| Summary: | 碩士 === 國立臺北科技大學 === 土木工程系土木與防災碩士班 === 106 === Reinforced concrete structure is exposed to open air. High temperature or chemical environment causes the concrete cover to crack. Then, moisture or chloride intrudes into the cracks, directly contacting the reinforcement steel and causing reinforcement steel to corrode. As the crack widens, corrosion accelerates and affects the interfacial bonding between concrete and reinforcement steel. The conventional non-destructive testing (NDT) focuses on the concrete damage without discussing the internal damage occurring to the interfacial bonding between reinforced steel and concrete. Therefore, this study intended to construct a damage assessment technique in order to measure the interfacial bonding between reinforcement steel and concrete (ductile-brittle interface), using guided wave to measure the damages occurring to reinforced concrete in order to detect and explain the bond damages, and at the same time introducing the conceptual model of material-interface-defect as the core index of bond damage assessment technique to examine the wave-propagating behaviors on the surface of reinforced concrete.
Rectangular specimen was produced using reinforced concrete with design strength 420 kgf/cm2 as the primary material for the experiment. The details of the specimen – reinforcement steel cover’s thickness 1.5, 4 cm, type of reinforcement steel, normalized thickness diameter ratio (c/db, cover’s thickness divided by reinforcement steel’s diameter), damage’s length (30 cm) and thickness (0.3 cm) – were used as experimental variables. Reinforcement steel was packed with plastic bubble wrap to simulate the opening of interfacial bonding for the guided wave to detect the damage preliminarily. Multi-channel seismic surface wave was measured. Broadband receiver and steel balls were used together in the experiment.
According to the preliminary detection, seismics serves as the comparison group when it is not under the influence of reinforcement steel. If reinforcement steel is found in seismics, reinforcement steel can be detected. If the bond is totally damaged, seismic signals indicate the specimen in the shallow level of concrete, having a noticeable amplitude of dispersion that is concentrated with an amplified effect, which will be investigated in a later stage. Based on the preliminary detection and explanation of the multi-channel seismic for the surface wave measured by guided wave, this study presented the difference between the guided wave signals with damage and the guided wave signals without damage based on the assessment of the damages occurring to the interfacial bonding in order to demonstrate the guided wave measurement method presented by this study has the potential to detect reinforcement steel and the damages occurring to the structures. In the subsequent researches, the bond damages resulted from actual damage (e.g. real fire) will be investigated.
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