Determination of the resonance frequency range of buildings in Golbaf and Sirch earthquakes

Geotechnical Geology

دوره 4، شماره 1، خرداد 2008، صفحه 20-29   

نوع مقاله: Original Research

نویسنده

Mohammadreza Khosravi Mashizi^*

Department of Geology, Faculty of Science, Islamic Azad University - Bardsir Branch, Bardsir, Iran

چکیده

Considering the importance of the resonance phenomenon in buildings and the numbers in the
world of this phenomenon and the fact that this phenomenon isn't considered yet in Kerman province, in this paper the earthquake resonance frequency range is calculated for the regions of Golbaf and Sirch, located in Kerman province, using 23 records of earthquakes that happened between 1981 and 2000. The results have been generalized for the whole province. After providing above accelerograms, a program has been written for the calculating power spectra and its smoothed curve, based on Canai-Tajimi model and its correctness checked by comparing available power spectra. The program read records respectively, and at first it calculated and exhibited total energy and power of earthquake at the end of ground motion in any frequency between zero and 25 hertz, and finally exhibited smoothed power spectra model assuming linear relationship with two neighbor points of accelerograms and direct solving of movement equations. Through all accelerograms 18 records were related to Golbaf and 5 records were related to Sirch and all of them had maximum acceleration of more than 0.05g.Resonance frequency range has been specified by earning the amount of central frequency and shape factor parameters for all the records. This range was calculated between 3.43 and 8.76 hertz. By generalization of the calculated result, to the whole province, one can say that the structures which have a main frequency range of 3.43 to 8.76 hertz increase the damage of the earthquakes. Therefore, in structural designing, the main frequency of that range should be avoided by changing the structural mass or rigidity.

کلیدواژه‌ها

Central frequency؛ Kanai-Tajimi؛ Power spectral density؛ Resonance frequency؛ Shape factor