基于已有试验结果和理论公式预测加固钢筋混凝土箱梁碳纤维布剪力贡献

PREDICTING CFRP SHEAR CONTRIBUTION OF STRENGTHENED RC BOX BEAM BASED ON EXISTING EXPERIMENTAL RESULTS AND THEORETICAL MODELS

对于纤维布抗剪加固矩形梁和T形梁,中外学者已进行了大量的试验和理论研究,并且提出纤维布剪力贡献计算公式,部分公式被不同国家的规范收录。但对于加固钢筋混凝土箱形截面梁的纤维布剪力贡献计算鲜有文献记录,因此本研究在已有试验和理论公式的基础上预测箱形截面纤维布剪力贡献计算。本文讨论了5种不同规范计算纤维布剪力贡献公式,同时收集了现有文献的181片纤维布抗剪加固矩形梁和T形梁试验结果,通过采用5种计算公式计算181片梁的纤维布剪力贡献值与试验结果对比,发现所有计算公式均有不同程度的离散,但fib Bulletin 14能较准确地计算矩形梁和T形梁的纤维布剪力贡献。此外,同样收集已有文献中的碳纤维布加固钢筋混凝土箱梁试验结果,采用已讨论的5种计算公式计算剪力,与试验结果相比,其计算值均大于试验值,研究发现规范中的计算公式都高估了纤维布的有效应变,而fib Bulletin 14的计算结果接近于试验值。因此,通过纤维布有效应变的试验值和fib Bulletin 14计算值的比较,引入有效应变修正系数1.31,计算出加固箱形梁纤维布剪力贡献值,与试验值能够较好地吻合。

A great number of experimental and numerical studies focused on the FRP shear strengthening rectangular and T-section beams,and the several models for calculating FRP shear contribution have been proposed,which were introduced to the codes and guideline of different countries.The research on the FRP shear strengthening RC box beam,however,is rarely presented in the literature.In this study,therefore,CFRP shear contribution of strengthening RC box beam is predicted by existing experimental results and theoretical models.Five models from different codes about predicting FRP shear contribution have been reviewed and discussed.181 FRP shear strengthening specimens with rectangular and T-sections collected from existing literature was calculated by the five models.Compared with experimental results,the predictions of FRP shear contribution have a certain scatter,but fib Bulletin 14 showed a relative accuracy in predicting the rectangular and T-section beams.Besides,based on the results from experiments of FRP strengthened RC box beam in shear,five models overestimated the FRP shear contribution because the effective strain of FRP sheets has been overestimated.Compared with other four models,the results predicted by fib Bulletin 14 are close to the experimental values,but still in unconservative side.Based on comparison of the effective strain of FRP calculated by fib Bulletin 14 and experimental values,a coefficient of 1.31,therefore,was also proposed,which divided the formula of the effective strain in the fib Bulletin 14 model according to the experimental effective strain in fiber.The model with the modified effective strain presented a rational prediction in CFRP shear contribution of strengthened RC box beams.