ESPI技术对外贴纤维混凝土加固承载的实验研究

采用电子散斑干涉技术,对外贴碳纤维加固混凝土梁的外贴材料位移的分布特征,进行了全场实时测量,通过实验获得的散斑干涉条纹图可以得到外贴材料与混凝土梁的粘结传力长度随粘结长度及初始载荷之间的关系;了解用于加固的碳纤维材料的应变分布特点和产生梁侧剥离破坏时的碳纤维表面位移(应变)的演化过程。实验还说明了电子散斑干涉技术不仅可用于位移的测量,而且也可用于结构安全监测和破坏预报。文中给出了对C20D、C25A和C60C侧贴碳纤维板加固在不同载荷作用直到构件破坏前的位移测试及对试件C60C轴线上的剪应力分析结果。

Experimental Study on Concrete Beams Strengthened by Externally Bonded FRP Composites Using ESPI Technique

The in-plane displacements or strains of strips of fiber reinforced polymer (FRP) composites, which are bonded to concrete beams for strengthening, was real-time and whole-field detected and inspected by the means of the electronic speckle pattern interferometry (ESPI) technique. Based on the experimental results, it shows that there is an effective length of load transfer from the concrete blocks to the FRP plates at initial load level; the effective length is different from the anchor length and the strain distribution on the plates is non-uniform. The ESPI technique can be employed to monitor very small displacements in the RFP reinforced concrete beams and to predict diagnostic warning before damage can be obtained when interferometric fringes indicate that strain distribution on the anchor plates are highly non-uniform. The method may also provide a better understanding of the still unknown interaction between the materials in complicated composites such as concrete and FRP, and give the possibility to verify or validate the existing theoretical models for CFRP composite behavior. The measurement and analysis results of the strips of FRP composites bonded to C20D, C25A and C60C concrete beams under different loadings are presented.