報告書番号

380006

タイトル（和文）

送電鉄塔用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 TRANSMISSION TOWER FOOTING PARTIALLY PENETRATING INTO THE SURROUNDING GROUND AT ITS BOTTOM SLAB

概要 （図表や脚注は「報告書全文」に掲載しております）

中部電力は送電鉄塔用基礎として，鋼枠拡底基礎を開発，基礎の拡底部が効果的に引抜き力に対して抵抗することを期待した。本研究は拡底の効果と耐荷力とを評価する目的で，模型実験と数値計算を行って以下の結論を得た。１拡底基礎の引抜き耐荷力は拡底部を持たない基礎の引抜き耐荷力の３０～１００％増となる。２鋼枠で拡底する部分の歯型形状の数は実用上耐荷力にほとんど影響しない。３三次元計算で引抜き耐荷力を評価すると，砂地盤の場合１．７ｔｏｎ，粘土地盤の場合１１５ｔｏｎであった。これらの値はそれぞれ模型実験では２．０ｔｏｎ，１００ｔｏｎに対応している。４設計基準に示されている円形基礎の半径Ｒを求めるために軸対称計算を行い，拡広部の面積と等しい面積の円の半径ｒの１．２３倍をＲとして設計に用いれば良いことを示した。

概要 （英文）

CHUBU ELECTRIC POWER CO. HAS DEVELOPED ELECTRIC TRANSMISSION TOWER FOOTING,THE BOTTOM SLAB OF WHICH PENETRATES INTOTHE SURROUNDING GROUND SO AS TO EXPECT THE PENETRATING PARTS TO RESISTEFFETIVELY AGAINST PULLING-OUT LOAD. IN ORDER TO MAKE CLEAR THE EFFECTOF THIS PENETRATING PARTS ON PULLING OUT RESISTANCE AND TO ESTIMATE THE RESISTANCE,EXPERIMENTAL ANALYSIS BY MODELS AND COMPUTATIONAL ANALYSISWERE MADE. IT IS CONCLUDED AS FOLLOWS. 1.THE PULLING-OUT RESISTANCE OFFOOTING SHAVING PENETRATING PARTS AT ITS BOTTOM SLAB EXCEED THAT OF THOSE WITHOUT PENE TRATING PART IN, FROM 30 TO 100 PERCENT. 2.THE SHAPE OR THE NUMBER OF PENETRATING PART HAS PRACTICALLY LITTLE EFFECT ON THE RESISTANCE. 3.THREE DIMENSIONAL F.E.M. UNDER THE CONDITION OF INCREMENTAL LOAD IS APPLIED FOR ESTIMATING PULLING-OUT RESISTANCE OF THIS TYPE OFFOOTING. THE COMPUTATIONAL RESULTS SHOWED RESISTANCE OF 1.7 TONS IN CASE OF SANDY GROUND AND 115 TONS IN CASE OF SILTY GROUND. THESE VALUES ARE CORRESPOND TO 2.0 TONS AND 100 TONS IN EACH EXPERIMENTAL CASE RESPECTIVELY. 4.AS A DESIGN CRITERIA PRACTICAL SOLUTION IS PROPOSED FOR ESTIMATING PULLING OUT RESISTANCE OF FOOTING HAVING A CIRCULAR SHAPE. IN THECASE OF THIS TYPE OF FOOTING HAVING PENETRATING PARTS,AXI-SYNMETRIC F.E.M. IS APPLIED FOR MAKING CLEAR THE EQUIVALENT VALUE OF RADIUS R,WHICHCAN BE REPLACED INTO THE PLACTICAL SOLUTION MENTIONED ABOVE. THE EQUIVALENT VALUE R IS FOUND TO BE THE PRODUCT OF 1.23 AND R. WHERE R IS A RADIUS WHICH GIVES THE SAME AREA OF THE FOOTING INCLUDING ITS PENETRATINGPART.

報告者

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