预制节段UHPC梁接缝直剪破坏机理和设计理论研究

Precast ultra high performance concrete (UHPC) segmental bridge is an innovative structure with a wide range of application prospect due to its excellent mechanical property and durability. Keyed joints between concrete segments represent the most important and weaker locations, which stress status is more complex. Currently, the shear failure mechanism of keyed joints in precast UHPC segmental beams is still vague, the relevant test data is scarce, the shear design theory is immature. In this project, multi-level researches (i.e., material and specimen) will be deployed to investigate the shear failure mechanism of keyed joints in precast UHPC segmental bridges. The mechanical index, such as cracking loads, ultimate loads and residual loads influenced by key number, confining stress and fracture toughness will be clarified. Based on linear elastic fracture mechanics and truss model, the theoretical model on direct shear strength of keyed joints in precast UHPC segmental bridges will be established, and verified by the experimental and numerical results. The updated design method of keyed joint in precast UHPC segmental beams extended from AASHTO 2003 code will be proposed according to the theoretical analysis, experimental studies and numerical investigations. Taken residual strength of keyed joints as main index, the convenient formula of shear-friction strength of keyed joints in precast UHPC segmental bridges will be investigated. The theoretical and scientific base will be improved for codifying the Chinese design code for precast UHPC segmental bridges.

预制节段超高性能混凝土(Ultra High Performance Concrete, UHPC)桥梁具有优异的力学和耐久性能，是有广阔应用前景的新型桥梁结构形式。接缝是预制节段UHPC梁的关键部位与薄弱环节，处于复杂受力状态。目前，对预制节段UHPC梁接缝直剪破坏机理认识不充分，试验数据稀少，设计理论不成熟。本项目围绕预制节段UHPC梁接缝直剪破坏机理进行多层次（材料和构件）研究。试验和数值模拟手段，探明键齿数量、水平约束力和断裂韧度等参数对开裂荷载、极限荷载和残余荷载等力学指标的影响。基于线弹性断裂理论和桁架模型构建预制节段UHPC梁接缝直剪强度的理论模型，并用试验和数值分析结果验证理论模型。提出AASHTO 2003规范应用到预制节段UHPC梁接缝直剪强度设计的修正方法。探索以残余强度为指标，基于剪摩擦理论的预制节段UHPC梁接缝直剪强度简明公式。为制定设计规范奠定理论基础。

预制节段超高性能混凝土(Ultra High Performance Concrete, UHPC)桥梁具有优异的力学和耐久性能，是有广阔应用前景的新型桥梁结构形式。接缝是预制节段UHPC梁的关键部位与薄弱环节，处于复杂受力状态。目前，对预制节段UHPC梁接缝直剪破坏机理认识不充分，试验数据稀少，设计理论不成熟。本项目围绕预制节段UHPC梁接缝直剪破坏机理进行多层次（材料和构件）研究。试验和数值模拟手段，探明键齿数量、水平约束力和断裂韧度等参数对开裂荷载、极限荷载和残余荷载等力学指标的影响。基于线弹性断裂理论和桁架模型构建预制节段UHPC梁接缝直剪强度的理论模型，并用试验和数值分析结果验证理论模型。提出AASHTO 2003规范应用到预制节段UHPC梁接缝直剪强度设计的修正方法。探索以残余强度为指标，基于剪摩擦理论的预制节段UHPC梁接缝直剪强度简明公式。为制定设计规范奠定理论基础。.本项目进行了大量的UHPC材料性能试验和UHPC接缝Z型试件的推出试验，研究了关键设计参数对接缝开裂模式、极限承载力、荷载滑移关系的影响，获得了大量关键的试验数据。建立了UHPC接缝键齿直剪破坏全过程分析的数值模型，并进行了大量的扩展参数分析。该研究揭示了UHPC接缝的直剪破坏机理，给出了直剪强度的预测模型，构建了直剪设计理论。