Modal-based damage assessment methods are efficient tools to identify location and magnitude of damage associated to change of modal properties (natural frequencies, modal damping ratios and mode shapes). However, while numerous applications of these methods to simple structural systems (i.e. simple shape structure made of homogeneous material, submitted to well-known boundary conditions...) have proved their efficiency, quite a few studies have been conducted to complex civil engineering structures. This paper presents then the experimental modal analysis applied to reinforced concrete beam-column joint. During tests, a full-scale specimen was subjected to cyclic loading to introduce damage. After each loading phase, specimens were excited with an impact hammer to determine the current modal parameters. The main objective of is to identify from the after-impact responses, the changes occurred in the modal parameters due to damage induced by loading. Structural tests and model used to interpret the experimental result are presented. The capability of the proposed approach to detect small level damage as well as the impact of the measurement errors are then discussed.