This paper pays attention to brittle fracture phenomenon at low temperature to investigate the cause of longitudinal surface cracking of asphalt pavement on steel deck bridges, and examined fractue properties around the brittle point of asphalt mixtures with tensile tests and FEM analysis. The results revealed that the asphalt mixtures considered in this study have different fracture properties and a certain mixture possibly fracrures under a pareticular loading and temperature condition where the other materials do not. Based on the brittle point and failure tensile strain, a method of numerically evaluating the possibility of occurrence of surface cracking on an asphalt mixture was developed, which can be easily applied to new types of asphalt materials and various types of bridge structures. This method was validated by long term field observation on an actual pavement on a steel deck. (It allows the geneal and quantitative evaluation of brittle pavement fracture, which has never been possible.)

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A difference in level, incline and closs slope on sidewalks are serious barriers for wheelchair users. However, even if they are small, unevenness of sidewalk would increase wheelchair traveling load in case of rough sidewalk. In this paper, longitudinal profile and wheelchair traveling torque measured on sidewalks in service were analized, and a method of evaluationg the sidewalk unevenness based on wheelchair traveling load is proposed. Test tracks with a variety of inclines and unevennesses were rated by panel members riding on the wheelchair, and it was found that the sidewalk unevenness index calculated by this method is also correlated to their ratings.

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If concrete is considered to be composed of solid particles and water, "excess water" can be defined according to the concept of excess paste theory. Through the mortar tests with various compositions using sands which have different gradings and solid volume percentage tests of cement-sand mixtures, the functions of excess water film around solid particles are investigated and the followings are clarified.
Mini-slump and mortar flow can be evaluated by the parameter of excess water thickness/average diameter of cement and sand particles. The largest solid volume percentage of cement-sand-coarse aggregate mixture is an aim of the mix proportion of concrete which gives the highest slump.

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Considering the mechanism of pozzolanic reaction of fly ash that occurs in cement matrix is derived from the reaction with Ca²⁺ under high pH condition, the authors proposed an accelerated chemical testing method, API-method, for assessing the pozzolanic reactivity of fly ash. The API-method estimates consumption amount of Ca²⁺ in equally mixed OPC and fly ash suspension under the reacting condition of 80°C for 18-hours. If the content of SiO₂ in fly ash satisfies the regulated amount 45% according to JIS A 6201, API-values showed good linear correlation (R=0.98) to the Activity-Index (AI) of mortar, so the API-method was thought to be an effective assessing method for pozzolanic reactivity of fly ash and AI.

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This paper reports an investigation of existing RC bridges damaged by salt attack. Also the characteristics of chloride ion penetration into the concrete are determined by analyzing the well cores obtained from the existing bridges. The investigated results are compared with the previous report on a nationwide database or design values defined by the standard specification. The observed chloride ion density on the concrete surface is much greater than the value of the previous report. Furthermore, its density comes under the influence of the river width, - namely overall length of a bridge -. On the other, the observed diffusion coefficient of chloride ion is lower than the limit value in the standard specification. This means that the observation ensure the sufficient safety margin.

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This paper describes experimental results of compression failure properties of concrete reinforced by PVA short fiber. Loading test was carried out on concrete cylinders with PVA short fiber by changing fiber content, the kind of aggregate, and the diameter of cylinder. As a result, it was confirmed that the compression behavior is improved by mixing PVA short fiber and that the load decreases gradually after the stress reaches its peak. It was also confirmed that the fiber effectively acts to control crack opening and enlarge the energy absorbed in the failure zone. In this study, the stress-strain relationship of compression side was proposed and was confirmed its applicability to fiber reinforced concrete by reflecting these tendencies.

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There is strong concern in which aged bridge steel decks are severely damaged by traffic loading fatigue. Hence economically effective retrofit process for this damaged steel deck has been heavily required in society. To satisfy this requirement, the authors suggest a new retrofit method, in which a pseudo-stain hardening fiber reinforced cement composite, ECC, is effectively utilized as strengthening top layer on steel decks. Shear load applied at interface between ECC and deck plates is designed to sustain with FRP plate shear connectors. This study aimed at demonstrating performance of composite structure retrofitted by the suggested method. For this purpose, shear loading experiments of the shear connectors and full scale fatigue experiments were conducted. These experimental results justified proposed design process in this retrofit method. Furthermore, these results were successfully reproduced with three dimension non-linear FEM analysis. Finally propriety of the design process was confirmed via field loading test of retrofitted bridge.

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In order to estimate the strength of the concrete, the concrete specimen from which the water cement ratio differed was produced, and the relationship between the transit dose and compression strength obtained by X-ray technique with contrast medium were required. In this experiment, a test using non-air entrained concrete and mortar was also carried out as a comparison material. And, an experiment was similarly carried out for the concrete in which the dynamic elastic modulus was made to change by the freezing and thawing action. As a result of the experiment, the estimation of each strength and relative dynamic elastic modulus of deteriorated air entrained concrete became possible by measuring the transit dose by X-ray technique with contrast medium for mortar, concrete and air entrained concrete.

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According to the limit state design based on reliability theory, the verification of the durability of concrete structures against various deteriorating factors is examined in this fundamental study. Especially, verification of salt attack is considered. Various kinds of uncertainty in the modeling of airborne chlorides transportation to corrosion initiation of reinforcing bar are evaluated using the previous observation or experimental results, and the probabilities that the threshold chloride concentration is exceeded during service life are calculated for concrete structures exposed to marine environments. Without any calculation of probability such as Monte Carlo Simulation, safety factor and design procedure to specify cover ensuring that the probability of corrosion initiation of reinforcing bar is almost the same as a target value, is proposed.

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In the study for extending amount of effective use of fly ash, and taking measure of exhaustion of aggregate, the fresh properties of the concrete using high volume fly ash as a part of fine aggregate were examined. As a result of experiments, the influence of fly ash replacement as a part of fine aggregate on the mixture proportion or the fresh properties became clear. And, by applying water layer model to the experimental result, the relevance of unit water or bleeding capacity, and water layer thickness of particle surface was shown. Furthermore, in the case of concrete with same slump, it became clear that the water layer thickness became constant without depending on quality and quantity of fly ash.

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Usually internal vibrators are used to compact fresh concrete. However, in a job site the details of compaction are never determined theoretically but by practical experience. This paper presents the evaluation methods for the compactability of plastic concrete that is compacted by internal vibrators. In this paper the progress of compaction is considered as an increasing process of density from initial state of concrete at thrown into a form to theoretical density of mixture proportion. Initial apparent density depends on a consistency (slump) of concrete. The magnitudes of acceleration for compacting concrete of slump 5 to 15cm are examined. The apparent density of a given concrete in a form is determined by vibration energy under different vibrating conditions, and compaction curve and compaction function are proposed. The relationships between relative density and compressive strength at arbitrary compaction degree are discussed in this paper.

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This paper presents the evaluation method for shear failure behavior of RC beams, focusing on the location of unbonded region and the development length in stirrups. The shear load bearing capacity of the RC beams with unbonded region in stirrups, which exhibits either diagonal tension failure or shear compression one, is well estimated by the proposed method. However, numerical analysis gives more detailed information about the relationship between the several factors and the shear failure behavior of RC beams. In diagonal tension failure, unbonded region in stirrups around the supports in tension side strongly affects the global response of the beams. In shear compression failure, unbonded region in stirrups near both the supports in tension side and loading point in compression side, however, affects the response of the beams mainly.

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We have to use some by-products to concrete for the conservation of natural resources or the sustainable development of human society in these days. The slag fine aggregates are also included in this category. However, the concrete containing the slag fine aggregate has a tendency to show the lower fluidity or the higher amount of bleeding. The relatively higher density or more angular particle shape of the fine aggregate causes these phenomena. Therefore, It's very significant to improve the qualities of concrete made with slag fine aggregate for the real effective use of the fine aggregate.
In this study, we investigate the influence of the properties of slag fine aggregates on the qualities of concrete from fresh to hardened stage. First, we basically investigate the influence of particle shape or density of slag fine aggregates on the fluidity or the bleeding of mortar. Consequently, we evaluate the suitable finer materials content to improve the fluidity of mortar based on the fine aggregate particle shape, and the required plastic viscosity of the paste, obtained by the adjustment of water cement ratio or the finer materials content in fine aggregate to control the bleeding of mortar. Then, we investigate the effects of these adjustments based on the results of the basic study on the fluidity, the bleeding, the strength development and the uniformity of fresh or hardened concrete.

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A validity of the existing prediction equations for the ultimate tendon stress in beams prestressed with unbonded tendons was examined by large number of experimental data. The predicted results of tendon stress at ultimate were discussed in terms of several factors that were found important to affect the ultimate tendon stress. A parametric study was performed in order to propose a new prediction equation for computing the tendon stress at ultimate in beams prestressed with internally unbonded tendons. The accuracy of the proposed equation for tendon stress was verified by comparing the predicted results with the experimental results, which were collected in the available literature.

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