A proposed dynamic foundation factor for the National Building Code of Canada

1991 ◽  
Vol 18 (6) ◽  
pp. 974-984 ◽  
Author(s):  
Kamel Elhmadi ◽  
Arthur C. Heidebrecht
Keyword(s):  
Parametric Study ◽  
Site Response ◽  
Site Amplification ◽  
Building Code ◽  
Dense Sand ◽  
Study Results ◽  
Soil Deposits ◽  
Class 1 ◽  
Soil Site ◽  
Strong Ground

Results of a parametric study on site response effects due to seismic strong ground motions are used in this paper to develop a new "dynamic foundation factor" for the National Building Code of Canada. In order to capture the effect of the site resonance, the proposed dynamic foundation factor, F*, is given as a function of the ratio between the fundamental period of the building and the site period, T/Ts (i.e., F* spectra in terms of T/Ts). The parametric study results suggested that the proposed F* spectra be dependent on four different classes of soil deposits. These classes are deep cohesive (class 1), deep cohesionless (class 2), shallow cohesive and cohesionless (class 3), and dense sand (class 4). For classes 1 and 2, the F* spectra are independent of the ratio of peak acceleration to peak velocity, av, of the seismic ground motion. For classes 3 and 4, however, the F* spectra are an increasing function of the ratio a/v. A scaling multiplier is introduced to take into account the influence of level of intensity, v. The proposed dynamic foundation factor is compared with the National Building Code of Canada 1990 foundation factor. Finally, actual sites are used to check the validity and consistency of the proposed dynamic foundation factor. Key words: seismic, foundation factor, soil, site, amplification, building, shear, force, period, spectra.

Influence of site amplification of seismic ground motions on forces in building structures

1991 ◽  
Vol 18 (6) ◽  
pp. 964-973
Author(s):  
A. C. Heidebrecht ◽  
P. Henderson ◽  
N. Naumoski ◽  
J. W. Pappin
Keyword(s):  
Site Response ◽  
Ground Motions ◽  
Site Amplification ◽  
Building Structures ◽  
Base Shear ◽  
Design Code ◽  
Seismic Design Code ◽  
Soil Site ◽  
Response Amplification ◽  
Different Characteristics

The results for nine sites with different characteristics subjected to earthquakes of varying intensity and frequency content are presented in the form of base shear coefficients, base shear coefficient ratios (surface to rock), and foundation factors. They indicate that large amplifications can be expected at structural periods close to the site periods, especially for low intensity excitation. Comparisons are made with the provisions of the National Building Code of Canada (NBCC) 1990. They show that, depending on the site and the nature and level of the excitation, the expected base shear can be well in excess of the values specified by the NBCC. Key words: seismic, design, code, soil, site, response, amplification, base, shear.

A Nonlinear Site Amplification Model for the Horizontal Component Developed for Ground-Motion Prediction Equations in Japan Using Site Period as the Site-Response Parameter

2021 ◽  
Author(s):  
Ruibin Hou ◽  
John X. Zhao
Keyword(s):  
Nonlinear Response ◽  
Site Response ◽  
Strong Motion ◽  
Site Amplification ◽  
Second Step ◽  
Ground Motion Prediction Equations ◽  
Ground Motion Prediction ◽  
Amplification Ratio ◽  
Soil Site ◽  
Site Period

ABSTRACT This article presents a nonlinear site amplification model for ground-motion prediction equations (GMPEs), using site period as site-effect proxy based on the measured shear-wave velocity profiles of selected KiK-net and K-NET sites in Japan. This model was derived using 1D equivalent-linear site-response analysis for a total of 516 measured soil-site shear-wave velocity profiles subjected to a total of 912 components of rock-site records. The modulus reduction and damping curves for each soil layer were assigned based on the soil-type description for a particular layer. The site period and site impedance ratio affect both the linear and nonlinear parts of this study, and were used as the site parameters in the 1D amplification model. A large impedance ratio enhances the amplification ratios when the site responds elastically and enhances the nonlinear response when the site develops a significant nonlinear response. The effects of moment magnitude and source distance on the linear part of the 1D amplification model were also incorporated in the model. To implement the 1D amplification model into GMPEs, a model adjustment is required to match the GMPE amplification ratio at weak motion and to retain the nonlinear amplification ratio at the strong motion of the 1D model. The two-step adjustment method by Zhao, Hu, et al. (2015) was adopted in this study with significant modifications. It is not possible to obtain a credible second-step adjustment parameter using the GMPEs dataset only. We proposed three methods for calculating the scale factors. Method 1 is a constant angle in a 30°–60° range for all spectral periods; method 2 was based on the GMPE dataset and 1-D model parameters; and method 3 was based on the strong-motion records used for the 1D site modeling. A simple second-step adjustment factor leads to smoothing amplification ratios and soil-site spectrum.

Site response effects for structures located on sand sites

1990 ◽  
Vol 27 (3) ◽  
pp. 342-354 ◽  
Author(s):  
P. Henderson ◽  
A. C. Heidebrecht ◽  
N. Naumoski ◽  
J. W. Pappin
Keyword(s):  
Key Words ◽  
Seismic Design ◽  
Site Response ◽  
Response Spectra ◽  
Building Code ◽  
Base Shear ◽  
Sand Soil ◽  
Low Intensity ◽  
Soil Site ◽  
A Site

Results are presented for 4 sand sites forming part of a site response study of 11 soil sites. The results are in the form of spectral accelerations and ratios, base shear coefficients, and foundation factors. They indicate that significant amplifications can be expected at sand sites, especially for low-intensity excitation. Comparisons are made with the provisions of the proposed National Building Code of Canada (NBCC) 1990. They show that, depending on the site and the nature and level of the excitation, the expected base shears can be well in excess of the values specified by the NBCC. Key words: seismic, design, sand, soil, site, response, spectra, amplification, base, shear.

The Seismic Provisions of the 1997 Uniform Building Code

2000 ◽  
Vol 16 (1) ◽  
pp. 85-100 ◽  
Author(s):  
Robert E. Bachman ◽  
David R. Bonneville
Keyword(s):  
The United States ◽  
Site Amplification ◽  
Major Elements ◽  
Building Code ◽  
Ground Acceleration ◽  
Reliability Factor ◽  
Nonstructural Components ◽  
Source Effects ◽  
Story Drift ◽  
Soil Site

Currently the most widely accepted code regulations in the United States for seismic design of structures and nonstructural components are those found in the Uniform Building Code ( UBC). The UBC seismic requirements were significantly revised in the 1997 edition. Among the issues addressed in the UBC revisions are near-source effects and ground acceleration dependent soil site amplification factors for both short- and long-period structures. Also, the design force levels in the 1997 UBC are based on strength design rather than allowable stress design, as had been used previously. Other significant changes include introduction of a redundancy/reliability factor, a more realistic consideration of story drift and deformation compatibility, and new equations for equivalent static forces for both structural and nonstructural components. This paper traces the recent history of the code development and describes the major elements of the 1997 UBC seismic provisions.

The site response of two rock and soil station pairs to strong and weak ground motion

1991 ◽  
Vol 81 (5) ◽  
pp. 1885-1899
Author(s):  
Robert B. Darragh ◽  
Anthony F. Shakal
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Soft Soil ◽  
Ground Acceleration ◽  
Ground Shaking ◽  
Soil Site ◽  
Rock Site ◽  
Loma Prieta ◽  
Strong Ground ◽  
Stiff Soil

Abstract The site response to strong and weak ground motion depends largely on the subsurface conditions at the soil site for the two rock-soil station pairs studied. The first station pair consists of a soft-soil site (Treasure Island) and a sandstone and shale site (Yerba Buena Island). These stations recorded strong ground shaking from the Loma Prieta mainshock and weak ground motion from four aftershocks. The range of peak ground acceleration is from approximately 0.00006 to 0.07 g at the rock site. Compared to the rock site, the strong ground motion at the soft-soil site is amplified by a factor of about 3 over a frequency range from 0.5 to 2.0 Hz. The amplification is much higher for weak motion and suggests a dependence on signal amplitude. For example, near 1 Hz, the site response shows an increasing amplification as magnitude (and the peak velocity at the rock site) decreases. For events of local magnitude 7.0, 4.3, 4.1, 3.5, and 3.3, the maximum soil-site amplifications are 4, 12, 17, 19, and 25, respectively. A second station pair consisting of a stiff-soil site (Gilroy #2) and a sandstone site (Gilroy #1) was also studied with contrasting results. These two stations recorded strong ground shaking from the 1979 Coyote Lake, 1984 Morgan Hill, and 1989 Loma Prieta mainshocks. Weak ground motion was recorded at these stations after the Loma Prieta mainshock. The range of peak ground acceleration is from 0.006 to 0.43 g at the rock site. Unlike the results for the soft-soil study above, the estimated stiff-soil site responses are not significantly different for strong and weak motion from 0.5 to 2.0 Hz. Near 0.7 Hz, the stiff-soil site responses range from 2.5 to 4.5 for strong ground shaking from three mainshocks and from 1.5 to 4.0 for weak ground shaking from thirteen aftershocks.

Ground Motion Site Amplification Factors for Sites Located within the Mississippi Embayment with Consideration of Deep Soil Deposits

2015 ◽  
Vol 31 (2) ◽  
pp. 699-722 ◽  
Author(s):  
Mojtaba Malekmohammadi ◽  
Shahram Pezeshk
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Site Amplification ◽  
Sediment Depth ◽  
Deep Soil ◽  
Mississippi Embayment ◽  
Soil Response ◽  
Amplification Factors ◽  
Nonlinear Site Response ◽  
Soil Deposits

In this study, site amplification factors for the deep soil deposits of the Mississippi embayment are computed using a nonlinear site response analysis program first to develop a model for nonlinear soil response for possible use by ground motion developers and second to address site amplification estimation. The effects of geology, sediment depth, and average shear wave velocity at the upper 30 m of soil ranging 180–800 m/s, as well as the effect of peak ground acceleration at the bedrock on nonlinear ground motion amplification for the upper embayment, are investigated. The site response computations cover various site conditions, sediment depth of 70–750 m, and peak acceleration of input rock motions of 0.01–0.90 g. The amplification (or de-amplification) at various frequencies implied by the sediment depth is greater than that implied just by site classification of the top 30 m of soil.

Empirical Study of Sediment-Filled Basin Response: The Case of Taipei City

2000 ◽  
Vol 16 (3) ◽  
pp. 681-707 ◽  
Author(s):  
Vladimir Yu Sokolov ◽  
Chin-Hsiung Loh ◽  
Kuo-Liang Wen
Keyword(s):  
Site Response ◽  
Propagation Path ◽  
Reference Spectrum ◽  
Spectral Ratios ◽  
Taipei Basin ◽  
Soil Deposits ◽  
Source Scaling ◽  
Attenuation Models ◽  
Basin Response ◽  
Strong Ground

We analyze the site response of the Taipei basin using the records obtained by the Taiwan Strong Ground Motion Instrumentation Program (TSMIP) network. Records of 66 earthquakes of M=2.6-6.5 with a hypocentral depth varying from 1 km to 118 km and hypocentral distances of up to 150 km are studied for 35 stations located within this triangle-shaped alluvium structure. The site response is obtained in terms of spectral ratios calculated by dividing of the site spectrum by the reference spectrum estimated for a hypothetical “very hard rock” site. The recently developed empirical source scaling and attenuation models for the Taiwan region are used for the reference spectra calculation. This approach allows us to evaluate the variability of spectral ratios due to uncertainties introduced by source and propagation path effects and variability in the site response itself. The characteristics of site response in the Taipei basin depend on the properties of soil deposits and, in general, may be described by 1-D models. However, there are some peculiarities of spectral ratios that show the influence of subsurface topography.

Simulation-based site amplification model for shallow bedrock sites in Korea

2021 ◽  
pp. 875529302098198
Author(s):  
Muhammad Aaqib ◽  
Duhee Park ◽  
Muhammad Bilal Adeel ◽  
Youssef M A Hashash ◽  
Okan Ilhan
Keyword(s):  
Linear Models ◽  
Site Response ◽  
Site Amplification ◽  
One Dimensional ◽  
Nonlinear Component ◽  
Nonlinear Site Response ◽  
Simulation Based ◽  
Linear And Nonlinear ◽  
Input Motion ◽  
Nonlinear Components

A new simulation-based site amplification model for shallow sites with thickness less than 30 m in Korea is developed. The site amplification model consists of linear and nonlinear components that are developed from one-dimensional linear and nonlinear site response analyses. A suite of measured shear wave velocity profiles is used to develop corresponding randomized profiles. A VS30 scaled linear amplification model and a model dependent on both VS30 and site period are developed. The proposed linear models compare well with the amplification equations developed for the western United States (WUS) at short periods but show a distinct curved bump between 0.1 and 0.5 s that corresponds to the range of site natural periods of shallow sites. The response at periods longer than 0.5 s is demonstrated to be lower than those of the WUS models. The functional form widely used in both WUS and central and eastern North America (CENA), for the nonlinear component of the site amplification model, is employed in this study. The slope of the proposed nonlinear component with respect to the input motion intensity is demonstrated to be higher than those of both the WUS and CENA models, particularly for soft sites with VS30 < 300 m/s and at periods shorter than 0.2 s. The nonlinear component deviates from the models for generic sites even at low ground motion intensities. The comparisons highlight the uniqueness of the amplification characteristics of shallow sites that a generic site amplification model is unable to capture.

scholarly journals Ocean-Bottom Seismographs Based on Broadband MET Sensors: Architecture and Deployment Case Study in the Arctic

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 3979
Author(s):  
Artem A. Krylov ◽  
Ivan V. Egorov ◽  
Sergey A. Kovachev ◽  
Dmitry A. Ilinskiy ◽  
Oleg Yu. Ganzha ◽  
...  
Keyword(s):  
Site Response ◽  
The Arctic ◽  
Laptev Sea ◽  
Ocean Bottom ◽  
Arctic Seas ◽  
Shirshov Institute ◽  
Study Results ◽  
Ocean Bottom Seismographs ◽  
The Laptev Sea

The Arctic seas are now of particular interest due to their prospects in terms of hydrocarbon extraction, development of marine transport routes, etc. Thus, various geohazards, including those related to seismicity, require detailed studies, especially by instrumental methods. This paper is devoted to the ocean-bottom seismographs (OBS) based on broadband molecular–electronic transfer (MET) sensors and a deployment case study in the Laptev Sea. The purpose of the study is to introduce the architecture of several modifications of OBS and to demonstrate their applicability in solving different tasks in the framework of seismic hazard assessment for the Arctic seas. To do this, we used the first results of several pilot deployments of the OBS developed by Shirshov Institute of Oceanology of the Russian Academy of Sciences (IO RAS) and IP Ilyinskiy A.D. in the Laptev Sea that took place in 2018–2020. We highlighted various seismological applications of OBS based on broadband MET sensors CME-4311 (60 s) and CME-4111 (120 s), including the analysis of ambient seismic noise, registering the signals of large remote earthquakes and weak local microearthquakes, and the instrumental approach of the site response assessment. The main characteristics of the broadband MET sensors and OBS architectures turned out to be suitable for obtaining high-quality OBS records under the Arctic conditions to solve seismological problems. In addition, the obtained case study results showed the prospects in a broader context, such as the possible influence of the seismotectonic factor on the bottom-up thawing of subsea permafrost and massive methane release, probably from decaying hydrates and deep geological sources. The described OBS will be actively used in further Arctic expeditions.

Estimation of Site Amplification from Geotechnical Array Data Using Neural Networks

2021 ◽  
Author(s):  
Daniel Roten ◽  
Kim B. Olsen
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Site Response ◽  
Site Amplification ◽  
Data Driven ◽  
Vertical Array ◽  
The Neural Network ◽  
Simplifying Assumptions ◽  
The Mean ◽  
Fully Connected

ABSTRACT We use deep learning to predict surface-to-borehole Fourier amplification functions (AFs) from discretized shear-wave velocity profiles. Specifically, we train a fully connected neural network and a convolutional neural network using mean AFs observed at ∼600 KiK-net vertical array sites. Compared with predictions based on theoretical SH 1D amplifications, the neural network (NN) results in up to 50% reduction of the mean squared log error between predictions and observations at sites not used for training. In the future, NNs may lead to a purely data-driven prediction of site response that is independent of proxies or simplifying assumptions.

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