One of the methods for replacing steel bridge members is to use attaching additional members to share the stress acting on the replacement members and replace them with new members. In this study, we conducted a steel I girder loading experiment using web bypass members to simulate lower flange connection plate replacement construction, and examined the applicability of the proposed method. As a result, the mechanical behavior of the steel I girder, stress properties, and reinforcing effects of the web bypass members at each construction step were clarified. In addition, we clarified the points that must be kept in mind when designing attaching additional members.

Fatigue life in orthotropic steel bridge deck using a newly developed steel plate, which specially improved crack propagation rate da/dN in the low ΔK range, was examined by the structural model fatigue tests. A fatigue crack initiated at the weld root of the trough rib and deck plate was simulated. The stiffness changes during cyclic loading and the fracture surfaces suggested the fatigue life improvement in the specimen whose deck plate was replaced to the newly developed steel plate. The mechanism in which the fatigue crack resistance improvement of the deck plate reflected on the fatigue life of the structural model specimens was discussed from viewpoint of ΔK change along the fatigue crack path.

This study investigated the impact of rough corrosion irregularities on the slip coefficient in high-strength bolted frictional joints of corroded railway bridges. Slip tests were conducted using test specimens joined by connecting plates coated with corrosion steel materials and inorganic zinc-rich paint. Some test specimens were re-exposed to assess the corrosion condition of the joint surface and changes in the slip coefficient. The slip coefficient using corrosion steel materials was below 0.40, and after approximately three years of re -exposure, there was a 20% increase in the slip coefficient compared to before exposure.

A series of shear, tension and peel tests were conducted to examine the fundamental mechanical behavior of adhesively bonded steel-to-steel joints. The effects of adhesive type (epoxy or acrylic resin), type of steel substrate, surface finish of substrate (as is, shot blast or milled), adhesion thickness and adhesion length were examined from the test results. Epoxy resin was superior to acrylic resin in shear and tensile strength, but inferior in peel strength and ductility in shear. Epoxy resin was sensitive to galvanization while acrylic resin was not. Quantitative data is presented along with examples of typical failure modes.

Recently, there are concerned that seismic motion exceeding the design external force will occur. When this seismic motion is input to a building equipped with hysteretic shear type dampers supported by stud-columns, unexpected deformations such as axial deformations of the dampers may occur. This study examines the influence of axial force on cumulative damage of hysteretic shear type dampers supported by stud-columns.

To investigate the reduction of stress in drilled crack-arrest holes by applying patch plates with high-strength bolts under combined axial and shear loading, static loading tests with a plate girder and parametric finite element analyses were conducted. The stress concentration factor for drilled holes was found to be influenced by the combined action of stresses, and the effectiveness of the patch plate diminished as the ratio of the shear stress increased. This study proposed a method to accurately estimate the effect of combined stress actions on reducing stress concentration in drilled holes with patch plates.

A lightweight and exceptionally rigid cast metal configuration has been carrying out technological development through the implementation of a topology optimization technique for a bracket designed for a bridge collapse prevention system. Nonetheless, the configuration derived from rudimentary unitary analysis did not result in optimal performance when subjected to combined analysis replicating the installation state. Consequently, for the purpose of enhancing performance, formulated an optimization method encompassing meticulously devised analytical conditions. The configuration obtained through this method is approximately 30% lighter than the conventional shape, while maintains equivalent or heightened rigidity.