Experimental Structural Analysis of Hybrid Composite-Concrete Beams by Digital Image Correlation (DIC) and Acoustic Emission (AE)

The use of composites such as textile reinforced cements (TRCs) and fibre reinforced polymers (FRPs) enables the development of lightweight structures. Such a lightweight solution for floor renovation consists of a hybrid composite-concrete cross section: prefabricated beams (TRC–CFRP reinforced hollow boxes with concrete on top) support sandwich panels together with a finishing concrete compression layer creating a monolithic hybrid floor. As the hybrid beams are the main structural element of this floor system, their load-bearing and failure behaviour should be fully understood. In order to examine the optimal design of these structures in terms of load bearing capacity, the beams are separately tested in four point bending while the amount of CFRP reinforcement and the concrete thickness are varied. The digital image correlation (DIC) and acoustic emission (AE) measuring techniques are applied in a complimentary way to monitor the bending and failure behaviour of the full scale hybrid beams. DIC visualises the development of surface strain fields together with the exact cracking patterns in relation to the applied load. AE contributes in defining the load at the onset of serious cracking activity. Furthermore, AE characterizes the contribution of the different fracture modes that may vary from concrete cracking, delamination between the successive layers of the TRC or debonding at the interphase between the TRC hollow box and the concrete on the one hand and the CFRP on the other hand.