Seismic fragility curves for reinforced concrete buildings

TitleSeismic fragility curves for reinforced concrete buildings
Publication TypeThesis
Year of Publication2011
Papailia A
Thesis TypeMSc
Abstract

The purpose of this study is the development of fragility functions for generic archetypal Reinforced Concrete (RC) frame, wall and wall-frame buildings. All of the buildings are regular both in plan and in elevation. Buildings designed for seismic loading, and buildings designed only for gravity loads, are considered. In the later case, the pure frame buildings are considered with or without masonry infills. The especial case of frame systems with their ground storey open and with all of their other storeys infilled (pilotis buildings) is also examined. The variable parameters are the number of storeys (2, 5 and 8) and the level of seismic design, in terms of design Peak Ground Acceleration and design ductility level. An additional parameter for the infilled frames is the amount of infills, while for the wall-frame buildings is the fraction of seismic base shear taken by the walls. Additional studies are carried out considering the effect of the material properties and of the bay length on the building performance under seismic loading. Furthermore, the seismic performance of systems with frames of different stiffness is also examined. Within the SYNER-G project it has been agreed to harmonise fragility functions to two limit states, namely yielding and collapse. The analysis performed for the estimation of the peak response quantities is according to Eurocode 8 – Parts 1 and 3 – with certain simplifying assumptions for the frames. The design and the evaluation of the building performance is based on the results of linear elastic (equivalent) static analysis, for earthquake forced distributed over the height according to an assumed linear mode shape, termed “lateral force method” in Eurocode 8. The analysis gives the median value of the fragility curve corresponding to the damage scale and damage measure of interest. The dispersion (β value) of the fragility curve takes into account explicitly the model uncertainty for the estimation of the damage measure given the intensity measure and the uncertainty of the capacity in terms of the damage measure. This latter uncertainty includes both the model uncertainty and the dispersion of material and geometric properties considering their best estimates.
This thesis consists of 11 chapters and 2 Appendices. Chapter 1 presents an introduction to the fragility curves and their importance. In Chapter 2 are presented all the necessary definitions and the background for the construction of fragility curves. A brief review of previous studies is presented in Chapter 3. In Chapter 4 the material properties and the geometry of the buildings considered are described. Chapters 5 and 6 refer to the analysis performed for the seismic design or assessment and the design of the buildings, respectively. The seismic vulnerability assessment according to Part3 of Eurocode 8 is presented in Chapter 7. In Chapter 8 are given some basic definitions for the probability theory used in the development of the fragility curves. In Chapter 9 (the larger one in this book) some indicative fragility results are presented. Comments on the results are also included in the same chapter. The final conclusions of the study are presented in Chapter 10. In Chapter 11 the literature used in this study is presented. In Appendix A, the reader can find a more extensive part of the fragility curves; but not all of them. In Appendix B some indicative information about the design of the members is presented.

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