For corrosion protection of bolted joints in steel structures, it is considered effective to coat the uneven surfaces with a highly adhesive material. Therefore, we focused on silicone, which has high durability, viscosity, and adhesiveness, and investigated a new anti-corrosion technology. Accelerated degradation tests and outdoor exposure tests were conducted to investigate the anticorrosion properties of silicone and the effects of salt and rust on the surface of steel plates. The test results confirmed that silicone inhibits the progress of corrosion and the effects of salt and rust under the coating film. From these results, the use of silicone as a corrosion prevention technology was discussed.

In this study, static loading experiments of high-strength bolt joints under tension and shear were conducted to verify the validity of the developed new slip capacity formula which is considered the contribution of prying force to slip resistance. Experimental results showed that joints with small joint flange thicknesses are prone to prying forces, and the slip capacity of these joints is greater than that of joints with large joint flange thicknesses. Additionally, the slip resistance is not expected to improve as much as the developed slip resistance formula because of the difficulty in generating prying forces due to thermal deformation of flange during the welding of the joint web and flange.

We have developed 1700 MPa-class ultra-high-strength bolts with a waisted shank and a new thread form to enhance tensile deformation capacity. This study evaluated the delayed fracture behavior of the developed bolts by an outdoor exposure test in Okinawa. Delayed fracture of the bolts became more pronounced when the fastening force increased from 391 kN to 445 kN. On the other hand, accelerated delayed fracture tests demonstrated that the new thread form was effective in enhancing the delayed fracture resistance. Based on the results of the exposure and accelerated delayed fracture tests, the ways to improve the delayed fracture resistance of the developed bolts were discussed.

Recently, some researchers reported that the slip factor of the bolted joint with inorganic zinc-rich paint plates is influenced by the contact surface pressure. Herein, literature research on the slip tests of friction-type bolted joints was conducted to extract the information on the effect of contact pressure on slip factor. From the statistic evaluation results, it was found that the lower bound of the 95% prediction band was smaller than 0.45 at a nominal contact pressure of greater than 70 MPa. In addition, the thickness of the splice plate that requires a reduced slip factor was indicated.

Thermal sprayed aluminum coating has been applied to many steel bridges in Japan since around 2000 due to its high corrosion resistance even in harsh salt environments. However, in recent years, partial deterioration has been observed in aluminum-sprayed bridges. In this study, we investigated a repair method for the partial deterioration of aluminum-sprayed bridges using laser cleaning, which has superior environmental performance. We applied laser cleaning to the corroded test specimens that had undergone aluminum thermal spraying, followed by repair spraying with Al-5Mg alloy. The results confirmed that this repair method exhibits high corrosion resistance.

This paper studied residual stress distribution in spiral welding pipes applied to the Multi-Pipes Integrated Bridge Pier by X-ray experimental measurements. It is known that the residual stress will affect the fatigue life of the welding structures, therefore the residual stress due to the bending and welding manufacturing process needs to be evaluated. In this paper, the X-ray measurement was conducted to investigate the residual stress distribution of spiral welding pipes manufactured by two companies. The stress in the hoop, axial, vertical to the welding, and parallel to the welding direction of spiral welding pipes made by different companies, was studied to advance manufacturing management and collect mechanical data due to the bending and welding manufacturing process.

Studied herein is the evaluation of compressive stresses in steel plated structures based on the localized out-of-plane vibration of the structural plates. It is verified that the frequency of the out-of-plane vibration of steel plates decreases as the compressive stress in the plates increases. By this, the geometrical dimensions and constraints of the plate elements are discussed in order to assess the feasibility of compressive stress evaluation in an actual bridge regarding the structural stability. It is concluded that the geometry of the structural member may not influence localized out-of-plane vibration in a circular membrane at arbitrary selected locations within plate elements when the out-of-plane displacement along the annulus is constrained.

This paper deals with the deformation capacity of welded joints undergoing ductile fracture. The objective is to clarify the influence of the difference of ductile crack growth behavior on the deformation capacity of welded joints. Cyclic loading test was carried out on full penetration butt welded joints with different welding specifications and ductile crack growth behavior during loading was observed. The differences of deformation capacity were analyzed focusing on ductile crack growth behavior. Finally, it was confirmed that differences in ductile crack growth behavior have a large influence on the deformation capacity of welded joints with ductile fracture.

The stair floor deck of the standard design pedestrian overpasses can cause a chain of corrosion along a water passes. In other words, it is necessary to take countermeasure to prevent corrosion while it is still minor for this part. However, currently problem is variation in the diagnosis of corrosion and effective record method need to be considered. In this study, corrosion form patterns of the stairs floor deck and occurrence rate of each pattern were considered by using inspection data. As a result, it was shown that by drawing the patterns obtained for cover plates, treads and risers on damage maps, it is possible to supplement the lack of information in the previous damage map and contribute to improving the validity of diagnosis.

For steel girder reinforced by one side patch plate with high strength stud bolts, reinforcement effect and the effect of patch plate connection structure had been confirmed, but it is unclear on fracture behavior of reinforcement section. In this study, experiment of steel girder repaired the lower flange subjected to bending had been carried out. The load-carrying capacity of steel girder reinforced with high strength stud bolts is equivalent to that of the high strength bolts, because the relationship between load and displacement, strain distribution on the reinforced section are roughly match the design. It is understand that yielding occurred on the lower flange at the maximum bending position, slipping occurred on the end of patch plate.

To investigate the influence of temperature on the bridge's response, a 40-hour real-time monitoring was conducted on a steel truss bridge. Analysis of the measured results indicated that the bridge's temperature is positively correlated with its natural frequency, which contrasts with the results from the finite element model. By adjusting the boundary conditions of the FE model to better reflect the actual conditions at the bridge's ends, the modified results aligned with the measured data. The results suggest that temperature variations induce changes in the internal stress distribution, which negatively impact the natural frequency. However, the boundary conditions introduce additional stiffness at the beam ends due to temperature effects, resulting in an overall increase in natural frequency with rising temperature.