christine A Goulet ◽  
...  
Keyword(s):  
Ground Motion ◽  
Time Domain ◽  
Random Vibration ◽  
Amplitude Spectrum ◽  
Motion Modeling ◽  
Peak Response ◽  
Vibration Theory ◽  
Random Vibration Theory ◽  
The Time Domain ◽  
The Impact

Traditional ground-motion models (GMMs) are used to compute pseudo-spectral acceleration (PSA) from future earthquakes and are generally developed by regression of PSA using a physics-based functional form. PSA is a relatively simple metric that correlates well with the response of several engineering systems and is a metric commonly used in engineering evaluations; however, characteristics of the PSA calculation make application of scaling factors dependent on the frequency content of the input motion, complicating the development and adaptability of GMMs. By comparison, Fourier amplitude spectrum (FAS) represents ground-motion amplitudes that are completely independent from the amplitudes at other frequencies, making them an attractive alternative for GMM development. Random vibration theory (RVT) predicts the peak response of motion in the time domain based on the FAS and a duration, and thus can be used to relate FAS to PSA. Using RVT to compute the expected peak response in the time domain for given FAS therefore presents a significant advantage that is gaining traction in the GMM field. This article provides recommended RVT procedures relevant to GMM development, which were developed for the Next Generation Attenuation (NGA)-East project. In addition, an orientation-independent FAS metric—called the effective amplitude spectrum (EAS)—is developed for use in conjunction with RVT to preserve the mean power of the corresponding two horizontal components considered in traditional PSA-based modeling (i.e., RotD50). The EAS uses a standardized smoothing approach to provide a practical representation of the FAS for ground-motion modeling, while minimizing the impact on the four RVT properties ( zeroth moment, [Formula: see text]; bandwidth parameter, [Formula: see text]; frequency of zero crossings, [Formula: see text]; and frequency of extrema, [Formula: see text]). Although the recommendations were originally developed for NGA-East, they and the methodology they are based on can be adapted to become portable to other GMM and engineering problems requiring the computation of PSA from FAS.

scholarly journals Detection of quasars in the time domain

2016 ◽  
Vol 12 (S325) ◽  
pp. 231-241
Author(s):  
Matthew J. Graham ◽  
S. G. Djorgovski ◽  
Daniel J. Stern ◽  
Andrew Drake ◽  
Ashish Mahabal
Keyword(s):  
Time Domain ◽  
Temporal Behavior ◽  
New Techniques ◽  
Astronomical Research ◽  
The Time Domain ◽  
New Facilities

AbstractThe time domain is the emerging forefront of astronomical research with new facilities and instruments providing unprecedented amounts of data on the temporal behavior of astrophysical populations. Dealing with the size and complexity of this requires new techniques and methodologies. Quasars are an ideal work set for developing and applying these: they vary in a detectable but not easily quantifiable manner whose physical origins are poorly understood. In this paper, we will review how quasars are identified by their variability and how these techniques can be improved, what physical insights into their variability can be gained from studying extreme examples of variability, and what approaches can be taken to increase the number of quasars known. These will demonstrate how astroinformatics is essential to discovering and understanding this important population.

scholarly journals A new iterative solver for the time-harmonic wave equation

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. E57-E63 ◽  
Author(s):  
C. D. Riyanti ◽  
Y. A. Erlangga ◽  
R.-E. Plessix ◽  
W. A. Mulder ◽  
C. Vuik ◽  
...  
Keyword(s):  
Wave Equation ◽  
Linear System ◽  
Time Domain ◽  
Multigrid Method ◽  
Harmonic Wave ◽  
Computational Time ◽  
Full Time ◽  
Iterative Solver ◽  
Time Harmonic ◽  
The Time Domain

The time-harmonic wave equation, also known as the Helmholtz equation, is obtained if the constant-density acoustic wave equation is transformed from the time domain to the frequency domain. Its discretization results in a large, sparse, linear system of equations. In two dimensions, this system can be solved efficiently by a direct method. In three dimensions, direct methods cannot be used for problems of practical sizes because the computational time and the amount of memory required become too large. Iterative methods are an alternative. These methods are often based on a conjugate gradient iterative scheme with a preconditioner that accelerates its convergence. The iterative solution of the time-harmonic wave equation has long been a notoriously difficult problem in numerical analysis. Recently, a new preconditioner based on a strongly damped wave equation has heralded a breakthrough. The solution of the linear system associated with the preconditioner is approximated by another iterative method, the multigrid method. The multigrid method fails for the original wave equation but performs well on the damped version. The performance of the new iterative solver is investigated on a number of 2D test problems. The results suggest that the number of required iterations increases linearly with frequency, even for a strongly heterogeneous model where earlier iterative schemes fail to converge. Complexity analysis shows that the new iterative solver is still slower than a time-domain solver to generate a full time series. We compare the time-domain numeric results obtained using the new iterative solver with those using the direct solver and conclude that they agree very well quantitatively. The new iterative solver can be applied straightforwardly to 3D problems.

Development Law of Seismic Subsidence of Loess through In Situ Explosion Test

2012 ◽  
Vol 594-597 ◽  
pp. 1822-1829
Author(s):  
Qiang Wang ◽  
Jun Jie Sun ◽  
Lan Min Wang
Keyword(s):  
Ground Motion ◽  
Time Domain ◽  
Ground Settlement ◽  
Contribution Rate ◽  
Time Space ◽  
Variation Characteristics ◽  
Stage Development ◽  
The Time Domain ◽  
Explosion Test

To reveal development law of seismic subsidence of loess, through in-situ explosion test at one loess site, ground settlement and layered underground settlement were monitored, by which the time-space-domain development of seismic subsidence of loess are gained. Furthermore, the time-domain development law of seismic subsidence in different directions is analyzed, so as the variation characteristics of layer-settlement and its contribution rate, and the development law of seismic subsidence distribution in the horizontal direction. The time-domain development of seismic subsidence of loess consists of rapidly growing stage and slowly growing stage. The former is under blasting ground motion, and its seismic subsidence ratio approaches to 46.5% invariably. While in the later stage, development of seismic subsidence ratio can be described by power function with index of 0-1. And, seismic subsidence distribution and contribution rate of layer-settlement are varying with time, which are consistent to the time-domain development law of seismic subsidence.

Structural Response to Non-Stationary Thunderstorm Outflows

2020 ◽  
Author(s):  
Dae Kun Kwon ◽  
Giovanni Solari ◽  
Ahsan Kareem
Keyword(s):  
Boundary Layer ◽  
Time Domain ◽  
Paradigm Shift ◽  
Stationary Process ◽  
Response Spectrum ◽  
Structural Response ◽  
Kinematics And Dynamics ◽  
Statistical Features ◽  
Simulation Based ◽  
The Time Domain

The mechanics associated with thunderstorm outflows differ significantly from traditional turbulence in boundary layer winds both in its kinematics and dynamics. The key distinguishing attributes are the contrasting velocity profile with height, a rapid increase in speed, and the statistical features of the energetic gusts in the wind field, exhibiting a strong non-stationarity. This raises serious questions regarding the applicability of conventional stationary process-based theories, thus calling for a paradigm shift. This chapter reviews popular approaches concerning the structural analysis of non-stationary thunderstorm outflows, such as evolutionary power spectrum-based analysis, wavelet-based analysis, thunderstorm response spectrum technique involving the equivalent wind spectrum, and hybrid simulation-based analysis in the time domain. Finally, some preliminary comparisons between the results obtained using these different methods are presented.

scholarly journals A New Elastoplastic Time-History Analysis Method for Frame Structures

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Qianqian Liang ◽  
Chen Zhao ◽  
Jun Hu
Keyword(s):  
Periodic Point ◽  
Time Domain ◽  
Response Spectrum ◽  
Time History ◽  
Specific Yield ◽  
Seismic Load ◽  
Structural Systems ◽  
History Analysis ◽  
The Time Domain ◽  
Fracture Stiffness

This study aimed to analyze the formation and application of the time-domain elastoplastic response spectrum. The elastoplastic response spectrum in the time domain was computed according to the trilinear force-restoring model. The time-domain elastoplastic response spectrum corresponded to a specific yield strength coefficient, fracture stiffness, and yield stiffness. However, the force-restoring models corresponding to different structural systems and the states of the structural systems at different moments were not the same. Therefore, the dynamic characteristics of a particular periodic point corresponding to a particular structure were meaningful for the elastoplastic response spectrum. In addition, the curve in the time-domain dimension along the periodic point truly reflected the real-time response of the structure when the structure encountered a seismic load.

Comparison of Seismic Analysis of Jacket Structures Using Response Spectrum and Time Domain Procedures

2013 ◽  
Author(s):  
Partha Chakrabarti ◽  
Atul Rikhy
Keyword(s):  
Linear System ◽  
Ground Motion ◽  
Time Domain ◽  
Response Spectrum ◽  
Ground Acceleration ◽  
Soil System ◽  
Soil Stiffness ◽  
Acceleration Time ◽  
Acceleration Time Histories ◽  
Time Histories

In seismically active areas of the world an offshore jacket structure has to be designed for seismic loads. Since the structure must meet both strength and ductility requirements, a two stage design for Strength Level Earthquake (SLE) and Ductility Level Earthquake (DLE) is generally used. Normal procedure for designing such a structure for SLE condition is to use Response Spectrum method of analysis (RSA). The main advantage of RSA is that it is computationally very efficient. Time Domain Analysis (TDA) is used mostly to analyze DLE condition. A response spectrum depicts the maximum response to a ground motion of a single degree of freedom system having different natural periods but the same degree of damping. A design response spectrum is a smoothened average of several earthquake motions. It is a property of the ground motion with a given recurrence interval at the particular region of interest. RSA is a frequency domain analysis technique based on mode superposition approach. API RP 2A specifies that the modal responses be combined using a Complete Quadratic Combination (CQC) of modal responses. For the directional response combination, API RP 2A recommends applying 100% of the spectral acceleration for the two orthogonal lateral directions and 50% for the vertical and using the Square Root of Sum of Squares (SRSS) combination to obtain the maximum response. With this approach it is possible to conduct only one analysis, with any reference system, and the resulting structure will have all members that are designed to equally resist earthquake motions from all possible directions. RSA based on mode superposition is valid strictly for a linear system. A jacket structure with its pile-soil system is not truly a linear system due to soil nonlinearity. Therefore, linearization of the pile-soil system is necessary. The stiffness of a pile is dependent on the pile head loads. Thus the response from the RSA will be very much load or deformation dependent for the pile-soil stiffness. Software used here for the analyses has an iterative analysis option for obtaining the appropriate linearized stiffness. TDA is a step by step time integration procedure for the entire system including the piles and there is no linearization involved for the foundation stiffness as the pile-soil stiffness at discrete points of the pile are calculated at each time instant within the program. The TDA is more precise for the given time history but more time consuming as a series of ground acceleration time histories are normally required for the TDA approach. The results from RSA are expected to be conservative especially for the design of piles. However, this can only be confirmed from a series of TDA performed using ground acceleration time histories. This paper demonstrates that more accurate and less conservative results can be obtained by using a combination of RSA and TDA even for SLE condition. However, several simulations for TDA are required for confidence in the design to ensure that all structural elements have achieved the maximum conditions. Essentially, RSA can be used for jacket member design and TDA can be used specifically for pile design. Thus the authors believe the design of an entire jacket could be more economical if this combined approach is judiciously used.

scholarly journals An Analytical Method for Elastic Seismic Response of Structures Considering the Effect of Ground Motion Duration

2021 ◽  
Vol 11 (22) ◽  
pp. 10949
Author(s):  
Qianqian Liang ◽  
Chen Zhao ◽  
Jun Hu ◽  
Hui Zeng
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Time Domain ◽  
Analytical Method ◽  
Vibration Mode ◽  
Response Duration ◽  
Response Spectra ◽  
Earthquake Ground Motion ◽  
Mode Decomposition ◽  
The Time Domain

The response to earthquake ground motion is composed of three basic elements, namely, amplitude, frequency, and duration. The seismic response of a structure is controlled by the particular combination of these three elements. The seismic response spectra reflect the earthquake ground motion’s frequency-domain features and provide the maximum response amplitude of a single-degree-of-freedom system to a given earthquake ground motion but do not consider the duration factor. However, the analysis of post-earthquake damage shows that the seismic response duration has a strong impact on the damage to structures. Therefore, it is necessary to develop a simple and practical analytical method to account for the seismic response duration. The present study was conducted based on the response spectra theory. We introduce an analytical method of elastic seismic response, which considers its duration by adding the time-domain dimension of earthquakes. The time-domain spectral matrix is used to solve the time-dependent seismic response through the vibration mode decomposition method. The time-domain vibration mode decomposition reaction spectrum not only takes into account the maximum seismic reaction of each vibration mode but also considers the seismic reaction of different vibration modes occurring at the same time, at each moment. The dynamic time duration of the structure’s seismic reaction is quantified by the time-domain seismic reaction spectrum to obtain a more accurate analysis method for the seismic reaction of the structure.

Apodisation in the time domain

1992 ◽  
Vol 2 (4) ◽  
pp. 615-620
Author(s):  
G. W. Series
Keyword(s):  
Time Domain ◽  
The Time Domain
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