Fragility analysis of wide-beam infill-joist block RC frames

Purpose: The purpose of the presented study is to develop fragility curves for the wide-beam infill-joist block reinforced concrete structures. Theory and Methods: Nonlinear time history analyses are performed for the set of selected ground motions. The performance levels are identified through pushover analysis and fragility curves are produced for ground motion parameters. Results: Fragility curves obtained for the wide-beam RC frames presents a different characteristic than the curves obtained for the conventional frames. Conclusion: Results show that wide-beam RC frame buildings are seismically more vulnerable than the conventional deep beam RC frame buildings based on structural models with similar properties. The possible reason seems to be low lateral stiffness of wide-beam frames that causes large lateral drift demands and therefore severe damage at the wide-beam column connections

Generation of fragility curves for Turkish masonry buildings considering in-plane failure modes

This study focuses on the seismic safety evaluation of masonry buildings in Turkey for in-plane failure modes using fragility curves. Masonry buildings are classified and a set of fragility curves are generated for each class. The major structural parameters in the classification of masonry buildings are considered as the number of stories, load-bearing wall material, regularity in plan and the arrangement of walls (required length, openings in walls, etc.), in accordance with the observations from previous earthquakes and field databases. The fragility curves are generated by using time history (for demand) and pushover (for capacity) analyses. From the generated sets of fragility curves, it is observed that the damage state probabilities are significantly influenced from the number of stories and wall material strength. In the second stage of the study, the generated fragility curves are employed to estimate the damage of masonry buildings in Dinar after the 1995 earthquake. The estimated damage by fragility information is compared with the inspected visual damage as assessed from the Damage Evaluation Form. For the quantification of fragility-based damage, a single-valued index, named as 'vulnerability score' (VS), is proposed. There seems to be a fair agreement between the two damage measures. In addition to this, decisions regarding the repair or demolition of masonry buildings in Dinar due to visual damage inspection are on comparable grounds with the relative measure obtained from VS of the same buildings. Hence, the fragility-based procedure can provide an alternative for the seismic safety evaluation of masonry buildings in Turkey. Copyright (C) 2007 John Wiley & Sons, Ltd

Importance of Degrading Behavior for Seismic Performance Evaluation of Simple Structural Systems

This study focuses on effect of degradation characteristics on seismic performance of simple structural systems. Equivalent single degree of freedom systems are used for which the structural characteristics are taken from existing reinforced concrete (RC) frame buildings. Simulation of degrading behavior is achieved by considering actual experimental data. To obtain the seismic response of degrading structural systems, two different approaches are used: inelastic spectral analysis and fragility analysis. According to the results obtained from both approaches, degrading behavior is dominant for mid-rise RC frame buildings as it significantly amplifies seismic demand. Hence, in performance-based assessment approaches, analytical modeling of such degrading structures should be carried out carefully

Fragility-based assessment of typical mid-rise and low-rise RC buildings in Turkey

This paper focuses on the seismic fragility assessment of typical low-rise and mid-rise reinforced concrete (RC) buildings in Turkey by considering Duzce Damage database, which was compiled after the two devastating earthquakes in 1999 that affected the Marmara region. A set of fragility curves is developed by making use of the building characteristics in the database. The generated fragility curve set is referred as "reference" since it forms the basis of a parametric study. Then the influence of sampling techniques, sample size, type of hysteresis model and limit state definitions on the fragility curves is investigated. The results revealed that the uncertainty in capacity and degradation characteristics have a significant influence whereas the other investigated parameters do not seem to have an important role on the final fragility functions. In the last part of the study, the damage observed in Duzce buildings after 1999 earthquakes is estimated by using the generated fragility curves for low-rise and mid-rise RC frame buildings. Estimated damage distributions seem to be comparable with the actual damage data

Energy based seismic evaluation of degrading systems

Ph.D. - Doctoral Progra

Seismic Risk Assessment of Masonry Buildings in Istanbul for Effective Risk Mitigation

Unreinforced and non-engineered masonry buildings are highly vulnerable to seismic hazard and constitute a significant percentage of earthquake losses, including both casualties and economic losses. This study presents an engineering application on seismic safety assessment of unreinforced masonry (URM) buildings in Istanbul, Turkey, a metropolitan city under very high seismic risk. Nearly 20,000 masonry buildings were examined through a two-stage assessment procedure in order to identify the addresses of those buildings which are under high seismic risk. Furthermore, the obtained database can be employed in the preparation of an earthquake mitigation strategy for the expected major earthquake in Istanbul. In the first-stage evaluation, buildings are examined visually from the street by considering their basic structural parameters and they are ranked within a priority list in terms of the calculated seismic risk. Next, the buildings identified with higher risk are evaluated in the second stage by using a more detailed procedure. The developed procedure is both an optimal and a practical tool in the seismic risk assessment of large masonry building stocks in a short period of time with limited resources. [DOI: 10.1193/1.3464344

A case study for seismic assessment and restoration of historic buildings: The Arditi residence

This chapter focuses on seismic assessment and restoration of one of the numerous historical buildings in Turkey; the Arditi Residence in Urla, Izmir. It is a 150 years old two story masonry building located in a seismically active region. From the structural point of view, the building can be regarded as a mixed system since three different techniques had been used during the construction. The Arditi Residence has been investigated in three stages: preliminary evaluation, seismic performance assessment and intervention. The building has been observed to possess serious deficiencies, which are not easy to handle due to the complexity of the construction system. On the other hand, the proposed intervention strategies should have the minimal impact on the historic information building carrying and provide a certain level of safety against the seismic demands. Overall, the chapter presents a contribution to seismic assessment and restoration of historical structures on the basis of Arditi Residence, a unique historical building with serious problems in an earthquake-prone region

Seismic energy dissipation in deteriorating systems through low-cycle fatigue

Energy dissipation characteristics of structural members which exhibit both strength and stiffness deterioration under imposed displacement reversals are investigated. In the experimental part, 17 reinforced concrete beam specimens were tested under constant and variable amplitude inelastic displacement cycles. The constant-amplitude tests were employed to determine the low-cycle fatigue behaviour of specimens where the imposed displacement amplitude was the major variable. A two-parameter fatigue model was developed in order to express the variation of dissipated energy with the number of displacement cycles. This model was then used to predict the energy dissipation of test specimens subjected to variable-amplitude displacement cycles simulating severe seismic excitations. It has been demonstrated that the remaining energy dissipation capacity in a forthcoming displacement cycle is dependent on the energy dissipated along the completed displacement path. Moreover, it is observed that total energy dissipation is dependent on the length of the displacement path. Copyright (C) 2003 John Wiley Sons, Ltd