外贴FRP加固桥梁界面应力的计算模型研究

Interfacial Stress Analysis of Externally Bonded FRP Strengthened Beam Bridge

现有大部分外贴FRP加固梁界面应力的理论计算模型都因假设胶层应力沿厚度方向为常数而无法得到准确的界面应力分布规律。针对这一情况,提出了一种更为合理的外贴FRP加固梁界面应力计算模型。不同于一些已有模型假设被加固梁和FRP板曲率相同,该计算模型将被加固梁、胶层、FRP板当成三层独立的线弹性欧拉-伯努利梁,分别考虑了各层梁不同的转动。在建立胶层上下界面的位移协调方程中考虑了界面的柔度,通过求解由界面位移协调方程推导而来的耦合控制微分方程组,得到了FRP加固梁各层内力和界面应力的解析解。该文提出的新模型全面考虑了胶层所受的轴力、剪力和弯矩,可以得到梁-胶层界面和FRP板-胶层界面不同的应力分布规律。与有限元模型和已有方法的计算结果比较表明,该模型计算结果是合理的。

Most of the existing theoretical models on interfacial stress analysis of FRP reinforced beam assumed that both the shear and normal stresses across the thickness of adhesive layer were constant,which could not get an accurate interfacial stresses distribution.To overcome the limitations,an improved model on interfacial stress analysis of externally bonded FRP strengthened beams is proposed.In the present model,the original beam、the adhesive layer and FRP plate are each modeled as a single linearly elastic Euler-Bernoulli beam,and therefore,they have separate rotations,which release the unrealistic restriction of the same curvatures of adherends used by some existing models.Deformable interfaces are assembled to establish the continuity conditions between the adherend-adhesive interfaces.By solving the coupled governing differential equations derived from the displacement compatibility equations,explicit closed-form expressions of beam forces and interface stresses are derived.The proposed model considers the axial force,transverse shear force and bending moment of the adhesive layer,and obtain different stresses distribution at the beam-adhesive and the FRP-adhesive interfaces.The validity of the present model is demonstrated by its excellent agreements with the results from numerical finite element analysis and existing model solutions.