On ballasted track, to prevent track irregularities from growing is important in order to keep good riding comfort. The roadbed vibration caused by train have a great influence on the growth of track irregularities. In this study, we considered the influence of roadbed vibration on track settlement by experiments using full-scale ballasted track model and simulation using the Discrete Element Method. As a result of the study, it is quantitatively showed that the track settlement increases as the roadbed vibration increases. Further, it is clarified that the track settlement rapidly increases if the roadbed acceleration exceeds the gravitational acceleration, and that the track settlement correlates with the velocity amplitude of the roadbed.

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 During the 2016 Kumamoto earthquakes, serious damages were observed in the highway overpasses supported by the piers with multiple rocking columns. In view of these damages, it was notified by the Japanese government that the existing piers with the multiple rocking columns must be upgraded to resist the seismic forces at least in the direction transverse to the bridge axes. As a result, non-negligible seismic transverse horizontal force and bending moment come to act on the foundations that were originally free from the seismic action. Therefore, the foundations for the upgraded piers must also be upgraded to resist the newly occurred seismic action. However, it is difficult to upgrade the foundations specifically in case when the highways are in service. In this paper, the validity of applying the controlled-stepping mechanism to the upgraded bridge piers is examined in order to avoid upgrading foundations by mitigating the seismic forces acting on the piers.

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 It is known that high strength bolted joints treated with zinc-rich paint and filler plate have a characteristic of large bolt pretension loss by relaxation. However, characteristic of bolt pretension is not clarified. In this study, the friction type of high strength bolted connection specimens with filler plate were made on steel plates, in which contact surfaces are to be rough without mill scale and have inorganic zinc-rich paint, then slip tests and relaxation tests were carried out on these specimens. From these results, we discussed the initial bolt pretensions on high strength bolted joints considering number of contact surface and condition of contact surface.

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 High strength bolted friction type joints are often used for the site connections of members in steel bridges. A bolt used for the joint is generally 8T or 10T class one. The slip resistance of the joint is determined by multiplying a slip coefficient factor by a bolt axial force. The bolt force is introduced dependent on the tensile strength of the bolt. The 14T class bolts with higher tensile strength are recently used. The slip coefficient factor for a design of the bolted connection is specified as a single value independent of a bolt axial force. However, it is confirmed by recent studies that the friction factor decreases as contact pressure becomes high. Therefore, as for the joints with 14T class bolt, it is necessary to use the slip coefficient factor lower than one established for the joints with conventional 10T class bolts. In this study, slip coefficient factor according to bolt tightening force has been made clear through slip tests and FE analyses on the joints with 8T, 10T and 14T class bolts.

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 This study intends to investigate effects of moving vehicles on the dynamic responses of curved girder bridges as well as effect of seismic input directions and vehicle loadings on the seismic response of curved girder bridges by means of a three-dimensional dynamic analysis considering the bridge-vehicle interaction. The dump truck is modeled as a discrete rigid multi-body system with 12 degrees of freedom. A probable cause of failure of tension bolts at the movable support of a curved box-girder bridge is analytically examined. Observations show that big uplift forces occur at the movable support of which two bolts had broken from traffic vibration analysis and seismic response analysis. The existence of heavy vehicles can increase or decrease seismic responses of the curved bridge according to the attack angle of earthquakes. The most severe reaction forces were obtained by the analysis utilizing the model without considering vehicles.

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 Optical fiber sensors have attracted increasing attention in research and applications related to civil engineering, because no other measurements can detect the locations of unpredictable events. For instance, for crack detection, it is necessary to employ a fully distributed sensor because crack locations are unknown a priori. The Brillouin optical correlation domain analysis (BOCDA) system, a distributed optical fiber strain sensor that offers high spatial resolution by using stimulated Brillouin scattering, has undergone significant development for distributed strain information all along optical fiber. In this paper, the authors demonstrate how a BOCDA-based optical fiber sensor can be employed to monitor surface cracks in prestressed concrete structure. For ten years, periodical monitoring has been executed to ensure a flawless pedestrian deck made of prestressed concrete. Moreover, durability of the surface-mounted optical fiber stain sensor has been confirmed for decade.

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