节段预制拼装预应力UHPC箱梁抗剪性能及设计方法研究

Precast prestressed UHPC segmental box girder bridge shows a bright future in its application. The shear stability of the webs with large height to thickness ratio and assembled joints and the shear resistance of joints have become key factors in its design, and they are the basis for reasonable shear design of this structure. The shear performance of the precast prestressed UHPC segmental box girder is studied in this project. The main contents include that, the shear stability of precast UHPC segmental box girder webs with large height to thickness ratio and assembled joints, is explored to reveal its shear stability failure modes and theoretical formulas by combined use of numerical simulation and theoretical analysis; the shear failure test and the corresponding numerical simulation analysis are conducted on the joints of UHPC box girder webs to study the contributions of (epoxy) joint interfaces, shear key and prestress for the shear resistance, and to reveal the shear failure mechanism and shear performance of different kinds of joints, including the dry joint with large key, the epoxy joint with large key and the epoxy joint with multiple keys. Then, the theoretical predictions for the shear resistance of joints in the UHPC box girder will be developed. Based on the previous research work, the shear design provisions for the precast UHPC segmental box girder will be developed, so as to provide theoretical supports on shear for the related guidelines and engineering design of this structure.

节段预制拼装预应力UHPC箱梁桥具有广阔的应用前景。带拼装接缝的大高厚比腹板抗剪切稳定能力和拼装接缝处的抗剪能力成为其设计控制的重要方面，掌握其性能是合理进行抗剪设计的基础。本项目围绕节段预制拼装预应力UHPC箱梁的抗剪性能展开研究，主要内容包括：拟通过数值仿真与理论分析相结合的方法探明带拼装接缝的预应力UHPC箱梁大高厚比腹板剪切失稳形态与计算公式；开展节段预制拼装预应力UHPC箱梁腹板接缝模型剪切破坏试验与数值仿真，分析（环氧树脂）接缝面、剪力键齿及预应力等对抗剪承载力的贡献，探明UHPC箱梁腹板大键齿干接缝、大键齿胶接缝、多键齿胶接缝的剪切破坏机理和抗剪性能，并建立其接缝抗剪计算方法；基于前面研究，最终建立节段预制拼装预应力UHPC箱梁抗剪的设计计算方法，从而为该类结构的标准编制及工程设计提供抗剪方面的理论基础与方法支撑。

节段预制拼装预应力UHPC箱梁桥因其优异力学性能及耐久性能具有广阔的应用前景。大高厚比腹板抗剪切稳定能力和拼装接缝处的抗剪能力成为其设计控制的重要方面，掌握其性能是合理进行抗剪设计的基础。本项目围绕节段预制拼装预应力UHPC箱梁的抗剪性能展开研究，取得了以下研究成果：（1）通过数值仿真模拟探明了预应力UHPC箱梁大高厚比腹板的两种剪切失稳形态，即整体失稳及局部失稳，基于薄板稳定理论建立了两种剪切屈曲模式的极限应力理论计算公式，为指导腹板的稳定设计计算提供了理论依据；（2）开展了UHPC大键齿干接缝的直剪破坏全过程数值模拟及广泛参数分析，揭示了其剪切破坏机理及大键齿尺寸对干接缝直剪承载力的影响规律，推荐了优化的大键齿合理尺寸范围，并拟合建立了考虑键齿尺寸影响的UHPC大键齿干接缝抗剪承载力计算公式；（3）开展了UHPC键齿胶接缝的直剪破坏试验与数值仿真，探明了键齿尺寸、侧向应力、钢纤维掺量及键齿数量等关键参数对UHPC键齿胶接缝抗剪性能的影响规律，揭示了UHPC大键齿胶接缝及UHPC多键齿胶接缝的剪切破坏机理；（4）基于库伦-莫尔剪切破坏准则，推导建立了UHPC大键齿胶接缝抗剪承载力设计计算理论；以现有UHPC及混凝土胶接缝抗剪承载力计算公式为基础，考虑多键齿接缝的折减效应，建立了UHPC多键齿胶接缝的抗剪承载力设计计算公式。本项目的研究成果将为节段预制拼装UHPC箱梁结构的标准编制及工程设计提供抗剪方面的理论基础与方法支撑。