基于弯扭耦合效应的管状翼缘钢板组合梁失效机理及承载能力研究

The use of steel I-shaped girders with tubular flanges (i.e., tubular flange girders or TFGs) has been proposed for curved highway bridges. Compared with conventional steel plate I-shaped girders (IGs), TFGs have substantially greater torsional stiffness and strength, which improves significantly the behavior of an individual curved TFG compared with a corresponding IG. One type of TFG with a hollow rectangular tube as the top flange and a flat plate as the bottom flange (i.e., the TFG1 section) is studied in this research. Compared to the previously studied TFG with rectangular tubes as the top and bottom flanges (i.e., the TFG2 section), a TFG1 has the advantage of avoiding the need for concrete infill or an internal steel diaphragm in the tubular bottom flange at the bearings, but still has sufficient torsional stiffness and strength to perform well as a curved bridge girder. In the research, the failure mechanism and ultimate capacity for curved TFG1s are investigated. A parametric study is conducted to study the parameter sensitivity of the failure mechanism, where the parameters that are varied include the span length, the horizontal curvature, number of interior cross frames, residual stress, geometric imperfection and other factors. A parametric study is conducted to study the key parameters to control the local buckling of hollow tubular flange. Detailing of cross frames for curved TFG1 bridges is studied. Conventional no load fit, steel dead load fit, total dead load fit detailing methods were studied. In addition, two new detailing methods for curved TFG1 bridges, individual steel dead load fit and remaining dead load fit were studied. The responses of example bridges with different detailing methods are compared, and the effect of different detailing methods to the failure mode and ultimate capacity is studied. Finally, a combination of key parameters and detailing methods are included to study the failure mechanism of curved TFG1s. A formula for ultimate capacity is proposed, and validated with the related experimental results.

目前钢弯梁多采用传统工字梁型式，这种钢板梁截面的截面抗扭惯矩比较小，横梁或横撑也是作为主要的受力构件来抵挡扭转，使得加工复杂、施工周期和成本较高。空心管状翼缘钢板梁截面是弯梁体系一种新型结构型式，该截面抗扭惯矩比较大，能够改善传统弯梁的受力性能。关于这种体系的线弹性范围内的结构性能已经较为成熟，但对其失效形式和承载力的研究不足。本项目研究从弯扭耦合效应的角度研究破坏形态、破坏机理和承载力计算方法。通过不同的参数分析，研究空心管状翼缘钢板弯梁在弯扭耦合效应的失效形式和机理，参数包括跨长、曲率、横梁数目、残余应力等，并研究空心管状翼缘局部稳定的控制参数。研究基于不同施工方法和施工过程对结构体系失效和承载力的影响，分析基于其优点的基于自重状态的施工方法可行性。最终综合理论分析、关键影响参数以及施工方法的影响和试验验证，确定空心管状翼缘钢板组合弯梁体系的承载力计算方法和公式。

近年来，为推进我国公路建设的转型升级，充分发挥钢结构桥梁在工程应用上的优势，钢板组合梁因其工业化建造程度高、自重轻、构造简单等优势，在全国各省市的桥梁建设领域逐渐推广开来，但同时传统工字形截面因其开口截面存在稳定性能及抗扭性能较差等缺点，因此针对这一问题，将原工字形截面的平板翼缘替换为矩形管翼缘，一定程度上弥补这一劣势，但目前在我国此种类型桥梁结构在工程应用中应用还比较少，因此有必要针对矩形管翼缘钢板组合梁开展研究。本文通过文献调研、有限元数值分析等手段对其截面设计参数、稳定性能、承载能力等结构特性进行了较为系统和全面的计算分析，论文的主要研究工作主要包括如下及部分：.首先，基于目前工字形截面钢板组合梁工程实践经验的基础上，通过控制主梁截面积、用钢量大致相同的基础上，分析二者在结构静力性能、稳定性能的差异，分析和归纳总结矩形管翼缘钢板组合梁在工程实践中的优势与劣势。其次，针对矩形管翼缘钢梁一些截面设计参数，如矩形管翼缘的宽厚比、腹板高厚比等参数，分析其对结构性能的影响，确定合理的设计取值范围；同时对中等跨径的双主梁矩形管翼缘钢板组合梁梁高和合理分段形式进行了讨论，得到一些有意义的设计指导经验。第三，通过调研对薄壁矩形管翼缘梁及传统薄壁受弯构件稳定性能相关文献，通过有限元数值分析和数据拟合的方法提出弹性扭转约束下的矩形管翼缘梁稳定性能拟合公式。第四，定量研究双主梁体系下的矩形管翼缘钢板组合梁部分相关结构设计参数对组合截面与非组合截面的抗弯承载能力影响。