A method to search rigorously three dimensional displacements and stresses of multi-layer slab is developed by using thick plate theory. In viewpoint of mechanics damaged RC slab strengthened by aramid or carbon fiber sheets on bottom surface can be treated similar to multi-layer slab. In this paper bond stresses operated on interfaces of once stiffened slab with released portion are mainly calculated by means of multi-layer slab and then stresses of twice reparative slab are mentioned numerically. From comparison magnitude of bond stresses of aramid sheets with carbon sheets around released portions under wheel loading, it is found that the maximum value obtained from aramid sheets are lower than value by carbon sheets.

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In this study, wheel load fatigue tests were carried out to evaluate the fatigue resistance of two types of test specimen that were strengthened by bonding CFS to strengthen an RC slabs. To evaluate the fatigue resistance, S-N curve equations are proposed from the equivalent number of loading repetitions to which a D-N curve and various degradation factors were applied in order to estimate the drying conditions, humidity conditions, and the period for re-strengthening. The results showed that the life time according to conventional prediction equations was several hundreds of years; the equivalent number of loading repetitions obtained from the proposed S-N equation was about 33% of the equivalent number of load repetitions from conventional wheel load fatigue tests, and approached the number of years' life of actual bridge slabs.

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In this study, the effect on the fatigue resistance of the area over which adhesive was used on the overlay interface of RC slabs strengthened by SFRC Upper Surface thickness increasing method was verified. The results showed that peeling at the thickening boundary occurred early in test specimens without adhesive. A strengthening effect of a factor of 1.6 relative to test specimens with no adhesive was obtained for test specimens that were partially bonded over construction joints. However, peeling occurred early in the areas where adhesive was not applied in test specimens that were partially bonded in the pattern of picture frames, where the effect of the adhesive was not seen. In test specimens where the adhesive was applied over the whole surface, the integrity was maintained as a result of the adhesive, and a strengthening effect of a factor of 4 was obtained relative to test specimens with no adhesive.

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In this study, the fatigue resistance of RC slabs were evaluated. These RC slabs were strengthened by applying adhesive to the existing side surfaces and the boundary of thes slab thickened and replaced the slab, partially and thickened the top surface with SFRC, as measures to strengthen RC slabs with deterioration or RC slabs that had been given primary strengthening that had partially fallen off. As a results, it was shown that by applying adhesive to the side surfaces of existing RC slabs with slab replacement together with strengthening by thickening with SFRC on the top surface, integrity was maintained and a strengthening effect of the RC slabs of a factor of 67 was obtained. Therefore, service life of slabs with deterioration or spalling can be extemded by applying the proposed partial replacement strengthening method.

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In this study, wheel running load tests were carried out on test specimens given primary and secondary strengthening to evaluate the fatigue resistance and verify the failure modes. The test specimens were 1) normal RC test specimen, 2) damaged RC test specimen reinforced SFRC overlay and then CFS reinforced at bottom, and 3) damaged RC test specimen reinforced CFS at bottom and then SFRC overlay. The result showed that, in the equivalent running cycle of the 2^nd and 3^rd test specimens, the fatigue strength were 140 and 128 times stronger than 1^st test specimen. Therefore, 100 years maintenance is possible by carrying out primary and secondary strengthening of RC slabs when the deflection of the slab reaches 1/400 of the span L.

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This study aims to obtain the suitable method for measuring water at the rough surface of concrete slabs, the applicability of microwave moisture tester, which is ordinary used at sites.In order to verify the performance of new developed water moisture tester with electrical resistance was checked throughout this empirical study. As a result, the good correlation between the value measured by the water moisture tester with electrical resistance and water content ratio of the concrete slab was found.

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The mechanisms of fatigue failure in concrete decks strengthened with steel plate bonding were examined based on the results obtained from a truck wheel traveling test. The preloading for the deck prior to plating induced severe deterioration indicating arch action and membrane action. The bonded plates fully restored the deteriorated deck to the condition indicating deck action. The plated deck also indicated the arch action in the process of the fatigue deterioration. Additionally, data containing previous tests suggest that the fatigue life of the plated decks may be evaluated using the modified Matsui's index P'_sx the same as non-plated decks, although the steel plates should be ignored in calculating the neutral axis of the transverse section because of the debonding of the joints between the plates.

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Wheel running test using real size specimens was carried out to confirm stress reduction effect, durability and fracture behavior of Steel Fiber Reinforced Concrete (SFRC) pavement on Orthotropic Steel Deck (OSD). After wheel running test, fatigue cracks in studs and peeling in epoxide resin adhesive were observed. Analytical studies have been conducted using 3-D finite element model in order to confirm the fracture behavior. In analysis, studs were modeled by spring element. Based on the results of wheel running test and analysis, we confirmed fracture behavior of SFRC on OSD.

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On highway bridges in snowy regions, it is necessary to widen existing slabs to ensure required width because the narrow width due to snow bank on shoulders affects safaty and amenity of running and walking. This study presents a widening method of existing RC slabs using FRP with light weight and high corrosion resistance and investigates fundamental behaviors of the composite slab such as stress characteristics, cyclic properties, ultimate load and failure modes by static loading test and cyclic loading test. As the results, significant damage was not observed in the test specimen under both static and cyclic loading with 100kN, referring to design wheel load. Also, in ultimate loading test, the strucrural integrity between RC and FRP slabs was ensured after failure.

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A steel-concrete composite slab is proved to have high durability by wheel-load running test. A number of highway bridge constructions with the composite slabs are increasing every year. At the recently, the composite slabs are applied for some replacement works of deteriorated RC slabs.The composite slab has steel plate under its bttom side, concrete state or fatigue damage of studs can't be check by eye inspection.In this paper, the authors show a study on applicability of infrared thermography as nondestructive testing for the steel-concrete composite slab at the time of constuction and maintenance.

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Using a MEMS sensor network, we develop a three dimensional visualization system of dynamic behavior for a bridge deck. In our system, time series of acceleration data measured simultaneously at multisite are transferred to a laptop computer at a base-station with the wireless data connection, and then converted to displacement data by a numerical integral method. From the visualization results, the characteristic vibration modes including bending and torsional higher modes can be identified by applying digital filters of narrow bands. Here, the data measurement for the deck of a pedestrian bridge is conducted, and some characteristic vibration modes are extracted from the visualization results. The vibration modes obtained from the experiment show good agreements with numerical results obtained by a finite element method based on the Lanczos method.

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