预应力高性能混杂纤维增强布加固HPC梁的DNLC单元研究
Research on DNLC element for HPC beams strengthened with high performance prestressed HFRP sheet

对于不同混杂配比的预应力高性能混杂纤维增强（HFRP）布，建立高性能HFRP布加固高性能混凝土（HPC）梁的双重非线性分层组合（DNLC）单元模型。根据实体退化单元理论，采用初应力等参层单元对高性能HFRP布的体外预应力效应进行模拟，同时正确地考虑HPC梁的材料非线性效应以及结构的几何非线性，验证DNLC单元分析模型的正确性，并对HPC梁的开裂荷载、普通钢筋应力、高性能HFRP布应力重分布等进行研究。结合试验资料分析表明，预应力碳/玻璃纤维混杂（CFRP/GFRP）布加固HPC梁的理论结果与试验数据吻合程度良好，采用等参层单元有效地模拟高性能HFRP布的预应力作用，及所推导的DNLC单元正确性。预应力GFRP纤维布加固的开裂荷载等均较低，预应力CFRP纤维布加固的开裂荷载等有所提高，但剩余强度过大。HPC梁开裂荷载前预应力高性能HFRP布应力发展缓慢，屈服荷载后，其发展迅速直至结构失效。 The calculative double nonlinear layered combinative(DNLC) element of high performance concrete(HPC) beams strengthened with prestressed hybrid fiber(HFRP) sheet were established for different kinds of mixture ratios. The prestress effect of HFRP sheet was effectively simulated by isoperimetric layer element with initial stress. After considering the material nonlinearity of the HPC beams and the geometry nonlinearity of the structures, the analytical model based on DNLC element was validated, and then the mechanical behaviors including the cracking loads, the stress development of the steel and the stress redistribution of HFRP sheet of the strengthened beams were studied. By comparing with the experimental results, the results of this method are in good agreement with the experimental results, which proves that the prestress of HFRP is efficiently modeled by isoperimetric layer element and the DNLC element is reliable. The characteristic loads of prestressed CFRP sheet are higher than those of prestressed GFRP sheet. However, the degree of increase of the cracking loads of prestressed CFRP sheet is smaller compared with hybrid fiber sheet and the residual strength of CFRP sheet is more than other hybrid fiber sheets. Before cracking loads, the stress redistribution of the hybrid fiber sheet changes a little and then after yielding loads, it increases fast until the structure fails. 国家自然科学基金（11232007；11272147）；江苏省自然科学基金（BK20130787）；中央高校基本科研业务费专项资金（NS2014003）