考虑纵筋整体屈曲的高强钢筋混凝土桥墩抗震性能及韧性指标研究

The application of high-strength reinforcing steel bars in concrete structures can save material usage and meet the development concept of energy saving and emission reduction in the construction industry. However, the longitudinal bars endure bigger compressive stress and are more prone to compression buckling under earthquake loading when high -strength steel bars are used in reinforced concrete (RC) bridge piers, which affects seismic performance and post-earthquake repair of RC bridge piers. As a result, the application of high-strength steel bars in engineering is limited. The seismic performance and resilience index of RC bridge piers with high-strength steel bars are studied in this project. Firstly, monotonic and low-cycle fatigue tests are carried out on high-strength steel bars with different constraint lengths (L/D) and yield strengths, and a constitutive model considering buckling and low-cycle fatigue is established for high-strength steel bars. Then, the interaction between longitudinal reinforcement, stirrup, cover concrete and core concrete is studied, and the refined numerical simulation method considering reinforcement global buckling is developed to reveal the earthquake failure mode of RC bridge piers with high strength steel bars. Finally, the resilience index considering post-earthquake recoverability is established and the limit values are given for RC bridge piers with high-strength steel bars, according to the pseudo-static tests and numerical simulation of RC bridge piers with high-strength steel bars. The seismic resilience evaluation of RC bridge piers with high-strength steel bars is realized in the end. The research results of this project can promote the development of bridge resilience seismic design theory and the application of high strength steel in bridge structure.

高强钢筋应用于混凝土结构可以节约材料用量，符合建筑业节能减排的发展理念。然而钢筋混凝土桥墩采用高强钢筋时，纵向钢筋承受较大的压应力，地震作用下更容易受压屈曲，影响桥墩抗震性能和震后修复，限制了高强钢筋的工程应用。针对该问题，本项目拟研究高强钢筋混凝土桥墩抗震性能及韧性指标。首先对不同约束长度（L/D）和屈服强度的钢筋进行单调和低周疲劳试验，根据试验和数值模拟建立考虑屈曲和低周疲劳的高强钢筋本构模型。然后研究桥墩破坏时纵筋、箍筋、保护层混凝土和核心混凝土相互作用，发展考虑纵筋整体屈曲的高强钢筋混凝土桥墩精细化数值模拟方法，揭示桥墩地震损伤破坏模式。最后根据高强钢筋混凝土桥墩拟静力试验和数值模拟参数分析，建立考虑震后可恢复性的高强钢筋混凝土桥墩韧性指标并给出界限限值，最终实现高强钢筋混凝土桥墩的抗震韧性评估。本项目的研究成果可促进桥梁韧性抗震设计理论的发展，推广高强钢筋在桥梁结构中的应用。

高强钢筋应用于混凝土结构可以节约材料用量，符合建筑业节能减排的发展理念。本项目针对高强钢筋应用于桥墩中面临的科学和工程问题，开展了系统研究。首先，在材料层面上开展了高强钢筋HTRB600的单调拉伸、压缩和低周疲劳试验，研究了高强钢筋的力学性能，尤其是屈曲和低周疲劳性能；在Coffin-Manson疲劳模型的基础上，引入屈曲系数，建立了考虑屈曲的高强钢筋低周疲劳寿命预测模型，实现了高强钢筋低周疲劳寿命精准预测。开展了大尺度高强钢筋混凝土桥墩拟静力加载试验，探究了高强钢筋混凝土桥墩地震损伤机制，研究了钢筋强度、混凝土强度和配箍形式等因素对桥墩抗震性能影响；研究了不同配箍形式对纵筋屈曲的约束机制，提出了针对不同配箍形式的纵筋屈曲长度计算模型，实现不同配箍形式下的纵筋屈曲长度的准确预测，进而解释箍筋约束形式对桥墩抗震性能的影响。基于OpenSees软件，提出了基于非线性梁柱单元的高强钢筋混凝土桥墩精细化数值模拟方法；通过钢筋低周疲劳试验、钢筋混凝土桥墩拟静力试验和振动台试验验证，验证了提出的精细化数值模型方法可以较好的预测高强钢筋混凝土桥墩的非线性响应和损伤发展过程；在此基础上，考虑地震动的不确定性，通过概率地震需求分析，对桥墩开展易损性分析，研究了高强钢筋对桥墩抗震性能的影响；研究表明，通过合理设计，采用高强钢筋在降低材料用量的同时可以保证桥墩的抗震性能。收集国内外钢筋混凝土桥墩拟静力试验数据，结合本研究试验，通过统计分析，提出了基于最大位移的钢筋混凝土桥墩残余位移计算方法，可以较好的预测桥墩残余位移；提出了基于残余位移的桥墩抗震韧性指标，进而实现高强钢筋混凝土桥墩的抗震韧性评估。本项目提供了有效的高强钢筋和高强钢筋混凝土桥墩试验数据，高强钢筋低周疲劳预测模型，高强钢筋混凝土桥墩精细化数值模拟方法以及抗震韧性评价指标，为高强钢筋在桥墩中的工程应用奠定了坚实的理论基础和数据支撑。