组合梁中可更换高强螺栓损伤元的受力性能及疲劳破坏机理研究

The “recoverable structure” has become a development trend in the field of structure, however, the replacement of the seismic damage element and shear connector in the traditional cast-in- situ composite beam is an important obstacle to its function recovery. In this project, high strength bolt would be used as shear connectors instead of stud, so as to realize the fabrication, deconstruction, and replacement of these component and damage-concentrated element. The methods of experiment, theory and numerical simulation combined with scanning electron microscope would be used to research the bolted composite beam, and the following works would be carried out: ① experiments: 12 groups of anti-slide coefficient test, 7 groups of static push-out test, 6 groups of static whole beam test and the 5 groups of fatigue push-out test would be carried out to obtain the basic mechanical properties; ② theoretical analysis:the whole force model of bolt before and after slipping, the combined action mechanism of composite beams, and the fatigue damage mechanism of bolt would be obtained useing the theory of elastic foundation beam, stiffness reduction and the microscopic test results; ③ numerical simulation: a large number of parametric analysis would be conducted considering the diameter, strength grade and distribution of bolts and other factors. The static calculation formulas of single bolt and composite beam, simplified fatigue strength formulas, and criterion of the loss of pretension force would be established to propose a complete set of design and calculation methods. This project can provide a basis for the design of bolted composite beams, which can promote the development of recoverable and assembled structures.

“可恢复结构”已成为结构领域的发展趋势，但传统现浇组合梁中损伤元及剪力连接件的更换是阻碍其功能恢复的热点难题。本项目采用高强度螺栓作为剪力连接件，以实现组合梁各部件及损伤元的简便装配、拆卸和更换。研究采用试验、理论和数值模拟结合的方法，利用电镜扫描等手段，对螺栓连接的组合梁开展以下工作：①试验：进行12组抗滑移系数测定试验、7组推出静力试验、6组简支梁静力试验及5组推出疲劳试验，获得结构基本受力特性；②理论：结合弹性地基梁理论、刚度折减理论及微观测试结果，分析螺栓滑移前后的全程受力模型、组合梁的组合作用机理和螺栓的疲劳破坏机理；③数值模拟：考虑螺栓直径、强度等级和分布形式等因素，进行参数化分析。研究拟得到单个螺栓和组合梁的静力计算公式，提出组合梁中螺栓的简化疲劳强度公式及预紧力损失判定标准，形成成套设计计算方法。该项目可为螺栓连接组合梁提供设计依据，对可恢复和装配式结构的发展起到推动作用。

本项目对组合梁中可更换高强螺栓损伤元的受力性能和疲劳破坏机理展开了系统研究。首先基于自行研发的小型钢-混凝土界面性能测试试件，对7组21个不同混凝土强度、钢板强度、表面加工的试件开展了抗滑移试验，测定不同因素对摩擦系数的影响，并对滑移后的试件重新组装并进行二次试验，获得损伤后钢-混界面的摩擦系数，证明一次磨损后的钢-混界面仍然可以满足抗剪设计要求，为组合梁的修复提供依据。通过扫描电镜观测磨损情况，从微观上解释了摩擦系数的变化机理。随后采用大型有限元分析软件ABAQUS建立了抗滑移试验的数值模型，并在验证模型准确性的基础上进行参数分析，基于试验和参数分析，提出了螺栓在组合结构中的优化构造细节以及螺栓直径、螺栓等级、混凝土强度、垫片尺寸的适配性。.在此基础上进行组合梁中高强度螺栓的静力推出试验，明确了螺栓的传力机理，获得螺栓抗剪键的滑移承载力、极限承载力和刚度，进而提出了三段式抗剪本构模型，同时提出了简化的抗剪承载力计算公式。通过有限元分析软件ABAQUS建立推出试验模型，并考虑混凝土材料的损伤，以螺栓预紧力、孔径比、螺栓等级为参数，探讨了拉剪共同作用下螺栓的全程应力发展过程。最后，对无后浇带组合梁的受力性能的进行参数分析，明确了各阶段螺栓预紧力的损失，定量分析了有无后浇带对组合梁整体刚度的影响，并根据拼接间隙和拼接位置的参数敏感性，优化了混凝土板的设计，通过改变跨中预制板的宽度，可以使无后浇带的组合梁达到与后浇组合梁基本相同的受力性能，为组合梁的完全装配提供了思路。综上所述，本研究为装配式组合梁在桥梁和装配式结构中的推广和应用提供了理论支持和技术保障。