FRP筋-钢筋复合增强ECC-混凝土组合柱抗震性能研究

This project proposes a new type of ECC-concrete composite column reinforced with hybrid FRP bar and steel, where the FRP reinforcement is placed in the corners and ECC is only used in plastic hinge zone of the columns. The proposed columns is expected to have excellent seismic resistance, good durability and high cost/performance ratio. In this project, the seismic behaviors of the hybrid reinforced ECC-concrete composite columns will be investigated through experimental studies, theoretical analysis and numerical simulations. Firstly, component tailoring of ECC material by means of micromechanical model will be conducted for designing greenness ECC materials with high volume fly ash. Based on mechanical tests and theoretical analysis, simplified constitutive models of ECC under uniaxial tension or compression will be proposed. Then, the moment-curvature relationships of the ECC column reinforced with hybrid steel and FRP bars will be comprehensively investigated by strip model. Also, the formula for the ultimate load-carrying capacity will be obtained and the corresponding simplified calculation method will be proposed. A number of hybrid reinforced ECC-concrete composite columns will be tested under reversed cyclic loading to study the effects of FRP reinforcement ratio and axial force ratio on seismic performance. After that, the working mechanisms of the hybrid reinforced ECC-concrete composite columns will be analyzed by finite element method. Interactions among FRP bars, steel， concrete and ECC will be investigated and the damage process of the composite columns will be revealed. Finally, hysteretic properties of the hybrid reinforced ECC-concrete composite columns will be numerically simulated and analyzed. Based on the parametric studies, the hysteretic models and seismic design methods for the hybrid reinforced ECC-concrete composite columns will be proposed, which provides references for elastoplastic time history analysis of hybrid steel and FRP bar reinforced ECC-concrete composite members under earthquake action.

本项目提出FRP筋-钢筋复合增强ECC-混凝土组合柱，将FRP筋置于易腐蚀的边角区、ECC仅用于柱构件塑性铰区域，致力于形成一种抗震性能优越、耐久性好及性价比高的新型柱构件。本项目拟通过试验测试、理论推导和数值仿真模拟等方式对FRP筋-钢筋复合增强ECC-混凝土组合柱的抗震性能进行深入研究。首先，基于细观力学方法设计高粉煤灰含量绿色ECC材料，建立ECC单轴拉、压简化本构关系。采用截面条带法推导FRP筋-钢筋复合增强ECC压弯构件正截面弯矩-曲率全曲线，得出承载力简化计算公式。然后，对组合柱进行低周反复荷载试验，研究配筋率和轴压比等试验参数对抗震性能的影响；在此基础上，通过有限元建模对组合柱的工作机理进行分析，研究FRP筋、钢筋、ECC和混凝土协同作用关系，揭示构件损伤劣化机理。最后，通过参数分析对组合柱的滞回特性进行探讨，确定其恢复力模型及抗震设计方法，为弹塑性地震时程反应分析提供参考。

FRP筋具有强度高、无磁性、密度低和耐腐蚀等优点。将FRP筋与钢筋复合使用可获得较钢筋混凝土构件更高的屈服后刚度与更小的残余变形。然而，FRP筋较差的抗压能力限制了其在柱构件中的运用，本项目提出新型FRP筋-钢筋复合增强高延性纤维增强水泥基复合材料（ECC）-混凝土组合柱构件，将FRP筋配置在方柱边角处，而ECC仅用于柱构件塑性铰区域，致力于形成一种抗震性能优越、耐久性好及性价比高的新型柱构件。具体研究的内容如下：.（1）对13根柱构件进行低周往复试验，考虑了FRP筋种类、配筋率、基体材料和轴压比等参数对柱构件抗震性能的影响。试验结果表明：ECC对内部筋材的约束效果比混凝土好，ECC替代柱构件底部混凝土能够有效避免FRP筋的受压屈曲进而提高构件抗震性能；FRP筋-钢筋复合增强柱在低周往复作用下其残余变形小于钢筋增强柱构件，且获得更高的屈服后刚度；随着轴压比的增大，承载能力增强，变形能力变差。.（2）基于材料简化本构关系，通过截面条带法编制程序获得柱构件的弯矩-曲率曲线。通过承载力分析可以发现试验值与理论值接近，该方法可以有效的模拟柱构件承载能力。可通过理论计算方法确定ECC层的浇筑高度，以满足塑性铰先发生在ECC区域，ECC很好的约束住FRP筋材，充分发挥ECC作用，达到提高构件抗震性能的目的。.（3）通过ABAQUS建模计算各柱构件荷载-位移滞回曲线，并分析了ECC强度、FRP筋与钢筋面积占比和FRP筋种类等参数对柱构件荷载-位移骨架能力的影响。分析结果表明：ECC强度的提高对承载能力提高不明显，且对变形能力影响不大；各类FRP筋材中CFRP筋增强构件的强度和刚度均优于其它FRP筋材增强构件；在FRP筋/钢筋面积比方面，随着FRP筋面积占比增大，承载能力和延性显著提高。最后，通过参数分析对组合柱的滞回特性进行探讨，确定了其恢复力模型及抗震设计方法。.本项目研究工作达到预期目标，共发表论文11篇，其中SCI、EI论文8篇，申请专利4项，已授权2项，登记软件著作权3项。