軽量コンクリート鉄道橋の施工
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概要
- 論文の詳細を見る
It is more than ten years since prestressed concrete (PC) was applied to the superstructure of concrete railway bridges in Japanese National Railways (JNR). Since then nearly 2000 PC bridge girders have been constructured in JNR. To make the PC girder span longer, the Tokyo Construction Division hit idea of using lightweight aggregate, and various researches and tests on concrete structure have been conducted since 1962, using artificial lightweight aggregate with burnt expanded shale. The live load of railway bridges is heavier than that of highway bridges. And the repeated stress by wheels of rolling stock have great effect on the fatigue strength of girders. Therefore, many kinds of basic tests have been conducted by placing stress on dynamic tests. When lightweight aggregate is used for prestressed concrete, its strength inevitably goes down. So, as the results of the tests conducted to research the tendency of decrease in the strength of lightweight concrete, it was decided to use natural aggregate together with lightweight aggregate. This has enabled us to obtain a compressive strength of 400 to 500 kg/cm^2 and a specific gravity lighter by 20 to 30 per cent than ordinary concrete. A few points made known as the result of our researches and tests are : The Young's modulus of lightweight concrete is 40 to 60 per-cent less than that of ordinary concrete. No special difference is seen in the bending strength, but there is a little decrease in the shearing strength. It is suggested, therefore, to make the allowable stress of diagonal tensile strength about 20 per cent less than for ordinary concrete. The elastic deflection at the time the girder is loaded is about twice as much as that in case ordinary concrete, and its value is almost in inverse proportion to the Young's modulus. Based on the result of our researches and tests, the Kanayama Overbridge of the Tohoku Main Line, the elevated approach bridge to the Arakawa Bridge of the Sobu Main Line, etc. have been constructed since 1965, and investigations on these bridge girders are being pursued.
- 社団法人日本材料学会の論文
- 1969-02-15