Damage evaluation of UHPC-GFRP hybrid beams based on acoustic emission technology under bending experiment

The ultra-high performance concrete (UHPC)-glass fiber reinforced polymers (GFRP) hybrid beam is a novel concrete structure. To evaluate effectively the damage status and crack propagation of the UHPC-GFRP hybrid beams under bending, the specimens UHPC-GFRP hybrid beam (UGCB) and GFRP hybrid beam (GNCB) were designed, and the damage process of the specimens was monitored under the bending of four-point based on the acoustic emission (AE) technology. Results indicated that UHPC material enhanced better the bearing capacity of specimen UGCB, and the signal characteristics of accumulated AE energy, events, and ringing count could characterize the damage development of hybrid beams. The AE Ib-value had a decreasing trend due to the continuous generation of the macro-cracks, and the damage of the specimen GNCB was more serious. The proportion of the amount of shear cracks in the specimens increased gradually in case of the bending, and the proportion of shear cracks of specimen UGCB was 65%, and the specimen GNCB was 70% when the specimens were damaged to failure, and the strengthening of the UHPC reduced effectively the generation of shear cracks. The boundary of the HI and Sr values of failure region corresponding to the failure of the hybrid beam was proposed, and the Sr value was more responsive to the development of microcracks. This study provides some reference for the evaluation of the damage development of the UHPC-GFRP hybrid beams.