Reliability of Strongly Nonlinear Structures and Systems under Seismic Excitations

9312640本研究旨在评估强非线性动力系统在强震激励下的可靠性(失效概率为1)。考虑了两类非线性系统：(L)高滞回结构，表现出大变形；(2)非结构系统，以摇摆、滑动或摇摆和滑动组合的形式响应地震激励，本质上是刚体。滞回结构的破坏被认为是由最大变形和总耗散的滞回能量来衡量的损伤累积到一个临界值。刚体类型系统的失效是由于相互碰撞、碰撞或碰撞造成的。当故障状态可达时，它为分布样本函数的样本空间提供一个吸收边界。一旦样本函数到达吸收边界，它就从总体中移除。因此，总概率不能在样本空间内保持不变。必须考虑这样的吸收边界；否则，可靠性估计是不保守的。此外，虽然滞回结构的失效主要表现在主要的失效模式上，但由宽频带组成的随机激励有时会使系统稍微偏离主导模式，从而允许一些能量被其他非主导模式所消耗。在这项研究中将考虑这些事实，以获得这些高度非线性系统响应的准确概率表征。***

9312640 Lin The research is directed at evaluating the reliability (1 probability of failure) of strongly nonlinear dynamical systems under severe earthquake excitations. Two types of nonlinear systems are considered: (l) highly hysteretic structures, exhibiting large deformations, and (2) non structural systems, which respond to seismic excitations in the form of rocking, sliding, or combined rocking and sliding, essentially as rigid bodies. Failure of hysteretic structures is conceived to be an accumulation of damage to a critical magnitude, which is measured by both the largest deformation and the total dissipated hysteresis energy. Failure of rigid body type systems occurs due to topping, colliding, or pounding against each other. When a failure state is reachable, it provides an absorbing boundary for the sample space in which the sample functions are distributed. A sample function is removed from the population, once it reaches the absorbing boundary. Therefore, the total probability cannot be conserved within the sample space. Such an absorbing boundary must be taken into account; otherwise, the reliability estimate is unconservative. Moreover, while failure of a hysteretic structure is manifested primarily in a predominant failure mode, a random excitation consisting of a wide band of frequencies has the tendency to push the system slightly from the dominant mode from time to time, thereby permitting some energy to be consumed by other non dominant modes. These facts will be considered in this research to obtain an accurate probabilistic characterization of the response of these highly nonlinear systems. ***