Large amount of steel pipe piles have been used for port facility, road-bridge and building foundation to date in Japan, since adopted for the pier structure at Shiogama Port in 1954. Their strength, toughness, resistivity against impact force stimulated pile drivers growing in size to meet the demand for rapid economic growth in Japan. After environmental pollution problem came up as social issues in 1960’s, bored steel pipe pile methods were developed to solve noise and ground vibration problem, followed by composite piles with steel pipe pile and soil-cement, large bearing capacity piles with enlarged foot protection, large sized screw piles and hydraulic press-in methods combined with direct rotation coming into practical use to comply with diversified requirement from construction market. Development of pile installation methods have affected technical progresses in design and structural engineering mutually. The present paper describes challenges of installation and design technologies on steel pipe piles in the past and recent years. It also refers to assignments for future development of the technology.

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  Cracks suspected of fatigue damage were found at the welded connection part at which a vertical member penetrates the steel deck in the single rib lohse bridge. Causes of these cracks are probably related to welding or fatigue problem and appropriate measures must be taken especially for the fatigue damage. This study presents the cause identification of the damage and crarifies its mecahism. By investigating a core taken from the cracked part, an unwelded zone were found in the root of weld and the break surface showed a similar face caused by fatuge damage. The stress measurement clarified the effects of live loads on the damaged part, with forcusing on the level of live loads and their loading positions.

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  Maintenance of existing infrastructure is increasingly important and the concern with a comprehensive strategy on bridge management has been growing. One of the biggest problems toward efficient and optimal maintenance is to quantitatively clarify the effect of repair, reinforce and rehabilitation investments. To do this, the fundamental data such as inventory and inspection data, are essential. This paper investigates the current bridge management on local governments by conducting surveys using questionnaire forms and interviews. Major findings are 1) the practical stock management system is in the early stage of developing. 2) many local governments have begun to develop their database and some of them do not have manuals or guidelines for inspection. Through the surveys, this paper revealed a relationship between the investment for maintenance, including repairment, reinforcement and renewal works, and the performance of the existing bridges. The effects of maintenance work on bridge conditions are quantitatively verified. The results lead to a better understanding about the need for local governments to invest on their bridge management activities.

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  Underpass structures for a public road and airport service pass were constructed under the south taxiways in the second manmade island of Kansai International Airport. Two major problems in this project were brought up. One was the prediction of uneven settlement of manmade-island, and the other was the design method of broad upper PC-slab in such a condition.
  In this paper, the design and construction methods of broad upper PC-slab for open culvert against airplane load are proposed, and their applications are confirmed by the loading test using heavy dump tracks and the measurement of slab deflection against a real maximum airplane load.

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  Repair methods of bridge cables were studied using two types of cable models which were exposed in the heavy corrosive environment. The first experiment with parallel strands of 19 wires showed that mass reduction of the outer wires with six repaired models (epoxy resin paint, zincrich paint, oil-filled, epoxy resin filled, zinc powder paste, dehumidification) was much lower than that of the model without repair. The mass reduction of the inner wires was much less than that of the outer wires and the epoxy filled and dehumidified models were very effective. In the second experiment with spiral strands of 7 wires, cross sectional areas of new strands reduced by 2.2% for the first four months and the model without repair continued to decrease. On the other hand, the repair models stopped mass reduction and the effectiveness of the proposed repair methods was validated.

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  In the design and construction planning of earthworks for land development or road construction, itera-tive investigation is usually executed to balance the cut-and-fill volumes and to minimize the conveying distance of soils. The conventional 2D drawing based method relies on the capability and experience of engineers in judging whether the design fits in with the circumstances and whether or not concrete retain-ing walls should be installed. Furthermore, it takes a great deal of effort and long time to calculate cut-and-fill volumes for a number of comparative cases iteratively. Thus, in this research, an earthwork plan-ning and cost estimation system was developed, based on the “block model,” as a low cost and general tool, using free 3D CAD and general-purpose spreadsheet software packages. Then, an actual earthwork project was applied as a sample, and the test showed the feasibility and practicality of the system.

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  Rapid tunnel driving largely contributes to reduction of construction cost and period. Therefore, the authors study rapid NATM tunnel driving for mechanical excavation applied to soft rock and inspected it in the tunnel site. The characteristic of this method is to adopt ‘early-high-strength shotcrete support system’ which contains shotcrete with the high strength at an early age without steel supports. The trial construction of rapid tunnel driving with this system has been executed in the Mineyama tunnel of the Shinkansen. This system has made it possible for the driving speed of the tunnel to be 304 m per month at the maximum. The result shows that rapid tunnel driving is practical and effective.

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  The efficiency of maintenance and operation will be drastically improved, if it is possible to detect abnormality in social infrastructures at an early stage, based on the relative change of vibration characteristic, which can be identified by conducting vibration monitoring continuously. This study focuses on a railway bridge on which trains with almost the same weight run at fixed timings every day, and proposes a vibration monitoring method utilizing the passing train load. In order to examine the effectiveness of the proposed method, the authors conducted a field test targeted at two real railway bridges, identified the natural frequency and vibration mode shape of the railway bridge, and empirically demonstrated the possibility that the natural frequency could be used as an indicator for abnormality detection through a few analyses.

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  Downsizings have been done in a lot of civil engineering governments in Japan. Through the administrative reforms, it is necessary for each civil engineering government to allocate the human resources for some road maintenance offices reasonably in view of retaining the customer service.
  In this paper, the optimal human resource allocation model under road demand uncertainty is formulated as portforio optimization. In the processes, we propose some practical policies and techniques of matching the expected performance based human resources with the road maintenance demands in the two phases which are consisted of a short-term view and a medium-long-term view, as numerical counting processes with reference to investment science. Furthermore, we also report on the application example against the approximate data concerning a prefecture for considering the applicability of the methodology.

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  In this paper, we proposed a method for robust automatic crack extraction from noisy concrete surface images. The proposed method has two preprocessing steps for robust extraction. After two preprocessing steps, probabilistic relaxation is applied to overcome the problem of threshold selection and also to prevent noises, and improved locally adaptive thresholding is used to extract cracks exactly and automatically. It is possible to classify width of cracks extracted by our proposed method. The experimental results show that the proposed method is effective to extract cracks from actual noisy concrete surface images, compared to the conventional method and other thresholding techniques.

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  This paper presents an improvement of the location tracking of the railway track monitoring system which consists of an MEMS accelerometer, an A/D converter, a GPS receiver, and an ultra small PC. The system has been developed so that railway tracks can be monitored more frequently by the use of a passengers’ vehicle than the measurements are performed by vehicles equipped with various sensors. The one of the concerns in order to make the monitoring system be settled easily and instantly in passengers’ vehicle is that an accuracy of location tracking. The proposed method is achieved by a combination of GPS locating and the uses of an existing digital map, acceleration responses being measured simultaneously. The results of comparisons between vertical acceleration responses and displacements showed a good agreement after the improved location tracking method was applied. The monitoring system has also been proved that track repairing activities can be detected by performing periodical monitoring.

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