【作者】 张巍；

【导师】 田石柱； 王宗林；

【作者基本信息】 哈尔滨工业大学 ， 防灾减灾工程及防护工程， 2012， 博士

【摘要】 近年来，预应力混凝土连续梁、连续刚构桥在投入运营10年左右常常出现下挠过大（10cm以上）的问题，给桥梁的安全性带来隐患。目前大多数学者将桥梁下挠的原因归于混凝土收缩和徐变的影响，而忽视了作为受力性能薄弱的节段间接缝连接刚度降低对桥梁挠度的影响。并且由于施工中常常忽视对节段间接缝界面的处理，使接缝段混凝土的力学性能都要低于一次性浇筑的整体混凝土。大跨径预应力混凝土梁桥一般采用平衡悬臂现浇法施工，全桥的接缝多达上百个，这使桥梁由一个整体受力的结构变为由若干个薄弱的接缝连接而成的“离散结构”。接缝的存在削弱了桥梁受力的整体性和连续性，因而很有可能成为导致桥梁出现过大的下挠的重要原因之一。然而，现在无论是在设计还是在实际施工中对此部位都没有做“特殊处理”，均将结构视为理想的无接缝整体，接缝段混凝土材料性能及力学性能与节段内整块混凝土完全一样，显然这是不符合实际的。为研究接缝段连接刚度对桥梁挠度的影响，补充和完善悬臂浇筑混凝土桥梁节段间接缝的设计理论及施工方法，本文开展了竖直节段接缝抗剪试验和抗弯试验。以试验结论为基础，研究了与目前一贯采用的竖直接缝不同的非竖直形式接缝，提出能同时提高接缝抗剪刚度和抗弯刚度的组合形式接缝，并得出了竖直接缝与组合接缝刚度对桥梁挠度的影响。接缝抗剪试验共计三片试验梁，根据接缝段连接刚度的不同分为一次性整体浇筑的无接缝试验梁、分段浇筑的有接缝试验梁以及接缝中加入抗剪钢筋的有接缝试验梁。通过对实测的三片试验梁在相应接缝段两侧相对挠度的对比，得出了接缝段截面相对于一次性整体浇筑截面的抗剪刚度降低系数，以及加入抗剪钢筋后的接缝段的抗剪刚度提高系数，并以此为基础提出了接缝抗剪钢筋的设计方法。竖直接缝抗弯试验同样包括三片试验梁（无接缝整体、有接缝、接缝加抗剪钢筋）但截面尺寸不同。通过对三片试验梁实测数据的对比分析，得出了接缝和结构整体的抗弯刚度降低系数，以及加入抗剪钢筋后的接缝段的抗弯刚度相对素接缝的提高系数，并提出接缝段混凝土等效弹性模量与等效剪切模量的关系。在竖直节段接缝试验研究的基础上，对非竖直形式接缝进行了理论分析。综合考虑倾角在结构变形方面起到的改善作用以及便与施工，本文拟定了5°、10°和15°的三种不同的接缝倾角，并建立与抗剪刚度试验梁和抗弯刚度试验梁截面尺寸相同的有限元模型进行对比分析，分别得出了不同倾角对于抗剪刚度和抗弯刚度的贡献。同样通过建立有限元模型对台阶式接缝进行了分析，得出了不同台阶宽度和高度对于接缝抗剪刚度和抗弯刚度的贡献。并提出通过加抗剪钢筋的竖直接缝、斜接缝及台阶式接缝的分析提出了斜接缝加抗剪钢筋的组合形式接缝，通过有限元分析验证了组合接缝能同时提高接缝的抗剪刚度和抗弯刚度。在上述试验和理论分析的基础上，提出了剪力键接缝、斜接缝、台阶式接缝以及组合式接缝的设计方法。最后，本文对节段接缝对桥梁挠度的影响进行了理论分析，并以实际工程为例，通过有限元分析得出了竖直接缝与本文提出的组合形式的接缝对桥梁挠度的影响程度，验证了本文提出的组合接缝形式能大幅降低因竖直接缝连接刚度降低导致的桥梁下挠。更多还原

【Abstract】 In recent years, many prestressed concrete continuous bridges and continuousrigid frame bridges appeared excessive downwarping (more than10cm) after about10years of service, most scholars presently attribute the the factors leadingexcessive downwarping to the shrinkage and creep of concrete, whereas ignoring theeffect of stiffness reduction at segmental joints on deflection of bridges. Due to theneglect in construction, it is generally weaker greatly for segmental joints concretecompared with monolithic concrete shaped at once casting on mechanical property.However, long-span prestressed concrete bridges generally constructed throughbalanced cantilever casting, the quantity of segmental joints can reach hundreds,which leads bridges to be discrete structure connected with numbers of weakersegmental joints rather than monolithic structure. It is potential for joints to be thefactor leading excessive downwarping, due to weakening the structure. Whereas, itis consistently assumed that structure is ideal monolith without joints in bridgesdesign and construction, and the quality of joints concrete is consistent with that ofsegments, which results in the deviation between theory and practice obviously.Thus, aiming at the effect of joints connection stiffness on deflection and thesupplement of segmental joints design of cantilever casting bridge, experimentswere conducted to assess the connection stiffness including the shear stiffness andthe flexural rigidity of segmental joints. Based on the above testing conclusions, itwas researched on non-vertical segmental joints shape differing with the presentvertical shape joints consistently adopted, and it was put forward for combined jointwhich can increase simultaneously the shear stiffness and flexural rigidity of joint.And it was educed of the effect of siffness of vertical joints and combined joint ondeflection of bridges.Shear experiments of vertical joints. The experiments includes3specimenswhich is respectively monolithic non-joints, joints roughened and joints roughenedwith shear-key according to the different shear stiffness at the corresponding jointssection. Through the analysis of the testing results of the relative deformation atjoints concering the3specimens, the reduction degree of shear stiffness and thecontribution of shearkey to enhancing shear stiffness of joints was educed. And itwas put forward for shearkey design method at segmental joints based onforementioned testing conclusion.Bending experiments of vertical joints. The3specimens in bending test aresimilar with that of the shear test(monolithic, jointed, shearkeyed) except the sectiondimensions. Through the analysis of the testing results, the reduction degree of flexural rigidity and the contribution of shearkey to enhancing flexural rigidit y ofjoints was educed. And it was presented for the relation between equivalent shearmodulus and equivalent elastic modulus of joint.Based on the experiment of vertical joint, finite element models were modeledto research non-vertical joint. Taking account of the stiffness improvement andconvenient construction, through the analysis of finite element modle with3different joint slope angle as5°,10°and15°, the contribution of different slopeangle joints to shear stiffness and flexural rigidity was educed. And it was putforward firstly for the slope angle of segmental joints which enhancing shearstiffness efficiently and constructing conveniently. Through the analysis of finiteelement modle, the contribution of different breadth and height of step to shearstiffness and flexural rigidity was educed. And it was put forward for the designmethod of stepped segmental joints.Based on the experimental conclusions and finite element model analysis, itwas put forward for the design method of shearkeyed joint、slope joint、stepped jointand combined joint.In the end, theoretical analysis was conducted to the effect of segmental jointson bridge deflection, and it was educed for the effect of stiffness of vertical joint andcombined joint on deflection of cantilever casting bridges by analysis of finiteelement models, and it was proved that the combined joint put forward in thisdissertation can reduces greatly the effect of vertical joints stiffness reduction ondeflection of cantilever casting bridges.更多还原