Abstract The use of adhesively-bonded CFRP crack-patching in old metallic bridges seems to be a promising fatigue strengthening technique, but the internal laminar structure of puddle iron could influence its efficiency, resulting in premature interlaminar failure within the metal before CFRP debonding. To investigate the fatigue behaviour of this retrofitting system, six double-strap joints with CFRP laminates adhesively-bonded to puddle iron plates taken from a 19th century bridge were tested. Three specimens were statically loaded until failure as control specimens, and other three were tested under tensile-tensile fatigue loading up to 2 million cycles at a frequency of 10 Hz, with stress ranges in the metal of 60, 75 and 90 MPa. An analytical model is used to compute the maximum principal stress range in the adhesive during fatigue loading, which is assumed as the governing fatigue strength parameter in the double-strap joint. Based on the experimental results of the present work, together with a database for joints with modern steel collected from literature, an S-N fatigue curve is obtained for CFRP-metal double-strap specimens, and a fatigue limit in terms of maximum principal stress range in the adhesive layer is proposed to be used in design guidelines.

中文翻译：

---

带有取自 19 世纪桥梁的水坑铁板的拉伸 CFRP-金属双带接头中粘合剂的疲劳行为

摘要 在旧金属桥梁中使用胶粘碳纤维布裂纹修补似乎是一种很有前景的疲劳强化技术，但水池铁的内部层状结构会影响其效率，导致碳纤维布脱粘前金属内部的层间过早失效。为了研究这种改造系统的疲劳行为，我们测试了 6 个双带接头，其中 CFRP 层压板粘合到取自 19 世纪桥梁的水坑铁板上。三个试样作为对照试样进行静态加载直至失效，另外三个试样在频率为 10 Hz 的拉伸-拉伸疲劳载荷下进行了高达 200 万次循环的测试，金属的应力范围为 60、75 和 90 MPa。分析模型用于计算疲劳加载期间粘合剂中的最大主应力范围，它被假定为双带接头中的控制疲劳强度参数。根据目前工作的实验结果，结合从文献中收集的现代钢接头数据库，获得了CFRP-金属双带试样的SN疲劳曲线，以及最大主应力范围内的疲劳极限。建议在设计指南中使用粘合剂层。