Shear strength degradation and the decline point on the P-δ curve are some of important factors to assess the failure mode and ductility of reinforced concrete columns. The present paper deals with shear degradation accompanying cyclic loading, concrete crack angle and ductility evaluation of reinforced concrete columns by experiments and analyses. In the first shear strength caused by degradation of concrete contribution and crack angle using The Modified Compression Field Theory are examined and calculated. A discussion focuses on degradation model of shear strength and crack angle far beyond the yield point of the main reinforcement. Then failure modes and ductility factors are estimated by comparing deformation analysis and the degrading capacity of shear strength.

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The aims of this paper are firstly to evaluate and to model the delamination characteristic of FRP sheet bonded on RC beam, and then to propose the evaluation methodlogy of constitutive law for the bond of sheet and finally to verify the applicability of the proposed method to smeared crack type FEM analysis. As a result, the follwing conclusions were obtained. The delamination of FRP sheet is generated by local yield of steel reinforcement near the loading point. The effective bond development length of RC beam is larger than that of the bond test specimen due to the effect of curvatureof the beam by bending. The bond consitutive law can be evaluated considering the difference of effective bond development length and can be applied to the smeared crack type FEM analysis.

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When the effectiveness of expansive concrete is discussed in analytical evaluation, the effective Young's modulus is one of the most important factors for the reliability of analysis. Although there have been conducted some experimental investigation on the Young's modulus of concrete at an early age, the general solution has not yet yielded. This paper discusses the effective Young's modulus of expansive concrete with use of high early strength cement at an early age based on the experimental results obtained from the two test series, one is the series of stress release using the standard uni-axially restrained test specimen and the other is the series of specially designed uni-axially restrained test specimen where a restraining bar with very little thermal sensitivity is used to compensate the thermal expansion of the bar. Moreover, the influence of creep at an early age on Young's modulus of concrete is discussed based on the thermal stress analysis by finite element method.

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In order to clarify the variation in pore structure due to the replacement ratio of ground granulated blast-furnace slag and the change of calcium dioxide volume caused by latent hydraulicity, the pore size distribution test and thermal analysis (TG-DTA) were carried out. Also, accelerated carbonation test was carried out to investigate the influence of replacement on the concrete using ground granulated blast-furnace slag. Results suggest that the amount of calcium dioxide in concrete with ground granulated blast-furnace slag can be estimated from the ordinary concrete, and the relationship between amount of calcium dioxide and carbonation rate is exponential reduction.

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Systematic sensitivity analyses were carried out in order to investigate the effect of temperature history on hydration, micro-pore structure development, and moisture profile in concrete. In the numerical modeling, temperature-dependent intrinsic porosity of hydrates and available space for hydrate precipitation were taken into account. The proposed method can well predict hydration processes for different mix proportions under various temperature conditions.

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The authors presented a computational system that can predict long-term degradation of cement hydrate due to calcium leaching. For simulating leaching of calcium ion, equilibrium of calcium ion in solid and liquid and ion transport were formulated on the basis of thermodynamics theory. The time-dependent material properties of cement hydrate were evaluated considering the inter-relationship of hydration, pore-structure development and moisture transport based upon fundamental physical material models. The proposed model can reasonably predict the calcium leaching in concrete.

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Steel-concrete composite members have been widely applied to immersed tunnels and anti-fire protection is required for them because their steel plates face road side. Fire test and numerical analysis by finite element method were carried out to investigate thermal properties of the composite member for vehicle fire in the tunnel. Maximum temperature of the material was within allowable temperature. However deformation of the steel plate was observed during the fire test due to elongation of steel plate and steam pressure. It was proved that the gap between the steel plate and core concrete should be considered for thermal analysis of the composite members.

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The structural behaviors of preliminarily cracked members and artificially cracked member are sometimes different from that of general RC members. It owes to crack path dependency that is unique to RC members. It is known that the effect is subjected to the direction and location of artificial crack. In this study, it is experimentally revealed that horizontally arranged ACD improves tied arch effect resulting in further shear capacity. Hence, optimum location and position of ACD are proposed and required condition is denoted.

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In recent years, new types of artificial lightweight aggregate with superior water absorption properties have been developed. The application of these high-performance lightweight aggregates is very interesting, because the improvements of the workability, strength and durability of lightweight aggregate concrete can be expected. However, few studies have been carried out on the shrinkage of high-performance lightweight aggregate with low water cement ratio.
Factors influencing shrinkage mechanisms of high-performance lightweight aggregate concrete, such as mix proportion, curing condition have been experimentally studied. The relations between autogenous shrinkage and drying shrinkage have been considered for this lightweight aggregate concrete.

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Multi-phase physicochemical modeling based on thermodynamic approach is studied on gel and capillary pores of nano-micrometers and large voids of micro-millimeters among soil foundation. A computational method about transportation of moisture and ions in pore structure for simulating concrete performance was extended for predicting time-dependent material properties of cemented soil. The proposed model was verified with experimental results of cement hydration, change of relative humidity and leaching of calcium ion from cement hydrate to underground water.

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An extensive experimental investigation was carried out to examine how controlling the bond of the longitudinal reinforcements can improve seismic performance, such as shear strength and ductility, of RC structures. The tested RC columns under reversed cyclic loading were of six different bond conditions, varying from perfect bond with the use of ordinary deformed bars, to perfect unbond. The results of the experiment revealed that the failure mode at the ultimate state could be changed from shear to flexure by reducing the bond strength of the longitudinal bars. The test results also showed that RC columns reinforced with bond controlled bars had significantly better shear strength and ductility than RC columns reinforced with ordinary bars. The subsequent analytical investigations using 3-D nonlinear finite element method indicated the validity of the suggested analytical model, and revealed the change of stress transfer mechanism inside the RC columns with various bond conditions of longitudinal bars.

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This study was carried out in aiming for utilization of molten slag of municipal solid waste as fine aggregate for concrete. Several examinations were executed by using 4 types of molten slag to investigate the characteristics of each slags and the requisites as fine aggregate in this study.
It was clarified that melting methods hardly affected to the chemical composition of slag. However, its physical property depended on the producting method. And, even poor-quality slag, that had unsuitable grading, can be utilized by processing of grinding. Furthermore, consistency of mortar using processed slag was better than that of natural sand. However, the more slag was processed, the less compressive strength of mortar became.

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To clarify the rebar corrosion rate due to carbonation and initially-induced chlorides, an exposure test and an investigation about existing concrete structures were carried out. As the result of an exposure test, it has been observed that the corrosion rate of the lower rebars becomes faster under the influence of macro-cell corrosion in the early stage. But the corrosion rate gradually becomes slower with the passing of the years, and drops into the value evaluated by Masuda's formula. It has been also confirmed that the rebar corrosion rate obtained by investigation of existing structures is nearly equal to that of an exposure test.

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Structural formation of mix and its realizing mix procedure for hybrid asphalt mix, that enables porous texture for surface and denseness for inside in the field were studied. As a result, it was found that steel roller compaction is contributable to the pillar structure and that asphalt mortar run-off can be controlled by kinematic viscosity of asphalt and gradation of sand particles.
Moreover several mix standards for the hybrid were suggested, including packing density measurement for surface and conventional apparent density measurement for inside.

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The reinforcing steel in concrete corrodes due to carbonation or chloride contamination of cover concrete. Apparent volume of corroded reinforcement is larger than original one, and expansion of reinforcement induces the pressure. Progresses of corrosion, the pressure of corrosion products makes cover concrete cracked, and then spalled. The piece of spalling may hurt someone.
In this paper, a modeling method of corrosion pressure is introduced. The maximum pressure and apparent volume increase of corroded steel are proportional to cover depth, and inverse proportional to length of corrosion. The scenario for avoiding spalling accident with the statistics is proposed.

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To analyze the characteristics of the longitudinal profile affected by frost heave, the longitudinal profile of an expressway in a cold region of Japan measured weekly from February to April of 2000 and from January to May of 2001 was analyzed. It was found that the increasing speed of winter IRI in cut segment greatly depended on the freezing speed and the maximum increment of winter IRI related to the maximum height of cut. The analysis of wave characteristics of the longitudinal profile showed that the content of long wavelength (>5.7m) was increased by the frost heave and its increasing speed was greatly affected by the freezing speed. It was also shown that the increase of wavelength 5.7-22.6m content due to frost heave caused an increase of dynamic load and the IRI in winter.

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After various studies on salt attacks technologies and considering minimum maintenance, the salt-damaged Yakabi Bridge was reconstructed as a high durability prestressed concrete bridge by using, for the first time in Japan, ground-granulated blast-furnace slag 6000, prestressing steel strands with each wire coated with epoxy, epoxy-coated reinforcing steel bars, and plastic sheaths.
This paper examines the renewed structure and its corrosion resistance through comprehensive analysis and research results from the five-year marine exposure test. The analysis verified that construction method of high durability PC structures using these materials was very effective as a measure against salt attack.

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Japan is surrounded by sea, and traffic roads are located near the sea. Bridges are subjected seawater, which deteriorates the reinforced concrete due to corrosion of the steel. Recent specification in such locations requires more thick cover than the previous requirements. The present study shows the relationships between cover thickness and punching shear strength of concrete slab. Test of reinforced concrete slabs with various cover thickness was carried out in the laboratory. The punching shear strength increases with increase of the cover thickness, and the increase of punching strength is not linear to the cover thickness. Test data are compared with the provisions of JSCE, and with the proposed equation of MATSUI. A simplified equation is herein proposed, which provides the better accuracy to the data.

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