Modal properties of partially damaged buildings

Abstract

During the lifespan of a structure many unpredictable events, that can endanger the life-safety of the inhabitants can occur. Such events are really hard to be predictd, during in the inital design phase due to their uncertain character. However in many cases during the history, the inadequate load transfer capacity of the bulidings, during an accidental action lead to catastrophic outcomes. The thesis focuses on the modal response of a 2D frame subjected to severall scenarios of column loss, having it`s body divided into five main chapters. The aim of the first chapter is to offer the general knowledge necessary to understand the importance of robustness in engineering. While the first part of the chapter focuses on offering the reader some of the major historical events that happened and highlights the importance of taking into consideration the occurrence of uncertainties during the service life of a building, it also presents the recommendations of nowadays building codes. Another subchapter focuses on presenting the available modal based damage identification methods. Ultimately by the end of the chapter, the general behaviour of a 2D structural frame during the loss of a column is described, such that a good foundation of informations is provided to the reader, in order to fully interpret the next chapters. In the second chapter the analyzed reference structure in terms of geometrical and mechanical properties, altogether with the applied modelling techniques and strategies to simulate the column loss during the eigenvalue analysis is described. In Chapter 3 the performed analysis results, considering three main column loss scenarios and two general situations are developed. Firstly the removal of the central column is done, while the IAP is kept in the elastic range. As it will follow the same column removal will be done also by considering the non linear behaviour of the IAP. In the next parts of the chapter, the same procedures will be applied in order to obtain the structural response in the case of the losses of intermediary and corner columns, respectively. In the body of the fourth chapter a parametric study, by increasing the number of spans from 4 to 6 and from 6 to 8, while keeping all the other geometrical and material parameters in the same range as in the case of the original reference frame is offered. Having the ultimate goal to find correspondence between the modal response of the aforementioned three frames. Lastly, in the fifth chapter the obtained results will be summarized, altogether with the general informations, that are concluded after the analyses.