scholarly journals PRACTICAL METHOD TO EVALUATE RESPONSE SPECTRA OF BEDROCK MOTIONS USING AMPLIFICATION FACTORS FOR SITE CLASSES

2004 ◽  
Vol 69 (582) ◽  
pp. 39-46 ◽  
Author(s):  
Yasuo UCHIYAMA ◽  
Saburoh MIDORIKAWA
Keyword(s):  
Response Spectra ◽  
Practical Method ◽  
Amplification Factors ◽  
Site Classes

Amplification Effects of Thin Soft-Surface Layers

2016 ◽  
Vol 32 (4) ◽  
pp. 2109-2126 ◽  
Author(s):  
W. D. Liam Finn ◽  
Francisco Ruz
Keyword(s):  
Soft Soil ◽  
Soil Layer ◽  
Tohoku Earthquake ◽  
Response Spectra ◽  
Surface Layers ◽  
Soft Layer ◽  
The 2011 Tohoku Earthquake ◽  
Amplification Factors ◽  
Soft Surface ◽  
Using Data

The amplification effects of shallow soft-surface layers with respect to an underlying hard-soil layer or rock are studied using data recorded from the 2011 Tohoku earthquake. Twenty-four sites have been studied with depths to rock ranging from 4–30 m. At each site, two records were available: one in rock at the bottom of the borehole at depths of 100–500 m and one on the surface of the soft-soil layer. Analyses of the soil-rock columns were conducted using the program SHAKE. Good agreement was found between calculated and recorded surface spectra, which demonstrated the reliability of SHAKE analyses for the sites under study. Therefore, SHAKE analyses were used to determine the outcrop motions at the top of rock. Amplification factors were determined by comparing characteristics of the surface and outcrop motions such as Fourier and response spectra. Computed amplification factors were correlated with V S30, V soil, and soft layer period, T = 4 H/ V soil. The results show clearly that the most reliable correlations for estimating the amplification of soft shallow surface layers less than 30 m are those based on V S30 and soft layer period, T.

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.

Estimates of Site-Dependent Response Spectra for Design (Methodology and Justification)

1994 ◽  
Vol 10 (4) ◽  
pp. 617-653 ◽  
Author(s):  
Roger D. Borcherdt
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Strong Motion ◽  
Response Spectra ◽  
Building Code ◽  
Ground Shaking ◽  
Geological Conditions ◽  
Site Classes ◽  
Code Provisions

Recent borehole-geotechnical data and strong-motion measurements constitute a new empirical basis to account for local geological conditions in earthquake-resistant design and site-dependent, building-code provisions. They provide new unambiguous definitions of site classes and rigorous empirical estimates of site-dependent amplification factors in terms of mean shear-wave velocity. A simple four-step methodology for estimating site-dependent response spectra is specified herein. Alternative techniques and commentary are presented for each step to facilitate application of the methodology for different purposes. Justification for the methodology is provided in terms of definitions for the new site classes and derivations of simple empirical equations for amplification as a function of mean shear-wave velocity and input ground-motion level. These new results provide a rigorous framework for improving estimates of site-dependent response spectra for design, site-dependent building-code provisions, and predictive maps of strong ground shaking for purposes of earthquake hazard mitigation.

Amplification Factors for Equipment Design Subjected to Seismic Loading

1998 ◽  
Vol 120 (4) ◽  
pp. 334-342
Author(s):  
R. Jategaonkar ◽  
L. G. Jaeger
Keyword(s):  
Ground Motion ◽  
Response Spectrum ◽  
Seismic Loading ◽  
Response Spectra ◽  
Structural Damping ◽  
Mathematical Technique ◽  
Ground Structure ◽  
Amplification Factors ◽  
Seismic Motion ◽  
Numerical Software

A mathematical technique is developed to evaluate the seismic response of primary equipment supported directly by the main structure and also the response of secondary equipment supported by the primary equipment. The method can be used for structures ranging from the simple to the complex, and is amenable to calculations based on standard spreadsheet or numerical software or, if desired, can be programmed. The technique can be used to develop amplification factors for seismic motion between ground, structure, and equipment. Alternatively, the method can be utilized to develop the ground response (or structure motion) spectra for various structural damping ratios and also floor response (or equipment response) spectra directly from a ground motion spectrum given as datum. The results are compared with the results from other well-established methods. The proposed method has an advantage over the other methods in that it enables direct computation of the third level response, i.e., response of the secondary equipment supported by the primary equipment; also, the method can be readily applied to any shape of ground motion response spectrum given as datum.

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