A Damping Modification Factor for Horizontal Acceleration Spectrum from Subduction Slab Earthquakes in Japan Accounting for Site Conditions

2020 ◽  
Vol 110 (4) ◽  
pp. 1942-1959
Author(s):  
John X. Zhao ◽  
Mingxiu Jiang ◽  
Xiaonan Zhang ◽  
Lili Kang
Keyword(s):  
Damping Ratio ◽  
Site Effect ◽  
Site Conditions ◽  
Design Spectrum ◽  
Horizontal Acceleration ◽  
Displacement Spectra ◽  
Modification Factor ◽  
Standard Deviations ◽  
Source And Path Effects ◽  
Site Classes

ABSTRACT We present a damping modification factor (DMF) model for the total acceleration spectrum from subduction slab earthquakes. The model can be used for scaling a 5% damped design spectrum not associated with a particular earthquake that occurred in a subduction slab. The DMF model uses site-period-based site classes as the site-effect proxy. DMF models were constructed based on the spectrum for 13 damping ratios and 34 spectral periods; the DMF values can be calculated for any damping ratio between 1% and 30% and at any spectral period between 0.03 and 5.0 s. At moderately long and long spectral periods, the DMF values for acceleration spectrum are similar to or less than those for the displacement spectrum for a damping ratio of less than 5%, whereas the DMF values for the acceleration spectrum are similar to or larger than those for the displacement spectrum when the damping ratio is more than 5%. The standard deviations for acceleration and displacement spectra are similar at short or moderately short spectral periods, but those for the acceleration spectrum are about twice those for the displacement spectrum at long spectral periods. All standard deviations decrease linearly with increasing damping ratios in the logarithm scale when the damping ratio is less than 5% and increase linearly with increasing damping ratios in a logarithm scale for the other damping ratios. A set of simple functions for calculating various standard deviations is presented. The spectra from the Zhao, Jiang, et al. (2016) study for slab events scaled by the DMF values for other damping ratios vary smoothly with spectral period and have a trough at short spectral periods for a large event, a short distance, and high damping ratios. The relatively large between-event and within-site standard deviations are from the source and path effects.

A Damping Modification Factor Prediction Model for Horizontal Displacement Spectrum from Subduction Interface Earthquakes in Japan Accounting for Site Conditions

2020 ◽  
Vol 110 (3) ◽  
pp. 1231-1246 ◽  
Author(s):  
Jun Zhou ◽  
John X. Zhao
Keyword(s):  
Damping Ratio ◽  
Quadratic Function ◽  
Horizontal Displacement ◽  
Site Effect ◽  
Residual Distribution ◽  
Period Range ◽  
Engineering Designs ◽  
Modification Factor ◽  
Standard Deviations ◽  
The One

ABSTRACT This article presents a damping modification factor (DMF) model without source and path parameters for subduction interface earthquakes in Japan using a similar dataset as the one used in the Zhao, Liang, et al. (2016) study. Site effect was modeled by site classes based on site periods. DMF models were constructed using the spectra for 13 damping ratios at 34 spectral periods. The DMF values can be calculated in a damping ratio range of 1%–30% and in a spectral period range of 0.03–5.0 s. The effect of damping ratios was modeled by a simple quadratic function of the damping ratios in the logarithm scale, and the effect of the spectral period was modeled by a simple fourth-order polynomial of the spectral period also in the logarithm scale. The DMF value is 1.0 at a spectral period of ≤0.02  s . At long periods >5.0  s, the DMFs for different damping ratios appear to converge to 1.0, satisfying the condition of constant displacement spectrum at long periods. For an extrapolation to >5.0  s for a damping ratio <5%, DMF=1.0 can be selected when DMF<1.0; for a damping ratio >5%, DMF=1.0 can be selected when DMF>1.0. For a damping ratio <5%, all standard deviations decrease linearly with increasing damping ratios in the logarithm scale; for a damping ratio >5%, all standard deviations increase linearly with increasing damping ratios in the logarithm scale. A smoothed displacement spectrum useful for engineering designs can be obtained by scaling the spectrum from Zhao, Liang, et al. (2016). The DMF values from this study are close to those of the published models at some spectral periods. The residual distribution suggests that DMFs are functions of earthquake source and path parameters.

A Damping Modification Factor Prediction Model for Horizontal Displacement Spectrum from Subduction Slab Earthquakes in Japan Accounting for Site Conditions

2020 ◽  
Vol 110 (2) ◽  
pp. 647-665 ◽  
Author(s):  
Jun Zhou ◽  
John X. Zhao
Keyword(s):  
Damping Ratio ◽  
Quadratic Function ◽  
Horizontal Displacement ◽  
Site Effect ◽  
Residual Distribution ◽  
Period Range ◽  
Engineering Designs ◽  
Modification Factor ◽  
Standard Deviations ◽  
The Difference

ABSTRACT A damping modification factor (DMF) model without source and path parameters is presented in this article for subduction slab earthquakes in Japan, using a similar dataset in the Zhao, Jiang, et al. (2016) study. Site classes based on site periods were used as the site-effect proxy. DMF models were derived from spectra of 13 damping ratios and 34 spectral periods, and the DMF can be calculated for any damping ratio between 1% and 30% and at any spectral period between 0.03 and 5.0 s. A simple fourth-order polynomial for the logarithm of the spectral periods and a simple quadratic function of the logarithm of damping ratios were used to model the effects of spectral periods and damping ratios, respectively. The model satisfies boundary conditions that require the DMF values equal to 1.0 at very short spectral periods; at long spectral periods, the DMFs for different damping ratios appear to converge to 1.0 to satisfy the constant displacement spectrum at long periods. Model standard deviations are smaller than those for the ground-motion prediction equations. All standard deviations vary linearly with the increasing logarithm of damping ratios. The DMFs presented in this study combined with the spectrum from the Zhao, Jiang, et al. (2016) study produce smoothed displacement spectrum that may be used for engineering designs. In a spectral period range of 0.2–3.0 s, the DMF values from this study are close to those by Daneshvar et al. (2016), but, at short periods, the difference is significant. The residual distribution suggests that DMFs also depend on earthquake source and path parameters. The model presented in this article does not include the effect of source and path variables so that this model can be used to scale a 5% damped spectrum without a known magnitude and a source distance.

scholarly journals INFLUENCE OF MATERIAL DAMPING ON THE RESPONSE OF UNDERGROUND STRUCTURES SUBJECTED TO EARTHQUAKE

2020 ◽  
Vol 26 ◽  
pp. 64-70
Author(s):  
Veronika Pavelcová ◽  
Tereza Poklopová ◽  
Michal Šejnoha ◽  
Tomáš Janda
Keyword(s):  
Damping Ratio ◽  
Underground Structure ◽  
Eurocode 8 ◽  
Viscous Damping ◽  
Material Damping ◽  
Underground Structures ◽  
Fixed Boundary ◽  
Design Spectrum ◽  
Rayleigh Damping ◽  
Element Simulation

The paper describes a finite element simulation of the response of a real underground structure subjected to earthquake using GEO5 FEM program. It concentrates on the influence of material damping with respect to a specific type of boundary condition prescribed at the bottom of the analyzed domain. It is seen that considering material damping is inevitable particularly in case of so called fixed boundary conditions to arrive at meaningful results. This is demonstrated on an artificial earthquake generated according to a design spectrum defined in Eurocode 8. A viscous damping ratio combined with the results of eigenvalue analysis is used to derive parameters of Rayleigh damping for three specific scenarios promoting the approach based on the lowest natural frequency as sufficiently accurate for the present task.

A New Ground-Motion Prediction Equation of Japanese Instrumental Seismic Intensities Reflecting Source Type Characteristics in Japan

2020 ◽  
Vol 110 (6) ◽  
pp. 2661-2692
Author(s):  
Ritsuko S. Matsu’ura ◽  
Hiroto Tanaka ◽  
Mitsuko Furumura ◽  
Tsutomu Takahama ◽  
Akemi Noda
Keyword(s):  
Site Effect ◽  
Prediction Equation ◽  
Philippine Sea Plate ◽  
Intraplate Earthquakes ◽  
Historical Seismology ◽  
Crustal Earthquakes ◽  
Ogasawara Islands ◽  
Standard Plate ◽  
Standard Deviations ◽  
New Equation

ABSTRACT A new equation for predicting Japanese instrumental seismic intensities at arbitrary surface sites in Japan for Mw 5.4–8.7 and distances ranging from 10 to 1000 km was derived from approximately 30,000 observed intensities for various types of earthquakes. The equation incorporates the differences in the subsurface characteristics immediately beneath each site using VS30. The equation can also predict the abnormal intensities (which are indispensable in Japan) due to subducting slabs using the depth of the slab surface beneath each site from the Crustal Activity Modeling Program standard plate model. The prediction equation can be applied to five source types: Pacific Ocean plate (PAC) interplate, PAC intraplate, very shallow crustal, shallow (≤50  km) Philippine Sea plate (PHS) intraplate, and intermediate-depth (>50  km) PHS intraplate earthquakes. Although the equation is applicable at various magnitudes and distances, the standard deviations (σ) are 0.5–0.6, which are smaller than those of other equations with narrower distance ranges. Smaller σ values were achieved by the inversion of 29,837 Japanese instrumental seismic intensities from 68 selected earthquakes of five source types with a common site effect at each station. A deep Mw 7.9 earthquake that occurred at a depth of 680 km in 2015 near the Ogasawara Islands and subjected all of Japan to long-duration shaking due to waves propagating through the mantle was effectively employed to constrain the VS30 term of the equation. The equations for PAC interplate and very shallow earthquakes were validated by seven earthquakes that were not used for the inversion; the standard deviations for these earthquakes fell in the range of 0.41–0.53. The formula for very shallow crustal earthquakes is also able to predict the intensities of PHS interplate earthquakes. Hence, this equation is useful not only for engineering applications but also for historical seismology to distinguish the source types of ancient earthquakes.

A Comparison of Ground-Motion Parameters for the Vertical Components from the Western and the Southwestern Parts of China with Recent Ground-Motion Prediction Equations

2020 ◽  
Author(s):  
Hao Xing ◽  
John X. Zhao
Keyword(s):  
Ground Motion ◽  
Normal Fault ◽  
Constant Term ◽  
Site Effect ◽  
Prediction Equation ◽  
Motion Prediction ◽  
Ground Motion Prediction ◽  
Vertical Ground Motions ◽  
Standard Deviations ◽  
Suitable Reference

ABSTRACT This study evaluated the source, path, and site effects of the vertical ground motions from the western and the southwestern parts of China (referred to as SWC hereafter) using 2403 records from 449 earthquakes, including the records from the 2008 Mw 7.9 Wenchuan earthquake and its aftershocks. Only 677 records are from 73 mainshocks, and 259 events do not have a known focal mechanism. There is a large magnitude gap in the dataset, for example, there is only one event between Mw 6.3 and Mw 7.8. The average numbers of records per recording station and per earthquake are small, and many sites do not have a measured shear-wave velocity profile. These shortcomings make it difficult to develop a robust ground-motion prediction equation (GMPE) without adding overseas data or using a reference GMPE developed from a large dataset. We compared the SWC dataset with five recent GMPEs, three based on the Next Generation Attenuation-West2 dataset, one based on Europe and the Middle East, and one based on the shallow-crustal and upper-mantle earthquakes in Japan. We decomposed the total residuals for each model into constant term, between-event, and within-event residuals and calculated the corresponding standard deviations. The maximum log likelihood and the standard deviations suggest that, among the five GMPEs, the Zhao et al. (2017) model without the normal-fault term may be the most suitable GMPE for a probabilistic seismic hazard study in the SWC region. Correction functions based on simple magnitude, path, and site effect parameters were used to correct the residuals and to obtain the leftover between- and within-event standard deviations. These standard deviations appear to suggest that the GMPE from Zhao et al. (2017) without a normal-fault term may be the most suitable reference GMPE for developing a new GMPE for the SWC region.

scholarly journals Seismic Analysis of a Large LNG Tank Considering Different Site Conditions

2020 ◽  
Vol 10 (22) ◽  
pp. 8121 ◽  
Author(s):  
Yi Zhao ◽  
Hong-Nan Li ◽  
Shuocheng Zhang ◽  
Oya Mercan ◽  
Caiyan Zhang
Keyword(s):  
Seismic Response ◽  
Structural Design ◽  
Well Being ◽  
Von Mises Stress ◽  
Site Conditions ◽  
Storage Tanks ◽  
Site Class ◽  
Lng Tank ◽  
Von Mises ◽  
Site Classes

Seismic resilience of critical infrastructure, such as liquefied natural gas (LNG) storage tanks, is essential to the safety and economic well-being of the general public. This paper studies the effect of different ground motions on large LNG storage tanks under four different site conditions. Key parameters of structural design and dynamic analysis, including von Mises stress of outer and inner tanks, tip displacement, and base shear, are analyzed to directly evaluate the safety performance of the large LNG tanks. Because the size of an LNG tank is too large to perform any experiments on a physical prototype, Smoothed Particle Hydrodynamics-Finite Element Method (SPH-FEM) simulation is used as a feasible and efficient method to predict its seismic response. First, the accuracy of the SPH-FEM method is verified by comparing sloshing frequencies obtained from theoretical formulation to experimental results and SPH-FEM models. Then, the seismic response of a real-life 160,000 m3 LNG prestressed storage tank is evaluated with different liquid depths under four site classes. Simulation results show that the tip displacements of the LNG tank at liquid levels of 25% and 50% under site class IV are nearly identical to that of 75% and 100% under site class II. In addition, the maximum von Mises stress of the inner tanks exceeds 500 MPa in all four site classes and jeopardizes the structural integrity of large LNG tanks. As a result, optimization of structural design and the establishment of an early warning system are imperative to the safety of LNG tanks at high liquid levels.

scholarly journals A study on sensitivity of seismic site amplification factors to site conditions for bridges

2018 ◽  
Vol 51 (4) ◽  
pp. 197-211
Author(s):  
Muhammad Tariq A. Chaudhary
Keyword(s):  
Seismic Design ◽  
Site Amplification ◽  
Site Conditions ◽  
Design Codes ◽  
Design Code ◽  
Bridge Design ◽  
Site Class ◽  
Vibration Period ◽  
Amplification Factors ◽  
Site Classes

Seismic site amplification factors and seismic design spectra for bridges are influenced by site conditions that include geotechnical properties of soil strata as well as the geological setting. All modern seismic design codes recognize this fact and assign design spectral shapes based on site conditions or specify a 2-parameter model with site amplification factors as a function of site class, seismic intensity and vibration period (short and long). Design codes made a number of assumptions related to the site conditions while specifying the values of short (Fa) and long period (Fv) site amplification factors. Making these assumptions was necessary due to vast variation in site properties and limited availability of actual strong motion records on all site conditions and seismic setting in a region. This paper conducted a sensitivity analysis for site amplification factors for site classes C and D in the AASHTO bridge design code by performing a 1-D site response analysis in which values of site parameters like strata depth, travel-time averaged shear wave velocity in the top 30 m strata (Vs30), plasticity index (PI), impedance contrast ratio (ICR) and intensity of seismic ground motion were varied. The results were analyzed to identify the site parameters that impacted Fa and Fv values for site classes C and D. The computed Fa and Fv values were compared with the corresponding values in the AASHTO bridge design code and it was found that the code-based Fa and Fv values were generally underestimated and overestimated respectively.

Ground motion amplification factors for the proposed 2005 edition of the National Building Code of Canada

2003 ◽  
Vol 30 (2) ◽  
pp. 272-278 ◽  
Author(s):  
W.D Liam Finn ◽  
Adrian Wightman
Keyword(s):  
Seismic Design ◽  
Ground Motions ◽  
Building Code ◽  
Soil Conditions ◽  
Site Conditions ◽  
Amplification Factors ◽  
Seismic Codes ◽  
Local Soil ◽  
Recent Developments ◽  
Site Classes

Foundation factors are used in seismic codes to capture the amplification effects of local soil conditions on ground motions and, hence, on seismic design forces. Recent developments in categorizing site conditions for seismic codes and assigning intensity- and frequency-dependent amplification factors to the various site classes are presented to provide a basis for understanding the new foundation factors proposed for the 2005 edition of the National Building Code of Canada.Key words: design spectra, site characterization, amplification factors.

Experimental investigation on coupled vibration characteristics of wind-excited tall buildings

2020 ◽  
Vol 23 (9) ◽  
pp. 1948-1959
Author(s):  
Wei Hao ◽  
Qingshan Yang
Keyword(s):  
Fourier Transform ◽  
Wind Speed ◽  
Complex Geometry ◽  
Damping Ratio ◽  
Time History ◽  
Tall Buildings ◽  
Vibration Characteristics ◽  
Coupled Vibration ◽  
Coupled Response ◽  
Standard Deviations

Contemporary tall buildings constructed with high-strength and light-weight materials become relatively flexible and lightly damped, and the fluctuating wind forces acting on the buildings may cause excessive vibrations, especially at the vicinity of vortex lock-in wind speed, where the natural frequency of the buildings is synchronized with the vortex shedding frequency. Given that tall buildings tend to be designed with unconventional shape involving innovative structural systems and complex geometry, the correlations among three force components may accentuate building motions significantly. In this study, the coupling characteristics between the alongwind and crosswind vibrations of tall buildings with symmetric shape and distinct natural frequencies in two directions are investigated through a serious of aeroelastic model tests. The response standard deviations and power spectral densities are calculated, respectively, based on the displacement data measured at multiple levels of wind speed and structural damping ratio. Then the coupled response is extracted from the alongwind response in frequency domain through Fourier transform and inverse Fourier transform, and the standard deviations of the coupled response are calculated based on time history analysis, which are compared with that of the crosswind response to investigate the relationship between the alongwind and crosswind motions. Moreover, the amplitude ratio, phase difference, and coherence of the response components are also calculated for further discussing the coupling effects and examining the coupled vibration characteristics.

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