In this study, an ensemble of ground motions is selected and scaled in order to perform code-compliant bidirectional Nonlinear Response History Analysis for the design purpose of both short- and long-period structures. The followed scaling method provides both the requirements of the Turkish Earthquake Code regarding the scaling of ground motions and compatibility of response spectra of selected ground motion pairs with the target spectrum. The effects of four parameters, involved in the followed scaling method, on both the amplitude of scale factors and seismic response of structures are investigated. These parameters are the number of ground motion records, period range, number of periods used in the related period range, and distribution of weight factors at the selected periods. In the analyses, ground motion excitations were applied to both fixed-base and seismically isolated structure models representative of short- and long-period structures, respectively. Results revealed that both the amplitudes of scale factors and seismic response of short-period structures are more prone to variation of investigated parameters compared to those of long-period structures.

No abstract

Binalar Hakkında Yönetmelik koşulları dikkate alınarak tasarlanmış deprem yalıtımlı bir yapı modeli için, spektrum tanımındaki değişime bağlı olarak maksimum yalıtım birimi deplasmanının nasıl etkilendiği incelenmiştir. Yapıdaki deprem yalıtım sitemi kurşun çekirdekli kauçuk yalıtım birimlerinden oluşurken, seçilen ve ölçeklenen deprem kayıtlarına ait yatay bileşenlerin eş zamanlı etkisine maruz bırakılmıştır. Analizler, çevrimsel yükleme altında yalıtım birimindeki dayanım kaybını dikkate alan ve almayan durumlar için tekrarlanmıştır. Yalıtım birimi dayanımını temsilen Q/W oranı ve yapının inşa edileceği alan seçilen parametrelerdir. Sonuç olarak, her iki deprem yönetmeliğinin tanımladığı spektrum eğrilerine göre tasarlanan yalıtım birimlerinin maksimum deplasmanlarında yapı koordinatına bağlı olarak farklılaşma %50 mertebelerine varabilmektedir. Yalıtım birimindeki dayanım kaybının dikkate alındığı durumlar için bu farklılaşmanın daha da fazla olduğu kaydedilmiştir.

This study investigates the response modification in a bridge seismically isolated with lead rubber bearings (LRBs), due to change of ambient temperature from 20 o C to -30 o C. Accordingly, a large-size LRB was tested after being conditioned at corresponding temperatures and changes in its hysteretic properties were noted. Use of analytical tool in modeling nonlinear response of the tested LRB was justified by comparing the experimentally observed and analytically obtained force-displacement curves. Then, verified analytical representation of an LRB was employed in nonlinear response history analyses conducted to quantify the change in response of a representative LRB isolated bridge when subjected to bidirectional ground motion excitations at 20°C and -30°C. Analyses results are also employed to assess the use of property modification factor, , to change isolator properties in order to represent low temperature behavior. It is revealed that for the selected ground motion records, the average isolator force remains almost the same for both ambient temperatures. Moreover, using property modification factor will result in accurately estimated isolator displacements, but overestimated isolator forces, in an average sense.

In this paper, new formulations to predict the change in mechanical properties, namely, post-yield stiffness and characteristic strength of lead rubber bearings (LRBs) at low ambient temperatures, are proposed based on test results. Proposed formulations consider not only the effect of low temperature but also the effect of exposure time to low temperature. Accordingly, a full-scale LRB was tested dynamically after being conditioned at temperatures of −20, −10, 0, and 20 °C for 3, 6, and 24 h. During the displacement-controlled cyclic tests, various levels of shear strain were applied to the isolator with loading frequencies of 0.1 Hz and 0.5 Hz. Then, force-displacement curves of LRB were recorded, and the corresponding amplifications in its hysteretic properties were noted. The accuracy of existing equations to estimate the amount of amplification in mechanical properties was evaluated through the experimental results. It was found that the existing formulas do not represent the effect of exposure time on LRB characteristics at low temperatures. On the other hand, the proposed equations result in highly accurate estimations of post-yield stiffness and characteristic strength of LRB at low temperatures for different exposure times.