拉挤GFRP型材翼缘-腹板结合部受力机理及疲劳性能研究

Pultruded glass fiber reinforced polymer (GFRP) profiles, which are made up by the third main construction material only ranking behind steel and concrete, could be used as main bearing components and strengthening members in the bridge engineering field and will have a good application prospect in future bridge construction. Similar to steel structures, there are various section forms for pultruded GFRP profiles used in bridge structures, such as I-shaped, channel-shaped etc. However, unlike welded steel profiles, GFRP profiles, especially flange-web joints, consist of various complex and anisotropic lamina lay-ups and easily form resin rich area making inter-laminar failure much susceptive under heavy bending, shearing and torsion vehicle loading. Thus, it is difficult for GFRP profiles to behave high strength, light weight and non-corrodible nature. .This research is to reveal the inter-laminar mechanism of flange-web joints, establish cohesive zone model (CZM) by comprehensively utilizing fracture mechanics, damage mechanics and composite material mechanics. In addition, it is also to improve inter-laminar mechanical performance of flange-web joints by optimizing lamina lay-ups and mixing short cut fiber with resin. Besides, static and fatigue tests on flange-web joints will be conducted in order to investigate tensile, shear and torsion mechanical performance and the bearing capacity calculation method and fatigue life prediction method will be proposed in the end. The purpose is to offer theoretical foundation for the design of pultruded GFRP profiles.

拉挤玻璃纤维增强复合材料（GFRP）型材可用于桥梁的主要承重构件或加固构件，是仅次于钢材、混凝土的第三种主要建筑材料，具有很好的应用前景。桥梁用拉挤GFRP型材有工字型、槽型等截面形式，与钢结构型材不同，其翼缘与腹板结合部由弯折的纤维织物-树脂铺层构成，易形成富胶区。结合部构造复杂且各向异性，在弯、剪、扭等作用下，结合部富胶区极易产生层间损伤，使GFRP型材整体性能难以发挥。.本研究拟综合运用断裂、损伤及复合材料力学理论，从细观层次上揭示GFRP型材结合部富胶区层间损伤机理，建立结合部富胶区裂纹粘聚力本构关系，通过研究结合部铺层构造改进和短纤维增韧技术，从而达到提高结合部层间性能的目的。在宏观层次上开展结合部静力及疲劳性能试验，探究结合部拉伸、剪切及扭转受力机理，建立结合部承载力计算方法和疲劳寿命预测方法。其目标为拉挤GFRP型材翼缘与腹板结合部合理设计提供理论基础。

桥梁中采用的拉挤GFRP型材有工字型、槽型等截面形式，其翼缘与腹板结合部由弯折的纤维织物-树脂铺层构成，易形成富胶区。因此，本课题将拉挤GFRP型材的翼缘-腹板结合部作为研究对象，开展了如下研究：（1）提出了新型损伤扩展准则和拉挤型材单层板厚度、纤维体积率评估方法，针对土木工程领域拉挤GFRP型材的特点，编制了可模拟单层板剪切非线性、加载/卸载的三维渐进失效材料用户子程序。（2）设计了新型结合部拉伸、剪切和弯曲试验装置，对6种不同FRP型材翼缘-腹板结合部开展试验，得到了结合部拉伸、弯曲及剪切性能承载力和刚度，提出了结合部三折线模型和双折线模型，并根据试验结果确定三折线模型和双折线模型参数。（3）开展了结合部湿热老化拉伸、弯曲、剪切性能加速试验，获得了结合部拉伸、弯曲和剪切性能在湿热环境中随时间变化规律，试验结果表明湿热老化对结合部弯曲性能影响最大，对结合部剪切性能影响次之，对结合部拉伸性能影响最小；（4）为研究结合部疲劳性能，开展了GFRP桥面板轮载疲劳试验，得到了不同荷载水平下的疲劳寿命、破坏模态，试验结果表明桥面板的刚度退化十分有限。