【作者】 王荣霞；

【导师】 郑刚；

【作者基本信息】 天津大学 ， 岩土工程， 2009， 博士

【摘要】 连续刚构桥是桥梁家族中较为年轻的成员,由于它梁体连续、梁墩固结,既能保持连续梁无伸缩缝、行车平顺的优点,又能保持T型刚构桥不设支座、不需转换体系的优点,能满足特大跨径桥梁的受力要求,在近几年得到迅猛的发展和建设。但是,目前很多大跨连续刚构桥在使用过程中出现了一个普遍的问题,就是跨中过度下挠。而连续刚构桥后期的挠度过大不但会破坏桥面的铺装层,影响桥梁的使用寿命和行车舒适性,甚至危及高速行车时的安全。所以跨中下挠成为当前制约大跨径连续刚构发展的一个急待解决的问题。由于问题的复杂性和多种原因并存,本文在总结相关文献的基础上,对主梁悬浇施工质量差而造成的节段接缝的剪切变形会导致结构过度下挠这一因素进行了深入的研究。目前关于这一现象虽然已有学者提出,但是尚缺乏系统、深入的理论研究。因此本文所做的工作对于改善此类桥梁的使用状况,更新设计理念具有重要的意义。本文主要研究内容如下:(1)以国内已建大跨悬浇PC箱梁桥为例,建立空间有限元模型,研究节段接缝的模拟方法;分析接缝的存在对主梁施工过程中竖向变形的影响。(2)研究不同混凝土徐变模式对节段接缝剪切徐变的影响;分析节段接缝的剪切变形对主梁长期挠度的影响。(3)基于桩-土-桥梁结构体系模型,分析接缝对全桥结构受力和变形性能的影响,特别是研究节段接缝在移动的汽车荷载下的动力影响效应。研究结果表明:(1)在主梁悬浇施工过程中,节段接缝的存在会使梁的竖向变形大于完整结构下的计算值。接缝剪切变形对跨中挠度的增加值随着悬浇节段的增加而不断增加,但是当增加到一定数值后又出现了减小的趋势。剪切变形增加值同相应的完整梁挠度的比值在整个悬浇过程中呈不断减小的趋势。(2)依据1985年和2004年建议的混凝土徐变的两种计算模式,计算结构长期挠度,结果表明按1985年规范比2004年规范的计算结果要大一些。(3)节段接缝对长期挠度影响显著,其挠度增大比例随着龄期的增长而加大,在本文实例计算中,接缝主梁在徐变计算龄期内会比完整梁的挠度增加约一倍左右。(4)基于桩-土-连续刚构全桥体系模型,当考虑桩土作用时,全桥结构的固有振动频率值会降低。同样,主梁刚度降低将导致全桥结构的固有振动频率的降低,振动周期加长,振型位移值也会改变。(5)桩-土-桥梁结构在动力汽车荷载作用下,结构各部位的位移和内力比静态荷载下均有较大的增加比例,而且这一比例对于完整梁结构取值稍大些,而接缝梁模型略小些,说明当主梁刚度减弱时,结构对动力响应作用的敏感程度有所减弱。(6)桩-土-桥梁结构在动力汽车荷载作用下,主梁节段接缝的存在对全桥结构的内力和位移均会产生影响,从动态响应的最不利效应看,随着上部主梁刚度的减弱,跨中挠度将增加,墩顶、桩顶水平位移减小,跨中最大弯矩值减小,主梁最大剪力减小,桩底轴向压力增加。更多还原

【Abstract】 Continuous rigid frame bridges, as the young bridge family member, has been developed and built rapidly in our and foreign country in recent years, just because of its continuous beam, fixed beam and pier top without support, which leads to traveling comfort. And also it needn’t converting structure system to meet the special loading requires of long span bridges.However, a common problem is caused in many long-span continuous frame bridge, which is over-deflection of mid-span section. As we know, over-deflection of this bridge may cause the failure of bridge deck paving, serving life and comfortable traveling in late loading period. So how to control this case becomes an urgent task to improve the property of this kind of bridge. Due to the complexity of the problem and variety of existing reasons, the paper aims at one main factor to study, which is the result of segmental joint shear deformation coming from bad cantilever construction. Although this phenomenon has been put forward by some researchers, but the deep systematic study in theory is lacked. So, the working of this paper may be important to improve the loading property and renovate the design concept of this bridge.The studied content of this paper are as follows:(1) Taking domestic built long-span cantilever constructed box bridge as an example, a three-dimensional finite element model is built. The simulation method of segmental joint and its influence on deflection in cantilever construction is analysed.(2) Using different calculation mode of concrete creep, the influence of shear deflection caused by segmental joint on beam long-term deflection is studied.(3) Based on pile-soil-bridge structure system model, dynamic response of the full bridge structure in deformation and loading properties is researched, particularly the dynamic influence of segmental joint with mobile car load.Based on the analysis above mentioned, the main achievements are as follows:(1)During the beam cantilever construction process, the vertical deflection of beam with segmental joint will be greater than without, because of shear deformation of the joints. The increased deflection value first increases with the increase number of the segment construction, and then it decreases gradually. While in the whole construction procedure, the ratio of joint shear deformation to the corresponding beam deflection without joint is continuously decreasing.(2)According to the two calculation modes of concrete creep proposed in 1985 and 2004, the long-term deflection is calculated, which shows that it is greater by specification in 1985 than in 2004.(3)The existing of segmental joints may have obvious influence on long-term deflection of beam, resulting in the over-deflection. The deflection increasing ratio increases with the concrete age. In the calculation of the example bridge, during the age of concrete, the beam with joints is about 2 times the deflection of that without joints.(4) In pile-soil-full bridge system model, the natural vibration frequency of the full structure is reduced with the consideration of pile-soil action. In same way, the beam stiffness reduction due to joints may cause the reduction of natural vibration frequency too, and also with longer period of vibration and dynamic displacement change.(5) In pile-soil-full bridge system model, the displacement and internal force in all pat of structure with dynamic car loading is larger than with static loading, and the increase ratio is different between the structure with segmental joints and without joints. The result shows that the dynamic response of structure with segmental joints is less sensitive to dynamic loading than without joints.(6) Based on pile-soil-bridge structure with dynamic vehicle loading, the existence of segmental joints may bring different internal force and displacement. Considering the most disadvantageous effect, with the reduction of upper beam stiffness, the deflection of mid-span l will increase, the horizontal displacement of pier and pile heads will reduce, and the maximum bending moment and shearing force of the main beam will reduce, axial pressure of pile bottom will increase.更多还原