Akimitsu Kurita

Trends in steel-concrete composite bridges in Japan

This paper presents trends in new types of steel-concrete composite bridge decks and piers in Japan, and focuses mainly on composite girders, slabs, and columns. Since 1953, many simple supported composite bridges were built in Japan, but this type of bridge has been built less often during the last two decades. Continuous composite girder bridges show a similar tendency. All continuous bridges constructed since 1973 have been non-prestressed. To increase the durability and load-carrying capacity of bridge slabs, and shorten construction times, various types of slabs for composite girders have been developed, mainly for simple span bridges. Composite girder bridges, using prestressed precast concrete slabs, have been developed recently in Japan. Other types of composite girder bridges include those with a corrugated steel web plate and external cables. The use of steel-concrete composite decks is likely to increase, due to the rapid deterioration of ordinary reinforced concrete slabs for highway bridges. Composite decks in Japan are generally partially precast, and are mainly steel plate-concrete slab composite or concrete-filled steel grillage composite. Applicable bridge types for composite columns are discussed briefly, and the mathematical theory of their strength and ductility is outlined.

Portal Frame Bridges in Japan: State of the Art Report

Abstract In Japan, the portal frame bridge (PFB) has been exclusively used in lieu of the integral abutment bridge (IAB) from about 1995. In the design of the PFB, the structural detailing of the girder–abutment connection becomes very important. Up to now, some structural details for girder–abutment connections have been proposed for bridges constructed in Japan. A brief history and a few completed PFBs are reported in this paper. The focus lies on PFB with steel composite girders in roadways. Some typical structural details of the girder–abutment connection and few constructed examples are introduced and discussed. A new type of approach slab, which has shear projections on its upper surface, has been developed in Japan and there are already some applied examples. A finite element analysis of the interaction among soil, asphalt pavement and approach slab was conducted and the results are reported and discussed in comparison with the conventional design.

Design of Fire Protection for Steel Girder Bridges

From the lessons of many fire accidents of bridge, it concludes that the fire protecting member for bridge, which locates at an intersection of viaduct mainly, is necessary. The authors present the result of the heat transfer analysis for steel girder applied the fire protection material and the structural detail for fire protection in this paper.

FATIGUE VERIFICATION AND ITS CONSIDERATIONS FOR THE STUD IN SIMPLE COMPOSITE GIRDER BRIDGE DAMAGED BY FIRE

鋼・コンクリート合成桁橋が車両事故や不審火などにより火災を受けた場合，鋼桁やRC床版をはじめ，ずれ止めの損傷の有無も確認する必要がある．しかし今日まで，ずれ止めの火災後の力学特性は明らかにされていない．そこで，筆者らは，JSSC標準の押抜き供試体を300°C～700°Cで加熱し,自然冷却した供試体のスタッドに対して静的および繰返し押抜きせん断試験を実施した．その結果，300°Cでは大きな問題は生じないものの，700°Cで加熱したスタッドは，疲労強度が著しく低下することが明らかになった．本文では，この試験結果に基づいて，単純合成桁橋が火災を受けた場合のスタッドに対する疲労耐久性の照査を種々の条件下で実施した結果とその考察について報告する．

APPLICATION OF GROUPED STUDS TO CONTINUOUS COMPOSITE GIRDER BRIDGES

連続合成桁の中間支点付近の負曲げモーメント領域における床版コンクリートのひび割れ対策は重要な課題である. その対策の一つとして橋軸方向にプレストレスを導入する方法があり鋼桁と床版が合成される前にプレストレスを導入することが可能なスタッドのグループ配置が有効である. 著者らはスタッドのグループ配置に着目し, 静的および疲労特性に関する基礎的研究を行い種々の成果を得た. しかし, スタッドをグループ化するときに床版コンクリートに設ける箱抜き孔周辺の応力集中が懸念されるため, 実物大の供試体を用い静的および疲労載荷試験により問題点のないことを明らかにした. さらに, これまでの研究成果を基に疲労の影響をも考慮した試設計を行いグループスタッドの連続合成桁へ適用性を確認した.