In this research, we suggested the method to estimate corrosion rate of reinforcement in concrete, because chloride ion has permeated into concrete. Assuming that the corrosion rate of reinforcing bar in concrete is in proportion to concentration of oxygen around reinforcing bar, and reaction rate of corrosion is decided by corrosion factors around reinforcing bar, then the time historical corrosion rate of reinforcing bar can be predicted. And from the result of this calculation, corrosion rate of reinforcing bar is fairly influenced by chloride-permeability and rate of inequality of chloride. Furthermore it is possible that chloride's concentration is high even there is no rust, so we indicate it is not enough to remove concrete around rust for repair.

View full abstract

In this study, a method for evaluating the failure probabilities of bridge systems and members based on a time-variant system reliability theory and a method for evaluating the failure probabilities of bridge systems and damage probabilities of members based on Markov chain were proposed. And the safety of RC bridge systems which are consisted of aseismic base isolation shoe, RC pier, and pile against earthquake is evaluated on the basis of the proposed method. Furthermore, the influences of member failure on the safety of bridge systems under earthquake are examined by use of the proposed method.

View full abstract

The test results evaluating the properties of self compacting concrete using high performance artificial lightweight aggregates which has been developed recently are discussed in this paper. The main subjects are the influences of unit weight of mortar, specific gravity and unit quantity of lightweight coarse aggregate, and water to powder volume ratio. As the results, it is possible to design the mixture proportion of self compacting lightweight concrete with high resistance to segregation by setting up unit quantity of aggregate, unit weight of mortar, and water to powder volume ratio according to material properties properly.

View full abstract

A caisson type concrete foundation is generally used for the power transmission towers in the mountains areas. Legs of the steel tower, attached with either rib-type plates or anchor-type plates, are embedded in concrete so as to resist tension force.
This paper discussed the elasto-plastic behavior and the ultimate strength of the rods attached with anchor-type plates, based on the experimental and analytical approach. Experimental results of the model specimens suggested that the failure mode was the splitting type. The ultimate strength is depending on the direction of force from the anchor plates to concrete. New model, as called “Force Transmission Model”, was proposed so as to estimate the ultimate strength of the rods attached with anchor-type plates. Furthermore, the finite element analysis based on the fracture mechanics was carried out to verify the new model.

View full abstract

This paper proposes a method which is about quantity evaluation of pull-out from footing of longitudinal bar of RC bridge piers and RC columns received cyclic loading with large deformation range. To evaluate of deformation capacity under earthquake is based on this pull-out of steel bar from footing. Furthermore, a study was made on the method to obtain pull-out of steel bar from footing of the reinforced concrete bridge piers and RC columns for applicable of deformation capacities over 10 of ductility ratio, a method capable of calculating accurately was proposed.

View full abstract

It is necessary to estimate damage levels of RC columns precisely in large plastic deformation range for reasonable seismic resistant design. We carried out reversal cyclic loading tests by RC model columns with large deformation capacities, and estimated damage levels correspond to plastic deformation levels in consideration for easiness of repairs. Furthermore, ranges of serious damages were examined. We also carried out reversal cyclic loading tests by repaired RC model columns, and repairing effects were confirmed. From these experiments and examinations, damage levels for seismic resistant design and repairing effects of RC columns in large plastic deformation range were made clear.

View full abstract

The aim of this study is to clarify the bond mechanism of Carbon Fiber Sheet (CFS) attached to concrete using epoxy resin and to propose the numerical methods which can simulate the bond behavior of CFS and its bond strength. A bond-slip-strain relation for CFS has been developed based on the bond characteristic which was clarified by means of experimental observation. A numerical method using the bon d-slip-strain relation can simulate the actual bond behavior. This paper also reports that a bond strength equation developed by the numerical analysis can predict the experimental results with good accuracy.

View full abstract

This paper describes horizontal behavior of composite bridge column consisted of reinforced concrete and steel tubes. First, steel tube-concrete bond test is conducted for analytical model. Second, based on this model, 2D FE analysis is carried out to explain experimental test results of column scale model subjected to cyclic horizontal load. Third, with using this analytical program, numerical experiments are carried out to predict not only flexural but also shear behavior as well. Based on these numerical and experimental test results, followings are practically proposed; 1)horizontal loading and ductility capacity. 2)Takeda Model based hysteresis model for dynamic analysis, and 3)shear loading capacity taking high strength winding strand and steel tubes into account.

View full abstract

Numerical analysis was attempted to make clear the relationship between flow behavior in the slump flow test and rheological coefficients of high-flow concrete. Compared with experimental data, it was ascertained that numerical analysis simulates flow behavior in the slump flow test accurately, if plastic viscosity-yield value ratio, η_pl/τ_y, exceeds 1.0sec. Then the influence of plastic viscosity and yield value on reaching time in 200mm and 250mm radius, and also a method of obtaining rheologacal coefficients of high-flow concrete were demonstrated by using numerical analysis.

View full abstract

In this study, nondestructive evaluation method for grouting performance in prestressed concrete (PC) members was investigated using an impact echo technique. PC bar was modeled as one-dimensional vibration system consisting of springs and dampers. Through the modal analysis, it was found that the grouting condition of fresh cement-paste was related to the damping characteristics of the system. From the experimental results, it was shown that the peak value in the frequency spectrum of the vibration of the PC bar decreased due to filled cement-paste in the sheath of PC beam. It was also confirmed that this method was applicable to practical use of full-sized PC slabs.

View full abstract

An evaluation method to predict the ductility capacity of reinforced concrete columns strengthened by wrapping carbon fiber sheet (CFS) is proposed. A series of cyclic loading tests were conducted for five circular reinforced concrete columns. Based on the existing 20 test results conducted by other researchers in addition to the 5 tests presented in this study, the fiber model specified in the Seismic Design Specifications of Highway Bridges 1995 was clarified for evaluating the ultimate displacement. The stress vs. strain model of concrete confined by both tie and CFS, which was developed by the first two authors, was used in the analysis. Introducing a modification factor for the rectangular columns, it is shown that the ultimate displacement for the 25 specimens can be satisfactorily predicted.

View full abstract

Polymer mortar is generally used for repairing concrete structures. However, its behavior in the setting characteristics has not fully been explored.
In this study, shrinkage strain and stress in the setting process of polymer mortoar with three kinds of resin were measured with an original test apparatus incorporating a non-contact type displacement meter and load cells.
Then, stress and deformation of two-layer composite beams composed of polymer mortar and ALC were investigated. Furthermore, from the viewpoint of energy at setting of polymer mortar, characteristics of polymer mortars used were discussed.

View full abstract

To evaluate the the increment of the density under the vibratory roller treatment for very stiff concrete in fresh condition, laboratory cyclic-loading tests were conducted for the small specimen. And it was found that the dentification could be occurred with the loading. When the cyclic shear stress of high amplitude was loaded under undrained condition, the value of pore pressure increased and resulted to failure. The relationship between the increment of density and the number of loading could be simulated as the hyperbolic line defined with the initial density and the loading amplitude. With this hyperbolic model, the increment of density in the field treatment could be predicted.

View full abstract

Detailed investigation was performed on the RC piers on the Hanshin Expressway Kobe Route which were damaged by the Great Hanshin Earthquake. Using these data, the relationship between the damage level and the ultimate bearing capacity was examined. Results showed that 72 piers ranked as As and A, all had reinforcement cut-off and sustained damage at this point. It was also showed that the average shear capacity index of these piers was smaller than that of piers which were ranked below B1. It was also found that 11 piers ranked As and A had no reinforcement cut-off, but failed at the middle section. These piers tend to have small values for the ratio of shear capacity vs. moment capacity and the shear capacity index.

View full abstract

The Chuo Expressway Fuchu Pavement Section has been in service and in good condition for morethan 20 years without any repair work. The contractor was awarded a letter of appreciation by the President of Japan Highway Public Corporation (JHPC) in 1991 for this excellent pavement. The reason for the high durability of this pavement was investigated analytically and experimentally. It is concluded that the key is the asphalt mixture of the surface course. The procedure for calculating the voids in mineral aggregate was proposed and its validity was demonstrated by the experimental results.

View full abstract

The authors presented a computational system that can deal with pH fluctuation and decomposition of cementitious materials exposed to various environmental actions. In order to evaluate a drop in pH due to carbon dioxide, the material models were developed for transport and equilibrium of carbon dioxide, ionization, ion equilibriums, and carbonation reaction based on thermo-dynamic theory. The material properties of concrete are evaluated considering the inter-relationship of hydration, moisture transport and pore-structure development processes based upon fundamental physical material models. The proposed system can reasonably predict the carbonation phenomena and pH profile in concrete for arbitrary conditions.

View full abstract

This paper presents an evaluation method for shear capacity of RC members retrofitted with externally-bonded Continuous Fiber (CF) sheets. The proposed method is on the basis of coupled mechanical models. Opening of diagonal shear crack is calculated by the simplified rigid rotational model. Bonding and debonding behavior of CF sheet is calculated by the constitutive model for the interface between CF sheet and concrete. Since it is based on the realistic mechanical assumptions, the method can automatically distinguish the failure mode of members, which are “compression shear failure” and “rupture of CF sheet”.
The accuracy and applicability of the proposed method were verified through analysis of number of experimental data in the literature. It was proved that the proposed method can predict shear capacity of members with higher accuracy than the equation used in the current design.

View full abstract

In this research, two dimensional elastic analysis was applied to specimens composed of layers with several different types of pavement mixtures. This analysis was intended for the mechanical evaluation of pavement mixtures through bending test on both surface and binder courses, with a steel plate attached, as well as with a reinforcement layer between them. A series of numerical results obtained gave basic informations for evaluating pavement mixtures quality and their various elastic constants due to layer thickness, material quality and adhesiveness of interfaces.

View full abstract

The cast iron coupler combined with two anchor bars is a joint device that can connect with two precast reinforced concrete elements easily and mechanically. In order to examine watertightness behavior of the joint with which two reinforced concrete beams were joined, tests for watertightness were carried out by a water-pressuring method. It was shown that watertightness of the joint was satisfacticable at service loading levels. And, the cast iron couplers can be used for precast reinforced concrete members even under the ground level.

View full abstract

A study on how correlation among FWD deflection data influences accuracy of the backcalculated pavement layer moduli is presented. FWD data were obtained from the Ministry of Construction, Road Test Section 609 and the data with stronger correlation were used in this study. Deflections without correlation and with similar correlation to the FWD data were generated using Monte Carlo simulation in order to investigate the effect of correlation on the backcalculation results. Furthermore, backcalculation analysis using theoretical deflection data with the same standard deviation but different correlations showed smaller variation in the backcalculation results for the deflection data with stronger correlation.

View full abstract

A method has been used to simulate shear failure in reinforced concrete elements considering localization phenomenon. This paper is dedicated to the modeling of the shear band localization in context of large strain accumulation in a narrow band without substantially affecting the strain in the surrounding material. This phenomenon frequently occurs accompanying inelastic deformation and material acoustic tensor looses its positive definiteness. Furthermore, finite element method is used to simulate this phenomenon. The model, when used in finite element context, gives mesh-insensitive results regarding to the width and direction of the shear band.

View full abstract