CFRP加固组合梁承载力性能实验研究

EXPERIMENTAL INVESTIGATION ON THE COMPOSITE BEAMS STRENGTHENED WITH CFRP SHEETS

对碳纤维复合增强材料(CFRP)条带加固的混凝土-钢组合梁抗弯性能进行实验研究。在考虑CFRP条带加固长度和宽度两个变量的基础上,采用四点加载的方式,研究加固和未加固组合梁在加载过程中的承载力性能。通过分析试件的荷载-位移曲线和其破坏模态,揭示在加固前后混凝土试件的初裂荷载和极限承载力的变化规律,并分析组合梁各类破坏模态的产生机理。实验研究结果表明:采用CFRP条带加固的组合梁承载能力会提高,当CFRP加固长度为试件总长的60%时,承载力的提高效率最高。同时提出一桁架模型,用以分析加固前后组合梁中混凝土板、钢梁腹板以及FRP条带的内力,为该类加固梁的极限荷载预测提供了依据。

This paper presents the works of investigating the structural behaviors of composite beams before and after being strengthened with CFRP strips at the tension soffit. Seven samples were examined by the four-point bending loading tests. Among the seven samples,one was un-strengthened and the remaining six were strengthened by bonding CFRP strips of different numbers,width and length,respectively. All samples were tested beyond their ultimate failure. By recording the load-deflection data for the entire history,the first crack load,the CFRP debonding load or concrete longitudinal failure loads were identified. Meanwhile,the typical failure modes are documented and their respective mechanisms are analyzed. Comparing the strengthened beams with the reference one,the ultimate strength of composite beams strengthened by CFRP strips is significantly increased,and the most effective one is the beam strengthened by the CFRP strip of 60% beam length. In addition,a truss model is proposed to calculate the internal forces in the concrete,steel beam and FRP strips,from which the prediction for the failure load can be performed.