| Budget Amount *help |
¥8,630,000 (Direct Cost: ¥8,000,000、Indirect Cost: ¥630,000)
Fiscal Year 2007: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000)
Fiscal Year 2006: ¥5,900,000 (Direct Cost: ¥5,900,000)
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| Research Abstract |
Generally, concrete inspections are applied to determine the current strength and durability of a structure. However it is difficult to determine the strength and performance of a structure from inspection results, therefore currently indirect estimation from visual observation of cracks, corrosion levels from nondestructive test among others are used. Therefore, developing a method to directly determine the current conditions of a structure in a standardized manner will enhance rationalization of management of structures.
In this study, first, various non-destructive tests (Ultrasonic Methods, Half Cell Potential Methods and Polarization Resistance Methods) were performed on reinforced concrete beams whose reinforcing bars have been corroded through electricity. The specimen was a rein-forced concrete beam of width 230 mm, height 230 mm and length 1500 mm with the tensile side having 3 reinforcing bar at a 75 mm span. The rebar cover was 33 mm from the sides and bottom of the specimen.
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Corrosion enhancement experiment was conducted to rebar. The specimen was placed on top of a metallic plate sat at the bottom of a stainless steel container full with 3% saline solution. A circuit was made with the metallic plate as the cathode and the rebar protruding from the specimen as the anode and 1Amp direct current fed into the circuit. Two periods of current flow, 14 days and 28 days were set in order to have specimens with varying levels of corrosion. Second, damage maps were made which reflect the results of nondestructive tests. The results were then input into finite element method (FEM) analysis and the mechanical performance of the test specimens investigated. Last, the adequacy of the FEM analysis results were confirmed by carrying out flexural loading tests on the rein-forced concrete beams whom reinforcing bar have been corroded.
The following conclusions were obtained in this study.
1. It was possible to grasp the extent of deterioration in a corroded reinforced concrete beam from deterioration maps estimated by results of various nondestructive test methods. Furthermore, the use of FEM analysis as an effective method in evaluation of structures' mechanical performance was confirmed.
2. It was possible to use FEM analysis utilizing results from nondestructive test, to simulate on the whole the crack properties and load-displacement response of reinforced concrete beams with corroded rebar. However, FEM analysis was unable to simulate loading tests with peculiar failure modes. From the above, it is of the view that the importance to replicate cracks on the concrete surface caused by corrosion, in the analysis model has been made clear. Less
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