Implications of Measured Near-Field Ground Motion for Structural Response

9416174 Iwan该项目的目的是确定与近场地震地面运动相关的潜在严重结构反应问题的性质和重要性，例如在北岭地震期间观察到的地震。从北岭地震中测量到的近场地面运动显示出非常高的速度和脉冲式地面位移。这些运动能够引起对各种不同类型结构的高需求，包括基础隔离建筑和多层建筑。在北岭地震近场观测到的高速脉冲对高层建筑的性能有很大的影响。由这些高速引起的结构中的应力波可能导致非常高的楼层漂移，进而导致结构元件的破坏。初步迹象表明，在北岭地震期间由近场速度脉冲引起的层漂移可能大大超过了规范的允许值。鉴于一些钢抗弯矩框架建筑在地震中表现不佳，这是一个急需解决的问题。在本项目中，采用简单的线性剪力梁模型来确定问题的大小，并确定在制定问题解决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。如果需要更改，则需要在更严重的后果发生之前尽快确定。* * *

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. ***