Investigation of spatially varying ground motions and soil-structure interaction effect on bridge girder pounding

研究的主题是地震动空间变化和土-结构相互作用对桥梁结构相对响应的同时影响。本研究项目为期三年，2005财年为最后一年。研究结果如下：如果土质较软，相邻结构的长细比不相同，即使它们具有相同的固定基频和相同的地面激励，也会发生冲击，因为在不同的长细比下，相邻结构会发生非同相振动。在频率比大于0.6的情况下，非均匀地震动和土-结构相互作用的同时作用会因接触力的增大而显著放大梁的损伤潜力。因此，由于多次后续撞击造成的损坏是可能的。在频率比大于1.6的频率比范围内，非均匀地震动比土-结构相互作用的影响更大。如果相邻结构具有不同的长细比，即使在频率比为1.0时，土-结构相互作用的影响也比非均匀地震动更强。尽管日本的设计规范是目前最先进、最严格的规范，并且隐含地包括了地面运动的空间变化的影响，但所要求的座位长度可能仍然不够，特别是当相邻的桥梁结构是柔性的，当两个结构经历不同的SSI时。如果支撑土在空间上不均匀，即使两个相邻结构具有相同的长细比、相同的基频和相同的地面激励，也可能发生不同的土-结构相互作用。这种不均匀的土-结构相互作用会显著影响结构的相对响应。在今后的设计规范中，应考虑到空间非均匀地激励的影响。少

The subject of the investigation is the simultaneous influence of spatial variation of ground motions and soil-structure interaction on the relative response of bridge structures. The duration of this research project is three years, and the fiscal year 2005 is the last year.In the following the results of the investigation are summarized :If the soil is soft and the neighbouring structures do not have the same slenderness, even though they have the same fixed-base fundamental frequency and experience the same ground excitation, pounding can take place, because with different slenderness both adjacent structures can vibrate out-of-phase.In the case of frequency ratio larger than 0.6 the simultaneous effect of non-uniform ground motions and soil-structure interaction can significantly amplify the girder damage potential due to larger contact forces. Consequently, damage due to multiple subsequent poundings is possible.In the frequency ratio range around 1.0 and also in the higher freque … More ncy ratio range above 1.6 non-uniform ground motions have stronger influence than soil-structure interaction. If the adjacent structures have different slenderness, however, soil-structure interaction can have stronger effect than non-uniform ground motions even at the frequency ratio of 1.0.Although the Japanese design specification is currently the most advanced and strictest regulation and implicitly includes the effect of spatial variation of ground motions, the required seating length may still not be adequate, especially when the neighbouring bridge structure is flexible and when both structures experience different SSI.Different soil-structure interaction can also occur, even though both adjacent structures have the same slenderness, the same fundamental frequency and experience the same ground excitation, if the supporting soil is spatially not uniform. This unequal soil-structure interaction can significantly affect the relative structural response. It should be incorporated together with the influence of spatially non-uniform ground excitation in future design regulations. Less