Effect of loading on the damage assessment of reinforced concrete beams

Quantitative condition assessment of structures has been traditional using proof load test leading to an indication of the load-carrying capacity. Alternative approaches using ultrasonic, dynamics, etc. are based on the unloaded state of the structure and anomalies may not be fully mobilised in the load resisting path and thus their effects are not included completely in the measured responses. This paper studies the effect of the load carried by a reinforced concrete beam, on the final assessment result of the crack damage. The assessment can only be performed with an approach based on static measurement. The crack damage is modelled as a crack zone over an area of high tensile stress of the member, and it is represented by a damage function. The nonlinear optimisation required for the assessment is solved iteratively. The identified damage extent from properly selected loads and from a low load level are compared, and it is concluded that accurate assessment can only be obtained when a load close to the one that creates the damage is used in the identification.