SU1390518A1 - Method of simulating seismic effect on a structure - Google Patents

Description

(21) 4124963 / 25-28

(22) 09/26/86

(46) 04.23.88. Bup. Number 15

(71) Research sector of the All-Union Design and Survey Research Institute Hydroproject them. S.Ya.Zhuk

(72) A.P. Kirillov, Yu.K.Ambriashvili, V.V. Piskarev and V.A. Zakharov

(53), 620.178.53 (088.8)

(56) USSR Author's Certificate No. 940097, cl. G 01 V 1/00, 1980.

USSR author's certificate number 552581, cl. G 01 V 1/00, 1977. (54) METHOD FOR MODELING SEISMIC IMPACT ON CONSTRUCTION

(57) The invention relates to a technique for dynamic testing of structures for seismic effects. The purpose of the invention is to improve the accuracy of seismic reproduction. An oscillator with attenuation is set on the vibrostand, its own frequency f. which is chosen equal to the frequency corresponding to the maximum difference йA of the envelopes of the response spectra for various recorded seismic effects and one of them having a response spectrum closest to the envelope. Accelerogram of the oscillator response is recorded when playing on the shaker table of the last action and determining the time T. for reaching the maximum response. Then, the indicated effect and harmonic oscillations are reproduced simultaneously on the vibration table, the acceleration amplitude of which and the initial phase are set taking into account the values of / 3A, fj, and the logarithmic decrement of oscillations of the oscillator. The accelerogram of the oscillation torus response to the cumulative effect is compared to the curve of the response spectra. The procedure described is repeated for oscillators with different natural frequencies until the accelerogram of the response with the envelope coincides. The accelerogram obtained in the final analysis simulates a seismic effect equivalent to that of all accelerograms from a given set. 1 il.

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The invention relates to a technique for dynamic testing of structures, in particular to methods for simulating seismic effects, and can be HcnojiiiSOBaHQ when testing structures for seismic resistance.

The purpose of the invention is to improve the accuracy of modeling.

The drawing shows the envelope of the response spectra of oscillators for various recorded accelerograms of seismic effects, the slope spectrum closest to the envelope, and the response spectrum of oscillators that was obtained using the proposed method.

The method is carried out as follows.

Build the envelope of the 1 response spectra of oscilloscopes of accelerograms of seismic effects of a given set. From a given set of choose the original accelerogram 2, the response spectrum of which is closest to the envelope. The natural frequencies f. Are determined, corresponding to large values of the difference / 5A of the envelope values and the response spectrum of the selected initial accelerogram. An oscillator with attenuation and a natural frequency f is installed on the shaker table and a signal corresponding to the selected initial accelerogram is reproduced on the shaker table. The time T is recorded, after which the response of this oscillator reaches its maximum value. The amplitude and phase of the additional harmonic signal are determined in accordance with the ratios

A-g

uA f

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H (1-expcf-f; TC) where cf is the logarithmic decrement of oscillations of the oscillator.

The total signal is reproduced on the shaker table according to the original accelerogram and additional harmonic effect.

The repetition of the described operations for other frequencies, using the accelerogram obtained from the preceding procedure to determine the response of the oscillators, is carried out on the basis of the required accuracy of the response spectrum (position 3) of the selected simulation accelerogram with the envelope of the response spectra of the accelerograms of the given set.

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Seismic estimates, for example, structures and equipment of atomic energy stations, select the accelerogram packet of earthquakes typical of a given area. On the test setup, which includes shaking tables, magnetographs, light beam oscillograph, function generator, time relay, analog adder, phase relay, linear oscillators with logarithmic decrement cG of oscillations corresponding to the logarithmic decrement of oscillations of the tested structure with natural frequencies f are installed on the shaker. previously defined. From the magnetograph, the vibrostand sets the motion corresponding to the initial accelerogram. After that, the editors of the oscillators installed on the stand are recorded with a light-beam oscilloscope. The oscillograms (accelerograms) measure the time T. of occurrence of maximum oscillator responses and determine the amplitudes and initial phases of the additional harmonic effects. Then set up a function generator for these natural frequencies f. and the amplitudes A defined above. Reproduced on a shaker through an analog adder accelerogram from a magnetograph and an additional harmonic effect from a function generator, the magnetograph triggered by a phase relay at the moment when the generator phase reaches the value Lf. . At the same time, a turnip of time, tuned to a time delay equal to Tj, is started and the obtained motion is recorded on another magnetograph. For the thus obtained new accelerogram, a response spectrum is constructed, which is compared to the envelope of the response spectra of all accelerograms. In that case, if the response spectrum of the obtained accelerogram differs from the envelope by more than 10%, then the procedure described is repeated until the response spectrum coincides with the envelope.

The resulting accelerogram simulates a seismic effect equivalent to that of all accelerograms from a given set, while retaining the static characteristics of a real accelerogram of an earthquake. Using the method will reduce the time of testing and increase

the accuracy of simulating the oscillations of the test- Mofi construction when reproducing seismic vibrations.

Claims (1)

Invention Formula A method of simulating a seismic effect on a structure, by which a modeling signal is reproduced on a shaker table, the parameters of which are determined from the condition that the response spectrum of linear oscillators on it is as close as possible to the response spectrum to a real seismic impact, characterized in that Due to accuracy, an oscillator with attenuation is set on the vibration table, the eigenfrequency fj of which is chosen equal to the frequency corresponding to the maximum difference DA of the envelopes of the response spectra on p zlichnye registered seismic effects and one of these influences on the response spectrum. Accelerogram of the response of the signal of the torus signal is recorded closest to the envelope when the accelerogram of this effect is reproduced on the pibro stand, the time T is determined through it, through which the response reaches its maximum value, then the accelerogram of the effect and the additional harmonic oscillations, amplitude L. accelerate and the initial phase of c. which are set in accordance with the ratios: A (1-exp J f (I-}, (f 2l / f; -Tj, where / is the logarithmic decrement of oscillation of oscillations, record the accelerogram of the oscillator response to the specified total effect, compare it with the envelope and repeat the described procedure when oscillators with other eigenfrequencies are installed on the vibrostand until the accelerogram of the response coincides with the envelope. L, m /: UO 25 fju.