Reliability-based Analysis and Design Loads for Slender Cable-Supported Bridges Subjected to Cable Loss

电缆突变失稳是索桥的一种重要的极端事件，它可能发生在故意攻击或电缆劣化的情况下。细长的大跨度桥梁可能同时存在大量的车辆或明显的风伴随着电缆的突然断裂。大多数电缆丢失事件在没有太多预警的情况下突然发生，因为可能存在交通和风等服务负荷。在现有的电缆损耗分析中，没有考虑到这种极端载荷和工作载荷的组合。电流抗负载因子设计（LRFD）规范没有考虑同时加载。提出了一种基于可靠度的细长大跨度斜拉桥在极端（电缆断裂）和交通、风等服务荷载联合作用下的动力分析方法。分析方法的开发以及风洞测试的验证是项目的一部分。该项目将对缆索支撑的大跨度桥梁在一条或多条缆索突然丢失的情况下的响应、安全性和可靠性进行研究。斜拉桥以缆索为主要支撑构件，缆索的损失会对桥体产生动载荷，造成灾难性的后果。将开发各种电缆故障和桥上移动交通的场景，以涵盖现实情况。将对极限状态进行非线性分析模拟，并通过风洞比例模型试验进行验证（正常的移动交通和风是场景加载的一部分）。该项目的最终目标是在各种实际荷载和事故条件下为大跨度索桥提供一致的可靠性。该项目的结果将通过出版物传播，并将提供给标准编写机构。

Abrupt cable loss is a critical extreme event for cable-supported bridges, which can happen under intentional attack scenario or deterioration of cables. Slender long-span bridges may have simultaneous presence of a large number of vehicles or significant wind along with sudden breakage of cables. Most cable-loss events occur suddenly without much warning when service loads like traffic and wind may be present. Such combined extreme and service loads have not been considered in the existing cable-loss analyses. The current load resistant factor design (LRFD) specification do not consider simultaneous loading. The proposed research is to develop a reliability-based dynamic analysis method for slender long-span cable-supported bridges under combined extreme (cable breakage) and service loads such as traffic and/or wind. Analytical method development along with validation with wind tunnel testing is part of the project.The project will pursue research in response, safety and reliability of cable supported long-span bridges in case of a sudden loss of one or more cables. The cable loss causes dynamic loads on the bridge which can have catastrophic consequences since cable-stayed bridges depend on cables as the main supporting element. A variety of scenario of cable failure and moving traffic on the bridge will be developed to encompass realistic situations. Non-linear analytical simulation will be developed for limit state situation which will be validated with scale model experiment in wind tunnel (normal moving traffic and wind are part of scenario loading). The ultimate goal of the project is to provide consistent reliability to long-span cable supported bridges under various realistic load and accident conditions. Results of the project will be disseminated through publications as well as will be made available to standard writing bodies.