間接邊界元素法在平面ＳＨ入射波之站址效應問題研究

Abstract

由經驗得知地震引起之災害因地盤差異而有顯著之不同。且震災程度之大 小受地盤的影響，即站址效應，遠較震央距之遠近為大。本研究即針對邊 界積分法在求解無限及半無限空間領域問題之優越性，以單層勢理論推導 之邊界元素法提供一求解平面ＳＨ入射波之站址效應問題的適用方法。本 研究主要探討入射波波長對最小元素長度之比值與數值解精確度之關係， 同時也比較二次形元素及常數元素之數值結果。當入射波波長與最小元素 長度之比值約為10，即一個入射波波長約含十個元素，可得精確之數值解 ，同時二次形元素比常數元素可得較精確之數值解。 Boundary Integral Equation Method is usually applied in problems with full and half space because of the ability to reduce the dimension of problems by one. In this paper, the Indirect Boundary Element Method formulated by the use of single-layer potentials, i.e. a distribution of sources placed on boundary surfaces, is used to solve the problems of site effect due to the plane harmonic SH waves. Form the numerical solutions, there may be likely to generate a 'rule of thumb' that an accurate solution can be obtained when the ratio of a wavelength. Also, the numerical solutions obtained by the quadratic elements is more accurate than those obtained by the constant elements.