Abstract
The utilization and effectiveness of a custom-made, portable and low-cost structural health monitoring (SHM) system that implements the PZT-based electro-mechanical admittance (EMA) methodology for the detection and evaluation of the damage of flexural reinforced concrete (RC) beams is presented. Tests of large-scale beams under monotonic and cyclic reversal-imposed deformations have been carried out using an integrated wireless impedance/admittance monitoring system (WiAMS) that employs the voltage measurements of PZT transducers. Small-sized PZT patches that have been epoxy-bonded on the steel bars surface and on the external concrete face of the beams are utilized to diagnose damages caused by steel yielding and concrete cracking. Excitations and simultaneous measurements of the voltage signal responses of the PZT transducers have been carried out at different levels of the applied load during the tests using the developed SHM devices, which are remotely controlled by a terminal emulator. Each PZT output voltage versus frequency response is transferred wireless and in real-time. Statistical index values are calculated based on the signals of the PZT transducers to represent the differences between their baseline response at the healthy state of the beam and their response at each loading/damage level. Finite Element Modeling (FEM) simulation of the tested beams has also been performed to acquire numerical results concerning the internal cracks, the steel strains and the energy dissipation and instability parameters. FEM analyses are used to verify the experimental results and to support the visual observations for a more precise damage evaluation. Findings of this study indicate that the proposed SHM system with the implementation of two different PZT transducer settings can be effectively utilized for the assessment of structural damage caused by concrete cracking and steel yielding in flexural beams under monotonic and cyclic loading.
Highlights
An extreme event such as an earthquake can inflict extensive cracking and severe damage on reinforced concrete (RC) infrastructures
The responses at the “Healthy” state and the “Damage 2” and “Damage 4” levels that correspond to the unloading state of the positive and negative, respectively, first loading cycle are more less the same. This is justified by the fact that piezoelectric of lead zirconate titanate (PZT) 1S is bonded on the steel tension reinforcing bar that remained elastic during the first loading cycle, no damage has occurred at the unloading state of “Damage 2” and “Damage 4” levels
The previous remarks provide sound indications that the proposed structural health monitoring (SHM) technique with the implementation of two different PZT transducer settings can be effectively utilized to access of structural damage caused by concrete cracking and steel yielding in flexural beams under monotonic and cyclic loading
Summary
An extreme event such as an earthquake can inflict extensive cracking and severe damage on reinforced concrete (RC) infrastructures. Numerous local nondestructive techniques such as acoustic emission, ultrasonic techniques, eddy currents, impact echo testing, magnetic field, penetrant dye testing, infrared thermography and Xray methods have been developed to diagnose or/and to localize cracks, irregularities and structural defects [10,11,12,13,14]. Each of these techniques has specific advantages and limitations, such as a need for prior knowledge or at least an approximation of the damage location, time-consuming inspection procedures and, difficulties to be applied to real-life structures [15,16,17]
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