近、远场强震下RC连续梁桥损伤及滞回耗能特性对比研究

Comparative Study of Damage and Hysteretic Energy Characteristics of RC Continuous Girder Bridge Caused by Near-field and Far-field Strong Earthquake

以某高速公路RC连续梁桥为对象,建立可考虑桥墩非线性力学行为的全桥有限元数值模型,挑选典型近断层和远场强震记录,采用非线性时程积分方法并自编程序提取关键指标,对比分析了两类地震下频谱、峰值加速度(PGA)、持时等要素对滞回耗能、结构损伤的量值及其分布的影响规律。研究表明,地震动频谱特性对于结构地震响应有显著影响,PGV/PGA越大,会导致滞回耗能和损伤的显著增加;在同样的PGA和持时水平下,近场地震下桥墩各部位的滞回耗能及损伤均明显大于远场,且损伤沿桥墩出现的高度更大;在靠近墩底的一定范围内,近场地震下的滞回耗能和损伤所占比例小于远场,而在该区域以上则大于远场,表明近场地震下桥墩滞回耗能和损伤沿墩高的分布更加均匀。对比发现,近场地震对桥梁结构提出了更高的耗能和变形需求,且向桥墩上部延伸更加明显,对桥梁抗震设计提出了更高的要求。

Taking an expressway RC continuous girder bridge as the research object, the finite element model of the bridge considering nonlinear mechanical behavior of bridge piers is built. Selecting Typical near-fault and far-field strong earthquake records, the influences of frequency spectrum, peak acceleration （PGA）, and duration on the values and distribution of hysteretie energy, structural damage is comparatively analysed by nonlinear time history integration method and key indexes extracted by self-programming. The study result shows that （1） the frequency characteristics of ground motion has significant influence on the seismic response of bridge structure, and the increase of PGV/PGA will lead to significant augment of hysteretic energy and damage; （2） at the same level of PGA and duration, the hysteretic energy and damage of the bridge piers under near-field earthquakes are far greater than those of far-field earthquakes, and the appearance position of damage is much higher; （3） in certain region near the pier bottom, the proportions of hysteretic energy and damage under near-field earthquakes are less than those of far-field earthquakes, while the above indexes are greater than those under far-field earthquakes outside that scope, which shows the distribution of hysteretic energy and damage under near-field earthquakes are much evener along piers. The comparison shows that near-field earthquake has more vigorous requirement of hysteretic energy and damage on bridge structure, and they expands upward along the pier height, which put forward much strict requirements for seismic design of bridge under this kinds of earthquake.