[in Japanese]

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If ground subsidence acts on piping that includes bent pipes, the highest stress often occurs not in a straight section but in a bent section. The author therefore has developed a method of estimating the stress generated by a change in diameter by adding an equation for the diameter change and bending moment to the bent pipe stress calculation equations proposed by Rodabaugh and George. To investigate the validity of this method, three kinds of bent pipe made using typical bent pipe manufacturing methods and having representative section wall thickness distributions were tested. As a result, it was confirmed that the stress estimated from the diameter change closely agrees with the measured value.

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Many damages occur at the concrete component of the highway bridge beam end in Hokuriku area. It is found from the site inspection that the damages are caused by salt permeation of road surface water containing a antifreeze through the flexible joints. In this report, we first analyzed the damage progression of the beam end of concrete bridges by using the inspection data, and created the damage progression estimation curve.

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Authors have been developing the roller compacted concrete with large quantity of fly ash as the substitute of fine aggregate. A design procedure of mix proportion was proposed and fatigue strength was determined for this concrete. Surface quality is one of the management items for pavement concrete. Therefore, in order to apply this concrete in site, the surfaces properties such as the flatness, and dynamic friction coefficient, durability against abrasion in method of ravelling test were also obtained experimentally in this paper. As the results, durability of this concrete in colder districts is expected to be superior to ordinary roller compacted concrete.

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The purpose of this study is to develop the method on estimating the compressive strength at early-stage. In order to consider the effect of temperature on strength development of concrete, the equivalent age based on the maturity and the Arrhenius equation were taken up in this study. The availability of four kinds of strength growth curve was investigated by the use of the compressive strength of concrete cured at constant temperature of three levels. This study proposed the equation of estimating the compressive strength with consideration to the difference in water-cement ratio. The proposed equation was able to assess the strength of ready mixed concrete with sufficient accuracy.

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Observational execution method with digitalized monitoring system was conducted in a large-scale vertical excavation of rock foundation composed of andesite and tuff-breccia of the Neogene Tertiary. The outcomes resulted from the real behavior by the reverse analysis and another analytical method show some important information for the design and execution of the excavation of the rock mass. For example there exists different deformation behavior between vertical and horizontal or between loading and unloading.

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This paper describes the repair of the bottom side of a RC hollow slab bridge damaged by deicing salt and contaminated chloride. It was clarified that removing of concrete 30mm deeper than rebar position and repair of cross section 55mm over thickness were necessary to the bridge by present conditions and prediction. In this experiments using actual bridge models, it was found to be able to remove concrete by water-jet chipping technology and compact repair mortar by spraying technology under such hard condition. Since it was found that the quality of the mortar was influenced by the execution/environment condition, the importance of designing for repair, controlling the quality of mortar and inspecting initially to repaired bridge under consideration of such influence was noted.

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In this study, the method to prevent a fatigue failure was investigated using a glass fiber reinforced plastic (hereinafter called GFRP) to welded joints. A cruciform welded joint bonded GFRP was examined fatigue test. From the experimental results, it was shown that the fatigue strength was improved by patching GFRP. In addition, through the FEM analysis using the model, it was found that defraying load by GFRP and smoothing figuration of welded place by primer had effect to decrease stress concentration at the toe of welding.

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In Japan, technical standard for asphalt facing work has not been established yet. Therefore, precedent construction work control standards for asphalt facing were mainly based on empirical knowledge.
In this paper, a unique construction work control standard for asphalt facing work was illustrated by clarifying the reasons obtained through laboratory tests and field trials. In order to achieve all-year-round construction and rationalized standardization, some new trials were executed including standardization on temperature of asphalt mixture mainly focused on the last compaction work, variable standardization on asphalt content according to meteorological condition and construction area, etc.

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A drastic change is expected in Japanese construction market of 21st century, and especially, true achievement in the reform of public works system is strongly desired as well as new figure of general construction industry is being sought. Recognizing a structural reform is indispensable for Japanese construction system, this study is commenced with “contractor's responsibility concept” creation, followed by examination of public works systems both in Japan and other countries through application of the said concept, leading to the purpose of proposing “reform subjects for new systems in which Japanese public works are to be executed having equality amongst related bodies”.

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In this paper, a time-dependent deterioration forecasting model is presented, whereby the deterioration process is described by the transition probabilities which are conditional upon the duration for usage. The model is formulated by the multi-staged Weibull hazard model defined by the convolution of multiple Weibull hazard functions. The model can be estimated based upon the inspection data which are obtained at the discrete points in time. The applicability of the model and the estimation methodology presented in this paper is investigated against the empirical data set of the highway utilities in the real world.

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The pre-stressed concrete halved jacking pipe is the special production that allows using to a pipe jacking work of which the pipe internal diameter is over 3000 mm. Before real curve jacking is carried out, the technical studies that includes limit curve radius, jacking pipe fit length, and allowable thrust force are required in oeder to keep pipes' smooth advamce. In addition, the structural feature that the pipe has two radial joints is required to maintain sufficient safety by examining the joint movement acted loads during jacking. Accordingly, some technical studies were tried in compliance with Japanese Sewage Works Association Standard, and the results of model pipe jacking tests on the S-shaped plane curve alignment were rearranged. As the result, general knowledge has been obtained to the applicability for a real pipe jacking project with plane curve line.

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Chilled gas pipeline buried through a boundary between permafrost and non-permafrost is frequently subjected to severe damege due to deformation since repetition of freeze and thaw in surrounding soil exerts frost heaving and settlement on the pipeline. The authors have been conducting real scale experiment in Fairbanks, Alaska and those phenomenon was observed. In order to establish an evaluation and design method for chilled gas pipeline, this study aims to relate the observed deformation with those by a simple model based on a beam on elastic foundation. The frost heave and the equivalent frost pressure assumed in the model are evaluated with Takashi's equation and two dimensional temperature distribution analysis. As a result, it is found that the proposed method estimates the deformation and the stress of pipeline adequately for design.

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