In this paper, authors propose a new type of hybrid frame bridge connection consiting of steel girder and reinforced concrete pier. Through static cyclic-loading test, useful experimental data is obtained as a new type of connection of steel superstructure and substructure. As a result, the stress transfer mechanism of the rigid-frame structure can be made clear and the seismic performance of this structure was also clarified. Because of doing away with expensive bearing, this new type of hybrid frame can be expected to construct the bridge with high seismic resistant capacity saving in total construction cost.
The effect of fine powders (Blaine specific area over 6000cm2/g) from distinct minerals on rheological property of fresh concrete is investigated in this paper. It is found that the vitreous powders play a strong dispersion effect, which increasing the fluidity of concrete and decreasing the plastic viscosity of matrix mortar significantly; Non-vitreous powders cannot achieve a considerable increment of the fluidity of the concrete although it can lower the plastic viscosity. It is inferred from the experimental results that rheological property of the concrete can be highly correlated with the surface characteristic of the powders.
In the past, we presented a model of the carbonation reaction of concrete. For that, the chemical equilibrium in the pore-water was measured by its pH. This time, the pore structure was modeled on the mix proportion, the methods of handling and environmental conditions. In this paper, the results of the carbonation analyses are compared, using this model and the measurements of neutralization in existing reinforced concrete structures (in service for 19 to 29 years). Thus, regarding existing reinforced concrete structures, the comparison shows that this analytical model is useful for (1) predicting the progress of neutralization and (2) being adapted for performance certification and service life estimation.
The strength characteristic in the earthquake of Air Mortar has not been sufficiently clarified until now. So we carried out the static horizontal loading tests and shaking table tests. The followings were obtained from the present study; 1) Shear strength was evaluated by two parameters, i.e., upper load pressure and compressive strength; 2) The Air Mortar embankment breaks by shear in the earthquake, so it has to have enough shear strength.
This paper deals with the fa-Ike deformation analysis of reinforced concrete columns subjected to cyclic lateral loading as well as constant axial loading. For the geometrical nonlinearity, the finite deformation formulation is taken into consideration under the assumption of the Bernoulli-Euler beam theory. On the other hand, for the material nonlinearity, the sophisticated constitutive models, which are the two-surface model for steel and strain-softening model for concrete, are adopted into the finite element program FEAP. The numerical results have been compared with the experimental data with respect to cyclic deformation behavior of RC column including the post-peak behavior. An important remark is obtained from the present study that strain-softening type of constitutive model should be carefully used in the finite element analysis. At the final stage of present paper, modeling the buckling of steel bar is taken into consideration in the finite element analyses.
Recently, many types of hybrid structures with steel and concrete materials have come to be increasingly developed.Conugated steel web PC box bridge is one of these hybrid structures.On the other hand, this type of bridge has not been adopted yet for railway bridges, while these bridges have been constructed forhighway bridges.In this paper, we aim to confirm fatigue durability of joint part connecting the corrugated steel web plate with the concrete slab.The static and fatigue loading tests were carried out under in-plane cyclic bending.As a result, it was clarified that both of two diffbrent types of jointpart, called constraint reinfbrced bar type and flat bar type, had enough fatigue durability.
In order to increase the ductility of RC piers, some kinds of jacketing method are applied by using steel plate, concrete and FRP sheets. However, these methods demand a wide open space to work easily with high quality. In this paper, in order to rationally perform the retrofit for RC piers located tight area, a new jacketing method with partially precasted AFRP sheets is proposed. The RC piers locating at one open space and other three sides closed, can be easily and rationally retrofitted by applying this method. An applicability of this method is experimentally discussed.
The composite girders are mainly used for bridges, in which cracking of concrete slab plays an important role. Crack width is calculated by using strain of reinforcement and crack interval. In this study, a new calculation technique for the estimation of the strain is proposed with EC 4. Moreover, simplified analysis for steel fiber reinforced concrete (SFRC) is also proposed. The proposed technique is validated by comparison with experiments of girders with the shaft tension.
Time-dependent changes in the temperature, strain, and crack width of a steel pipe-concrete composite pier structure were measured. These were then numerically simulated by 1-D and 2-D thermal stress analysis to elucidate the mechanism of thermal cracking and formulate a method of assessing measuresagainst thermal cracking including crack width prediction. Gaps between the internal and surface temperatures were found to cause surface cracking during the rising phase of temperatures. It was also found that the presence of concrete in the pipes and its rigidity affect the temperature history anddegree of restraint, which cause effective strain on the surfaces. Prediction of the changes in the temperature and effective strain, as well as the resulting crack width, was found feasible using a simple 1-D model by setting adequate physical property values for the internal pipe elements. The crack-inhibiting effect of moderate-heat portland cement was verified by this method.
In this study, the relationships between the percentage of reactive andesitic aggregates contained in river gravel, the alkali and chloride content in concrete and the degree of deterioration of concrete due to ASR in Hokuriku region were investigated by means of the visual inspection for concrete structures and the various tests using the cores taken from them. The applicability of accelerated curing method according to the Canadian and Danish specification to evaluate the alkali-silica reactivity of aggregate or the residual expansion ability of concrete was comparatively examined. By judging from the results of inspection whether or not the expansion of ASR-affected concrete structure had already been stopped, the appropriate repair and maintenance method should be adopted for the individual one.