There is a method of bonding CFRP plate as a repair method for steel structures. In order to reduce the stress of the steel plate, it is necessary to bond the CFRP plate with sufficient bonding length. By reducing the thickness of the adhesive layer, the bonding length can be shortened. Test specimens in which CFRP plates were bonded to both sides of a steel were prepared and subjected to static tensile tests. We studied the bonding length when the adhesive layer is thin by finite element analysis modeling the test specimens.

CJP groove weld joints between column made of BCP325, and through-diaphragms were fabricated with CO₂ gas-shielded arc welding process with YGW18 electrode to examine the effect of weld heat input on the weld metal strength. The welding was performed by the welding robots. From coupon test results with the specimens extracted from the corner and flat part weld joints, it was found that the weld metal strength at the corner joint was a few % lower than that at the flat part joint, resulting in undermatched weld joint for the comer base metal. The weld heat input had small effects on the weld metal strength near the weld toe, where the ductile crack initiates when the column subjects to flexure.

An increases in strength at the corner portion of cold-formed rectangular HSS due to its manufacturing process, may results in undermatched CJP welded joint at the corner regions. This paper investigates the impact of the properties of CJP corner welded joints: the weld metal strength and the shape of weld toe on the cyclic fl exural responses. The results of cyclic loading tests of the cantilever column and associated fi nite element analyses showed the plastic deformation capacity determined by the fracture initiated from the weld toe was significantly affected by the weld toe shape, rather than the weld metal strength.

In fabricating curved girders, automatic welding robots cannot be applied to welding of horizontal stiffeners to the web panel due to the girder curvature and manufacturing costs increase. Elimination or reduction of the number of horizontal stiffeners is desirable. In this study, FE analysis was carried out varying the curvature and the width-thickness ratio of the web panel. To evaluate the bending buckling strength, the relationship between the bending buckling strength and the curvature has been clarified considering the initial deflection and the residual stress. From the results, it was found that the influence of the curvature on the bending buckling strength of the web panels is small if the radii of curvature are between ∞ and 40m.

Anti-symmetric Z-type NC braced frame is a new structural system that has seismic response reduction capability based on incremental torsional deformation. This torsional deformation is due to the characteristics of NC brace, especially it is necessary to reveal the effect of frame eccentricity in such a system. Against the background, this paper discusses behavior of Anti-symmetric Z-type with eccentricity. First, static loading tests with several eccentric levels were carried, and then time history analyses using the absolute value and sign of eccentricity, building natural period, brace stiffness ratio, and seismic ground motion as variables were conducted.

The yield strength of high strength bolted T-stub joint has different definitions depending on design codes. In addition, the stress status at these yield strength points is not clarified. The purpose of this study is that the validation of current design codes is clarified by observing the stress status of joint flange and axial force of high strength bolt by FE analysis. The first result of this study is that the optimal design code is dependent on the joint yield mode. The second result is that the joint yield strength is able to be estimated accurately by combining current design codes.

Lap joints are used for angle steel members in truss towers for power transmission. Buckling strength with lap joints decreases because of the additional bending moment due to eccentricity, but the current design formula does not reflect that eccentricity as a parameter. In this paper, firstly, based on the Ježek’s theory, an evaluation formula for the inelastic buckling strength considering lap joints is shown. Secondly, the ultimate strength of members based on the current design formula is estimated and the structural safety of existing steel truss towers are revealed. Finally, a simple design formula is proposed.

Low cycle fatigue in steel caused by earthquakes can result in large cyclic strain failures. In the studies conducted to date, low cycle fatigue crack propagation has primarily been investigated under constant amplitude loading. However, actual seismic motions are characterized by amplitude changeability from high to low or from low to high levels, and the effect of these alterations on crack growth in steel has not yet been clarified. Accordingly, this study examines crack propagation patterns under two-steps variable amplitude loading, which has two different uniform amplitude steps. The first part of this paper examines crack growth rates under constant amplitude conditions to obtain basic characteristic. Then, several patterns of two-steps variable amplitude loading are investigated. Research results show that, when compared to constant amplitude conditions, crack growth rates in steel increase when the amplitude decreases from high to low levels. Finally, a formula containing finite element analysis parameters was constructed and verified, thus providing a new method for obtaining good estimations of the crack growth rate.

In this study, the differences of the three-dimensional seismic response behaviors of the steel I girder bridges that constructed in many cases were clarified. And, The design issues of the steel I girder bridges under the L2 earthquakes are summarized. Of comparing the result of the design with the result of the entire bridge dynamic analysis, it was confirmed that the L2 seismic responses of the members exceed the allowable design level for the L1 earthquakes. These exceeding responses are considered to be problems for the existing bridges, but, the damages of the bridge members are consistent with the damages of the steel I girder bridges caused by past large-scale earthquakes.