Structural Safety Assessment and Strengthening of Concrete Dams and Gated Spillways Subjected to Severe Loading Conditions

承受恶劣荷载条件的混凝土坝和闸控溢洪道的结构安全评估和加固

• 批准号: RGPIN-2019-04568
• 负责人: Leger, Pierre
• 金额: $ 2.62万
• 依托单位: École Polytechnique de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=754665
• 关键词: Structural; Safety; Assessment; Strengthening; Concrete

The long term objectives of the proposed research program are to develop effective structural assessment and rehabilitation strategies of concrete hydraulic structures that will permit substantial saving of costly remedial work. The proposed research program presents two complementary projects. Project 1: Seismic Safety of Concrete Dams: 3D Shear Key Finite Element Model and Experimental Validation for Multi-Axial Loadings: Several existing gravity dams have been constructed with contraction joint shear keys between monoliths. In the initial 2D design, these keys are not considered able to provide load transfer between dam blocks. However, shear keys are providing some interlocking mechanisms between monoliths. Shear keys are thus resilient features that could be considered to minimise seismic residual sliding displacements compromising post-earthquake crest block gate operation. So far, shear keys have been most often modelled with very simplified contact elements ignoring (i) 3D load transfer interactions between axial-shear-moment-torsion leading to stress concentrations and potentially premature failure, (ii) effects of initial openings due to thermal effects, (iii) the potential for brittle failure upon failure of a stiffer or weaker key. The project objectives are to conduct experimental validation of a novel thin joint "shear key" FE element considering multi-axial failure envelopes. The experimental testing program will be performed on small concrete blocks with shear keys using a novel high capacity 6 degrees-of-freedom testing machine. Comprehensive FE analyses will be performed to assess the effects of modeling parameters to control with confidence residual seismic sliding displacements, including strengthening actions using passive or active anchors. PROJECT 2- Concrete Dam Safety Assessment and Strengthening: Reliable Use of Passive Anchors: Existing cracked concrete components are often stabilised using passive steel anchors. However, strength assessment considering 3D loadings needs to be improved for reliability and optimisation. Moreover, old concrete spillway piers, designed almost exclusively to resist hydrostatic thrusts, contain lift joints that are intercepted by a small amount of reinforcing bars, not confined along the perimeter. These bars are ignored in stability assessment because of uncertainties regarding related failure mechanisms. This project objectives are to develop, and experimentally validate, advanced FE and simplified methodologies (i) for a reliable use of 3D passive steel anchors strengthening schemes, and (ii) to take into account the small amount of existing reinforcement in piers. 3D failure envelopes under dominant tensile and biaxial shear loads will be experimentally obtained. Using the experimental findings and FE simulations, case studies considering existing piers will be conducted. Design guidelines and simplified analysis method for practical engineering applications will be developed.

拟议研究计划的长期目标是开发混凝土水工结构的有效结构评估和修复策略，从而大幅节省昂贵的补救工作。拟议的研究计划提出了两个互补的项目。项目 1：混凝土坝的抗震安全：3D 剪力键有限元模型和多轴荷载的实验验证：一些现有的重力坝是在巨石之间采用收缩缝剪力键建造的。在最初的二维设计中，这些键不被认为能够提供坝块之间的荷载传递。然而，剪切键在整体结构之间提供了一些联锁机制。因此，剪力键是弹性特征，可被视为最大限度地减少地震残余滑动位移，从而影响震后顶部块闸门的运行。到目前为止，剪切键通常使用非常简化的接触单元进行建模，忽略了 (i) 轴向剪切力矩扭转之间的 3D 载荷传递相互作用，导致应力集中和潜在的过早失效，(ii) 由于热引起的初始开口的影响影响，(iii) 较硬或较弱的钥匙失效时发生脆性失效的可能性。该项目的目标是对考虑多轴失效包络的新型薄接头“剪切键”有限元元件进行实验验证。实验测试程序将使用新型高容量 6 自由度试验机在带有抗剪键的小型混凝土块上进行。将进行全面的有限元分析，以评估建模参数的效果，以可靠地控制残余地震滑动位移，包括使用被动或主动锚的加固作用。 项目 2 - 混凝土大坝安全评估和加固：被动锚栓的可靠使用：现有开裂混凝土构件通常使用被动钢锚栓进行稳定。然而，考虑 3D 载荷的强度评估需要改进，以实现可靠性和优化。此外，旧的混凝土溢洪道桥墩几乎专门为抵抗静水推力而设计，其升降接头被少量钢筋拦截，而不是沿周边限制。由于相关失效机制的不确定性，这些条在稳定性评估中被忽略。该项目的目标是开发并通过实验验证先进的有限元和简化方法（i）可靠地使用 3D 被动钢锚加固方案，以及（ii）考虑桥墩中现有的少量钢筋。将通过实验获得主要拉伸和双轴剪切载荷下的 3D 失效包络线。利用实验结果和有限元模拟，将进行考虑现有桥墩的案例研究。将开发实际工程应用的设计指南和简化分析方法。