Understanding the cracking behaviour of reinforced concrete elements subjected to the restraint of imposed strains

了解受外加应变约束的钢筋混凝土构件的开裂行为

• 批准号: 2599856
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2021
• 资助国家: 英国
• 起止时间: 2021 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2599856
• 关键词: Understanding; cracking; behaviour; reinforced; concrete

The overall aim of the project is to provide practising engineers with the ability to correctly design RC elements for the restraint of short and long-term imposed strains. Crack width and spacing in walls with edge or combined edge and end restraint depend on aspect ratio and height which is not accounted for in current design. Furthermore, a combination of different idealised restraint types occurs in practice. The research project will quantify these influences. The internal crack profile, which affects leakage and reinforcement durability will also be studied. Through the experimental testing and NLFEA proposed here the project will be able to provide engineers with improved design methods for controlling restraint induced crack widths in RC structures such as retaining walls, bridge abutments, reservoir walls, large basements, tunnels and slabs. The result of this enhanced ability to design more accurately will be better estimation of serviceability performance, which will reduce episodes of non-compliance and hence repair costs / time delays / litigation. The experimental output will be compared with numerical studies in order to sufficiently develop a theory enabling the design of reinforcement for crack control under all restraint conditions. The main objectives sought are: 1. To develop physical understanding of behaviour through an experimental study which will examine the influences on crack width of imposed deformation, wall geometry, restraint type and the amount and arrangement of reinforcement. 2. To develop NLFEA models which enable the realistic calculation of crack width in walls with combinations of edge and end restraints (Figure A3 in BS8007 and Figure L.1 in BS EN1992-3) 3. To develop a design oriented analytical procedure for the design of crack control reinforcement in walls subject to restraint of imposed strain. The procedure will be informed by the laboratory tests and NLFEA. It will give a coherent treatment of the various possible forms of restraint and imposed strains. 4. Further validation of the resulting procedures by comparison with field data from walls, where sufficient information exists to enable the free strains and restraint to be established Restraint induced cracking in RC is currently a significant cost to the UK construction industry both in terms of lost productivity and repair cost. Current codes are inadequate to design out this problem and further guidance is needed. Lately, there is great drive to contribute to such tasks as seen in the Construction Industry Challenge 2025. Construction 2025 has a specific target of a 33% reduction in overall costs - this can be achieved through efficiency in design which is also an expected outcome of this research. The work sits solidly within the EPSRC theme of 'Engineering', with the improved understanding of the serviceability limit state performance of RC elements bridging further to 'Energy' and 'Global Uncertainties'. The output will be appropriate to many of the UKRI Research Areas (Built Environment, Coastal and Waterway Engineering, Ground Engineering, Engineering Design, Structural Engineering and Water Engineering); the numerical and analytical studies also make it fit perfectly with the strategy of investment into the research area of non-destructive evaluation of structures (Performance of Mechanical Structures) and the £138M UKCRIC capital investment. The project is part of a much larger funded EPSRC collaborative project between the University of Leeds and Imperial College London. The collaboration between the two universities facilitates better learning, knowledge transfer and exchange of ideas; pooling of resources will also ensure better dissemination across the academic community. The directly involved Neville Centre (NC) of Excellence in Cement and Concrete Engineering at UoL through its academic Steering Committee members, will provide dissemination means and forum for relevant collaborations.

该项目的总体目标是为执业工程师提供正确设计 RC 元件以抑制短期和长期施加应变的能力。具有边缘或边缘和端部组合约束的墙壁中的裂缝宽度和间距取决于纵横比和高度，而当前设计中没有考虑到这一点。此外，实践中还出现了不同理想化约束类型的组合。该研究项目将量化这些影响。还将研究影响渗漏和钢筋耐久性的内部裂纹轮廓。通过实验测试和此处提出的 NLFEA，该项目将能够为工程师提供改进的设计方法，用于控制 RC 结构（例如挡土墙、桥台、水库墙、大型地下室、隧道和楼板）中约束引起的裂缝宽度。这种增强的更准确设计能力的结果将是更好地估计适用性性能，这将减少不合规事件，从而减少维修成本/时间延误/诉讼。实验输出将与数值研究进行比较，以便充分发展一种理论，能够在所有约束条件下设计用于裂缝控制的钢筋设计。寻求的主要目标是： 1. 通过实验研究发展对行为的物理理解，该实验研究将检查施加变形、墙体几何形状、约束类型以及钢筋数量和布置对裂缝宽度的影响。 2. 开发 NLFEA 模型，能够通过边缘和端部约束的组合实际计算墙体裂缝宽度（BS8007 中的图 A3 和 BS EN1992-3 中的图 L.1） 3. 开发面向设计的分析程序，用于设计受外加应变约束的墙体裂缝控制钢筋。该程序将由实验室测试和 NLFEA 通知。它将对各种可能形式的约束和施加的压力进行一致的处理。 4. 通过与墙壁的现场数据进行比较，进一步验证所得程序，其中存在足够的信息来建立自由应变和约束。 RC 中的约束引起的裂缝目前对于英国建筑业来说是一个巨大的成本，无论是在生产力损失还是维修成本方面。当前的代码不足以解决这个问题，需要进一步的指导。最近，正如“2025 年建筑业挑战”中所看到的那样，人们对此类任务做出了巨大的贡献。“2025 年建筑业挑战”的具体目标是总体成本降低 33%，这可以通过提高设计效率来实现，这也是本研究的预期结果。这项工作牢牢地融入了 EPSRC 的“工程”主题，加深了对 RC 元件的适用极限状态性能的理解，进一步连接了“能源”和“全球不确定性”。成果将适用于 UKRI 的许多研究领域（建筑环境、沿海和水道工程、地面工程、工程设计、结构工程和水利工程）；数值和分析研究也使其完全符合结构无损评估研究领域（机械结构性能）的投资策略以及 UKCRIC 的 1.38 亿英镑资本投资。该项目是利兹大学和伦敦帝国理工学院之间规模更大的 EPSRC 合作项目的一部分。两所大学之间的合作促进了更好的学习、知识转移和思想交流；汇集资源还将确保在整个学术界更好地传播。伦敦大学水泥和混凝土工程卓越内维尔中心 (NC) 通过其学术指导委员会成员直接参与，将为相关合作提供传播手段和论坛。