Multilevel Reliability-Based Optimization of Structural Systems

非确定性结构系统的最优化方法 在随机荷载作用下，几乎总是考虑使用性能， 极限状态分别。 这些方法的一个主要缺点 在一个极限状态下的设计决策必须在 关于其在其他极限状态下的后果的明确信息 关心。 这要么导致相当大的金钱浪费， 过度设计或结构系统的低可靠性。 该项目的主要目标是制定一个有效的， 多目标可靠性优化的一种有效方法 受性能约束的结构系统 同时在正常使用和极限状态下。 几乎 没有进行结构优化的基础研究， 发展这样的方法。 将对最近的研究进行综述， 识别不确定性的概率行为模型 在服务和极限随机荷载下的结构构件。 这些 个别模型将被纳入一个通用系统模型， 将用于开发一个多目标的可靠性为基础的 一种满足性能约束的优化方法 同时处于两个服务端极限状态。 该方法 将扩展到适应generel响应灵敏度的 最佳解决方案，以改变随机参数，定义 载荷和构件阻力。 预计结果 将是相当大的价值，有效的设计结构， 多个基于可靠性的性能约束下的系统。

Current optimization approaches to nondeterministic structural systems subject to random loads almost invariably treat the serviceability and ultimate limit states separately. A major drawback to these approaches is that design decisions at one limit state must be made in the absence of explicit information as to their consequences at other limit states of concern. This leads either to a considerable waste of money because of overdesign or to a low reliability of structural systems. The essential objective of this project is to develop an efficient and effective method for the multi-objective reliability-based optimization of structural systems subject to performance constraints imposed simultaneously at both serviceability and ultimate limit states. Almost no basic studies in structural optimization have been performed to develop such a method. A survey of recent research will be made for identifying probabilistic behavior models for nondeterministic structural members under service and ultimate random loads. These individual models will be incorporated into a general system model which will be used for developing a multi-objective reliability-based optimization method whereby performance constraints will be satisfied simultaneously at both service end ultimate limit states. This method will be extended to accommodate generel response sensitivities of the optimum solution to changes in the random parameters that define the loading and the member resistances. It is anticipated that the results will be of considerable value for the efficient design of structural systems under multiple reliability-based performance constraints.