QUASI-IMPULSIVE STRUCTRAL FAILURE DUE TO NEAR-SOURCE EARTHQUAKE

1995年兵库县南部地震（科比地震）造成的结构破坏促使作者开始研究近源地震的准脉冲效应和由此产生的结构破坏的脆性类型。自1999年以来，在科学研究补助金的资助下，进行了为期三年的国际合作研究。在这些重要的研究成果中，以下是对科比的芦屋滨高层公寓大楼和桥墩发生特征性破坏的主要原因进行特别关注的摘要：1.在应力波的控制下，结构响应的瞬态阶段起着重要作用，严重影响随后的振动阶段响应，并可能导致随后的重大破坏，在严重地震的情况下，例如近源地震。这种重要性的程度取决于地震动剖面、场地条件和结构特性，如形状、尺寸、边界或支承条件等。2.实际严重损伤位于结构部分附近，在那里能量传输必须发生突变。3.重型钢骨架的实际主要断裂发生在这样的位置附近，据了解是由这种效应引起的。4.其中一个支撑柱节点附近发生的特大型破坏是由支撑在轴向拉力和横向剪力的共同作用下发生断裂，并传递到相邻的柱截面上，最终导致完全断裂。5.屈服铰集中出现在重合层中会导致严重的全层倒塌。这是特别危险的，当发生在结构对地震反应的早期阶段。这些现象已被发现从一个精确的三维有限元动态分析。

Structural damage suffered from the 1995 Hyogoken-nanbu Earthquake (Kobe Earthquake) motivated the authors to initiate investigation into the quasi-impulsive effects of near-source earthquakes and the resulting brittle type of structural failure. An international cooperative research has been carried out for three years since 1999, funded from Grant-in-aid for Scientific Research. Among, significant research results, the following is abstracted with special attention on main causes of characteristic failure undergone at Ashiyahama high-rise apartment complex and bridge piers in Kobe: 1.Governed by stress waves, the transient phase of structural response plays an important role, affecting heavily the following vibratory phase response, and possibly causing subsequent significant damage, in the case of severe earthquakes such as a near-source earthquake. The degree of this importance depends on ground-motion profile, site conditions and-structural properties, such as shape, size, boundary or support condition, etc. 2.Actual severe damages were located near structural portions where abrupt changes, in energy transmission must have taken place. 3.Actual main rupture in the heavy steel skeleton occurred near such a location, and is understood as caused by this effect. 4.The particular large scale rupture experienced near a brace-column joint was initiated by the brace breakage, which was caused by the combination of a great tensile axial force and transverse shear, and was transmitted to the adjacent column cross-section, which resulted in complete rupture. 5.Concentration of yield-hinge occurrence in a coincident story can cause severe whole story collapse. This is particularly dangerous, when occurred in an early phase of structural response to an earthquake. These phenomena have been found from an exact three-dimensional finite element dynamic analysis.