基于温度效应的CFRP加固钢结构疲劳性能与控制方法研究

Lots of steel bridges need to be strengthened or repaired due to fatigue damage around the world. The strenthening technique with exterally bonded CFRP (carbon fiber reinforced polymer) possesses many advantages, such as easy installation, ignorable increased loading and without residual stress. However, the great difference of the thermal expansion coefficient between steel material and CFRP may bring in high level of shear stress in their interphases,under the temperature effect due to season change or sun irridation (alternating temperatues and temperature difference). This will lead to cumulative fatigue damage. In view of this, the project will study the temperature effects on the cumulative fatigue damages between the CFRP - steel strucutre through double-lap joint test. An equavalient relationship between the temperature effect and fatigue loading will be explored and established. The effects the toughness of adhesives, chemical treatment of the steel surface and theglass fiber insulating layer on the initiation and development of craks in the CFRP and steel structure interface will be investigated. Accordingly, a control method to reduce the interfacial fatigue damage due to temperature effects will be proposed. The variation of the fatigue life and damage modes of the steel beam strengthened with CFRP due to the temperature effects will be investigated, and the interfacial design methods will be proposed. The present study will offer key basic knowledge for the design of steel strucutre strengthening with CFRP plates. The study possesses acadamic and application significance.

国内外大量钢桥迫切需要疲劳加固维修，外粘贴碳纤维复合材料（CFRP）加固技术具有施工方便、不增加负载及不引入残余应力等优点。但由于钢材与CFRP热膨胀系数差别显著，季节变换与日照等引起的温度效应（温度交变与温差）将导致CFRP-钢结构的界面剪应力较大，易产生疲劳累积损伤。为此，本项目拟采用双搭接拉伸试验方法研究上述温度效应对CFRP-钢结构界面疲劳累积损伤的影响规律，建立温度效应与疲劳荷载的等效关系；研究胶粘剂性能、钢表面化学处理、玻璃纤维复合材料（GFRP）隔离层等对界面疲劳裂纹萌生及扩展的影响规律，提出考虑温度效应的CFRP-钢结构界面疲劳性能控制方法；研究温度效应对CFRP-钢梁抗弯疲劳寿命和破坏模式的影响规律，给出考虑温度效应的CFRP-钢梁抗弯疲劳加固的设计方法。本项目的研究将为CFRP加固钢结构的设计提供关键的科学依据，具有重要的学术和应用价值。

由于碳纤维复合材料（CFRP）与钢材的热膨胀系数相差大，CFRP加固钢结构在服役过程中由于环境温度变化可能导致界面损伤脱粘，影响CFRP增强钢结构的长期服役性能。本项目系统研究了CFRP-钢界面粘结的温度特性及其控制方法研究，并在此基础上，研究了不同温度海水下CFRP-钢粘结性能演化规律与机理，获得了CFRP-钢界面粘结的温度特性及其控制方法，阐明了CFRP-钢界面在不同温度海水浸泡条件下的界面粘结演化规律，获得了CFRP-钢界面破坏模式、粘结-滑移关系、应变分布等演化规律，为CFRP增强钢结构在海洋环境下的设计应用奠定了基础；研究了温度效应对CFRP-钢界面损伤的影响规律，建立了温度效应与疲劳荷载对于CFRP-钢界面粘结性能影响的等效关系；基于CFRP-钢单搭接试验方法，完成了CFRP-加固钢梁抗弯疲劳加固试验研究，获得了温度效应下CFRP-钢梁的静力学性能，提出了考虑温度效应的CFRP加固钢梁的抗弯设计方法。