Study on Change in Modal Parameters of RC Beams Due to Fatigue Type Damage

Vibration monitoring of civil engineering structures has gained a lot of interest over the past few years, due to the relative ease of instrumentation and the development of new powerful system identification techniques. The damage assessment consists of relating the dynamic characteristics to a damage pattern of the structures. This paper presents experimental results obtained within the framework of the development of a health monitoring system for civil engineering structures, based on the changes of dynamic characteristics. As a part of this research, Reinforced concrete beams subjected to cyclic loading to introduce damage. After each loading phase, an experimental modal analysis is performed on the beams with the impact hammer to obtain dynamic characteristics. Beams were excited with the impact hammer over a frequency range of interest 0-4000Hz. Frequency response functions (FRFs) were obtained using OROS Dynamic vibration analyzer. The FRFs were processed using NV Solutions modal analysis software to identify natural frequencies, Damping ratios and the corresponding mode shapes of the beams. A characteristic decrease of natural frequencies and an increase of structural damping were observed.