ABSTRACT
In the prefabricated concrete structure with wet connection, the interface of the pre-cast layer and the cast-in-place layer is a relative weak part. When subjected to cyclic loading, the degree of the structure damage needs to be quantified using some indexes as the damage indicators for the assessment and life prediction. Some traditional indicators such as deflection, stiffness, energy dissipation and stress (strain) state have been proposed. However, those traditional fatigue indicators may have difficulties to characterize the damage of the composite members since the interface damage actually dominates the structure damage. In this study, a magnetic signal detection method based on piezomagnetic effect is proposed as a new damage indicator to characterize the fatigue damage of composite beams. Static tests and fatigue tests were carried out on 15 T-shaped prefabricated concrete composite beams with 3 different design sections. The damage development of the composite beams is characterized by the mid-span deflection, stiffness, consumed energy and magnetic signal. The results show that the magnetic signal can reflect the fatigue damage process of composite beams with interfacial debonding. Setting the shear key at the interface has a great effect on the inhibition of interfacial debonding, which can be shown a more obvious performance improvement by using the magnetic signal. Compared with the traditional indicator, the fatigue damage detection based on the piezomagnetic effect is more sensitive to interface fatigue damage.
