Reinforced concrete half-joint structures: Structural integrity implications of reinforcement detailing and deterioration

半节点是一种特殊类型的钢筋混凝土结构。仅在现有的英国公路局网络中，就有400多座半接缝的混凝土桥梁。这种结构形式的优点包括沿桥面和支撑跨度的水平运行面，预制梁在施工过程中可以很容易地吊装到位和支撑。然而，这种结构固有的缺点是存在与接缝泄漏相关的问题。这使得水分在梁座处积聚，从而增加了混凝土和钢筋恶化的倾向。由于对轴承座接头的接触有限，导致检查和维护问题，这种情况更加不利。更复杂的是，梁座区域的细节代表了一个潜在的敏感结构细节。有些半关节结构脆弱性可能从一开始就存在，例如在最初的设计或施工中，有些可能随着时间的推移而发展，例如恶化。自2006年加拿大魁北克协和天桥（de la Concorde立交桥）的一段坍塌以来，有一半的联合细节受到了严格审查。5人死亡，6人受伤。因此，一个关键的挑战是了解从协和立交桥倒塌中吸取的教训，以及半节理结构的固有脆弱性。该项目将为更准确地评估半关节结构提供改进的分析工具和实验证据，并将为整个英国的半关节结构管理策略提供信息。过于保守的强度评估可能导致不必要的关闭或车辆重量限制，这两种情况都是昂贵的。非保守的强度评估可能会危及公共安全。因此，该项目的成果具有国家和国际重要性。钢筋混凝土结构在剪切作用下的行为是出了名的复杂，目前还没有公认的统一理论。这是分析半关节结构的一个主要困难。目前的工作将在半关节结构的背景下探索、比较、扩展和适应现有的理论。进一步的目标是在分析和实验方法中纳入详细的缺陷和/或退化，从而提高对服役结构的预测能力。将调查不合规细节的负载分担影响以及结构性能对恶化结果（如强度损失）的敏感性。这种方法反映了将作为破坏性或非破坏性测试策略的一部分进行整理的信息类型，并提供了一个通用的、健壮的和可重复的框架，其他人可以从中对其结果进行基准测试。将在小型和大型标本上进行实验，以提供预期行为的基本验证。小规模试验将用于表征一个恶化系统的粘结锚固行为。大规模试验将提供具有非柔顺细节的半节理结构的实验数据库，并确定组成材料强度降低的影响。这将为此类结构的行为提供重要的实验证据，并突出最关键的细节和退化组合。虽然该项目的灵感来自并将解决那些建造、拥有和维护钢筋混凝土桥梁的人所面临的困难挑战，但潜在的基础科学和工程理解的发展将产生更大的影响。更全面地了解与复杂钢筋混凝土细节相关的失效模式和敏感性，将有助于深入了解各种现有基础设施资产的寿命性能。

A half joint is a particular type of RC structure. Within the existing UK Highways Agency network alone there are 400+ concrete bridges with half joints. The advantages of this structural form include a level running surface along the bridge deck and the support spans, and precast beams can be easily lifted into place and supported during construction. However, a disadvantage inherent in this type of construction is that there are problems associated with leakage through the joint. This enables moisture to accumulate at the beam seats thereby increasing the propensity for the deterioration of the concrete and reinforcement steel. The situation is adversely compounded by limited access to the bearing seat joint which leads to both inspection and maintenance issues. A further complication is that the detail in the beam seat region represents a potentially sensitive structural detail. Some half-joint structural vulnerabilities may have been present from the outset e.g. in the initial design or construction, some may develop with time e.g. deterioration. Half joint details have come under intense scrutiny since the collapse of a section of the de la Concorde Overpass in Quebec, Canada in 2006. Five people were killed and six others injured. Thus, a key challenge is to understand the lessons to be learned from the Concorde Overpass Collapse, and the inherent vulnerabilities in half joint structures.This project will provide improved analytical tools and experimental evidence for the more accurate assessment of half-joint structures, and will inform the management strategy for half-joint structures throughout the UK. Overly conservative strength assessments can result in unnecessary closures or vehicle weight limits, both of which are costly. Non-conservative strength assessments potentially put public safety at risk. The outcomes of this project are therefore of national, and international importance.The behaviour of reinforced concrete structures in shear is notoriously complex and there is no generally accepted unifying theory. This presents a major difficulty in the analysis of half-joint structures. The current work will explore, compare, extend, and adapt existing theories in the context of half-joint structures. A further goal is to incorporate detailing deficiencies and/or deterioration within the analytical and experimental approaches to thereby enhance the predictive capability for structures in service. The load-sharing implications in non-compliant details and the sensitivity of the structural performance to a deterioration outcome, such as a loss of strength will be investigated. This approach reflects the type of information that would be collated as part of a destructive or non-destructive testing strategy, and provides a general, robust and repeatable framework from which others can benchmark their results. Experiments on small and large scale specimens will be undertaken to provide the essential validation of the expected behavior. Small-scale tests will be used to characterise the bond anchorage behaviour in a representation of a deteriorated system. The large-scale tests will deliver an experimental database of half-joint structures with non-compliant details and determine the influence of strength reductions in the constituent materials. This will provide an important experimental evidence of the behavior of such structures, and highlight the most critical detailing and deterioration combinations. While the project has been inspired by, and will address, the difficult challenges faced by those who build, own and maintain reinforced concrete bridges, the development of the underlying fundamental scientific and engineering understanding will have far greater implications. A fuller understanding of the failure modes and sensitivities associated with complex reinforced concrete details will provide insight into the life-time performance of a wide range of existing infrastructure assets.