To investigate the behavior of composite beams under lateral-torsional buckling, a numerical model with rotational and horizontal springs, which consider the restraint by concrete floor slab, at the top flange is often used. This paper studies the effects of the arrangement of headed studs on the rotational restraint to the top flange by the slab. First, a loading test of slab-beam subassemblies is conducted, and the test results regarding rotational stiffness and maximum strength are compared with calculations based on past methods. Second, new calculation methods are proposed to consider bearing deformation of the slab and validated through the test results and FEA results.

This paper discusses residual strain accumulation of stainless steel under cyclic tensile loading. In fatigue tests of stainless steel carried out by the authors, the phenomenon of increased displacement during the test was observed. The phenomenon is called ratcheting and was investigated in detail by measuring the strain during fatigue tests using strain gauges. As a result, large residual strain was developed when the maximum stress during the test exceeded the 0.2% proof stress of the materials. In addition, by considering the effects of temperature and strain gauge performance on the test result, it was shown that ratcheting is negligible when the stainless steel is used below the elastic limit.

This paper presents the results of material tests and analyses to support the selection of constitutive laws and material parameters for reproducing the cyclic elasto-plastic behavior of SBHS500, a high-performance steel for bridges, in steel members using commercial structural analysis software. Targeting on three types of constitutive laws with different expressions of strain hardening, material parameters were selected for each of them under multiple conditions to find the appropriate method for determining material parameters in terms of the reproducibility of test results. The results of cyclic elasto-plastic loading analysis using the identified material parameters for a four-sided simply supported plate as the basic element of a steel member showed the trend of the analytical results with each constitutive law.

This study focuses on the joints of an earth-retaining beam joints. In this study, the effects of errors in the initial bolt axial force and bolt hole misalignment on joint performance and residual deformation were investigated through parametric FE analysis. The analysis results indicate that the initial axial force of the bolts used to tighten the splice plate affects the yield strength, while the misalignment of the bolt holes influences the maximum bearing capacity. Residual deformation occurs between the end plates when the axial force of the bolt tightening the splice plate is low; however, the magnitude of the residual deformation is minimal.

Bolted joints of prominent-size members require many bolts because the slip and after-slip resistance decrease proportionally to the number of bolts. Unevenness of the load transfer ratio and shear deformation of each bolt should be solved to utilize all bolt’s strength and make the large-size joint compact. A countermeasure we developed is the application of a new faying surface treatment composed of polyurea resin and nickel mesh. This paper conducts a pilot tensile tests of coupon specimens applied with the treatment to investigate whether it contributes to mitigate the unevenness. The obtained results indicate that the treatment enhance shear deformation capacity of faying surface and equalize the load transfer ratio of bolts.

Many fatigue tests have been conducted to reproduce a root crack in deck-to-U rib welded joints and to investigate its fatigue durability. Nevertheless, no unified fatigue strength evaluation method for the root crack has been established. In this study, total of 154 fatigue test results were reproduced in the analysis to obtain artificial notch stress at weld root, and the test results were rearranged by the notch stress. Two million cycles fatigue strength and its standard deviation based on the notch stress are discussed in this paper. Two million cycles fatigue strength tends to be higher when the mean stress in cyclic loading is in compression. By correcting the test results with the stress ratio, all test results located around a unified fatigue strength curve.

In this study, shear-loaded experiments on 4.8, 8.8, and 12.9 class bolts were conducted under both elevated temperatures and ambient temperature after heating and cooling processes. The test results on the reduction factors of shear strength at fire and the residual shear strength at post-fire were accumulated. Those test results contribute to the evaluation of the structural fire-resistance performance on the bolted connections.

The purpose of this study is to investigate the out-of-plane deformation of splice plates in the high strength bolted friction joint under compression load. Compression tests of high strength bolted joint with double frictional surface were carried out. From the test results, two types of deformation mode appeared, one is the lower fixed end of specimen moves horizontally, and the other is the lower fixed end does not move. Maximum compressive strength of the former mode whose generalized slenderness ratio is less than 1 is well predicted by the bending buckling equations of the past.

In this study, as a preventive maintenance method against root cracks at welded joints of cover plates, the tap bolt joint method with tap holes in both plates was proposed based on the concept of reducing the relative displacement between plates which is the cause of root crack initiation. As a fundamental study on the tap bolt joint, the fatigue strength of the joint and relative displacement of plates were evaluated by fatigue tests and FEA. It was revealed that the fatigue strengths were distributed around JSSC-E to F classes under cyclic tensile axial loads, JSSC-A class under cyclic compressive axial loads and much higher than JSSC-S class under cyclic shear loads.

In recent years, SBHS500 (Steels for Bridge High-performance Structure) has been standardized in Japanese Industrial Standards and in Japanese Design Specifications for Highway Bridges. Compared with conventional steels, there is a lack of information on SBHS500. In this study, tensile tests of SBHS500 and axial compression tests of cruciform stubcolumns were conducted, comparing the results with those of conventional steels. Analytical study was also conducted using a method that was validated by comparing experimental results and analytical ones. Based on the information obtained in both experimentally and analytically, evaluation formulas for the load carrying capacity of outstanding plates were proposed.

Numerous damages of steel roof bearing connection of RC gymnasia have been reported at recent major earthquakes. One of major failure modes is concrete break-out failure due to a lack of edge distance between anchor bolts and concrete surface. To increase the shear strength of the connection, it is proposed that an anchor bolt is arranged at the center of the RC element, and stiffened by welding steel plates. A series of static tests has been conducted and results show that the ultimate strength of conventional connections is determined by concrete break-out strength while those of proposed connection is increased.