SFCB约束混凝土桥墩受力性能及其基于震后可恢复性的抗震设计方法研究

Aiming at the reinforced concrete pier column with insufficient using function after earthquake because of permissible residual deformation. The steel fiber composite bar (SFCB) with secondary stiffness ratio is used to confine column pier instead of steel hoops in this project and ensure the post-earthquake rehabilitation. Firstly, the effect of post yield stiffness on axial compressive performance of SFCB confined concrete is studied to reveal its mechanism. Considering SFCB post yield stiffness, strength, size-effect and constraint method, a unified model of restrain coefficient is built to obtain its one-to-one relationship between concrete confined by SFCB and without constrain. Secondly, the seismic performance of full-scaled concrete pier confined by SFCB is investigated, in terms of failure process, failure mode, hysteretic property, ductility and energy dissipation. The damage evolution and failure mechanism are investigated. The effect of restrain coefficient on residual deformation is studied and the displacement-based residual deformation is developed with restrain coefficient. Finally, based on the residual deformation as performance criteria, the seismic design method for post-earthquake rehabilitation of SFCB confined concrete column are developed, which provide further insights for the design and application of SFCB confined concrete pier .

针对震后钢筋混凝土桥墩产生永久残余变形导致桥梁使用功能受限的问题，本项目拟采用具有稳定二次刚度的钢-纤维复合筋（Steel Fiber Composite Bar，简称SFCB）替代钢箍筋约束混凝土桥墩，实现桥梁震后可恢复性。首先，研究二次刚度对SFCB约束混凝土轴压性能的影响规律，揭示二次刚度对约束混凝土的作用机理。建立考虑SFCB二次刚度、强度、尺寸效应、约束形式等多因素影响的约束系数统一模型，实现SFCB约束混凝土与素混凝土性能的一一对应关系；其次，研究地震作用下SFCB约束足尺混凝土桥墩的破坏过程、滞回、延性及耗能等特性，揭示损伤演化规律及可恢复机理。研究约束系数对侧向残余变形的影响规律，建立考虑约束系数的荷载-侧向残余变形模型；最后，以侧向残余变形为性能指标，建立基于震后可恢复性的SFCB约束混凝土桥墩抗震设计方法，为SFCB约束混凝土桥梁的抗震设计与应用提供理论基础与决策支撑。

混凝土结构的钢筋锈蚀易引发结构耐久性失效，特别是钢筋骨架最外层的箍筋更容易受到外界有害物质的侵蚀。为了提高混凝土结构的耐久性，本项目提出采用复合箍筋、网格箍筋增强混凝土结构。本项目进行了三方面的研究：一是研究了复合箍筋增强混凝土梁的抗剪性能。复合箍筋混凝土梁抗剪破坏形态为斜压破坏、剪压破坏和斜拉破坏，受剪跨比的影响。复合箍筋混凝土梁抗剪承载力比钢箍筋混凝土梁承载力大，随着配箍率与混凝土强度的增大而增大，随着剪跨比的增大而减小。斜裂缝宽度与发展速率比钢箍筋混凝土梁大。二是研究了荷载-海水耦合作用下CFRP网格箍筋增强混凝土梁的徐变性能。持荷水平越高，挠度达到稳定时间越晚，挠度值越大。修正后ACI209R预测模型的挠度计算结果与试验结果比较吻合，能够对荷载-海水浸泡耦合作用下CFRP网格箍筋梁变形徐变规律进行准确地预测。三是研究了荷载-海水耦合作用后CFRP网格箍筋增强混凝土梁的抗剪性能。海水浸泡与持荷不改变破坏模式，两种作用均会提高混凝土梁极限抗剪承载力。研究成果将拓展复合箍筋与CFRP网格箍筋在土木工程领域的应用，对建设材料及相关技术具有重要的推动作用，研究成果还将为复合箍筋与CFRP网格箍筋混凝土结构的设计与应用提供理论基础与数据支撑，具有重要的科学与工程意义。