Ölçeklendirilen yakın saha deprem kayıtlarının farklı doğrultularda etkimesi durumunda yalıtım birimi maksimum yer değiştirmelerinde gözlenen değişim

Bu çalışmada, sismik taban izolasyonu uygulaması kurşun çekirdekli kauçuk yalıtım birimleri (KÇKYB)kullanılarak gerçekleştirilen bir yapıda, maksimum izolatör deplasmanlarındaki (MİD) değişim deprem etkimeaçısına bağlı olarak incelenmiştir. Bu amaçla, seçilen deprem kayıtlarının orijinal halleri 10º aralıklarla 180ºboyunca döndürülerek aynı deprem hareketinin farklı etkime açılarına sahip versiyonları oluşturulmuştur.Yürütülen doğrusal olmayan dinamik analizlerde, dikkate alınan deprem hareketine ait her iki yatay deprembileşeni oluşturulan yapısal modele eş zamanlı olarak tatbik ettirilmiştir. Analizlerde kullanılan depremhareketleri, yakın saha kaynaklı kayıtlar arasından seçilmiş olup, tasarım deprem (TD) ve maksimum deprem(MD) seviyelerini temsil edecek şekilde ölçeklendirilmiştir. Analizlerde, maruz kalınan harekete bağlı olarakKÇKYB’nin histeretik eğrilerinde, kurşun çekirdekteki ısınmaya bağlı, dayanım kaybını dikkate alabilenmalzeme modeli kullanılmıştır. Ayrıca, incelemeye konu olan deprem etkime açısına bağlı MİD’deki değişiminizolasyon periyoduna olan hassasiyetini belirleyebilmek adına dört farklı özellikte izolatör tasarlanmıştır.Yapılan analizler sonucunda, orijinal deprem kayıtlarının döndürülmesi sonucu MİD’deki artışın ihmaledilebilir seviyede (ortalama olarak %2 mertebesinde) olduğu gözlenmiştir. Bu artış miktarının TD ve MDseviyeleri için farklılaşmadığı tespit edilmiştir. Ayrıca, deprem hareketinin farklı etkime açısına bağlı olarakortaya çıkan MİD’deki artışın, izolasyon periyodundaki değişimden etkilenmediği görülmüştür.

Change in maximum isolator displacements due to change in orientation of scaled near field ground motion records

In this study, the change in maximum isolator displacements (MIDs) of a seismically isolated structure is studied as a function of ground motion orientation. The isolator units of the analyzed structure is composed of lead rubber bearings (LRBs). For this purpose, selected as-recorded original forms of ground motions are rotated from 0º to 180º with 10º increments to obtain new records with different orientations. In nonlinear response history analyses, both horizontal components of ground motion records are subjected to structure simultaneously. Employed motions are representative of near-field records and scaled to represent two different seismicity levels namely, design based earthquake (DBE) and maximum considered earthquake (MCE). In the analyses, a deteriorating hysteretic behavior, where the deterioration is a function of temperature rise in the lead core, is used to idealize LRBs. Furthermore, to find the effect of isolation period on this amplification, the isolation period is considered to be a parameter. Thus, four different isolators are designed. The analyses results revealed that the variation in MIDs due to change in ground motion orientation is negligible and approximately equals to 2% in an average sense. Same observation is valid for seismicity levels of both DBE and MCE. Also, isolation period is found to be an ineffective parameter in terms of variation in MID when different orientation of motions is of concern.

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