## 1 Introduction
Its collapse potential was evaluated and fragility functions obtained through incremental dynamic analyses. The assessment methodology and the modeling procedures for RC walls in a high-rise building has been presented in [18], where the assessment of the seismic capacity of tall buildings using nonlinear finite element modeling was conducted. In this study, the behavior of RC shear walls was validated through experimentally cyclic static tests. In addition, several pushover analyses and response history analyses were performed. Due to many unknowns and the unreliability of the modeling, it is very important to determine the collapse mechanism of the structure on the basis of the global ductility being assessed, and the critical elements being detected. A valuable study on the topic of RC buildings is presented in [19]. Another interesting study that may be applied to instrumented buildings has been presented in [20] where authors have developed a decision-making framework for post-earthquake assessments. The proposed framework, illustrated on the testbed hotel, comprises seismic instrumentation which measures the dynamic response during a seismic event, uncertainty modeling, dynamic response reconstruction, damage estimation, and performance-based assessments and decision-making. This performance-based framework may be used by structural engineers, emergency managers and other relevant personnel to help them make informed and swift decisions regarding post-earthquake assessments of critical instrumented building structures. The paper [21] presents and discusses five procedures for the assessment of the seismic performance of low-rise RC buildings at different levels of complexity, applied to three RC building examples (a bare frame, a frame with infills forming a soft first story and a dual frame-wall). The procedures differ regarding both the input data needed and the accuracy of their results. The results of the procedures at the simpler levels are more conservative, while the procedures at the higher levels yield, in the case of the tested examples, similar results, although they differ in the amount of input data and computational work needed. The authors concluded that the initial effective stiffness of the structure proved to be the most important quantity which determines the seismic demand, while the capacity/demand (C/D) ratio is not much influenced by the selection of the assessment parameter. Further research on the definitions of capacities, especially the shear capacity, has been suggested. In line with the state-of-the-art experimental and numerical procedures for the assessment of the realistic seismic performance of structures, this paper presents comprehensive, but still simple and easily implementable, methodology. This methodology, explained in more detail in the next section, applies a thorough approach for the assessment of structural performances during seismic actions with the aim of reducing the uncertainties of all significant parameters in calculations. The analysis stages from the simpler linear analyses to more complex nonlinear ones complement and verify each other in order to avoid errors and a wrong interpretation of the results. The assessment methodology is presented in detail on the case-study of an existing irregular RC hospital building, constructed as the wall system, located in a very seismically-active part of Croatia. The results of the comprehensive seismic performance assessment include the building collapse mechanisms and identification of critical structural elements. Following detailed seismic assessments, specific measures for a target retrofit are proposed. In addition to prevention measures, results of the performed assessment may be used to facilitate post-earthquake procedures (e.g., damage assessments and evaluations of building load-bearing capacities), particularly for situations in which a rescue of occupants has to be initiated by civil protection and rescue intervention teams and when partial collapses have to be resolved [22].