Static and dynamic stiffness of reinforced concrete beams

In this paper experimental studies of reinforced concrete beams are reported. The influence of load on deflections and basic eigenfrequency was investigated. Eigenfrequencies were registered using the operational modal analysis. Static stiffness (on the basis of deflections) and dynamic stiffness (on the basis of eigenfrequencies) were obtained indirectly (with calculations). A comparative analysis shows that these figures differ in value. The paper is completed with the theoretical analysis.