Structural Damage Detection in Reinforced Concrete Beams Using Modal Damping Measurements

摘要

Damage detection by evaluation of dynamic system characteristics has received considerable attention in recent years. The development of new powerful systems in data acquisition and signal processing allows to determine accurately the dynamic system characteristics. It is noted that eigenfrequencies and mode shapes are the most commonly used dynamic parameters for the description of the structural behavior and damage evaluation in structures. Damping properties are less used in this framework because of difficulties in performing accurate damping measurements and because of the complexity of the damping phenomena in reinforced concrete structures. The present paper applies the energy balance approach on cracked reinforced concrete beam, in order to understand the evolution of material damping with crack damage. An approach based on finite element modeling is proposed. In the model, two degradation processes in the reinforcement concrete material are considered: the decrease of rigidity in the section where the crack damage occurs and the friction effect due to relative motion of the crack edges. It appears that the two processes lead to opposite damping evolution; the decrease of the rigidity in the concrete matrix results apparently in the decrease of the total damping of the reinforced concrete beam while the friction effect has as tendency to increase the total damping.