報告書番号

381005

タイトル（和文）

送電鉄塔用深礎鋼枠拡底基礎の引抜き耐荷力の評価

タイトル（英文）

PULLING-OUT RESISTANCE OF ELECTRIC TOWER FOOTING PARTIALLY PENETRATING INTO THE SURROUNDING GROUND AT ITS BOTTOM WELL

概要 （図表や脚注は「報告書全文」に掲載しております）

深礎鋼枠拡底基礎の引抜き耐荷力に関する数値解析（軸対称回転体有限要素法）を行って以下の結果を得た。１原位置での深礎拡底基礎の引抜き実験を数値解析した結果，実験によって得られた引抜き耐荷力４２０ｔｏｎに対し，数値解析で得られた引抜き耐荷力は４４０ｔｏｎが対応しており，用いた軸対称回転体の非線形弾性有限要素法の有用性を確めた。２直径２．５ｍの柱体底部から４５ｃｍを部分的に鋼枠で拡底する深礎基礎について，根入れ深さ１０ｍ，１５ｍ，２０ｍ，の場合について数値解析を行い，それぞれ５５０ｔｏｎ，１００５ｔｏｎ，２１９５ｔｏｎの引抜き耐荷力が得られた。３ＪＥＣ－２式，井筒・ケーソンに用いられている引抜き耐荷力の設計式と上記の結果とを比較した結果，井筒・ケーソン等で用いられている設計式に，歯型面積を加えた面積を持つ円の直径Ｄの１．２倍を与えるのが実用的である。

概要 （英文）

IN ORDER TO ESTIMATE PULLING-OUT RESISTANCE OF ELECTRIC TOWER FOOTING WHICH HAS A WELL AND PARTIALLY PENETRATES INTO SURROUNDING GROUND AT ITS BOTTOM,COMPUTATIONAL ANALYSIS WAS CARRIED OUT BY USING AXI-SYMMETRIC FINITE ELEMENT METHOD IN WHICH NON-LINEARITY OF MECHANICAL PROPERTIES WERE TAKEN INTO CONSIDERATION. RESULTS OBTAINED ARE AS FOLLOWS: 1 EXPERIMENTAL RESULT OF PULLING OUT TEST IN SITU CANSUCCESSFULLY BE SIMULATEDBY THE APPLIED METHOD. THE RESISTANCE 420 TONOF TEST IN SITU RESULTED IN 440TON OF COMPUTATION.IT IS CONFIRMED THATFINITE ELEMENT METHOD CAN BE WELL APPLIED TO ESTIMATE PULLING OUT RESISTANCE OF THIS TYPE OF ELECTRIC TOWER FOOTING. 2 DEEP WELL WHICH HAS THE DIAMETER OF 2.5M AND THE PENETRATING PARTS OF 45CM IN A SHAPE OF DENTS,IS USED AS MODEL OF COMPUTATION.THREE DEPTH OF 10,15 AND 20M ARE SELECTED.OBTAINED PULLING OUT RESISTANCES ARE 550,1005 AND 2195 TONS RESPECTIVELY. 3 AS CONVENTIONAL DESIGN METHODS,TWO EQUATIONS ARE PROPOSED.THEONE IS JEC-2 BASED ON SUPPOSED COUNTER-BALLANCED WEIGHT OF SURROUNDINGGROUND AND THE ANOTHER IS BASED ON SHEARING RESISTANCE ALONG THE CONTACT AREA BETWEEN WELL OR CAISSON AND SURROUNDING GROUND.BY COMPARING RESULTS OBTAINED BY THESE TWO EQUATIONS WITH THOSE OBTAINED FINITE ELEMENTCOMPUTATIONS,IT IS FOUND OUT THAT EQUATION PROPOSED FOR CAISSON OR WELL CAN PRACTICALLY BE RECOMMENDED FOR THE ESTIMATION OF PULLING-OUT RESISTANCE OF THIS TYPE OF ELECTRIC TOWER FOOTING.FOR CALCULATING THE EFFECT OF PENETRATING PARTS,EQUIVALENT AREA WHICH IS SUPPOSED TO BE THE AREADETERMINED BY AN ENVELOPE OF PENETRATING PARTS SHOULD BE TAKEN INTO CONSIDERATION.

報告者

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