Fatigue Reliability of Structures Sujected to Earthquake Loading

地震荷载结构的疲劳可靠性

• 批准号: 8707789
• 负责人: Richard Nielsen
• 金额: $ 5.91万
• 依托单位: Regents of the University of Idaho
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-08-01 至 1990-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8707789&HistoricalAwards=false
• 关键词: Fatigue; Reliability; Structures; Sujected; Earthquake

The design of many engineered structures is governed by considerations of material fatigue failure. For example, offshore structures must withstand continuous oscillatory wind and wave loads. Under extreme conditions, the loading may fluctuate significantly over short time periods. Substantial damage, and most failures, are caused by these short-time loads. Existing methodologies for evaluating the probability of fatigue failure assume that the loading process is stationary (that is, the loading characteristics do not change with time), which may not be appropriate for extreme loading conditions. This study develops a reliability model for fatigue failure that accommodates nonstationary loading processes. The model describes the response of the structure to nonstationary loads as a random process. The crossing statistics of this response process are calculated in order to determine the expected number of load reversals; the accumulated damage resulting from these load reversals is determined using the methods of fracture mechanics. Finally, the estimated damage can be compared to a limiting criteria so as to calculate the probability of failure. This methodology improves upon existing procedures for the design of structures prone to fatigue failure under nonstationary loads, such as those caused by an earthquake. This information can also be used to specify rational design, inspection, maintenance, and repair schemes for many types of structures.

许多工程结构的设计都是由考虑因素决定的 材料疲劳失效。 例如，海上结构物必须 能承受连续的风和波浪载荷。 号冒着极大 条件下，负载可能会在短时间内大幅波动 时期 实质性的损害和大多数故障都是由这些因素造成的。 短时负荷 评估疲劳失效概率的现有方法 假设加载过程是静止的（即，加载 特性不随时间变化），这可能不合适 用于极端负载条件。 本研究建立了一个可靠性模型 适应非平稳加载过程的疲劳破坏。 该模型描述了结构对非平稳载荷的响应 作为一个随机过程。 这个响应过程的交叉统计量 以确定预期的负载数量 反向;这些负载反向造成的累积损坏是 使用断裂力学的方法确定。 最后 可以将估计的损坏与限制标准进行比较，以便 计算失败的概率。 这种方法改进了现有的设计程序， 在非平稳载荷下容易疲劳失效的结构，例如 地震造成的。 这些信息还可以用于 规定合理设计、检查、维护， 多种类型结构的维修方案。