This paper investigates the reduction of axial force in corroded high-strength bolts. FEA revealed that the root mean squared value of the thickness reduction was a useful parameter for evaluating the residual axial force for the corroded bolts. Furthermore, the effect of corroded bolt shape on the residual axial force was examined by using FE models based on 3D scanning result. To improve the accuracy of residual axial force measurement, the correction formula which consider the thickness reduction of bolt head on the axial force measurement was proposed. The proposed evaluation method indicated that the residual axial force can be estimate with the accuracy of ±15%.

This paper is intended to summarize findings from tensile test of carbon steel during fire and numerical analysis of partial factors for fire resistant design of steel girder bridge as a parameter reliability index. The specimens were rolled steels for welded structures. As parameters for evaluating, we have employed steel type and fire temperature. The numerical analysis of partial factors based on classical reliability theory. In conclusion, we confirmed that the decreasing inclination of steel strength is almost same as Eurocode. Furthermore, we calculated resistance coefficient based on tensile test under high temperature.

The current design criteria on width to thickness ratio of high strength steel in Japan is too strict for use in practice. Research of the past revealed that evaluating the deformation capacity of H-shaped beam made of HT780 steel based on the angle at maximum strength of H-shaped beam made of 490 N/mm² grade steel is an effective method to reduce weight of steel. The purpose of this paper is to reveal more efficient design method for H-shaped beam made of HT780 steel by using stiffener at neutral axis of web.

This paper deals with low-cycle fatigue life of full-penetration weld joint. The objective is to clarify the influence of the shape and the hardness distribution near the weld toe on low-cycle fatigue life. Cyclic loading was applied to the two types of weld joints which had different shapes and hardness distributions near the weld toe. Low-cycle fatigue life of the weld joint with smooth shape and hard weld metal was superior because of late crack initiation. Digital image correlation (DIC) method also demonstrated that the difference of the hardness distribution caused the different strain distribution and it led to the difference of deformation capacity until crack initiation.

A nine-year atmospheric exposure test was performed on Zn-30mass%Al thermal spray coating under the corrosion environment using the artificial sea water. A similar corrosion test carried out to compare the properties with Hot-dip-Zinc coating. Atmospheric corrosion properties of thermal spray coating were evaluated by surface observation, X-ray diffraction, film thickness measurement and element analyses using EPMA. From these analysis results, the thickness of thermal spray coating was not impacted greatly under corrosion environment using the artificial sea water. In addition, corrosion resistance of Zn-30mass%Al thermal spray coating is much higher than that of Hot-dip-Zinc coating.

In this study, for shortening erection period of temporary bridges, we propose to use the double end plate connection using high strength bolts at the connection of temporary bridges. The past experiment has confirmed that double end plate connection using high strength bolts can apply to bridge main girder connection. However, the design method is not clear. In this study, we have clarified the bending strength of this connection from the analytical results. Furthermore, in consideration of these results, a simplified calculation method of bolt axial force for this type connection proposed.

Low cycle fatigue is a failure mode exhibiting a small number of loading repetitions to failure. Former work conducting research on constant displacement amplitude presented crack growth rate was related to cyclic J-integral range, but the data were limited. This research aimed to provide additional information to cover study done at the past so that a formula for obtaining crack growth rate can be precisely proposed. Research work was conducted with applying two different cyclic displacement means of loading histories to CT specimen. Cumulative plots in crack growth rate addressed to past and current research work were found enforcing formula used for obtaining crack growth rate under larger cyclic strains proposed at the past.