Exposure test of high-strength friction-grip bolts fastened by yield-point method has been conducted for more than 20 years, but delayed fracture of the bolts has not been found. Most of the high-strength friction-grip bolts for Honshu-Shikoku bridges were fastened on the sea by yield-point method, by which high-strength bolts are fastened with higher force than by conventional torque method. Delayed fracture of bolts often occurs in severe corrosive environment and with high stress in the bolts. The exposure test has been conducted to study the characteristic of delayed fracture of the bolts. However, delayed fracture of the bolts has not been found.
This paper reports a fracture mechanism of steel finger type expansion joints in highway bridges. Based on investigations on the damaged actual steel finger type expansion joints, a fracture process of the joints was estimated. The fracture process was supported by FEM analyses conducted on the damaged joints. In conclusion, the present study has demonstrated that the fracture mechanism of steel finger type expansion joints has a typical fracture process of the members by fatigue and corrosion.
Plate buckling preventions of steel plate panels are keys to enhance seismic performance of existing steel bridges and additional stiffeners can improve their buckling strength and ductility. Then focused on in this study is a seismic retrofitting technique of steel plate panels with lack of ductility using an L-shaped member attached with high strength bolts. Also focused on is the influence of an initial stress on the strengthening effects. 5 short column specimens with steel hollow cross section before/after being strengthened are used in compression tests. It is concluded that the bolted additional stiffeners as well as the welded ones effectively work for buckling prevention of steel plate panels.
The aim of this study is to develop of a new shear panel damper using stainless steel which possesses high ductility and a large dissipation capacity. In order to investigate the hysteretic performance of shear panel using stainless steel, an experimental work was carried out under cyclic horizontal loads. The experimental parameters were kind of steel(SS400, SUS304, SUS329J4L) and width-to-thickness of shear panel. From the experimental results, it has been made clear that shear panel damper using stainless steel exhibits good hysteretic performance up to large deformation. The total energy dissipation of specimen SUS329-30 was 1.44 times larger than that of specimen SS400-33.
In order to investigate the effect of applied force on slip behavior and resistance of high-strength bolted friction joints, tension and compression tests were carried out. The slip behavior is almost similar in both tests of joints with 3 rows of bolt and the slip resistance obtained by compression tests increased about 9% compared with the tension tests. From the compression tests with 3-12 rows of bolt, it is obtained that the slip resistance of joints with more than 6 rows of bolt didn’t decrease and kept to an average value of 0.59 for the slip coefficient.
As a new damper which is suited to seismic retrofit for existing high-rise buildings, the authors have developed a passive variable friction damper (VFD) with displacement dependent damping force characteristics. In the present paper, in order to evaluate the response control effects of high-rise buildings incorporating VFDs, earthquake response analyses were conducted using thirty-story frame structure models with VFDs, with conventional friction dampers, or without dampers. The results indicated that VFDs can mitigate response story shear forces and column axial forces compared with conventional friction dampers.
For investigating the effect of heating and cooling process assuming fire of steel bridges on characteristics of welded joints of structural steel members, a series of experiments were carried out. The heating under transformation point did not affect the joint performance regardless of cooling process. The heating over transformation point caused the softening or the hardening according to cooling rate. The degree of them was larger in the base metal rather than in the weld metal because the amount of carbon in the base metal was more than that in the weld metal. Furthermore, the change of microstructure of base metal made by TMC process was more sensitive compared with that of weld metal.
In the current specifications for highway bridges in Japan, interactions between lateral torsional buckling and the local buckling of the flange plate and/or web plate, and between the local buckling of a flange plate and a web plate are not considered for the ultimate bending strength for steel I-girders. In this study, a series of finite element analysis were performed on homogeneous and hybrid steel I-girders. The ultimate bending strength through the analytical results were compared with the estimated ultimate strength based on several formula proposed by other reearchers. In addition, design equations were proposed for the bending strength of both homogeneous and hybrid I-girders considering the interaction between the local buckling and the lateral torsional buckling.
In order to evaluate the slip behavior of high strength bolted friction joints by FEM analysis, modeling to introduce the axial force to bolts is examined. As a result, the fastening force model is estimated appropriate, and the applicability of this model to FEM analysis for evaluation a slip test with number of rows of bolts and a girder bending test with the joints with super high strength bolts is examined.
Over the past few years, several studies have been made on mechanical characteristic of perforated-rib shear connector (PBL) and burring shear connector (BURRING) by push-out test for building structures. The purpose of this study is to examine the effect of BURRING and PBL on bending behavior of steel-concrete composite beams. Full-scale bending tests are performed on four composite beam specimens using BURRING, PBL and headed stud shear connector. The composite beam specimens were designed to be partial composite. It was found from the result that the rigid shear connectors showed a good performance.The results of this experiment will change design of shear connector on steel-reinforced concrete joints.
This paper describes a methodology of earthquake-resistant structural design of the steel-braced multi-story frames specifying the maximum inter-story drift angle. The authors have been studying on a new structural design method of the steel frames with the conventional or ordinal steel braces as the vibration-control devices. It was clarified that the steel braces can reduce the maximum inter-story drift angles in a frame under earthquake through past researches by the authors. Eventually, the paper concludes that the presented design method of the multi-story frames with the ordinal steel braces introducing an equivalent one-mass system is useful and powerful in the specifying-oriented structural design.
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