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Calculation Method of Site Predominant Period Under Inclined Seismic Waves

A calculation method and seismic wave technology, applied in the field of geotechnical engineering investigation, can solve the problem of inaccurate excellent period of the site

Active Publication Date: 2020-03-31
XIAN UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] The purpose of the present invention is to provide a calculation method of the site's excellent period under the action of inclined seismic waves, which solves the problem that the existing calculation method usually regards the seismic wave as a vertical upward plane shear wave, which leads to the inaccurate calculation of the site's excellent period. The invented method can consider the impact of seismic wave incident angle on the excellent period, and provide more comprehensive site natural vibration characteristic parameters for determining actual engineering design

Method used

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  • Calculation Method of Site Predominant Period Under Inclined Seismic Waves
  • Calculation Method of Site Predominant Period Under Inclined Seismic Waves
  • Calculation Method of Site Predominant Period Under Inclined Seismic Waves

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Effect test

Embodiment 1

[0099] The stratigraphic parameters of a second-floor site are shown in Table 1. Taking the SV wave incident angle of 20° as an example, the process of determining the site’s prominent period under the action of oblique seismic waves is introduced in detail. The specific steps are as follows:

[0100] (1) Determine formation parameters, as shown in Table 1;

[0101] (2) Determine the number of sampling points for the duration of the impulse response. In this example, take the duration of the impulse response t l =5s, time sampling interval △t=0.001s, number of sampling points nt=5000;

[0102] (3) Calculate the ray parameter p w , select the SV incident angle θ=20°, the number of formation layers n=20, vs 2 = 500 m / s, then p w = sin20 / 500 = 0.00068404 s / m;

[0103] (4) Calculate the one-way propagation time of the seismic wave in the first layer:

[0104]

[0105]

[0106] (5) Calculate the reflection coefficient of the seismic wave incident on the ground; according...

Embodiment 2

[0115] The formation parameters of a 7-story site are shown in Table 3. Select incident angles of 0°, 5°, 10°, 15°, 25°, 30°, and 32°, and calculate according to steps 1 to 8, respectively, to obtain different incident angles The calculation results of the excellent cycle of the site under the conditions are shown in Table 4.

[0116] Table 3 Site 2 formation parameters

[0117]

[0118] Table 4 Site 2 Cycle of Excellence

[0119]

Embodiment 3

[0121] The formation parameters of an 11-story site are shown in Table 5. Select incident angles of 0°, 5°, 10°, 15°, 25°, 30°, and 35°, and calculate according to steps 1 to 8, respectively, to obtain different incident angles The calculation results of the excellent cycle of the site under the conditions are shown in Table 6.

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Abstract

The invention discloses a calculating method of a predominant period of a field on condition of an oblique seismic wave. The method comprises the following steps of firstly determining each parameterof the field and the seismic wave and a seismic pulse response duration and a time sampling interval; calculating a reflection coefficient which is generated in incidence to ground; then, calculatingthe reflection coefficient and the transmittance coefficient of a longitudinal wave and a transverse wave in obliquely incidence into each stratum interface I, then calculating the pulse response of the longitudinal wave and the transverse wave at each stratum interface for obtaining the pulse response in incidence into the ground surface; and finally, calculating a pulse response time history ina horizontal direction of the ground and performing discrete Fourier transform for obtaining a Fourier spectrum of the pulse ground vibration, thereby determining the predominant period of the field.The calculating method of the predominant period of the field on condition of the oblique seismic wave settles a problem of low accuracy of the calculated predominant period of the field caused by a fact of considering the seismic wave as a vertically upward planar shear wave in an existing calculating method. The method according to the invention is not limited by the number of soil layers and furthermore has advantages of high calculation precision and high speed.

Description

technical field [0001] The invention belongs to the technical field of geotechnical engineering investigation, and relates to a method for calculating the excellent period of a site under the action of oblique seismic waves. Background technique [0002] When the natural vibration period of the building structure is close to or consistent with the natural vibration period of the site, the system formed by the two will resonate during the earthquake process, and the site natural vibration period amplified due to the resonance is called the excellent period. In order to avoid resonance between ground buildings and engineering sites during earthquakes, it is first necessary to determine the excellent period of the site. When applying the wave velocity method to calculate the excellent period of the site, it is assumed that the covering soil layer and its underlying bedrock are horizontal layered sites whose mechanical properties change along the vertical layer and extend unifor...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01V1/30
CPCG01V1/306
Inventor 范留明
Owner XIAN UNIV OF TECH