A Comprehensive Methodology to Estimate the Current Safety and to Predict the Remaining Useful Life of Suspension Bridge Cables

评估悬索桥缆索当前安全性并预测剩余使用寿命的综合方法

• 批准号: 0115901
• 负责人: Raimondo Betti
• 金额: $ 27.43万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-09-15 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0115901&HistoricalAwards=false
• 关键词: Comprehensive; Methodology; Estimate; Current; Safety

In the US, various transportation systems, including long-span cable suspension bridges,have been allowed to deteriorate because of inadequate investment in maintenance and life extension technology, and particularly because of clearly insufficient support for research in the area of structural assessment and protection. In-depth inspections of the main cables in the suspension bridges in the New York metropolitan area have found a quite large number of broken wires inside the cables and at the anchorage, showing extensive deterioration and brittle fractures. These findings pose the difficult task of determining the actual strength of main suspension cables in existing bridges. The safety evaluation of suspension bridge cables has always been done considering as a safety factor the ratio between the estimated cable strength over the computed ultimate load. However, in view of the many uncertainties involved with the cable deterioration pattern and with wire corrosion mechanisms, and considering the relatively small proportion of wires that are inspected and/or tested, such a safety factor is useful only as a first approximation, but not in assessing the overall safety of the bridge. A better and moreappropriate measure of the overall safety of main suspension cables is the use of probabilistic indicators such as the reliability or the safety index. Without a well-defined methodology for estimating the residual strength of an existing cable, suspension bridge owner agencies do not have a clear idea of what to search for in a cable inspection and so they base their maintenance program mainly on previous experiences and on trial and error attempts. This grant proposes to go beyond the objectives of the NCHRP Project 10-57 by developing a comprehensive methodology for a rigorous safety appraisal of the cable system in existing suspension bridges. The ultimate objectives of this study will focus on 1) the estimation of the actual residual strength and of the actual safety of main cables in suspension bridges based on results of inspections and laboratory testing of cable wires, and on 2) the prediction of the remaining useful life of suspension bridge cables using the same results. In this way, the estimated overall safety of the cables of different bridges can be directly compared. A new cable model that accounts for limited and different ductility of the corroded bridge wires will also be developed, using a probabilistic framework to account for the random nature of the deterioration pattern. The determination of the statistical parameters to be used in the new prediction model will be done using a unique set of inspection and test data, collected over 30 years of bridge testing by the Carleton Laboratory at Columbia University, and on the results of current research projects on wire deterioration. This project will make a significant contribution to the bridge engineering community with the introduction of a more rigorous description of the overall safety and remaining useful life of main cables in existing suspension bridges.

在美国，由于对维护和寿命延长技术的投资不足，特别是对结构评估和保护领域的研究支持明显不足，包括大跨度悬索桥在内的各种交通系统都被允许恶化。对纽约大都会地区悬索桥主缆进行深入检查后发现，主缆内部和锚碇处存在大量断丝，表现出大面积的劣化和脆性断裂。这些发现提出了困难的任务，确定现有桥梁的主悬索的实际强度。悬索桥缆索的安全性评估通常将缆索强度估计值与极限荷载计算值之比作为安全系数。然而，考虑到电缆劣化模式和电线腐蚀机制涉及的许多不确定性，并考虑到检查和/或测试的电线比例相对较小，这种安全系数仅作为第一近似值有用，而不是评估桥梁的整体安全性。一个更好的和更适当的措施的整体安全的主悬索是使用概率指标，如可靠度或安全指数。如果没有一个明确的方法来估计现有电缆的剩余强度，悬索桥业主机构没有一个明确的想法，在电缆检查中寻找什么，所以他们的维护计划主要基于以前的经验和试错尝试。该补助金旨在超越NCHRP项目10-57的目标，开发一种全面的方法，对现有悬索桥的缆索系统进行严格的安全评估。本研究的最终目标将集中于：1）根据缆索钢丝的检查和实验室测试结果，估计悬索桥主缆索的实际剩余强度和实际安全性; 2）使用相同结果预测悬索桥缆索的剩余使用寿命。 通过这种方式，可以直接比较不同桥梁缆索的估计整体安全性。一个新的电缆模型，占有限的和不同的延展性的腐蚀桥梁电线也将被开发，使用概率框架来解释的随机性质的恶化模式。新预测模型中使用的统计参数的确定将使用一组独特的检查和测试数据，这些数据由哥伦比亚大学的卡尔顿实验室收集，并基于当前关于钢丝老化的研究项目的结果。该项目将对桥梁工程界做出重大贡献，对现有悬索桥主缆的整体安全性和剩余使用寿命进行更严格的描述。