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Abstract
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From the past up to now, selecting a reliable structural system as well as analyzing and designing it accurately
have considerably attracted the attention of researchers and engineers. An appropriate evaluation of the dynamic
characteristics of the structures such as natural frequency and damping ratio has a considerable effect on the
accurate analysis and design of structures. In addition, the vulnerability assessment of structures plays a significant
role in selecting a resilient structural system against the seismicity of the area. In the light of these facts,
one of the most important challenges is that the effects of non-structural components (NSCs) are commonly
considered as a concentrated/distributed mass in most FE models and their stiffness and damping ratio are
ignored. Therefore, this research aims to figure out the effects of NSCs on the dynamic characteristics and the
vulnerability indices of concrete structures using microtremor measurements. For this purpose, the ambient
vibrations of four concrete buildings (with two bending frame and two shear wall structural systems) during the
construction process are measured in three independent stages: (1) after the completion of the structural system;
(2) after the completion of the interior and exterior partition walls; (3) after the completion of the flooring,
facade, and parapet elements (when the building is completely constructed). Afterward, to extract the dynamic
characteristics and to compute the vulnerability indices of the structures, the measured microtremors are subjected
to two signal processing techniques, i.e., floor spectral ratio (FSR) and random decrement method (RDM).
It is observed that, by taking the effects of NSCs into account, the values of both dynamic characteristics of the
concrete structures (i.e., natural frequency and damping ratio) are increased when the buildings are under the
erection process. Furthermore, the obtained results for the concrete structures with the bending frame
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