碳纤维布粘贴加固BFRP筋-ECC-混凝土组合梁受弯性能研究

工程结构服役期间经常由于使用功能改变或使用荷载增加而需要对结构进行加固改造。为研究经碳纤维布粘贴加固后的玄武岩纤维增强塑料（BFRP）筋-工程用水泥基复合材料（ECC）-混凝土组合梁的受弯性能，对3组共12根不同ECC高度替换率（0、0.29和0.58）的BFRP筋-ECC-混凝土组合梁底分别粘贴1、2和3层碳纤维布的加固构件及未加固构件进行静力受弯性能试验。研究碳纤维布粘贴层数和ECC高度替换率对组合梁受弯承载力和破坏形态的影响。试验结果表明：采用受拉性能优异的ECC替代受拉区部分混凝土形成的ECC-混凝土组合梁不仅可提高构件承载力，还可有效改善构件抵抗开裂和变形的能力;组合梁底粘贴3层碳纤维布，裂缝宽度可降至未加固试件的10%，受弯承载力提高20%，挠度降低50%。借鉴钢筋混凝土理论，基于合理的基本假定和简化的材料本构模型，提出粘贴碳纤维布加固的组合梁受弯承载力计算式，并给出碳纤维布强度折减系数，理论预测值与试验实测值吻合良好。

Study on flexural behavior of BFRP reinforced-ECC-concrete composite beams strengthened with carbon fiber sheets

The engineering structures usually need to be strengthened during their service period for the changing of service function or the increasing of service load. The flexural behaviors of a new type of basalt fiber reinforced polymer (BFRP) bars-engineered cementitious composite (ECC)-concrete composite beams strengthened by carbon fiber sheets (CFS) were investigated in this paper. The static flexural experiments of totally 12 BFRP-ECC-concrete composite beam specimens with three types of ECC height replace ratios (0, 0.29 and 0.58) strengthened by four kinds of CFS layers (one, two, three layers of CFS strengthened and unstrengthened specimens) were conducted. The effects of the number of CFS layers and the height replace ratios of ECC on the bearing capacity and failure mode of the strengthened composite beams were studied. The test results show that, using ECC layer with good tensile performance to replace the concrete in tension zone, the anti-deformation and anti-crack ability as well as the bearing capacity of the ECC-concrete composite beams have been improved. Compared with the unstrengthened specimens, the flexural capacity of the specimens strengthened by three layers of CFS is improved by 20%, while the deflection and crack width are reduced by 50% and 10%, respectively. Based on the theory of reinforced concrete structures, the reasonable basic assumptions and simplified constitutive models of materials, the calculation formulae for bending capacity of BFRP reinforced ECC-concrete composite beams strengthened with CFS were developed and the strength reduction factors of CFS were given. The predicted results are in good agreement with the test results.