新型FRP-金属板桁组合张弦梁抗扭机理与计算方法研究

A novel FRP-metal string structure with plate-truss composite girder has been previously proposed for emergency bridging systems with light-weight, long-span, high load-carrying capability and modular feasibility. However, the theory lag restricts its application and popularization. As a new type of structure, it is necessary to explore its torsional mechanism and design-oriented calculation methods. In this proposal, a pure torsion test and a refined numerical analysis are carried out on a full-scale specimen to explore the torsional responses and the load transfer mechanism of the new integrated plate-truss composite girder. The corresponding theoretical model and its equivalent analytical model are derived. Subsequently, the on/off-axis bending tests and the parametric numerical analysis are conducted on a full-scale string girder bridge to clarify the bending-torsion coupling behavior, the torsional responses and their key controlling factors. Besides, the coordination mechanism of the main girder and the string part is experimentally and numerically explored. Based on the analytical models of the upper plate-truss composite girder, the theoretical solutions and the simplified calculation methods are established for the entire string structure subjected to pure torsion. According to the linear-elastic bending-torsion coupling working mechanism and the established torsional calculation method of the new string structure with plate-truss composite girder, along with the existing flexural calculation method of the conventional string structure with solid-web beam, the bending-torsion coupling design and calculation method and procedure are established for the entire string structure. The research results of this project can provide theoretical principle for performance-based design and engineering application of the new string girder structural system.

FRP-金属板桁组合张弦梁是一种新型应急桥梁结构，具有轻量化、大跨度、高承载和模块化特征，但理论滞后制约了其推广应用，亟需开展此新型结构的抗扭机理与计算方法研究。为此，本项目将开展新型一体式板桁组合结构的足尺模型纯扭试验和精细化数值模拟，揭示上部主梁的纯扭力学响应规律和传力机理，建立相应的理论计算模型和等效分析模型；开展整体张弦桥跨结构的正、偏载堆载试验及参数化数值分析，探明其弯-扭耦合响应、纯扭力学响应及主控影响因素，揭示主梁与张弦部分的协调作用机制，并结合上部主梁的理论分析模型建立此新型张弦结构的抗扭计算模型，给出简化计算方法；基于张弦桥跨结构的线弹性弯-扭耦合工作机制和抗扭计算方法，同时引入已有张弦实腹梁的抗弯计算方法，给出此新型张弦结构的弯-扭耦合设计计算方法及程序。本项目研究成果可为该新型张弦梁结构体系的性能设计与工程应用提供理论依据。

FRP-金属板桁组合张弦梁是一种新型应急桥梁结构，采用了新结构形式、新型连接技术和高性能复合材料，具有轻量化、大跨度、高承载和模块化特征，展现出广阔的应用前景，但理论滞后制约了其应用推广。偏载及扭转是大跨桥梁最常见的受力形式之一，本项目通过足尺模型试验、数值模拟和理论分析相结合的方法，对此新型结构体系的弯曲、扭转及弯-扭耦合性能、工作机理及计算方法进行了深入研究。主要研究内容和重要结果包括：（1）开展了张弦梁桥上部箱桁主梁的正、偏载试验和有限元数值分析，得到了箱桁主梁的弯曲、扭转和弯-扭耦合力学性能；开展了关键杆件移除效应对箱桁主梁线弹性力学响应影响规律的试验研究，通过下部横联系移除前后两种不同结构形式主梁间力学行为的对比分析，分别揭示了一体式箱桁主梁和分体式桁梁的抗扭机理，并给出了箱桁主梁抗扭刚度的优化提升措施。（2）针对此类空间桁梁以刚度控制设计的特点，基于均匀化思想和等效剪切变形原理，分别构建了可用于结构抗弯和扭转刚度预测的等效分析模型及理论计算方法。（3）开展了张弦梁桥跨结构的正、偏载试验及有限元分析，得到了张弦梁的弯曲、扭转和弯-扭耦合力学特性；通过参数化数值分析，得到了关键杆件设计变量、组合节点等效刚度及复合材料弹模变化对张弦桁梁弯曲和扭转变形的影响规律，提出了可有效提升结构抗扭刚度的设计建议。（4）综合张弦梁桥跨结构的试验和有限元分析结果，揭示了上部箱桁主梁与下部张弦的协调作用机制以及张弦梁的抗扭机理，建立了可用于结构初步设计中扭转变形预测的简化分析模型与计算方法。本项目研究成果可为该新型张弦桁梁结构体系的性能设计与工程应用提供理论依据，并为其它组合空间桁梁和张弦结构的相关研究提供参考。