Nondestructive evaluation of stress states of steel bars reinforcing concrete structures

Adapting and remodeling existing buildings has become an important task. Changes in use of existing buildings of reinforced concrete structure require an analysis of the load state of each component, especially of the floors and ceilings. The longitudinal stress in the reinforcing bars is helpful information for the estimation of the remaining load capacity. Nondestructive micromagnetic and ultrasonic methods are in use to evaluate the stress state of machinery components already. Since the present state of the micromagnetic techniques already allow for an on-site application, the ongoing studies concentrate on micromagnetic techniques to evaluate the longitudinal stress state of bars reinforcing concrete structures. First applications and the adaptations needed for a reliable stress analysis on-site are the subject of this contribution. The stress results still show unacceptably large deviations from the reference values, but improvements of the sensor and of the preparation of the measuring positions have more accurate results in prospect.