報告書番号

383020

タイトル（和文）

軟質地盤上の大型基礎の動的挙動に関する実証研究（その１）起振時における基礎の振動特性

タイトル（英文）

EXPERIMENTAL STUDY ON DYNAMIC BEHAVIOR OF LARGE SCALE FOUNDATION (1) -DYNAMIC BEHAVIOR OF THE FOUNDATION DURING VIBRATION TEST-

概要 （図表や脚注は「報告書全文」に掲載しております）

原子力発電所の第四紀地盤立地のためには，埋設部の深い大型構造物の挙動解析が不可欠である。原工試センターの保有する振動台基礎は砂礫地盤に建設されている基礎としては最大級であり，その起振実験は上の目的に有用な知見を提供する。このため同基礎の振動特性を把握して各種解析手法のベンチマークとすることにした。この結果，上下・水平方向起振とも約２Ｈｚに卓越する共振点を有し，高振動数域では急激に減衰することが判った。２Ｈｚの共振点は剛体モードであり，高次振動は基礎版の曲げ振動である。また上下方向では水平方向に比して側面の埋戻効果は少なく無視できる程度であった。これらの挙動は，半無限弾性論では主要な共振点と全体の傾向が良く表現され，３次元数値解析では全体傾向とともに主要な曲げ振動も含めて良く模擬されている。この成果は各種解析手法が軟質地盤上の大型構造物の動的解析に適用しうることを示している。

概要 （英文）

THE FORCED VIBRATION TEST OF A LARGE-SIZED FOUNDATION HAS BEEN CARRIED OUT AS ONE OF THE STUDIES ON THE ASEISMIC STABILITY OF THE NUCLEAR POWER PLANT ON THE SOFT GROUND. THE PRINCIPAL FEATURES OF THE VIBRATIONAL BEHAVIOURS OF THE FOUNDATION ARE AS FOLLOWS. (1)IN THE HORIZONTAL EXCITATION, RESPONSE CURVES OF THE FOUNDATION PARALLEL TO THE EXCITING FORCE FORM A STEEP PEAK AT 2HZ, AND THE AMPLITUDESDECREASE AS EXCITING FREQUENCIES INCREASE. (2)IN THE VERTICAL EXCITATION, RESPONSE CURVES ARE SIMLAR TO THE CURVES IN HORIZONTAL EXCITATION WITH THE PEAK AT 2 HZ. STRICTLY SAYING, HOWEVER, RESPONSE CURVES OF THE POINTS MEASURED VERTICALLY HAVE GREAT DIFFERENCES FROM ONE TO ANOTHER IN AMPLITUDES, AND THE FOUNDATION BEHAVES AS A FREE-FREE PLATE. (3) USING THE SOLUTION BASED ON THE ELASTIC HALF SPACE THEORY,AND THAT THE FOUNDATION IS EMBEDDED AS IT IS, THE RESPONSE CURVES CALCULATED AGREE WELL AS THE ONE OBSERVED BOTH IN AMPLITUDE AND IN PHASE.IN THIS MODEL, THE SPRING CONSTANT WHICH ACTS ON EMBEDDED SIDE PARTS OF THE FOUNDATION IS ABOUT A HALF OF ONE WHICH ACTS ON BASE OF THE FOUNDATION. (4)IN ORDER TOSTUDY THE USEFULNESS OF THE METHOD MENTIONED ABOVE. THE CALCULATED RESULTS HAVE BEEN COMPARED WITH THE OBSERVED ONES BY OTHER NUMERICAL METHODS. THE 1ST ONE IS TB3D WHICH CONSISTS OF 3D REGION WITH RECTANGULAR COORDINATES AND THE REGULAR REGION WITH CYLINDRICAL COORDINATE CALLED TRANSMITTING BOUNDARY. THE 2ND ONE IS TAJIMI S THIN LAYERED METHOD BY APPLICATION OF 3D POINT LOAD SOLUTION. THE 3RD ONE IS SMITH S METHOD WITHSUPERPOSED BOUNDARIES. AS A RESULT OF COMPARISON, IT IS SHOWN THAT THEHALF SPACE METHOD IS VALID AND EFFECTIVE EVEN FOR THE EMBEDDED FOUNDATION.

報告者

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