Responding to the demand for high strength and high ductility steels, high strength steel with a low yield ratio is recently produced and becomes available in the market. This paper outlines the guideline of structural design to utilize thenew high strength steel, 60 kgflmm.² class high performance steel, in building structures. The guideline was developed by an ad hoc committee where research works have been done intensively on some important items in stability design and connection design. Along the guide, the new steel can be used as a steel material in the current design practice.

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This paper describes the present situation of the use of high tensile strength steel in Japan for civil structures such as bridges, penstocks, water gates and storage tanks. In bridges where weight saving is especially needed, 490-570 N/mm² class steel is used commonly and 690-780 N/mm² class steel is used sometimes. On the other hand in energy facilities upon which high pressure acts, 780 N/mm² class steel is used for penstocks and gas holders, 570 N/mm² class steel for oil storage tanks, and 690 N/mm² class (9% Ni) steel guaranteeing low temperature strength for liquefied natural gas storage tanks.

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This paper reports on the studies concerning Fire Resistant steel for building construction, both in the aspect of steelmaking in the development of steel products and in the aspect of high-temperature strength properties of steel products, joints (high-strength bolts) and structural members, while illustrating the usefulness of Fire Resistant steel by citing an example of a fire-safe design of a high-rise building using Fire Resistant steel without fire protection.

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A new hysteretic damper installed in K-braced frame using low yield stress steel is presented. The mechanism, restoring force characteristics and energy absorbing capacity of the proposed K-braced frame are examined by cyclic loading tests of ( hysteretic damper and model frame ) and elasto-plastic large deformation finite element analyses of the model frame. Through this investigation, it is clarified that the present K-braced frame has very good characteristics as a damper for building frames.

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In the demand of the expanding use of high-strength steel and in pursuit of easy-to-use steel, the authors have developed a new 111780 steel which can be welded with only lowpreheating temperature. The authors clarified that, in reducing the HAZ hardness, which is important in solving problems inherent in conventional steel, B in steel has a great influence. 0n the basis of chemical composition of a low-C, B-free, the authors investigated the other chemical compositions with particular attention to real izing Cu-precipitation hardenabi 1 ity for strengthening the base metal. As a result, a Cu-Nb-V complex-precipitation type steel was selected, whose strength is obtainable over a wide range of tempering temperature. The authors succeeded in securing the base metal performance by applying the thermo-mechanical-controlprocess (TMCP) technology which ensures precipitation hardening and grain minimization simultaneously. Also, weld hardening was greatly reduced compared to conventional steel and preheating temperature of less than 50°C was attained.

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Some measures are necessary in the structures of bIaglev guideway to reduce the magnetic drag force, which resists the movement of vehicle. The object of this paper is to study on the application of austenitic high manganese steels which are one type of non-magnetic steels. Firstly, the effect of using austenitic high manganese steels for reducing the magnetic drag force is described. Secondly, the results of investigations of welding performance and processing performance, and those of fatigue tests of welding joints are described.

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Relations between noment(M) and rotation(θ) at the end of the beams with H shape section are calculated by numerical integration, where the dispersion in mechanical properties is considered on the basis of statistical data. By application of Monte-Carlo method yield strengths and tensile strengths of steel are generated. Referring to the standardized stress-strain curves moment(M)- curvature (θ) relations are calculated. By use of the results M-θ relation can be obtained. As the results, it is concluded that the secondary and the thirdly gradients of M-θ curve are strongly influenced by dispersion of of the yield ratio of steel.

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This paper describes the summary of structural design method and construction procedures of ″Edo-Tokyo Museum″ constructed at Ryogoku site, Tokyo, in march 1993. The unique outlook of the building is derived from the origin of Japanese trailitional housing style. In order to make such unique design realize, several new procedures and consept have been developed. One of the important elements for the construct ion process is welding procedure for the steel joint. As the most reasonable and real istic method, field electroslag welding method was newly adopted.

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In the Landmark Tower, a super high-rise building possessing 70 levels above ground and a height of 296m and completed in 1993 in Minato Mirai area of Yokohama, low yield ratio steel of 60k (570N/mm²) grade for building structures is used for the steel columns which are subjected to a large axial force. On the basis of the results obtained through the experimental study of 60k grade thick steel plate, a method for heat control in welding process was established.

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It has been pointed out for a long time that conventional high strength steel is not fully capable of securing plastic deformation performance because of its high "yield ratio (i.e. a ratio of its yield point to its tensile strength)." It has been a issue in the architectural industry for many years to create a high quality structural steels having a low yield ratio of which yield point do not vary widely. Recently it is becoming possible to manufacture such high-quality, high-strength steel. The authors had a chance to use this steel as a part of composite steel and concrete columns for a high-rise building; the authors introduce in this paper the structural design of that building.

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The weld joint strength is affected by the weld metal aril throat of penetration groove. In ease that the strength of weld metal is lower than the thse, metal, it is so called the soft welds he objective of this paper to make certain that softwelds applied to beam-to-column connections are of adequate strength and defordmtion caricity Columns are ode of 780MPa tensile strength steel with low yield ratio.

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In recent years, various kinds of fine steel were developed for high-rise buildings, long span bridges and other structures with high performance related to noise or sound reduction, magnetic shielding, etc. This paper reviews these steels in regard to their backgrounds of developments, required performance, new manufacturing processes, metallurgical concepts and mechanical & structural properties . Strength, weldability and special performance were mainly discussed.

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A comparative study on the specifications for the design of compressive member with discrete sectional sizes is presented. Three specifications are taken into consideration. They are Specifications for Highway Bridges of Japan Road Association(JSHB), Specifications for Design of Steel Railway Bridges of Japanese National Railways(JR) and Guideline for the Design of Main Towers of Honshu-Shikoku Bridge Authority(HSBA). The discrete values of the sectional sizes of the square boxsections, rectangular box sections and. I-sections are calculated by enumeration method and the results are studied from several points of view.

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Most of steel beams of buildings have openings in their webs to be penetrated by duct pipes. The scales and positions of openings are decided, according to the equipmental requirement and the structural design is done respectively. When beams with so many and large openings as possible and the design method are prepared, it is very useful for equipmental planning, structural design and fabrication of steel members. On this point of view, beams with many and large rectangular openings in their webs are fabricated and the full-scale test is carried out to investigate their stiffness and strength and a simple method to calculate their allowable strength and deformation is proposed.

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In this paper, beam-column connection test subjected to axial force and horizontal force is carried out to examine the ultimate strength of concrete filled steel circular column made of high quality 590N/mm2 tensile strength steel tube. Also, stubcolumn test is carried out for the purpose of estimating the maximum load capacity of confined concrete. As the result of the tests, it is confirmed that the ultimate strength of the column can be estimated taking into consideration the tri-axial stress condition of concrete and bi-axial stress condition of steel tube.

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Development of constitutive model is fundamental requirement to the realistic analytical description of the response of steel construction under cyclic loading such as severe earthquakes. however, previous two-surface models and nested surface models can not give an accurate prediction of hysteretic behaviors of structural steels. In this paper, by introducing the concept of monotonic curve region instead of bounding surface, a constitutive model is proposed. And the experiments in uniaxial cyclic loading conditions for different kinds of structural steels show that the present model has a powerful possibility to describe the hysteretic behavior.

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