This is a preface to six papers, which conducted a thorough comparative investigation on seismic design codes for steel building structures in Japan and the United States. The study is associated with the globalization of earthquake resistance technologies. The working group organized by the Subcommittee of Steel Connection of the Architectural Institute of Japan surveyed codes and associated regulations proposed by SAC Joint Venture of the United States after the Northridge Earthquake. Similarities and differences of the current Japanese design are examined for steel and electrode materials, design of beam-to-column connections and column bases connections, and the scheme of the seismic design oriented toward performance based design.

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After Northridge earthquake, research projects on seismic resistance of steel structures were performed in the U. S., and the design criteria for beam-to-column connections are recommended in FEMA-350. On the other hand, a recommendation for design of connections, in which the results of recent researches after Kobe earthquake are reflected, was published in Japan. In this paper. the differences of design concepts are discussed, and the data of the U. S. are compared with those of Japan in material properties and structural performances of full-scale specimens.

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During Kobe and Northridge earthquake, many steel buildings were found to have experienced brittle fractures at beam-to-column connections. After those earthquakes, various problems caused by welding material or welding process have been studied both in Japan and U.S. However, little study results have been utilized each other. This paper compares Japan with U.S. on the following three points. The first one is the properties of welding material used well in Japan and the U.S. The next one is the rationality of the combination of welding material and base metal to give beam-end fully plastic deformation. The last one is whether the above-mentioned welding material has enough toughness to apply its connection into Special Moment Frame.

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After Northridge Earthquake and Hyogoken-Nanbu Earthquake, many experimental studies on beam-to-column connections have been conducted in both US and Japan. As a result, it was revealed that welded unreinforced flange, bolted web connections (WUF-B) in US were lack of plastic deformation capacity. This paper presentscomparison of design method of WUF-B between US and Japan. And it discusses influence of panel zone strength and beam depth on plastic deformation capacity. Furthermore, a new type beam-to-column connection, which is developed in US and called free flange connection, is introduced.

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Overview of American steel column base design method and practice is presented and compared with Japanese method and practice. Base plates are used mostly in US steel structures. A rare report of damaged base plate in US reveals characteristic features of American base plate design practice. such as not extending column steel into grade beams, and usage of shear lag to resist shear. After years of indifference. American design procedures are being currently updated, while Japanese procedure was revised after Kobe earthquake. While material strength for design and design load for base plates are different between the two countries, base plate design to resist axial force and bending are similar.

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This paper presents a study on U.S. and Japanese seismic design code and provisions. Recently, seismic design method in U.S. is varied in design seismic load, and especially for seismic rehabilitation of buildings in nonlinear static procedure and dynamic analysis. Overview of design codes and provisions in U.S. and comparison of spectral response acceleration as design seismic load and dynamic procedure between U.S. and Japan are presented, then method for the estimation of target displacement as the nonlinear static procedure is introduced in this paper.

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FEMA-350 is a recommended criteria of performance-based design for steel structures and published in 2000 as the final result of a research project motivated by damage in steel structures by the Northridge Earthquake. This paper presents an overview of its structural performance evaluation methodology and reviews the statistics in order to know the magnitude of supposed variations. Concerned with deformation capacity of beam rotation improved after the Northridge Earthquake, structural test data are compared with those of connections improved in Japan after the Kobe Earthquake.

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The effect of weld penetration on fatigue behavior of welded beam-column connections was focused in this study. Fatigue tests were performed on modeled beam-column connections with fillet and partial penetration welds. The desired weld penetration depth was 0mm for fillet welds and 7mm (one-third of flange plate thickness) for partial penetration welds. Fatigue cracks were initiated from weld roots and/or toes in the fillet welded joints and from weld toes in the partial penetration welds. Fatigue lives were estimated by three kinds of stress ranges, nominal stress range calculated from the beam theory, stress range considering shear lag and hot spot stress range.

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In order to improve the fatigue strength of welded joints, the weld toes with high stress concentration are generally finished by grinding. For the purpose of examining the influence of grinding methods on the fatigue strength of web-gusset welded joints, fatigue tests on web-gusset fillet welded specimens were performed. However, the influence was not examined sufficiently because the weld roots were sometimes fatigue crack origins in finished specimens. In this study, web-gusset specimens were fabricated by full penetrated welding in order to prevent the root-failure. Fatigue tests and stress analyses on the specimens have been carried out.

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There has been a concern on fracture in weld zones between interior diaphragms and a built-up box column at a beam-to-column connection. The concern may become increased when large heat input welding such as electro-slag welding is employed. From this background, it is necessary to consider designs to prevent fracture in beam-to-welded box column connection. Then, in order to confirm the stress in vicinity of joint, finite element analyses were carried out first. It was shown through the analyses that the longitudinal stress area of beam web was smaller than that of the reference 5)'s calculation equation. In addition, a parametric study showed that the stress distributions were influenced by the thickness of column plate, the thickness of diaphragm plate, etc.

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The buckling strength of a compressive steel member is determined based on theoretical and experimental investigations in current steel structural design. The design buckling strength is calculated corresponding to the slenderness ratio and it is small compared with the yield compressive strength, particularly in the elastic region. We study how the strength of the compressive steel member reaches the yield strength regardless of the slenderness ratio with the aim of simplifying the design formula and obtaining esthetically good design of the member. To obtain the yield strength, we adopt a hybrid section member, which is composed of mild and high strength steels, in the plastic buckling region and a gradually extended section member toward the center of the member in the elastic region. The box-shaped and H-shaped steel members are used in the analyses.

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In recent years, plate-section member is used as the column of small buildings in order to express transparency. The purpose of this paper is to discuss the compressive buckling strength of plate-section columns with eccentric lateral support at the center of their length. This paper proposes the buckling strength of compressive member with eccentric lateral support. It is compared with elastic numerical eigenvalue analyses and inelastic large deformation analyses. The eccentric lateral support is useful for plate-section columns. Also this paper discusses the rigidity of support member and proposes the demand of rigidity, compared with the results obtained by the inelastic large deformation analysis.

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This paper is concerned with the demand for ductility of column base in steel moment frames. Numerical response analysis was carried out for 15 frames against a variety of ground motions. In this paper, the magnitude of plastic deforma tion introduced into column base is described. Maximum plastic rotation, maximum increment of plastic rotation during a half cycle of vibration, and the range of variable plastic rotation are considered as the parameters that represent the magnitude of plastic deformation. The results are summarized as formulas to predict those param eters based on maximum story drift angles.

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This paper describes the experiment and the seismic response analysis about steel frame with exposed type column bases under variable axial force.The experiment of the steel frame of three different column bases was carried out to discuss influence of hysteretic characteristic of column bases on elasto-plastic behavior of steel frame.The result of the seismic response analysis of steel frames of a different column base model showed that the structure characteristic of column base under variable axial force have few influence on the maximum story drift of frame and the cumulative plastic rotation of beams.

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It is important to clarify the stress transfer mechanism through the contact surface between steel and concrete in steel-concrete hybrid structures. Then, we carry out the static test of the specimen which is composed of the steel plate and two concrete blocks, and investigate the bonding behavior of the contact surface under the bearing force. In this case, two different ways of applying the bearing force are examined. However, the relation between the maximum shear stress and the bearing stress as well as the relation between the shear stress and the slip does not depend on the application method of the bearing.

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Peak accelerations of the ground motion exceeded 400 gal in Hiroshima-city during the Geiyo Earthquake (M6.4), occurred at 15:28, 24th March 2001. Although recorded peak accelerations were comparable to the Hyogoken Nanbu Earthquake, the damage of the steel structures was negligible. To clarify the reasons, we investigated acceleration response spectra of the seismic motions recorded in Hiroshima Prefecture and selected the P-584 steel circular pier in Hanshin Expressway as a numerical model, which occurred dynamic buckling during the Hyogoken Nanbu Earthquake. We show the computational results of the nonlinear dynamic response of the pier and clarify the characteristics of the Geiyo Eartquake motion from a viewpoint of destractive power.

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Steel brace-type dampers, which were connected appropriately with steel structures, have been used to reduce seismic responses of the structures. Arranging braces with proper rigidity and strength for each story made it possible for structural members such as beams and beam-columns to behave elastically during big earthquakes. We made earthquake response analyses to investigate the conditions required of the braces on which drift angles of all stories were nearly equal and on which the structural members remained elastic. The cumulative damages of the steel brace-type dampers, which absorbed a lot of earthquake energy, were also clarified. The following were taken into consideration in carrying out the analyses: 1) effect of the ratio of brace rigidity to frame rigidity and their distribution in height direction of the structures, 2) allocation system of the braces, and 3) difference in the restoring force characteristics of the braces.

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This research is concerned with plastic deformation demand of energy absorption members in strong column type steel moment frames with eccentricity. In this paper, equivalent single mass and tri-degree of freedom system, which is based on generalized hardening hinge method, are proposed. And it discusses whether the system is available according to comparison with earthquake response of the systems and that of space frame models using fishbone-shaped frames.

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Structural performance of beam-to-column connections constructed by mechanical joint with hysteretic dampers has been presented. Wide flange columns and beams are connected by means of double angle and high strength bolts, and buckling restrained braces, referred to as knee brace dampers, are implemented to improve lateral stiffness of the frame as well as to dissipate seismic input energy. The lateral bracing requirements to prevent knee brace dampers from both the buckling and local failure are derived, and are verified by the tests.

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Dehumidification system h a box girder is the effective tool to reduce the LCC of bridges. The effectiveness of dehumidification system is examined in this study by applying Computational Fluid Dynamics (CFD) combined with transport equations of moisture and temperature to the flow inside a box girder. CFD evaluates that this system consisting of long ducts with small side holes is useful to reduce the total moisture and to avoid locally high relative humidity.

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