Mustafa KOÇER, Abdulhamit NAKİPOĞLU, Burhan ÖZTÜRK, Mohammed GAMAL AL-HAGRİ, Musa Hakan ARSLAN
Introduction: In order to facilitate the analysis of determining the seismic load that will affect a structure in a possible ground motion, spectral analysis method is more widely used than dynamic analysis methods. Here, while a static analysis method, which is much simpler than a more realistic and complex method, is preferred, the response spectra used are proposed as the design spectrum in today's seismic codes. Response spectra, which have an important place in the design of the earthquake-resistant structure, are curves plotted between maximum responses of damped single degree of freedom system at a constant damping ratio subjected to specified earthquake ground motion, in terms of acceleration, displacement or velocity magnitudes, and its time period or frequency. Aim: Determination of spectral acceleration values and control periods defined in Turkish Seismic Code 2007 (TSC 2007) and Turkish Building Seismic Code 2018 (TBSC 2018). Scope: TSC 2007 and TBSC 2018 were compared through the calculation of these values for 4 selected provinces in 4 different seismic zones, according to the seismic hazard map published in 1996 and TSC 2007. Limitations: According to TSC 2007, for the 1st degree seismic zone Kocaeli province, for the 2nd degree seismic zone Eskisehir province, for the 3rd degree seismic zone Kayseri province and for the4th degree seismic zone Konya province were selected. For TSC 2007, the values were determined using the spectral acceleration coefficients defined for these regions. However, for TBSC 2018, they were obtained from earthquake acceleration map found in the website of the Disaster and Emergency Management Presidency (AFAD), considering the center coordinates of these provinces. Method: The design spectrum curves of the regions were plotted separately according to each soil class and four different seismic ground motion levels for both the seismic codes. The values obtained for the curves were interpreted through the arrangement of two separate tables for the design earthquake in terms of spectral acceleration magnitudes and control periods. Results: While the spectral acceleration coefficients for the same seismic zone do not differ from one soil class to another in TSC 2007, these values show slight differences according to soil classes in TBSC 2018. In TBSC 2018, as the soil class gets softer, the acceleration coefficients increase. For Kocaeli province center selected for the 1st degree seismic zone according to TSC 2007, the spectral acceleration coefficient value showed a maximum increase in the ZC soil class of about 60% in the TBSC 2018. Likewise, for Eskisehir province selected for the 2nd degree seismic zone, this value reached the maximum level in the ZE soil class with an increase of 28%. In Kayseri province selected for the 3rd degree seismic zone, the highest increase of 63% was found in the ZE soil class and for Konya province, which was selected for the 4th degree seismic zone, the highest increase occurred again in the ZE soil class and the increase amount was calculated as 175%.While the highest spectral acceleration values in all the provinces, excluding Kocaeli, were found in the softest soil class ZE, it was found in ZC soil class in Kocaeli province. Conclusion: In TSC 2007, the control periods, TA and TB, vary only in accordance with the soil classes, however in TBSC 2018 these values also vary according to the seismic zones. Although, in TBSC 2018, the plateau between the control periods for different soil classes and the same seismic zone extends the same as in TSC 2007, when examining for different seismic zones and the same soil class, the control periods and the regions between them increase. Although the results are limited to these regions, in general, for soft soil groups, TBSC 2018 is on the safer side than TSC 2007.

Anahtar Kelimeler: Code, Design, Spectral Acceleration, Spectrum, TBSC 2018, TSC 2007