随机局部腐蚀作用下钢管混凝土K形节点的力学性能分析

赵文杰; 张静怡; 侯超

doi:10.13206/j.gjgS21100801

随机局部腐蚀作用下钢管混凝土K形节点的力学性能分析

doi: 10.13206/j.gjgS21100801

南方科技大学海洋科学与工程系, 广东深圳 518055

基金项目:

深圳市科技计划资助项目（RCYX20210706092）。

详细信息

作者简介:
赵文杰,男,1997年出生,硕士研究生。

通讯作者:
侯超,男,1988年出生,博士,副教授,houc@sustech.edu.cn。

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出版历程
- 收稿日期: 2021-10-08
- 网络出版日期: 2022-05-27

Mechanical Performance Analysis of Concrete Filled Steel Tubular K-joints Subjected to Random Local Corrosion

Department of Ocean Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China

摘要

摘要: 桁式钢管混凝土组合结构由于传力明确、整体性能好，具备优越的结构性能与经济优势，在腐蚀环境下服役的跨海特大桥梁、沿海塔架、海洋平台等大型基础设施中得到广泛的应用。在此类结构中，主要承重构件与关键连接节点受到荷载与腐蚀长期耦合作用的影响，对结构的安全性与可靠性提出了严峻的挑战。在实际工程中，钢材表面的腐蚀作用通常以随机分布的局部腐蚀为主；以往，受试验条件与数值模拟技术的限制，对随机局部腐蚀作用下的钢管混凝土关键节点力学性能研究尚不多见，在一定程度上制约了对此类主体结构全寿命服役性能的认识及其科学设计方法的制定。基于此，对随机局部腐蚀与长期荷载耦合作用下钢管混凝土K形节点这一典型桁式组合节点的全过程力学性能展开深入研究。
建立了可以考虑钢管外壁随机局部腐蚀及其对材料非线性约束作用的复杂时变影响的钢管混凝土K形节点精细化有限元分析模型。基于实际环境中海工钢结构随机局部腐蚀的分布规律，通过Python与ABAQUS的模型搭建，进行随机蚀坑分布生成、腐蚀单元识别与蚀坑区域自动化网格划分，实现了对弦、腹杆钢管外壁的随机局部腐蚀的模拟。此外，模型中考虑了腐蚀过程中材料间非线性约束作用的时变劣化以及核心混凝土的长期变形特性，且模型的准确性得到系列试验结果的验证。利用有限元模型，深入分析了节点在局部腐蚀作用下的破坏模态、全过程荷载-变形关系与剩余极限承载力；明晰了腐蚀类型（均匀分布或随机局部分布）、体积腐蚀率等重要参数对节点力学行为的影响规律。考察了随机局部腐蚀作用下影响钢管混凝土K形节点力学性能的重要参数，包括体积腐蚀率、材料强度、弦杆径厚比、腹弦杆管径比等。在参数分析结果的基础上，提出了钢管混凝土K形节点腐蚀后剩余强度的简化计算方法，结合有限元结果验证了公式的有效性。
分析结果表明：随机局部腐蚀作用下的钢管混凝土K形节点的破坏模态主要为受压腹杆的局部屈曲，在受压腹杆的蚀坑集中区域往往会出现应力集中而发生局部屈曲失效；由于弦杆内填充混凝土，节点区域力学性能得以改善；与均匀腐蚀相比，局部腐蚀对钢管混凝土K形节点力学性能的影响更为显著，且局部腐蚀的随机分布会进一步降低节点的承载力，即当体积腐蚀率一定时，随机局部腐蚀节点承载力比非随机局部腐蚀情况多降低2%~5%；腹杆体积腐蚀率对节点承载力起控制作用。
- 钢管混凝土K形节点 /
- 随机局部腐蚀 /
- 长期荷载 /
- 全过程分析 /
- 节点剩余强度
Abstract: Concrete filled steel tube(CFST) composite truss structures have superior structural performance and economic advantages due to the clear force transmission and excellent integrity. These structures have been widely used in large-scale infrastructures that serve in corrosive environments, such as cross-sea bridges, coastal towers, and offshore platforms. In such structures, the main bearing members and key connecting joints are affected by corrosion and sustained loads, which is a severe challenge to the safety and reliability of the structure. In practice, randomly distributed local corrosion normally occurs on the surface of steel. Due to the limitations of test facilities and numerical simulation technology, the research on CFST K-joints with random local corrosion is still limited, which restricts the understanding of the life-cycle performance and the establishment of scientific design methods for those structures. Thus, this paper aims to study the full-range performance of CFST K-joints subjected to random local corrosion and sustained load.
A detailed finite element analysis(FEA) modelling was presented to study the performance of CFST K-joints under random local corrosion and sustained load, which could take the random local corrosion of the outer steel tube and the complex time-dependent effects of the nonlinear material confinement into consideration. Based on the distribution trend of random local corrosion for steel structure in actual ocean environment, the simulation of random local corrosion on the surface of chord and brace was realized by combining Python and ABAQUS simulations, which can generate random pit distribution, identify corrosion elements and automatically mesh on the pitting corrosion area. In addition, the long-term characteristics of the core concrete and the time-dependent deterioration of nonlinear steel-concrete composite action are considered in the model. The established model was validated against reported test data and then used for further analysis, including the possible failure modes, the full-range load-deformation relationships, the residual ultimate strength, and the influence law of important parameters such as corrosion type(uniform distribution or random local distribution), volume loss rate, etc. The key parameters affecting the performance of CFST K-joints with random local corrosion were systematically evaluated, including the volume loss rate, the material properties, the diameter-ratio between chord and brace, the chord member diameter-thickness ratio, etc. Finally, simplified calculation methods for the residual strength of CFST K-joints were proposed based on parametric analysis. The accuracy of the formula was verified by the finite element results.
The results show that the failure mode of CFST K-joints with random local corrosion is mainly the local buckling of the compression brace, while the stress concentration tends to occur in the pitting corrosion concentrated area that leads to the local buckling failure. Due to the concrete infill in the chord, the mechanical performance of the joints is improved. Compared with uniform corrosion, local corrosion has a more significant effect on the performance of CFST K-joints while the random distribution of local corrosion further reduces the bearing capacity of CFST K-joints. When the volume loss rate remains constant, the ultimate joint capacity with random local corrosion is found about 13.2% lower than that with uniform corrosion; the volume loss rate of brace controls the ultimate strength of CFST K-joints.
- concrete filled steel tubular K-joints /
- random local corrosion /
- long-term sustained loading /
- full-range analysis /
- residual strength of the joint

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