CHARACTERIZING NEAR FAULT GROUND MOTION FOR THE DESIGN AND EVALUATION OF BRIDGES
CHARACTERIZING NEAR FAULT GROUND MOTION FOR THE DESIGN AND EVALUATION OF BRIDGES
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发表时间：
2002-03
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通讯作者：
P. Somerville
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作者：
P. Somerville
近断层地震动与普通地震动的不同之处在于，它们往往包含强相干动态长周期脉冲和永久地面位移。动态运动以大的长周期运动脉冲为主，该运动脉冲发生在垂直于断层走向的水平分量上，由破裂方向性效应引起。最近地震的近断层记录表明，该脉冲是窄带脉冲，其周期随着震级而增加，正如理论所预期的那样。这种脉冲周期的震级依赖性导致响应谱有一个峰值，其周期随着震级的增加而增加，使得中等震级地震的近断层地面运动可能超过中间周期（大约1秒）的较大地震。近断层地震动中的静态地面位移是由地震发生的断层两侧的相对运动引起的。这些位移在具有表面破裂的断层上是不连续的，并且可能使跨越断层的桥梁遭受显着的差异位移。静态地面位移与大动态运动几乎同时发生，表明静态和动态位移需要被视为重合载荷。
Near-fault ground motions are different from ordinary ground motions in that they often contain strong coherent dynamic long period pulses and permanent ground displacements. The dynamic motions are dominated by a large long period pulse of motion that occurs on the horizontal component perpendicular to the strike of the fault, caused by rupture directivity effects. Near fault recordings from recent earthquakes indicate that this pulse is a narrow band pulse whose period increases with magnitude, as expected from theory. This magnitude dependence of the pulse period causes the response spectrum to have a peak whose period increases with magnitude, such that the near-fault ground motions from moderate magnitude earthquakes may exceed those of larger earthquakes at intermediate periods (around 1 second). The static ground displacements in near-fault ground motions are caused by the relative movement of the two sides of the fault on which the earthquake occurs. These displacements are discontinuous across a fault having surface rupture, and can subject a bridge crossing a fault to significant differential displacements. The static ground displacements occur at about the same time as the large dynamic motions, indicating that the static and dynamic displacements need to be treated as coincident loads.