预应力钢筒混凝土管内壁复式碳纤维加固试验与计算分析

Laboratory testing and calculation analysis of reinforcement for prestressed concrete cylinder pipe with compound carbon fiber

碳纤维加固预应力钢筒混凝土管(PCCP)具有非开挖、工期短、对周边环境影响小的特点。但是,由于碳纤维与混凝土的极限拉应变相差近百倍,传统碳纤维加固PCCP技术无法有效发挥碳纤维的应力水平。本文提出复式碳纤维加固PCCP技术,即在碳纤维与PCCP之间增设自主研发的高压缩弹性垫层,利用垫层的压缩性为碳纤维变形提供空间,显著提升碳纤维的环向应变水平。为了验证复式碳纤维的加固效果,采用直径为0.75 m的钢筒进行模型试验,试验结果表明,当内水压力为1.0 MPa时,复式碳纤维加固技术较传统碳纤维加固技术中碳纤维环向微应变提升20倍以上,被加固结构的微应变降低40%以上。基于拉梅公式的力学模型计算结果与试验结果基本一致,随着垫层厚度或碳纤维层数的增加,钢筒的环向微应变降低,但降低的速度逐渐减小。该技术利用了碳纤维高强和高模量的特性,实现了碳纤维与PCCP共同承受内水压力的效果。

Carbon fiber reinforcement technology for Prestressed Concrete Cylinder Pipe(PCCP) has the characteristics of trenchless,short construction period and little impact on surrounding environment. Because of the difference of ultimate tensile strain between carbon fiber and concrete by nearly one hundred times,the existing carbon fiber reinforcement technology for PCCP cannot effectively play the stress level of carbon fiber. In this paper,a new solution of the compound carbon fiber on PCCP is proposed,which is referred to add a self-developed high compressible and elastic cushion between the carbon fiber and PCCP.The circumferential strain level of carbon fiber can be improved remarkably by using the compressible amount of cushion to provide space for the deformation of carbon fiber. In order to verify the effect of carbon fiber reinforcement structure, model tests were carried out on a steel cylinder with a diameter of0.75 m. The laboratory testing results show that the circular strain of carbon fiber in compound reinforcement structure is 20 times higher than that in conventional reinforcement structure,and the strain of reinforced structure is reduced by more than 40% when the internal water pressure is 1.0 MPa,which is consistent with the calculated results of the mechanical model based on Lame′s formula. With the increase of cushion thickness or layers of carbon fiber,the circular micro-strain of steel cylinder decreases,but this decreasing speed slows down gradually. This technology takes advantage of the characteristics of high tensile strength and high elastic modulus of carbon fiber,achieves the effect that carbon fiber and PCCP jointly bear the internal water pressure.