【作者】 陈晨；

【导师】 杨才千；

【作者基本信息】 东南大学 ， 结构工程， 2021， 博士

【摘要】 T梁桥广泛地应用于我国中小跨桥梁,随着服役时间和车辆荷载的增加,桥梁的横向连接损伤已经成为了一种不可忽视的破坏形式,研究如何快速、有效地增强T梁桥横向连接具有重要的现实意义。本文提出了三角形桁架和K型桁架加固T梁桥的方法,分别研究了二者对T梁桥力学性能的影响并给出加固设计方法,主要研究内容及成果如下:(1)通过试验和有限元模拟的方法,在T梁桥模型的基础上研究了三角形桁架加固方式和安装高度对T梁桥结构整体性、荷载横向分布以及横向刚度的影响。分析了不同加固方式下,T梁桥的自振频率和模态振型。结果显示,三角形桁架能显著改善T梁桥的荷载横向分布,提高T梁桥整体性。当荷载作用在T梁桥的1/2跨时,1/4跨、1/2跨和3/4跨加固的效果最好,最大挠度减小27.6%,桥面板的最大应变减少62.4%。(2)通过试验和有限元模拟的方法,在T梁桥模型的基础上研究了K型桁架安装位置和数量对T梁桥结构整体性和横向刚度的影响。并分析了K型桁架对T梁桥动力特性的影响。结果显示,K型桁架加固能显著增强T梁桥的横向联系,降低T梁桥的最大挠度和梁底的纵向应变。跨中边梁加载时,三分点加固效果最好,最大挠度减小30.0%。(3)使用试验的方法,研究了跨中两道K型桁架加固钢筋混凝土T梁桥的力学性能,详细分析了各工况下混凝土T梁桥加固前和加固后的荷载横向分布、挠度、应变、开裂荷载、极限承载力、支座位移以及破坏模式。建立了K型桁架加固钢筋混凝土T梁桥的有限元模型,并与试验进行了对比。结果显示,K型桁架加固可提高钢筋混凝土T梁桥的整体性,改善T梁桥的荷载横向分布,降低T梁桥的挠度。此外,K型桁架加固对提高开裂荷载和极限承载力,抑制裂缝发展也有明显帮助,其中,极限承载力最大可提高11.0%。(4)总结现有钢桁架横隔板的刚度计算公式,在此基础上提出了适用于三角形桁架和K型桁架加固T梁桥的刚度计算方法。基于刚接梁法,分别得到了三角形桁架和K型桁架加固下各主梁的内力影响线,并与基于应变和挠度得到的内力影响线进行了对比。分析了K型桁架在T梁桥中的受力变形特性,并计算了桁架杆的刚度。结果表明,基于所提出的三角形桁架和K型桁架的刚度计算方法得到的主梁内力影响线能够较好的与试验和有限元模拟吻合。K型桁架杆的刚度受上翼缘的宽度,K型桁架斜杆与T梁梁肋所成角度,以及T梁扭转刚度的影响。(5)分析了三角形桁架和K型桁架加固对预应力混凝土T梁桥挠度和应力的影响,研究了桁架数量、截面尺寸、安装位置等设计参数对加固效果的影响,提出并建立了桁架加固预应力混凝土T梁桥的设计方法。并以跨度30m的预应力混凝土T梁桥进行设计,采用三角形桁架或K型桁架加固后跨中最大挠度均可减少12.5%以上。综合考虑,推荐K型桁架横向加固T梁桥。更多还原

【Abstract】 T-girder bridge has been widely used in the short to medium span bridge in China.With the increasing of life cycling and vehicle load,the transverse connection of the bridge has been damaged seriously.So,strengthening the transverse connection of the T-girder bridge quickly and effectively is of great practical significance.In this paper,two methods have been proposed,i.e.,triangle brace steel diaphragm and K brace steel diaphragm.The influence of the two diaphragms on the mechanical properties of the T-girder bridge has been studied.Design methods for the two diaphragms strengthening T-girder bridge have been proposed.The main research content and conclusions of this work are as follows:(1)The influence of strengthening methods and installation height of the triangle brace steel diaphragm on the integrity,load distribution and transverse stiffness of the T-girder bridge is studied based on a bridge model by experiments and simulations.The natural frequency and modal shape of T-girder bridge strengthened with different numbers of triangle brace steel diaphragm have been discussed as well.The results show that the load distribution and integrity of the strengthened T-girder bridge can be improved significantly.When the load is applied on the midspan of the bridge,strengthening at quarter span of the bridge has the best effectiveness.The maximum deflection decreases 27.6% and the maximum strain decreases 62.4%.(2)The influence of the location and number of the K brace steel diaphragm on the integrity and transverse stiffness of the T-girder bridge is studied based on a bridge model by experiments and simulations.The dynamic properties of the T-girder bridge strengthened with K brace steel diaphragms are studied as well.The results show that the K brace steel diaphragm can strengthen the transverse connection and decrease the maximum deflection and longitudinal strain of the T-girder bridge significantly.When the load is applied at the midspan of the exterior girder,the maximum deflection reduces 30.0% with the K brace steel diaphragms installed at thirds span.(3)The mechanical properties of the concrete T-girder strengthened with two K brace steel diaphragms at midspan are studied by experiments.The load distribution,deflection,strain,crack load,ultimate bearing capacity,support displacement and failure mode of the concrete Tgirder bridge with or without K brace steel diaphragms are analyzed in detail under different load cases.The finite element models of the concrete T-girder bridge strengthened with two K brace steel diaphragms are established and compared with the experiments.The results show that K brace steel diaphragms can improve the integrity and load distribution of the T-girder bridge,and decrease the deflection of the T-girder bridge.Moreover,the crack load and the ultimate bearing capacity of the T-girder bridge are increased and the development of cracks is prevented efficiently.The ultimate bearing capacity increases 11.0% at most.(4)The stiffness calculation methods of bracing steel diaphragms are summarized and the stiffness calculation methods for triangle brace steel diaphragm and K brace steel diaphragm have been proposed respectively.The internal forces influence line of each girder has been obtained by rigid-jointed girder method based on the proposed stiffness calculation methods.The results are compared with those obtained based on the deflection and strain respectively.The mechanical property of K brace steel diaphragm in strengthening the T-girder bridge is analyzed and the stiffness of the brace is calculated.The results show that the internal forces influence lines obtained based on the proposed stiffness calculation methods agree well with the experiment and simulation.The stiffness of the brace is influenced by the width of the top flange,the angle between the diagonal brace and the web,and the torsional rigidity of the Tgirder.(5)The impact of triangle brace steel diaphragm and K brace steel diaphragm on deflection and stress of the prestressed concrete T-girder bridge is studied.The influence of the diaphragm number,cross section size of the brace and installation location on the strengthening effect is studied.The design methods for strengthening T-girder bridge with triangle brace steel diaphragm or K brace steel diaphragm are proposed.Additionally,a 30 m prestressed T-girder bridge strengthened with triangle brace steel diaphragm or K brace steel diaphragm is presented.The results show that the maximum deflection of the T-girder bridge reduces more than 12.5%with triangle brace steel diaphragm or K brace steel diaphragm.Based on the study in this work,K brace steel diaphragm is more recommended.更多还原