報告書番号

382052

タイトル（和文）

ＵＨＶ赤城実規模試験線の動的試験－その（４）鉄塔単体の数値モデルと動特性

タイトル（英文）

VIBRATION TESTS OF A PROTOTYPE UHV TRANSMISSION TOWER (4) -NUMERICAL MODEL AND DYNAMIC PROPERTIES OF TOWERS

概要 （図表や脚注は「報告書全文」に掲載しております）

本報告は鉄塔単体の数値モデル化とこれによる数値解析結果を述べ，そのＵＨＶ鉄塔の耐震・耐風設計への適用を図ったものである。主な結果は以下のとおり：１．現行の静的手法により設計された基礎は鉄塔上部に比して剛であり，通常の地盤では鉄塔の動的挙動は基礎固定の場合について検討すれば十分である。２．鉄塔の各パネルを曲げ変形とせん断変形を考慮した一様断面３次元梁要素に置換する方法を検討し，この要素を用いた固有値解析，定常応答解析によれば立体トラスモデルを用いる場合の１／１０以下の計算時間で精度の良い結果が得られることを示した。この結果，大自由度の多径間連成系の解析が比較的容易に行える見通を得た。上記手法により梁に置換したモデルで２次モード以上の振動性状を求めるためには，せん断変形の影響を正しく考慮する必要があることを明らかにした。

概要 （英文）

EIGEN-VALUE AND FREQUENCY RESPONSE CALCULATIONS OF A UHV TOWER WERE PERFORMED USING SIMPLIFIED EQUIVALENT BEAM MODELS AND SPACE TRUSS MODELS AND THEIR RESULTS WERE COMPARED WITH THE EXPERIMENTAL RESULTS ALREADY REPORTED IN A PREVIOUS PAPER.MAIN RESULTS ARE AS FOLLOWS. (1) NUMERICAL EIGEN-VALUE STUDY ON THE FOUNDATION-TOWER SYSTEM USING AN EQUIVALENT BEAM MODEL AND A SPRING-MASS FOUNDATION MODEL SHOWS THAT THE FOUNDATION-TOWER SYSTEM HAS PRACTICALLY THE SAME MODAL PROPERTIES AS THE BASE-FIXED TOWER.PARAMETRIC STUDY ALSO SHOWS THAT A TOWER CAN BE CONSIDERED RIGIDLY FIXED AT THE BASE FOR THE WIDE RANGE OF GROUND RIGIDITIES.(2) MODAL AND FREQUENCY RESPONSE PROPERTIES OF THE TOWER CAN BE OBTAINED ACCURATELY BY SPACE TRUSS MODELS.EQUIVALENT BEAM MODEL MADE UP OF THE SAME NUMBER OF THREE-DIMENSIONAL BEAM ELEMENTS AS THE TOWER PANELS ALSO GIVES FAIRLY EXACT DYNAMIC PROPERTIES OF THE TOWER WHEN SHEARING DEFORMATION IS TAKEN IN TO ACCOUNT. THIS EQUIVALENT BEAM MODEL,WITH ITS REDUCED DEGREES OF FREEDOM AND LESS COMPUTATIONAL TIME,FACILITATES THE MODELING OF MULTI-SPAN TOWER-CONDUCTOR SYSTEM. (3) SHEAR COEFFICIENTS OF EACH TOWER PANEL WHEN MODELED AS AN EQUIVALENT BEAM IS LARGER THAN THOSE OF RECTANGULAR OR CIRCULAR CROSS-SECTIONAL BEAMS AND ESPECIALLY FOR THE SECOND AND THIRD MODAL PROPERTIES SHEARING DEFORMATION SHOULD BE APPROPRIATELY TAKEN INTO ACCOUNT. (4) VERTICAL OR TORSIONALVIBRATION MODES OF CROSS-ARMS OF THE UHV TOWER EXIST IN THE LOWER FREQUENCY RANGE THAN THOSE OF TOWERS CURRENTLY IN USE. THIS IMPLIES THAT THE DYNAMIC STIFFNESS OF CROSS-ARMS OF THE UHV TOWER IS SMALLER THAN THATOF CURRENTLY IN-USE TOWERS.

報告者

キーワード