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

缆索突然损毁是缆索支承桥梁的一种关键极端事件，在故意攻击或缆索劣化的情况下可能发生。细长的大跨度桥梁可能同时存在大量的车辆或大风以及缆索的突然断裂。当可能存在流量和风等服务负载时，大多数电缆丢失事件都会在没有太多预警的情况下突然发生。在现有的电缆损耗分析中，没有考虑这种极端和服务负荷的组合。目前的荷载抗力系数设计规范没有考虑同时加载。本研究旨在发展一种基于可靠度的细长大跨度拉索支承桥梁在极端(拉索断裂)和服务荷载(如交通和/或风)共同作用下的动力分析方法。分析方法的开发以及风洞试验的验证是该项目的一部分。该项目将继续研究缆索支撑的大跨度桥梁在一根或多根缆索突然丢失的情况下的响应、安全性和可靠性。由于斜拉桥依赖于拉索作为主要支撑构件，因此拉索损失会对桥梁造成动载，从而造成灾难性后果。将开发各种电缆故障和桥梁上移动交通的场景，以涵盖实际情况。对极限状态的情况进行非线性分析模拟，并通过风洞缩尺模型试验进行验证(正常运行的交通和风是情景荷载的一部分)。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缆索支承桥梁提供一致的可靠性。该项目的成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.