Investigation into reliability of existing Infrastructure and the calibration and capacity to use FRP for retrofit repairs on degraded reinforced conc

项目名称调查现有基础设施的可靠性以及使用玻璃钢对退化的钢筋混凝土结构进行翻新修复的校准和能力现代国家的现有基础设施随着工程结构的设计期(约50年)结束而对社会和资产所有者构成越来越大的风险。用途的改变、交通荷载的增加、材料的退化，再加上规范设计的变化，导致许多结构被认为是不安全的。此外，在发展中国家，现有的基础设施可能没有或有限的设计文件可用于协助检查程序，导致决策过程中的不确定性增加。过去和现在的调查和检查程序还提供了主观数据，这些数据在不同国家之间可能有很大差异，这使得如果不从昂贵的测试方法(破坏性和间接测试方法)中进行详细的进一步分析，就很难改进任何结构评估模型，而对大多数现有结构的监测是有限的或根本不存在的。因此，由于当前性能的不确定性、现场收集的数据有限以及大量的钢筋或预应力混凝土中小跨度桥梁，需要对现有结构进行评估，这使得这些结构变得尤为关键。此外，如果评估表明需要进行维修、翻新或修复，才能使结构恢复到高于所需标准的可靠性状态，则现行设计规范不适用。事实上，设计部分系数和特征参数是为新结构定义的，这可能与在现有结构中观察到的显著不同。这可能是因为与剩余寿命不到10年的结构相比，材料生产、常用结构模型中的假设和设计为50年预期寿命的荷载的一致性得到了改善。结合前面讨论的现有结构中的不确定性，可以修复结构的唯一方法是以高昂的成本设定非常保守的假设，或者根据当前结构中材料和构件的当前状态和施工时的设计程序，对其应用可靠性技术，并在一系列概率结构模型中评估它们与预期可能的修复方法的组合。这应该使资产所有者能够确定适当的行动方针，以最低的成本提供足够的可靠性，无论维修、拆卸和更换是最可行的选择。因此，可以应用于建筑物的修复方法是有意义的，因为许多维修都是以高昂的成本进行的，例如桥面的外部后张拉。同时，FRP(纤维增强聚合物)以其低质量、高抗拉强度以及能够在一系列表面形状上应用于结构外部的潜力，使其成为钢板等更传统方法的有趣替代品。然而，由于缺乏标准，使得制定明确针对受损或劣化的现有结构的加固构件的设计规范成为关键目标：开发一种劣化混凝土桥梁的评估和设计概率工具。因此，本PHD的目标是开发一种劣化混凝土桥梁的评估和设计概率工具，调查FRP作为修复方法的可靠性和适用性，为将来应用于修复设计规范的简单解决方案奠定基础。

Project title Investigation into reliability of existing Infrastructure and the calibration and capacity to use FRP for retrofit repairs on degraded reinforced concrete structuresExisting infrastructure in modern countries is becoming an increasing risk to society and asset owners as engineered structures reach the end of their designed periods (around 50 years). Changes of use, increased traffic loading, material degradation in addition to variations in code designs result is many structures being deemed as unsafe. Furthermore, in developing countries, the infrastructure in place can have no or limited design documentation available to aid inspection procedures, resulting in increased uncertainty in the decision making process. Investigation and inspection procedures from past and present also provide subjective data that can vary greatly between nations, making it difficult to improve any assessment models of structures without detailed further analysis from expensive testing methods (Destructive and indirect testing methods) whilst monitoring in the majority of existing structures is limited or non-existent. As a result, the need to assess existing structures due to the uncertainties in the current performance, limited data collected on site, and the large number of reinforced or pre-stressed concrete small to medium span bridges make these structures particularly critical. Furthermore, where an assessment dictates that repairs, retrofitting or rehabilitation is necessary to return the structure to a reliability state above the required criterion, the current design codes are inapplicable. In fact, design partial factors and characteristic parameters are defined for new structures which can significantly differ from those observed in existing structures. This can be a result of improved consistency of material production, assumptions in commonly applied structural models, and loads designed for fifty year expected life-times compared to that of a structure with a remaining life of less than 10 years. Combining this with the uncertainties in existing structures discussed prior, the only method with which structures can be repaired is by setting very conservative assumptions at large costs or by applying reliability techniques for the materials and elements in the current structure based on their current state and design procedures at the time of construction, and assessing their combination with the anticipated possible repair methods in a series of probabilistic structural models. This should enable asset owners to identify appropriate courses of action to provide sufficient reliability at minimal costs, whether repairs, demolition and replacement are the most viable options.The methods of rehabilitation that can be applied to structures is therefore of interest with many repairs performed at significant costs such as external post-tensioning of bridge decks. Meanwhile, the potential of FRP (Fibre Reinforced Polymers) applied to the exterior of structures with their low mass, high-tensile strength and the ability to apply them over a range of surface shapes, make them an interesting alternative to more traditional methods like steel plates. However, the lack of standards makes the development of design codes for strengthening elements explicitly for damaged or deteriorated existing structures critical Objective:Develop an assessment and design probabilistic tool for deteriorated concrete bridgesAs a result, the objective of this PhD is to develop an assessment and design probabilistic tool for deteriorated concrete bridges investigated the reliability and applicability of FRP as repair methods providing groundwork for a simple solution which can be applied in 'repair' design codes for the future.