After the Hyogo-ken Nambu Earthquake, it is of overriding importance to investigate influences of welding conditions, especially heat input and inter-pass temperature, upon the quality and the execution efficiency of welding parts in structured steel buildings . In this paper, an experiment to quantify effects of these conditions was carried out, and a relationship between heat input and inter-pass temperature was defined. As a result, it was clarified that heat input is the only index to control the quality and the execution efficiency.

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Recently, a lot of fatigue cracks have been found in steel bridges due to the increase of the large-scale vehicles in number as well as weight. In order to consider a repairing and retrofitting method, it is necessary to estimate whether the crack propagates more or not . In this study, a method to estimate the fatigue crack propagation rate is proposed, which is based on the crack opening width measured by image analysis on a digital image recorded with a portable digital microscope. The accuracy and limitation of the method were investigated through a fatigue test carried out on a fatigue crack in welded joint specimen

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The purpose of this paper is to make clear the behavior of friction-type connections fastened with high-strength bolts from the major slip limit . To achieve this objective, an investigation of the relationship between design strength and ultimate limit state, a classification of the limit states of HSFG bolted joint in past experimental studies is conducted. Furthermore a modelling of the contact problem between fastener hole and high-strength bolt using iso-parametric finite element method is carried out . For the results of elasto-plastic finite element analysis, the mechanism of behavior from major slip is clarified and the ultimate limit state including ductility of bolted joint is evaluated.

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The purpose of this study is to clarify the structural performance of the exposed-type column base with U-shaped and bonded-type anchor bolts. The study is made in two steps, first to investigate the optimum anchor bolts and then full-scale column base performance examination.

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In order to examine behavior of an exposed-type column base of steel structures with simplified vertical anchor reinforcement, cantilever beam-columns with RC footing beam are tested under cyclic horizontal force. The test parameter is axial force, strength of anchor bolts and direction of horizontal force. Based on the test results, strength and stiffness of the exposed-type column base are discussed. And it is shown that previous design formulas about those are effective for column base with simplified vertical reinforcement.

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In this paper, fill-scale tests of composite beam subassemblages are performed and the following conclusions are derived.1)The accumulated plastic deformation capacities, η(Σ_bθ_p1)and ηs+(_bθ_s⁺) of composite beam are reduced to maximum 50 and 30 % of steel beams, respectively.2) n of non-scallop type is 1.5 times as much as conventional scallop type.3) Incremental strain of skeleton stress-strain curve in the bottom flange of the composite beam is 2.0 times as much as steel beam when the position of neutral axis is in the upper flange.4) Strain at fracture of the flange of composite beam specimen corresponds to the calculated one according to APD fracture evaluation flow.

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Fracture behaviors of composite beam-to-SHS column connections have scarcely been studied. In this study, a series of tests on beam-to-column connections were carried out with regard to mechanical properties of beam materials (low toughness hot-Rolled H-section vs high toughness hot-Rolled H-section) and geometrical condition of the welded joints.The obtained results are as followings:(1)The specimens with composite beam have smaller deformation capacity than the specimens with steel beam has. It was considered to be attributed to the strain concentration at the beam tension flange by the shift of the position of plastic neutral axis at the beam end.(2)General yield and maximum strength of beam end joint can be estimated by assuming yield line mechanism, respectively.

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This paper presents pull-out tests of perforated plate considering the difference of concrete placing direction and formula proposed for evaluating the shear strength based on the test results. These tests were carried out to apply the perforated plate shear connectors to the girder-topier rigid connections in a steel-concrete hybrid bridge. The shear force in perforated plate within the region of the rigid connection acts in all directions though the uniform direction is observed in usual composite girder bridges. Furthermore, the behavior of perforated plates is significantly complex compared with the headed studs, because of the existence of the void and laitance due to the bleeding in the holes. Test results indicate little difference in the ultimate shear strength of the perforated plate regardless of the concrete placing directions, and the proposed formula of the shear strength represent sufficient safety compared with previous test results.

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In the current Japanese Specifications for Highway Bridges, the design methods for compression members made of high strength steel are not coded. The design of such members is, therefore, carried out on the basis of the concept similar to that of mild steel, and the design concept is not rational for the members made of high strength steel. In this study, the ultimate strength of columns is investigated through a parametric study based on elasto-plastic and finite displacement analyses considering the inherent characteristics of residual stress distribution and stress-strain relationship of high strength steel. Then the buckling design method for columns made of high strength steel is investigated through the numerical results.

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In this paper, the method of setting M-φ models for the steel bridge piers with circular sections is studied. The method of setting M-φ models by using radius-thickness ratio parameters of pipe bridge piers was proposed and the adequacy of the proposed method was verified by comparing the simulation by the proposed method with cyclic loading experimental results, elasto-plastic finite displacement analysis results and the simulation by the previous method.

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In t his paper, the effectiveness of steel bellows as energy absorbing restrainers is investigated for steel continuous girders supported by rubber shoes. The steel girders are assumed as three span continuous beams sandwiched in between rigid abutments. Steel bellows are installed between both ends of girders and abutments in left and right sides as restrainers. The yield strength of bellows needs to be optimized so that deformations of bellows are within elastic region to middle earthquakes, and suitable plastic deformations of the bellows are produced for large earthquakes and their energy absorption reduces inertia forces and response displacements of girders. The design methods using equivalent linear method are utilized to determine dimensions of steel bellows based on response spectrum method. Nonlinear dynamic response analyses are carried out to examine the validity of the design method and the effectiveness of steel bellows are confirmed.

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A new type of hysteretic dampers is presented to be used for spatial structures. The new hysteretic damper is a short steel tubular member that is subjected to shear forces and not any axial force. The new damper is able to resist against horizon tal seismic loads of any direction. The hysteresis curves of dampers are experimentally investigated. As a result, it was made clear that the hysteretic curve is a slip type and the initial rigidity is dependent on the length of panel zone. The ultimate strength can be estimated with the maximum value of shear stress in considering the tubular damper as a thin wail cylinder. Furthermore, the dampers can be easily replaced after damaged.

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This paper presents a study on the U.S. and Japanese seismic design provisionstipulated for moment resisting and braced steel frames. Width-to-thickness requirements, bracing length requirements, structural classification, seismic force reduction coefficients, and design seismic forces are compared, and differences and similarities are discussed. Unreduced seismic forces are relatively similar between the two countries but significant differences are present for the seismic force reduction coefficients that allow for the system ductility. Expected strength capacity of braced frames is estimated in consideration of seismic force reduction coefficients, strength carried by braces relative to frames, buckling and post-buckling strengths of braces. Japanese braced frames are generally stronger than the corresponding U.S. braced frames, with the difference most conspicuous for frames arranged with braces of medium lengths. A combination of larger design seismic forces and large seismic force reduction coefficiets enforced in the Japanese provisions are responsible for the difference.

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