SFRC焊钉-橡胶连接件的传力机理与疲劳性能研究

Construction quality of studs connector was easily controlled, mechanical behavior of studs connector was not direction-oriented, studs connector had been widely used in steel and concrete composite structure bridge. Steel bridge pavement, steel and concrete joint section which used studs connector were usually crack and crushed of the concrete under the moving vehicle load, and the fatigue performance of studs connector were poor. Aim at above problems, new type of connector was put forward, which was SFRC rubber-sleeved studs connector and had some advantages as followed, tensile capacity of the concrete was high, and the shear stiffness of the connector was fairly low, and the shear capacity of the connector was high, and fatigue performance of the connector was good. The influence parameters including steel fiber content, thickness and height rubber-sleeved, diameter of studs, grade of concrete, etc. were considered, through experimental study and nonlinear finite element analysis, force transfer mechanism among the plate, SFRC, rubber-sleeved and studs were revealed, the shear failure and fatigue break down phenomenon of the new connector were explained, evolution model and the influence parameters of shear stiffness, shear capacity, failure modes and fatigue performance of the new type connector were proved. A shearing capacity formula and element analysis method of the new type connector were advised, and the design method and forms of application of the new type connector were proposed. Research of the project was important engineering significance for enrichment and development the structure type of steel bridge pavement and steel and concrete joint section, meanwhile, and was important theory significance for development and modification computing theory and method of connector.

焊钉连接件施工质量易于保证，受力不具有方向性，在钢-混组合结构桥梁中得到广泛应用。针对采用焊钉连接件的桥面铺装及结合段中存在混凝土易开裂、压碎和焊钉疲劳性能差等问题，提出SFRC焊钉-橡胶连接件构造形式，具有混凝土抗拉能力高，连接件抗剪刚度低、抗剪承载能力大和疲劳性能好等优点。本研究主要考虑钢纤维掺量、外套橡胶厚度及高度、焊钉直径和混凝土标号等参数影响，通过试验研究和非线性有限元分析，揭示钢板、SFRC、橡胶套与焊钉之间的传力机理，解释SFRC焊钉-橡胶连接件的抗剪、疲劳破坏现象，探明SFRC焊钉-橡胶连接件抗剪刚度、抗剪承载力、破坏模式和疲劳性能的演变模型及影响因素；建立SFRC焊钉-橡胶连接件的抗剪承载力计算公式和有限元模拟方法，提出新型连接件的设计方法和应用形式。项目研究对丰富和发展桥面铺装及结合段的结构形式具有重要的工程意义，对于发展和完善连接件计算理论与方法具有重要的理论意义。

焊钉连接件施工质量易于保证，受力不具有方向性，在钢-混组合结构桥梁中得到广泛应用。针对采用焊钉连接件的桥面铺装及结合段中存在混凝土易开裂、压碎和焊钉变形性能及疲劳性能差等问题，提出了SFRC焊钉-橡胶连接件构造形式。在理论分析的基础上，开展了63个SFRC焊钉-橡胶连接件的抗剪推出试验和19个SFRC焊钉-橡胶连接件的疲劳性能试验研究。同时，采用正交试验方法，考虑材料、几何和边界非线性，进行了精细化有限元分析。此外，鉴于开孔钢板连接件的混凝土 “榫”与焊钉-橡胶连接件的橡胶套筒功能相似，为系统研究SFRC连接件的抗剪机理，开展了30个SFRC开孔钢板连接件抗剪性能的对比试验研究。系统总结了SFRC焊钉-橡胶连接件和开孔钢板连接件的设计方法和工程应用。研究表明：①SFRC能一定程度上提高焊钉-橡胶连接件的抗剪承载力、抗剪刚度和疲劳寿命，其抗剪承载力可采用普通混凝土焊钉连接件乘以一个包括钢纤维体积率等参数的公式描述。钢纤维的掺入不改变焊钉-橡胶连接件的抗剪和疲劳破坏形态，其中SFRC焊钉-橡胶连接件抗剪破坏表现为焊钉根部剪切断裂破坏，焊钉杆同时出现弯向剪力方向的弯曲变形；疲劳破坏表现为焊钉杆剪切破坏和焊趾撕裂破坏。在正常配筋的钢混组合结构中，钢纤维体积掺量建议值为0.8%~1.2%；在未配置钢筋的桥面铺装中，钢纤维体积掺量建议值为3%~6%。②厚2.5mm（焊钉直径的1/8.8），高50mm（焊钉总高度的1/2）的橡胶套筒能有效降低抗剪刚度而不削弱其抗剪承载力，焊钉杆的弯曲变形的高度随套筒高度的增加有所提高。该连接件变形性能的提升明显，在往复荷载下具有较好的变形恢复性能。③应力幅值是影响SFRC焊钉-橡胶连接件疲劳性能的主要因素，橡胶层厚度对疲劳变形性能影响明显。该新型连接件可应用于钢桥面铺装和钢混结合段等钢混组合结构中，项目研究为SFRC焊钉-橡胶连接件的设计和工程应用提供基础支撑，对丰富和发展桥面铺装及结合段的结构形式具有重要的工程意义，对于发展和完善连接件计算理论与方法具有重要的理论意义。