预应力碳纤维布加固钢筋再生混凝土梁受弯承载力研究

试验浇筑4组再生粗骨料掺量为0%、40%、70%、100%的钢筋再生混凝土梁，根据预应力碳纤维布拉断破坏和剥离破坏的界限加固量，每组对2根钢筋再生混凝土梁进行预裂破坏后，分别进行预应力碳纤维布一层和两层加固，然后对4组钢筋再生混凝土梁进行受弯承载力试验。试验表明：随着预应力碳纤维布加固量的增大，加固梁的受弯承载力增大，梁屈服时，纯弯段受拉区横向裂缝数量增多且宽度较小；随着再生粗骨料掺量的增大，加固梁受弯承载力降低，梁屈服时，裂缝数量减少、宽度增大。最后依据试验结果与平截面假定，结合再生粗骨料掺量对钢筋再生混凝土梁受弯承载力的影响，考虑钢筋再生混凝土梁的二次受力，建立了预应力碳纤维布加固钢筋再生混凝土梁的受弯承载力计算公式。计算结果表明：受弯承载力计算值与试验值吻合较好，可以为预应力碳纤维布加固钢筋再生混凝土梁设计提供参考。

Study on flexural capacity of reinforced recycled concrete beams trengthened with prestressed CFRP sheets

 Four groups of reinforced recycled concrete beams were prefabricated, whose replacement rate of recycled coarse aggregates were 0%, 40%, 70% and 100%, respectively. According to the theoretical strengthening quantity of prestressed CFRP sheets between tensile failure and debonding failure mode, one beam of each group under pre-cracking was strengthened with a layer of prestressed CFRP sheets, while the other one was strengthened with two layers of sheets. Next, experimental study on flexural capacity of all beams was conducted. The test results show that with the increase of prestressed CFRP sheets, the flexural capacity of the strengthened beams increases, while the number and width of transverse cracks in the tensile zone of the beams increases and decreases when the beams yield, respectively. The flexural capacity of the strengthened beams decreases with the replacement rate of recycled coarse aggregates. When the beams yield the number and the width of transverse cracks in the tensile zone decreases and increases, respectively. Finally, based on test results and plane section assumption, design formulas are proposed to calculate the flexural capacity of reinforced recycled concrete beams strengthened with prestressed CFRP sheets. In the formulae, the effects of replacement rate of recycled coarse aggregates and the secondary loads of the strengthened beams are considered. The calculation results agree well with the test results, which indicates that the proposed formulas can provide good reference for design of reinforced recycled concrete beams strengthened with prestressed CFRP sheets.