The strength of lapped splices of deformed bars is influenced by: splice length, concrete strength, cover, the arrangement and the quality of transverse bars, etc. In this study, in order to determine the effect of transverse bars on the strength of the splice the use of a form of modular ratio (N) is proposed, together with an equation, using this modular ratio, for calculating the splice strength. Also, values of the modular ratio corresponding to different reinforcement ratios (1.28-4.03%) and different temperatures (ambient--100°C) are measured and at the same time lapped splice tests are carried out. Comparisons of experimental values with calculated indicated that the proposed equation is adequate.

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Authors propose a probabilistic approach for the evaluation of thermal crack occurrences, which introduces thermal crack index, random variable defined in terms of the ratio of the concrete tensile strength to the thermally induced tensile stresses due to external restraints.
Furthermore, this report discusses some factors affecting the thermal crack ocurrence probability. It becomes clean that the degree of external restraint, tensile strength and calculation method of thermal crack index are the most contributing factors.

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The authors developed a new method of jointing reinforcing bars, coupler-pressure welding, in order to control the quality of joints even by the inspection of their appearance and establish the pressure welding technology such as mechanical method of joints that was allowed to omit inspecting by failure tests on cut out test specimens. In this report the performance of joints made by this method is evaluated from the results of performance tests of joints based on recommendations of joints in reinforcing bars, and some factors influenced on the fatigue strength of the joints are discussed.

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The authors made statical and fatigue experiments for microconcrete under compression or tension to compare these results with those of normal concrete. It was concluded that microconcrete had an intermediate fatigue characteristics between normal and light-weight concrete. It was considered whether microconcrete could be used for fatigue model specimen. Further the authors tried to apply the equation for fatigue amplitude proposed in the critical state design to microconcrete.

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The objectives of this study are to evaluate the shear forces at occurrence of diagonal crack and at shear failure based on experimental data on cut-off members and to examine the appropriateness of the method of calculating the load-displacement relationship by the cross-section division method for the bending moment considering moment-shift.
The principal conclusions obtained are as listed below.
(1) For evaluation of shear capacity, it will suffice to make corrections for shearspan ratio (a/d), tensile reinforcement ratio and cut-off location in design equation by CEB.
(2) In computation of deflection, the calculated values would coincide with experimental values until yielding of member considerably.

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To investigate the mechanism of concrete cracking by rebar corrosion, an accelerated test by electrolytic corrosion has been done. Additional chemical analysises were also carried out to confirm corrosion characteristics. During acceleration, free chlorides moved toward the anode and corrosion products did not move away from the steel-mortar interface. X-ray diffraction results indicated that corrosion products consisted mainly of Fe₃O₄. Not only resistance of concrete against internal pressure but also corrosion rate had influence on weight-loss of steel for cracking. When the corrosion rate was more than 0.5mpy, 3-9mg/cm² of weight-loss was enough for cracking and an elastic analysis was effective for its presumption.

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The dispersion of flexural cracks in a reinforced concrete member is an important characteristic closely related to the durability of the member. The axially-loaded tension test is widely used for readily ascertaining crack dispersion, but there are fine aspects of this testing method which still remain to be clarified. The study reported here examines in detail the forms of axially-loaded tension testing methods, dimensions of specimens to be used, and the methods of calculating maximum crack width. Tests on the influences of surface configurations of deformed bars and quality of concrete on crack dispersion are performed by the axially-loaded tension method, and it is shown that except for special cases, the influences of these are small and that reinforcing bar diameter and reinforcement ratio have predominant effects.

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In order to clarify the inelastic behavior of R/C frame structures subjected to earthquake motions, skaking table tests and pseudodynamic tests were carried out using small scale two-story one-bay R/C structures, and inelastic response analyses based on the one component model were conducted. Since the inelastic behavior of the R/C frame depends strongly on the strength and the capacity of the ultimate displacement of each R/C member, the new force-displacement model in consideration of the ultimate displacement of each member was proposed to obtain accurately the inelastic response of the R/C frame. The inelastic responses calculated using the proposed model resulted in satisfactory agreement with the measured ones when shear failure occurred in some members of the R/C frame after yielding.

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An experimental study was performed to clarify the influence of high alkali content of portland cement on the properties of concrete by addition of potassium sulfate. The results suggest that increase of alkali content in cement not only causes the flash set of fresh concrete resulting in slump loss but reduces the strength of concrete. Addition of blast furnace slag to these high alkali cements makes up for the loss in slump and strength to a large extent.

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A series of drying shrinkage tests of the concrete members that are restrained externally by steel bars or channels has been carried out systematically to investigate the influence of degree of restraint, mix proportion of concrete, size of the cross section, moist curing time and additional bars on the shrinkage cracking.
In addition, an analytical method to estimate the shrinkage stress as well as the cracking time is presented herein.
The good agreement between the estimated values and measured ones is obtained.

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The temperature distribution in concrete wall is calculated as an one-dimensional problem of heat conduction. The flux of heat from the wall surface is considered to be three components, i. e. solar radiation and heat transfer of convection and emission. The results are compared with the observed temperature in a model tank and three real water tanks. Fairly good agreement independent of place, date, direction and inclination confirm the propriety of the calculating process.
Some information on the highest surface temperature are obtained referring to the direction of the wall, the absorption coefficient of solar radiation and the correction factor to atmospheric transmissivity.

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Experiments were conducted to generally clarify the alkali-silica reactivity of ferro-nickel slags. The slag samples tested include one slag that was found to be most reactive in the previous study, three samples prepared by reheating the most reactive slag up to 700, 1000 or 1100°C, and one glassy slag. The slags which were composed of only forsterite and glassy phase and contained little CaO as their compositions were found to be reactive. In the case of these slags, amorphous silica in them was considered to be responsible for their reactivity. When about 15% CaO existed in slag, the dissolution of silica in alkali solution was greatly suppressed, thereby making the slag innocuous. The reactive slag could be converted to innocuous one by reheating it to 1100°C. Replacing a part of cement with such mineral fines as fly ash and blast furnace slag was quite effective in reducing the expansion of concrete due to alkali-silica reaction.

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Bond tests of deformed bar embedded in massive concrete which have no effect of splitting crack were carried out. Bond-slip relationships obtained from extremely short embedment test are different from those obtained from long embedment test. Relationships between bond stress and slip depend on the location along a bar in short embedded pull-out test and in short embedded axial tension test. Bond-slip relationship of aluminium bar is different from that of steel bar. These results can be obtained by the analysis of using an unique bond-slip-strain relationship. The bond-slip-strain relationship model is formulated. This model includes the effect of bar diameter and concrete strength. In the case of condition that the strain is zero where slip is zero, the bond stress can be expressed only by the slip. The bond-slip relationship is formulated in simple form.

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The necessity of developing a computer-aided bridge rating system has been pointed out for maintenance, diagnosis, repair and rehabilitation of existing bridges. There are multiple processes of damage with a lot of damage factors in existing bridges in service. In this paper, an engineering prediction model for a bridge rating system is proposed based on the fuzzy hierarchy structural modeling. The fuzzy set theory which introduced the idea of a vagueness function and Dempster and Shafer's theory is applied to final stage of rating. A few concrete bridges on which field data have been collected are analyzed to demonstrate the applicability of this rating system.
The results obtained are sufficient to apply the rating to cracked reinforced concrete bridge girders and slabs.

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In many cases, concrete pavements have been deteriorated by cracks at the slab edges along the transverse joints due to traffic loads. Thus the mechanical behavior of concrete slabs near the joints should be considered in the thickness design of concrete pavements. The mechanical behavior of concrete slabs can be analyzed by the plate FEM, when it incorporates joint models. Accordingly, it is necessary to develop joint models which represent the mechanism of load transfer across joint. In this study, the mechanism of joint is divided into two functions: (1) aggregate interlocking and (2) dowel action and bending action of the dowel bar. The numerical calculations are conducted using those joint models and compared with the experiment data obtained by lwama.

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A study of design recomendations in various countries for the avoidance of reinforcement corrosion suggests that no real consensus exists on the levels of concrete cover and permissible crack width which should be specified.
This paper attempts to asses the distribution of cracking, the factors of crack width, and the control of corrosion by reference to data carried out in 75 reinforced concrete bridges. And the possibility of a more rational design approach to corrosion control is discussed.

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Cyclic loading tests were carried out using cantilever type reinforced concrete beams, in order to obtain a reliable equation to estimate the ductility which is one of the most important properties in earthquake resistant design. The factors adopted were main reinforcement ratio, web reinforcement ratio, a/d, axial compressive stress, compressive strength of concrete, number of repetitions of loading, maximum size of coarse aggregate and so on. The effects of these factors on the ductility were investigated one by one. The results were summarized to a series of equations to estimate the ductility as a term of ductility factor. It was proved that the derived equations can essentially evaluate the effects of the factors on the ductility and can estimate the ductility factor with satisfactory accuracy, even a little modification may be needed on the effect of the maximum size of coarse aggregate and the effect of longitudinal reinforcements arranged along the side faces.

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Bond characteristics in post-yield range of deformed bars were investigated by means of pull-out test. In the test, the bars were embedded in massive concrete in order to have no effect of splitting crack and unbond region was set at loaded end to have no effect of location along the bar. Bond stress in post-yield range is much lower than that in elastic range and it decreases suddenly with yielding of steel. Slip at the loaded end is mostly controlled by location at which steel bar yields. Bond-slip relationship in post-yield range depends on properties of steel bar such as yield strength, hardening strain and tensile strength. Bond-slip-strain relationship obtained from test in elastic range is applicable in post-yield range. The lower bond stress and different bond-slip relationships can be expressed by the analysis of using the unique bond-slip-strain relationship.

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This paper describes the physical properties of set-retarded concrete. It was pointed out in the previous paper that the extraordinarily set-retarded concrete could reduce the thermal stress in massive concrete. Further experimental works were carried out to investigate the influences of the following variables to the set-retarded concrete properties types, dosages, and addition time of retarders, and curing temperature. The following properties of this concrete were abtained through this study: setting and hardening characteristics, durability, bond strength at joints, and estimation method on the early compressive strength.

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Small amount of tensile reinforcement causes brittle failure in reinforced concrete beams. Bending test of beams with low reinforced ratio were carried out and design method to prevent the brittle failure is discussed. Cracking strength of beams can be estimated by Sioya's cracking criteria. Ultimate strength should be determined with considering of strain hardening of steel bar. i) As a minimum requirement ultimate strength shall not be less than the cracking strength. ii) In case of the most conservative design, yield strength should be larger than the cracking strength. iii) In the range between i) and ii), suitable judgement should be conducted in taking account of the importance of structural members.

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Uniaxial tensile tests were conducted on prismatic reinforced concrete specimens. Stress distribution along bar in addition to the total elongation was measured and average stress-average strain relationship of steel in post-yield range was obtained. In the average stress-average strain curve, steel starts to yield below its yield strength and the length of yield plateau is zero.
The average stress-average strain curve can be predicted by assuming a stress distribution of steel. Instead of assuming a bond stress versus slip relationship or the bond stress distribution, the stress distribution was assumed directly. The stress distribution can be simply expressed by sine curve.

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In recent studies on prediction of the behavior of reinforced concrete structures, it has been reported that compressive strength of cracked concrete is lower than that of uncracked concrete. But the overall behavior and the mechanics as to the strength reduction were not clear.
In order to examine the strength reduction, the authors conducted the experimental research using hollow-cylinder type of reinforced concrete specimens.
The result shows that strength reduction can be expressed by the function of crack width and crack spacing. But within the experimental range, however, avarage tensile strain normal to crack uniquely decides the nonlinear behavior of cracked concrete.

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The fatigue failure criterion for asphalt mix based on the energy dissipation theory was presented and it was extended to cover wide range of mix stiffness modulus. A special emphasis was placed on the low stiffness range in an attempt to establish a reasonable criterion which is also valid for the top surface of mix slab. By laboratory wheel tracking fatigue tests, it was found that fatigue cracks can take place at both surfaces of the slabs, and that the predicted fatigue lives by the new criterion correspond well with the structural failure points in both cases.

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A new framework for the prediction of fatigue failure life of asphalt pavements was presented. The new fatigue failure criterion based on energy dissipation theory, which was verified to be valid for wide range of mix stiffness modulus, was combined with the theoretical temperature estimation method. Traffic and environmental effects were incorporated into the new prediction system as probabilistic variables. In this system, the fatigue failure is assumed to take place at both top and bottom surfaces of the mix slab. With the method, an attempt was made to predict the fatigue failure lives for some routes of national highways in Japan, showing reasonable agreement between the predictions and the observations.

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In internally restrained specimens, strains of a restraining bar increased from the end of the specimen, but at the points more than two times of the width apart from the end face, the strains were almost constant. The strains of concrete showed the inverse inclination of ones of the bar. An arrangement of transverse reinforcing bars decrease these phenomena. In externally restrained specimens, transverse expansive strains decreased near the end face of the specimen due to a restraint between end plate and expansive concrete. As for a longitudinal strains on the surface of concrete obtained by a contact type strain-gauge, the value near the end plate was larger than the value of mid part of the specimen which was free from the restraint between end plate and concrete.

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Expansive-shrinkage strains of uniaxially restrained expansive concrete were obtained by A type and B type specimens specified in JIS A 6202 “Expansive Additive for Concrete”. Uniaxially restrained expansive strains obtained by A type specimens were almost the same as the values by B type. Drying shrinkage strains obtained by A type specimens were also almost the same as the strains by B type, up to a limit value. However, beyond the limit value, the shrinkage strains obtained by B type were larger than the values by A type. Drying shrinkage strains on the surface of concrete obtained by contact type strain-gauge were larger than the values of restraining bar obtained by dial gauge. Instead of B type, A type specimens can be adopted to measure shrinkage strain as well as expansive strain.

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