Modeling of Seismic Motion Time Histories with Time-Variable Predominant Frequencies

Vestnik MEI ◽  
2020 ◽  
Vol 6 (6) ◽  
pp. 129-134
Author(s):  
Vladimir P. Radin ◽  
◽  
Viktor P. Chirkov ◽  
Elena V. Poznyak ◽  
Olga V. Novikova ◽  
...  
Keyword(s):  
Risk Taking ◽  
Natural Frequencies ◽  
Random Processes ◽  
Seismic Load ◽  
Predominant Frequency ◽  
Load Spectrum ◽  
Seismic Motion ◽  
Dangerous Situation ◽  
Motion Time ◽  
Time Histories

Seismic motions occurring at sites with soft soils and located hundreds of kilometers away from the earthquake focus can be long-lasting and show changes in the frequency spectrum. Although these motions are characterized by low values of peak ground accelerations, they can lead to resonance vibration of buildings and structures. An especially dangerous situation occurs when the seismic load frequencies decrease simultaneously with the natural frequencies of the structure that is damaged during the earthquake. For designing buildings and structures, and for carrying out probabilistic assessment of seismic risk taking into account the changes in time of the seismic load spectrum, an ensemble of seismic motion time histories is required. The article presents a method for modeling unsteady random processes with a variable predominant frequency in the Simulink software system environment.

Three Dimensional Seismic Isolation System Using Hydraulic Cylinder

2002 ◽  
Author(s):  
Shinichiro Kajii ◽  
Naoki Sawa ◽  
Nobuhiro Kunitake ◽  
K. Umeki
Keyword(s):  
Seismic Isolation ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Hydraulic Cylinder ◽  
Seismic Load ◽  
3D Seismic ◽  
Isolation System ◽  
Response Characteristics ◽  
Seismic Motion ◽  
Hydraulic Cylinders

A three-dimensional (3D) seismic isolation system for FBR building is under development. The proposed vertical isolation system consists form hydraulic cylinders with water-based liquid and accumulators to support large vertical static load and to realize low natural frequency in the vertical direction. For horizontal isolation, laminated rubber isolator or sliding type isolator will be combined. Because the major part of the feasibility of this isolation system depends on the sealing function and durability of the hydraulic cylinder, a series of feasibility tests of the hydraulic cylinder have been conducted to verify the reliability against seismic load and seismic motion. This paper describes the specification of the seismic isolations system, seismic response characteristics and the results of the feasibility tests of the seal. This study was performed as part of a government sponsored R&D project on 3D seismic isolation.

Vibro-Acoustic Analysis and Topology Optimization of Anti-Tetra Chiral Auxetic Lattices Driven by Different Colored Noises

2020 ◽  
Vol 20 (11) ◽  
pp. 2050113
Author(s):  
A. Hosseinkhani ◽  
D. Younesian ◽  
M. Ranjbar
Keyword(s):  
Boundary Conditions ◽  
Natural Frequencies ◽  
Acoustic Analysis ◽  
Honeycomb Structure ◽  
Geometrical Parameters ◽  
Acoustic Behavior ◽  
The Finite Element Method ◽  
Load Spectrum ◽  
The Core ◽  
Radiated Sound

In this paper, we study vibro-acoustic behavior of auxetic sandwich panels subjected to different excitations and boundary conditions. The core of this panel has the auxetic feature (with negative Poisson’s ratio or NPR) with anti-tetrachiral honeycomb structure. Mechanical behavior of the core is formulated using theoretical relations presented for this kind of auxetic. Using the Finite Element Method, the modal analysis and spectral analysis of the structure are accomplished. Different random colored noises are applied as the system excitation. First, a parametric study is performed; and some interesting results are observed from investigating the effects of geometric parameters, boundary conditions, and noise color on the vibro-acoustic behavior of the structure. These parameters affect the natural frequencies, level of radiated sound, and mass of the structure. An optimization algorithm is applied to the geometrical parameters in order to simultaneously reduce the level of radiated sound and preserve the amount of total mass. By the use of the Genetic Algorithm (GA), we could achieve a remarkable noise attenuation gain. It is shown that the GA choses different optimized parameters for the structure according to the location of the load and frequency content of the load spectrum.

scholarly journals A Procedure to Select Earthquake Time Histories for Deterministic Seismic Hazard Analysis: Case Studies of Major Cities in Taiwan

2017 ◽  
Author(s):  
Duruo Huang ◽  
Wenqi Du
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Ground Surface ◽  
Strong Motion ◽  
Response Spectra ◽  
Dynamic Responses ◽  
Motion Time ◽  
Acceleration Time Histories ◽  
Time Histories ◽  
Deterministic Seismic Hazard

Abstract. In performance-based seismic design, ground-motion time histories are needed for analyzing dynamic responses of nonlinear structural systems. However, the number of strong-motion data at design level is often limited. In order to analyze seismic performance of structures, ground-motion time histories need to be either selected from recorded strong-motion database, or numerically simulated using stochastic approaches. In this paper, a detailed procedure to select proper acceleration time histories from the Next Generation Attenuation (NGA) database for several cities in Taiwan is presented. Target response spectra are initially determined based on a local ground motion prediction equation under representative deterministic seismic hazard analyses. Then several suites of ground motions are selected for these cities using the Design Ground Motion Library (DGML), a recently proposed interactive ground-motion selection tool. The selected time histories are representatives of the regional seismic hazard, and should be beneficial to earthquake studies when comprehensive seismic hazard assessments and site investigations are yet available. Note that this method is also applicable to site-specific motion selections with the target spectra near the ground surface considering the site effect.

An Advanced Test Method to Determine Viscous Damping of Floating Structures

2010 ◽  
Author(s):  
Z. J. Huang ◽  
B. J. O’Donnell ◽  
T. W. Yung ◽  
S. T. Slocum
Keyword(s):  
Low Frequency ◽  
Test Method ◽  
Total Force ◽  
Viscous Damping ◽  
Damping Force ◽  
Restoring Force ◽  
Viscous Forces ◽  
Motion Time ◽  
Research Company ◽  
Time Histories

ExxonMobil Upstream Research Company developed an advanced model test method to determine reliable damping values for predicting low frequency motions of an FLNG barge and an LNG carrier. Since viscous damping forces are a very small portion of the total force on the model, how to separate the viscous forces from the total forces is the key technical challenge. To better isolate viscous damping forces, an inertial compensation system consisting of springs was employed in the test. The spring stiffness was designed such that the restoring force cancelled the large inertial loads at the oscillation frequency. Furthermore, double-body models were built and were deeply submerged to minimize surface wave damping. With such an experimental setup, the total force measured was mainly the viscous damping force. Viscous damping was derived from the measured force and motion time histories.

Rotational Components of Seismic Motion Based on Surface Wave

2005 ◽  
Author(s):  
Hong-Nan Li ◽  
Yan-Gang Zhao ◽  
Chen Li ◽  
Li-Ye Sun
Keyword(s):  
Vertical Axis ◽  
Engineering Practice ◽  
Phase Velocities ◽  
Seismic Motion ◽  
Rotational Components ◽  
Rayleigh And Love Waves ◽  
Time Histories ◽  
Torsional Component ◽  
Rotational Motions ◽  
The Given

In this paper, the appropriate methods are presented to obtain the seismic rotational components caused by the arrival of the surface waves applying the theory of elastic wave propagation. The rocking component around a horizontal axis and the torsional component around a vertical axis are generated respectively by the Rayleigh and Love waves. At the same time, the calculation formulations of phase velocities about these waves with frequent dispersion are derived and introduced to the rotational components, which may be more suitable for engineering practice. A procedure is developed to compute the time histories. Finally, numerical results have shown that the rotational motions have more energy than the translatonal motions in high frequent range by using the given methods.

Prediction of System Natural Frequencies Using an Explicit Finite Element Code With Application to Belt-Drives

2004 ◽  
Author(s):  
Tamer Wasfy ◽  
Michael Leamy ◽  
Rick J. Meckstroth
Keyword(s):  
Finite Element ◽  
Multibody Systems ◽  
Natural Frequencies ◽  
System Response ◽  
Finite Element Code ◽  
Frequency Range ◽  
Harmonic Force ◽  
Explicit Finite Element ◽  
Belt Drives ◽  
Time Histories

A time-accurate explicit finite element code is used to predict the natural frequencies of a typical class of flexible multibody systems — automotive accessory belt-drives. The system considered consists of a belt, two pulleys, and a tensioner. Two techniques are used to find the system natural frequencies: (a) applying a sharp impulse to the system and extracting the system natural frequencies from the resulting displacement/strain time-histories via an FFT; and (b) applying a harmonic force to the system and sweeping through a frequency range, while at the same time, monitoring for large system response. In the present paper a comparison between these two techniques is presented for a typical accessory drive. Also, recommendations are offered on how to best use each technique to efficiently extract the system’s natural frequencies.

Disaggregation of seismic hazard

1999 ◽  
Vol 89 (2) ◽  
pp. 501-520 ◽  
Author(s):  
Paolo Bazzurro ◽  
C. Allin Cornell
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Seismic Source ◽  
Source Effects ◽  
Motion Time ◽  
Time Histories ◽  
Definition Of ◽  
Rupture Mechanism ◽  
Selection Of

Abstract Probabilistic seismic hazard analysis (PSHA) integrates over all potential earthquake occurrences and ground motions to estimate the mean frequency of exceedance of any given spectral acceleration at the site. For improved communication and insights, it is becoming common practice to display the relative contributions to that hazard from the range of values of magnitude, M, distance, R, and epsilon, ɛ, the number of standard deviations from the median ground motion as predicted by an attenuation equation. The proposed disaggregation procedures, while conceptually similar, differ in several important points that are often not reported by the researchers and not appreciated by the users. We discuss here such issues, for example, definition of the probability distribution to be disaggregated, different disaggregation techniques, disaggregation of R versus ln R, and the effects of different binning strategies on the results. Misconception of these details may lead to unintended interpretations of the relative contributions to hazard. Finally, we propose to improve the disaggregation process by displaying hazard contributions in terms of not R, but latitude, longitude, as well as M and ɛ. This permits a display directly on a typical map of the faults of the surrounding area and hence enables one to identify hazard-dominating scenario events and to associate them with one or more specific faults, rather than a given distance. This information makes it possible to account for other seismic source characteristics, such as rupture mechanism and near-source effects, during selection of scenario-based ground-motion time histories for structural analysis.

A numerical study of P-, SV-, and SH-wave generation in a plane layered medium

1980 ◽  
Vol 70 (4) ◽  
pp. 1015-1036 ◽  
Author(s):  
C. Y. Wang ◽  
R. B. Herrmann
Keyword(s):  
Elastic Medium ◽  
Numerical Study ◽  
Theoretical Ground ◽  
Matrix Operations ◽  
Surface Displacements ◽  
Motion Time ◽  
Starting Point ◽  
Time Histories ◽  
Simple Matrix ◽  
Dislocation Sources

abstract A solution for the surface displacements due to buried dislocation sources in a multi-layered elastic medium is found using the Haskell (1964) paper as a starting point and more importantly, for notation. Through the introduction of some simple matrix operations, the Haskell (1964) solution is made simultaneously more compact and computationally stable. Time histories are computed for a perfectly elastic medium by performing classical contour integration in the complex wavenumber plane. A new aspect in the evaluation of those contours is introduced because of the recognition of nonzero singularity contributions of the Hankel and modified Bessel functions at k = 0. Theoretical ground motion time histories are presented to show the usefulness of the formulation. The overall objective of this paper is to incorporate the modifications made since 1964 to the Haskell (1964) paper in an easily understandable, step-by-step development.

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