Composite members made of steel and concrete have been widely adopted for undersea tunnels. Since steel plates are exposed to the internal side of the tunnel, vehicle fire countermeasures are required. First, the RABT heating test for the composite members without the fireproof board was executed, and the damage and the deterioration of the internal concrete were examined. Next, the transmission mechanism of heat in the air layer between the fireproof board and the steel was aloso examined by the element test to mesure the heat flow by the radiation, convection, and the conduction. Furthermore, the RABT heating test with fireproof board was executed, and the internal temperature was measured and the effect of the air layer was confirmed. Finally, validity of the proposed analytical model was confirmed by comparing the heat analysis results with the heat tests results.
Adequate curing of concrete at early ages is very important to demonstrate a required performance after hardening such as strength, durability and cracking resistance. In this study, compressive strength tests of ordinary portland cement concrete that cured under various moisture curing condition were conducted in order to estimate the effects of extension of moisture curing period and water supplying curing. And the influence of moisture curing conditions on the hydration reaction of cement were evaluated and the compressive strength development were estimated considering the volume of hydration products of cement. As a result, it was assumed to be clear to be able to evaluate the strength development behaviors of concrete under various moisture conditions by considering the influence of water retaining condition on the hydration velocities of cement.
In this paper, experiments and finite element analyses were conducted in order to evaluate effects of ASR on structural performance of RC and PC structures. From the experimental results, it was confirmed that the ASR expansion was affected by the restraint of reinforcement and the magnitude of prestress. The material properties of concrete damaged by ASR had anisotropic characteristics depending on the degree of ASR expansion. Therefore, when the structural performance of RC and PC structures were evaluated by using the material properties of core concrete, the direction and place where cylinder specimens were cored should be considered. On the other hand, by means of proposed analytical method, ASR expansion behaviors of RC and PC beams and changing of their structural performance were evaluated. As the results, it was confirmed that PC structure had much advantage comparing with RC structure regarding the structural performance under ASR damage because of restraint by prestress against the ASR.
This research focuses on the Fiber Reinforcement Concrete(FRC) and its performance on musical tones. Thepossibility of future musical instruments made of this concrete is discussed. Recently, the technical properties of FRC had been improved and the different production styles, such as unit weight of binding material and volume of fiber in the structure, hardly affects the results of the acoustics. However, the board thickness in the FRC instruments is directly related with the variety of musical tone. The FRC musical effects were compared with those produced with wood on wind instruments. The sounds were compared with those produced with woodwind instruments. The sound pressure level was affected by the material and it becomes remarkably notorious in the high frequency levels. These differences had great influence on the spectrum analysis of the tone in the wind instruments and the sensory test. The results from the sensory test show dominant performances of brightness, beauty and power in the FRC instruments compared with those made of wood.
In upper slabs of caisson foundation, a seismic desi gn is difficult with an incr ease in earthquake load. So we carried out loading tests and FEM analysis for upper slabs of caisson foundation. As a result, we proposed a new design method which takes into co nsideration the effective width on the pull out side based on crack pattern of test specimens, which is not considered in the existing design method. Moreover, we proposed a rational design method based on load carrying mechanism for upper slabs of caisson foundation.
The surface penetrants (silane-type) are expected to help control the deterioration of concrete caused by combined action due to freeze-thaw and chloride. Although the method offers high economic efficiency and workability and cases of its implementation are increasing, no durability verification method and deterioration prediction method after construction have yet been established. A field test and exposure test were conducted on the wheel-guard concrete of a road bridge and seaside testing ground in Hokkaido to evaluate the persistence of the effect of these materials. Persistence of the scaling control effect was confirmed in the case of application to a replacement member. In addition, the effect on the reduction of the life cycle cost was evaluated based on the findings of the study.
In this study, reed planting tests were carried out at the Biyo-center, an experiment station on the Lake Biwa shore, in order to evaluate the feasibility of a planting method with porous concrete (PoC method). Reed planting tests with coconut-fiber mats (mat method), which were generally used around Lake Biwa, were simultaneously carried out to compare with the PoC method. The reeds planted by the PoC method grew better than the ones planted by the mat method, and the number of reeds which were washed away by waves was smaller than that planted by the mat method. The result of the observation of reeds planted in the PoC showed plant maturation, and reeds could ta ke root into the PoC without interference with the voids of the PoC. As a result, it was shown that the reed planting tests with the PoC method was simple and effective, so it would become in harmony with the environment around Lake Biwa.
The relationship between the crack density and compressive strength of the core cylinder, which drilled from actual structure damaged by ASR, was investigated. The results showed that even if the crack density increased about 1.0m/m2, the compressive strength decreased only 2N/mm2. Then, the new method for estimating future compressive strength using the accumulation crack density in the current is proposed. In addition, the declining tendency of compressive strength by the ASR expansion was early proportional to the expansion, and it was examined on the reason for becoming gentle curve afterwards. As a technique, the detailed observation of ASR crack which arose in the loading test for the plane was carried out, after cylindrical specimen for test was cut in longitudinal direction. As the result, It was proven that the proportion in which line of rupture overlaps with the ASR crack was low, and the load is resisted by interlocking between coarse aggregate and concrete in the crack plane.
Tortuosity estimation model for a path of capillary pores was proposed using th e results of the thermo gravimetry under non-isothermal condition. This model is formulated based on the relative relationship between saturated porous sample and free water about the amount of dehydration in the elevated temperature process under same condition. The present model was applied to the measurement results of hardened cement pastes with a variety of types of water cement ratio (W/C), resulting in tortuosity being estimated ranging from 1.688 to 1.445 when W/C was 0.3 to 0.6. The formation factor calculated using the tortuosity conforms to Archie's law.
The cross-sectional area of reinforced concrete bridge piers and the number of longitudinal reinforcing bars required for bridge piers can be reduced by usin g high-strength reinforcing steel with a yield strength of 685 N/mm2. Reduction in the quantity of materials for bridge pier structures is effective in enhancing constructibility and reducing construction cost because pier foundations can be made smaller. As an example of use of high-strength reinforcing steel in reinforced concrete bridge piers, high-strength blast furnace steel has been used to reinforce tall (about 60 to 120 m) bridge piers made with concrete with a design strength of 50 N/mm2. In this study, verification was made, through a series of structural experiments, with respect to the structural characteristics of concrete piers reinforced with high-strength electric furnace steel. This paper re ports the findings that may help promote the use of high-strength reinforcing steel in reinforced concrete piers.
The total of 40 RC slabs extracted fr om existing port structures was tested in order to evaluate the relationship between visually judged deterioration grades and load carrying capacities. Wide variations were observed in the relati onship in each deterioration gr ade, however, the load carry ing capacity tended to be smaller than the design expectations when the symptom of deterioration appeared on the surface of concrete members. Moreover, the relationship was greatly influenced by localized deterioration and its position in the member. Based on the statistical analysis on the relationship between deterioration grades and load carrying capacities, the probabilistic evaluati on methods of the load carrying capacities of RC slabs and whole RC members in an open-type wharf were proposed as qu antitative evaluation methods of residual structural performance of existing port RC structures.