Implications of Measured Near-Field Ground Motion for Structural Response

9416174 Iwan本项目的目标是确定与北岭地震期间观测到的近场地震地面运动有关的潜在严重结构反应问题的性质和重要性。从北岭地震测得的近场地面运动表明，速度非常高，地面位移呈脉冲状。这些运动能够导致对各种不同类型的结构的高水平需求，包括基础隔震建筑和多层建筑。北岭地震近场观测到的高速脉冲对较高的多层建筑的性能有很大影响。这些高速在结构中引起的应力波可能会导致很高的楼层漂移，进而可能导致结构元件的失效。初步迹象表明，北岭地震期间由近场速度脉冲引起的故事漂移可能大大超过了规范允许的值。鉴于一些钢结构框架结构在地震中的抗震性能较差，这是一个亟待解决的问题。在这个项目中，使用简单的线性剪切梁模型来确定问题的大小，并确定在开发解决问题的方案时最重要的因素。这项研究的结果将为多层结构的抗震设计是否需要改变以考虑近场效应提供见解。如果需要改变，需要在更严重的后果发生之前尽快确定这些改变。***

9416174 Iwan The objective of this project is to determine the nature and importance of potentially serious structural response problems associated with near-field earthquake ground motions such as those observed during the Northridge earthquake. Measured near- field ground motions from the Northridge earthquake indicate very high velocities and pulse-like ground displacements. These motions are capable of causing high levels of demand for a wide range of different types of structures including base-isolated buildings and multi-story buildings. The high velocity pulses observed in the near-field of the Northridge earthquake are of great concern for the performance of taller multi-story buildings. The stress waves in the structure that are caused by these high velocities can result in very high story drift that may, in turn, cause failure of structural elements. Preliminary indications are that story drifts induced by near-field velocity pulses during the Northridge earthquake may have significantly exceeded the code allowable values. In light of the poor performance of a number of steel moment resisting frame buildings in the earthquake, this is an issue that demands urgent resolution. In this project, simple linear shear-beam model is employed to determine the magnitude of the problem and to identify the factors that are most important in developing solutions to the problem. The results of this investigation will provide insights in to whether changes are needed in the seismic design of multi-story structures to account for the near-field effects. If changes are needed, they need to be identified as quickly as possible before more serious consequences occur. ***