Smart monitoring of strengthened beams made of ultrahigh performance concrete using integrated and nonintegrated acoustic emission approach

Summary Ultrahigh performance concrete (UHPC) is one of the recent advancements in construction building materials and popularly used as a precast applications or strengthening material. The current paper attempts to improve understanding about fracture and failure mechanisms of UHPC application as a strengthening material using acoustic emission (AE) technique. The paper proposes an integrated and nonintegrated approach to relate the mechanical energy with AE energy for (i) undamaged reinforced concrete (RC) beams and (ii) damaged RC beams strengthened with UHPC. The integrated approach evaluates the damage mechanisms by evaluating sentry function (logarithmic ratio of mechanical and acoustic energy), while nonintegrated approach considers superimposition of flexure and AE response, load versus AE energy behavior and damage index. To validate the proposed approach, experiments are conducted on (i) control RC beams and (ii) RC beams strengthened with UHPC layers of t, 1.5t, and 2t thickness (where t = 10 mm). From the study, it is found that analysis of structures using both the approaches can overcome corresponding limitations. Hence, to completely characterize the damage, both methods are recommended.