单索面混凝土斜拉桥扁平多室薄壁箱梁复合受力下的扭转性能研究

The girder of the single-cable-plane concrete cable-stayed bridge has the characteristics of thin-walled, wide, flat and one box with multiple chambers. It exhibits composite forces of compression, bending, shear and twisting. The spatial torsional effect and the torsional anti-crack problem are very outstanding under the one-side loads of vehicles. This project intends to research the basic theoretical problems, e.g., the reasonable torsional stiffness, the coupling mechanism of compression and torsion, the mechanical mechanism of the torsional ability improved by the transverse-isolated-plate. The following problems will be studied by adopting the methods of theoretical analysis and indoor model test in this project: (1) The total torsional stiffness of the wide flat multi-cellular thin-walled concrete box girder, and how to arrange the box and cells to obtain more reasonable torsional stiffness. (2) Under the composite forces of compression, bending, shear and twisting, the coupling effect of compression and torsion, the updated relationship of shear flow by the axial force of the box girder. (3) The theoretical model of the warp and distortion of the wide, flat, thin-walled and one box girder with multiple chambers reducing by the transverse-isolated-plate; as well as the mechanical mechanism of the sectional resistance-torsion bearing capacity of the box girder improving by the transverse-isolated-plate. Through the study of the torsional bearing capacity of the main girder structure under the two limit states of normal use and carrying capacity, the basic theory problems related to the torsion performance of the wide box girder of the single-cable-plane concrete cable-stayed bridge will be discussed, as well as the relevant box girder design theory will be perfected. Also, the reasonable design and structural safety for this kind of bridge will be ensured, to provide theoretical and practical supports and advices for the perfection of the related specification.

单索面混凝土斜拉桥箱梁具备薄壁、翼宽、扁平和单箱多室的特点且呈现压弯剪扭复合受力状态，在汽车偏载作用下空间扭转效应和扭转抗裂问题十分突出。本项目拟对合理抗扭刚度、压扭耦合机理、横隔板提升抗扭能力的力学机理等基础理论问题开展深入研究。项目拟采用理论分析和室内模型试验的方法研究：（1）宽幅扁平多室薄壁混凝土箱梁截面的总体抗扭刚度及各箱室如何布置可获得更合理的抗扭刚度；（2）压弯剪扭复合受力状态下箱梁的压扭耦合效应及轴力对剪力流的修正关系；（3）横隔板减少宽幅扁平多箱室薄壁混凝土箱梁翘曲、畸变的理论模型和提升截面抗扭承载能力的力学机理。项目通过主梁结构正常使用和承载能力两个极限状态时扭转性能的研究，探讨单索面混凝土斜拉桥宽体箱梁与扭转性能相关的基础理论问题，完善相关箱梁设计理论，确保该类桥梁的合理设计和结构安全，为相关规范的完善提供理论和实践上的支撑和建议。

单索面混凝土斜拉桥的混凝土箱梁向着薄壁、宽幅、扁平和单箱多室的方向发展。而单索面混凝土斜拉桥的斜拉索位于主梁中心线上，斜拉索并不参与主梁的抗扭。因此主梁在汽车偏载作用下的空间扭转效应和扭转抗裂问题尤为重要。本项目旨在分析主梁受偏载作用下的压弯扭复合受力，明确扭矩在复合受力下的影响。主要的内容包括：1、基于乌曼斯基第二理论推导斜腹板单箱三室箱形截面的扭转几何特性计算公式，并针对临海大桥的主梁截面分别采用解析法和板壳有限元法分别计算混凝土箱梁的扭转效应，得到主梁在扭转荷载作用下的应力分布规律。2、针对主梁截面的各项参数，分析参数在成桥状态下对抗扭性能的影响。3、利用BP神经网络学习训练，建立截面参数和扭转畸变角的映射关系。以质量为约束函数，得到针对抗扭问题的最优截面布置。4、基于ABAQUS二次开发的断裂相场模型实现对单索面混凝土斜拉桥薄壁箱梁的数值模拟研究。5、对现有的SMMT-H模型的丰富，研发了适用于单箱多室混凝土截面梁的全过程分析新模型。