Damage Evaluation of Reinforced Concrete structures at lap splices of tensional steel bars using Bonded Piezoelectric Transducers

Using bonded piezoelectric transducers (PZT), this study evaluates damage to reinforced concrete beams at lap splices of tensile rebars. Four reinforced concrete beams with a span of 2700mm and a cross-section of 200 x 250mm were cast and simply edge-supported on roller supports 2250mm apart. In the zone of constant moment, the tensile reinforcements of the beams were spliced with varying lap lengths (10 ϕ , 20 ϕ , 30 ϕ and 40 ϕ ). Two PZT patches (one to operate as an actuator and the other as a receiver) were bonded on steel rebars and placed 50mm apart from their lapping edges. The wave propagation technique was used to record the signals experimentally, and the signals were processed further using wavelet packet analysis. By setting the time lag results of waves under pulse excitation, the damage of beams were identified. Damage indices were calculated based on the wavelet packet energy to ascertain the damage levels. The PZT was very sensitive to detect the pull-out bond failure and ductile flexural failure at the lap slices of steel rebars in the beam and it gives an advance indication before the structural collapse due to brittle failure.