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: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737705
• 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制定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。该研究计划提出了两个互补的项目。项目一：混凝土坝的地震安全性：三维剪切键有限元模型和多轴荷载的实验验证：几个现有的重力坝已经建造了收缩缝剪切键之间的整体。在最初的2D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，剪切键在整料之间提供了一些互锁机制。因此，抗剪键是弹性特征，可以考虑将地震残余滑动位移降至最低，从而影响地震后顶部闸门的运行。到目前为止，剪切键最常采用非常简化的接触单元建模，忽略了（i）轴向-剪切-弯矩-扭矩之间的三维载荷传递相互作用，导致应力集中和潜在的过早失效，（ii）由于热效应引起的初始开口效应，（iii）较硬或较弱键失效时脆性失效的可能性。该项目的目标是进行实验验证的一种新的薄接头“剪切键”有限元单元考虑多轴向故障包络线。实验测试程序将使用一种新型的高容量6自由度试验机上的小混凝土块与剪切键。将进行全面的有限元分析，以评估建模参数的影响，从而有信心地控制剩余地震滑动位移，包括使用被动或主动锚的加固作用。 项目2-混凝土坝安全评估和加固：被动锚栓的可靠使用：现有开裂的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提高可靠性和优化。此外，旧的混凝土溢洪道墩，设计几乎完全抵抗静水推力，包含电梯接头，被拦截的少量钢筋，不限制沿着周边。由于相关失效机制的不确定性，这些杆在稳定性评估中被忽略。本项目的目标是开发和实验验证先进的有限元和简化方法（i）可靠地使用三维被动钢锚加固方案，（ii）考虑到桥墩中现有的少量钢筋。主要拉伸和双轴剪切载荷下的三维破坏包络线将通过实验获得。利用实验结果和有限元模拟，考虑现有桥墩的案例研究将进行。将开发实际工程应用的设计指南和简化分析方法。