Reliability-Based Analysis and Design Loads For Slender Long-Span Bridges

在风荷载和交通荷载共同作用下，细长大跨度桥梁会产生较大的响应，这通常是由于荷载与桥梁结构的动力相互作用引起的。这些大的响应可能会导致疲劳积累、劣化，有时还会导致桥梁系统的相关安全问题。在美国，国家桥梁清单中包含的800多座大跨度桥梁被归类为断裂危害性桥梁。本项目将研究这些动力相互作用及其对大跨度桥梁结构造成破坏的可能性。该项目将专注于了解桥梁结构的动态行为，并开发一个综合的动态模型来评估大跨度桥梁在风和交通联合荷载下的寿命性能。将制定一种基于可靠性的分析方法，利用改进的交通流模拟结合风洞试验数据来定义等效车轮载荷和由此产生的因数设计载荷，以确保在几个预期性能水平上达到目标可靠性水平。这项研究将有助于工程师可靠地预测细长大跨度桥梁系统的响应、性能和剩余寿命。这将有助于确定现有桥梁的潜在损坏来源和风险，最终目的是设计改造措施，以提高大跨度桥梁结构的性能和延长其使用寿命。基于可靠性的分析和设计方法将有助于荷载校准和实现所有桥梁结构的一致风险水平，这是任何设计规范的基本意图。由于缺乏大跨度桥梁的设计规范，这种一致的风险水平现在并不一定得到保证。研究成果将通过常规机制和委员会工作广泛传播给其他研究人员和从业者。该项目将为研究生提供高级培训。还计划开展外展教育活动，为大学预科学生提供机会，让他们亲身体验风洞实验，参与尖端研究，从而有助于培养人们对下一代工程师的兴趣。

Under wind and traffic loading, slender long-span bridges can experience large responses which are typically caused by the dynamic interaction of the loads with the bridge structure. These large responses can cause fatigue accumulation, deterioration, and, at times, related safety issues for the bridge system. In the United States, more than 800 long-span bridges contained in the national bridge inventory are classified as fracture-critical. This project will study these dynamic interactions and their potential to cause damage in long span bridge structures. The project will focus on understanding the dynamic behavior of bridge structures and develop an integrated dynamic model to assess the lifetime performance of long-span bridges under combined wind and traffic loads. A reliability-based analytical approach which utilizes improved traffic flow simulations combined with wind tunnel test data will be formulated to define equivalent wheel loads and the resulting factored design loads to ensure a targeted reliability level at several levels of expected performance. This research will help engineers to reliably predict the response, performance, and remaining life of slender long-span bridge systems. It will help to identify potential sources and risk of damage to current bridges with the ultimate objective of designing retrofit measures to improve performance and prolong the lives of the long span bridge structures. The reliability-based analysis and design methodology will be helpful in load calibration and in achieving a consistent level of risk for all bridge structures, which is the fundamental intent of any design specification. Such a consistent level of risk is not necessarily guaranteed now due to the lack of design specifications for long-span bridges. The research results will be widely disseminated to other researchers and practitioners through conventional mechanisms and committee work. The project will provide advanced training to graduate students. Outreach educational activities are also planned to provide an opportunity to pre-college students to participate in cutting edge research with hands-on experience with wind tunnel experimentation, thus helping to foster interest in the next generation of engineers.