Steel buildings constructed in Hokkaido were surveyed in order to understand the current state of design and construction. Data on geometric, material, and structural features of 120 buildings, whose design was approved between 2010 and 2022, was extracted from design drawings. The buildings could be categorized based on the columns used: square-HSSs or Isections. The former adopted two-way moment-resisting frames. The latter tended to use braces in one of the two framing directions. The adopted design methodology, vertical loads, design lateral strength, and fundamental vibration frequency are analyzed. Trends in dimensions, steel grade, and arrangements of structural members are discussed.

Fatigue cracks have been reported at out-of-plane welded gussets in main girders of existing steel highway bridges on severe traffic routes. This paper describes a simplified method to estimate live load stress of main girder due to the passage of the F load (F load stress) for fatigue evaluation using load distribution factor (LDF). Structural dimension data were prepared through the design of 29 bridges with various parameters such as span length, girder spacing, etc., based on the past design code. F load stress data obtained by FE analyses of 29 bridges were also prepared. Regression analyses were conducted based on the data sets, and simplified equations that provide approximate estimates for the analysis values were extracted.

Nine cantilever cold-formed rectangular HSS columns were tested under cyclic loading. The primary parameters were the welding methods, semi-automated (hand welding) and robotic welding, and the shape of the weld toe at the corner region. All specimens initiated the ductile crack from the toe of the weld at the corner and failed in a brittle manner. However, the plastic deformation capacity of specimens until the failure was consistently improved with an increase in flank angle even for the column with low fracture toughness, regardless of welding methods and the difference in the strength of the weld metal.

In order to evaluate the axial forces of high strength hexagon bolts used for bridges in service, it is necessary to evaluate their forces non-destructively. The non-destructive evaluation of axial forces of the bolts is often carried out by using vibration characteristics such as impact test and ultrasonic test from excitation. The vibration characteristics can be affected by dimensional variations of the bolts, but no case studies investigating dimensional variations have been reported. Therefore, we measured the initial shape of unused high strength hexagon bolt sets in detail, presented their statistics, and examined the evaluation of axial force using the statistics.

In this study, we analyzed the detailed stress properties of the target part and estimated the crack initiation position by reproducibility analysis for the crack that occurred in the neck near the fulcrum of the I-beam bridge. In addition, welding repair construction tests were conducted to determine the repair method. After that, a load test was carried out on the repaired bridge, and the effect of the repair was confirmed from the difference in stress properties before and after the repair. Finite element analysis was then used to reproduce the tests and confirm detailed stress characteristics that could not be confirmed in the tests, as well as the effects of deformations occurring in the actual bridge on the stresses.

In this study, FEM analysis was conducted using a numerical analysis model that can consider the contact pressure dependence of the friction coefficient between joint surfaces, to verify the validity of the new slip capacity formula and to study the details of joint structures that can be expected to improve the slip strength. The analysis of a small joint flange thickness, in which an enlarged washer was inserted to reduce the contact pressure when the bolt axial force is introduced, resulted in a larger slip strength than that of a large joint flange thickness. The increase in the slip strength was similar to that expected by the new slip resistance equation.

Since steel bridge girder ends are weak points for corrosion, it is necessary to develop highly durable corrosion prevention techniques. The authors developed a method of restoring corrosion protection performance based on Cold Spray technology and applied it to the girder ends of an actual bridge with corrosion damage. In this study, the corrosion protection performance of the cold spray coating was demonstrated by focusing on the mechanism of corrosion damage in each structural member through continuous observation of the condition under corrosive environment for 8 years.

High-performance steel materials (SBHS, SM570) are stronger than SM490, so they are effective in improving the seismic performance of bridge structures. However, it cannot be used for seismic design of bridge piers, etc., and the performance of high-strength steel cannot be fully exhibited. In order to enable seismic design using high-performance steel materials, it is necessary to accumulate data on the plastic region of high-strength steel materials.

This paper targets steel beam to box-section column connections with exterior diaphragms whose depth are smaller than those of conventional ones. An evaluation method of yield strength of beam flange connections is proposed considering partial penetration welds of the exterior diaphragm. Mechanical behavior and effects of parameters on yield strength of connections are examined by a loading test and finite element analysis. As a result, it is clarified that calculated values based on the evaluation method can correspond to results of the test and the analysis within ±10% errors.

To develop a stainless steel high-strength bolt with higher corrosion resistance for use in joining stainless steel members, a prototype bolt was made from SUS316L. To increase the strength of the bolt, a wire-drawing process was used instead of the more common heat-treatment method. As a result, it was found that the elastic modulus of the shaft cross-section decreased continuously from the core to the surface. The modeling of a bolt with this feature was examined by considering various factors, and the effects of the feature on the stress concentration in the radius of the lower neck and thread were studied analytically.