混凝土徐变对连续梁桥预拱度设置的研究

发布时间：2018-08-13 08:31

【摘要】：在悬臂施工中,为保证两悬臂端在同一水平线上,需要设置合理的预拱度,使成桥线性达到设计的预测值。施工中影响预拱度的设置因素有很多,其中,混凝土徐变的影响贯穿桥梁的施工过程以及使用过程。由于徐变产生的挠度难以确定,并且徐变的影响因素又有很多,所以混凝土徐变对预拱度的影响受到广泛的关注。本文在已有的研究成果上,采用MIDAS/Civil分析软件对老漳河大桥建立有限元模型,计算在不同的徐变模型下产生的预拱度,并与实测数据比较;同时,模拟分析老漳河大桥在混凝土徐变、预应力荷载、挂篮荷载作用下的施工预拱度,并研究了在各因素作用下成桥预拱度的变化规律。得出结论如下:(1)ACI徐变系数预测模型的预测值较为准确,在桥墩附近的预测值稍微偏小,整体的徐变预测值与实测值基本相符,而JTG D62-2004桥涵设计规范模型和CEB-FIP模型对结构挠度的整体预测偏小。在对预拱度预测时,不仅可以按照JTG D62-2004桥涵设计规范预测外,还可考虑ACI预测模型,对预测值进行调整。(2)通过对模型的分析,短期来讲,在施工中的最大悬臂状态下,混凝土徐变使梁段产生的竖向变形最接近总变形,是设置施工预拱度时的首要考虑因素。(3)长期来讲,混凝土徐变仍是引起梁桥长期下挠的主要原因,桥梁挠度会随时间的发展而不断的增加。其中,引起混凝土徐变的湿度、温度也会对下挠有影响。相对湿度越大,下挠就越小;相对温度降低,下挠增加。因此,设计时需要建立与施工环境相符的模型,并考虑影响徐变的因素,提高桥梁的长期可靠性。(4)对于其他因素,如纵向预应力损失和汽车荷载,也是影响成桥预拱度的重要因素。其中,顶板纵向预应力损失产生的挠度比底板预应力损失产生挠度变形大。所以在预拱度设置时,也需要充分考虑,使预拱度的预测更加精确。
[Abstract]:In the cantilever construction, in order to ensure that the two cantilever ends are on the same horizontal line, it is necessary to set a reasonable pre-arched degree to make the bridge linearly reach the predicted value of the design. There are many factors that affect the pre-arch degree in construction, among which, the concrete creep affects the construction process and the use process of the bridge. Because the deflection produced by creep is difficult to determine, and there are many factors affecting creep, the influence of creep on pre-camber of concrete has been paid more and more attention. In this paper, based on the existing research results, the finite element model of Laozhang River Bridge is established by using MIDAS/Civil analysis software, and the pre-arch degree produced under different creep models is calculated and compared with the measured data. The pre-arch degree of Laozhang River Bridge under concrete creep, prestressed load and hanging basket load is simulated and analyzed, and the variation law of pre-arch degree of the bridge under the action of various factors is studied. The conclusions are as follows: (1) the prediction value of ACI creep coefficient prediction model is more accurate, the prediction value near bridge pier is slightly smaller, and the overall creep prediction value is basically consistent with the measured value. JTG D62-2004 bridge and culvert design code model and CEB-FIP model for the overall prediction of structural deflection is small. In the prediction of pre-camber, not only according to JTG D62-2004 bridge and culvert design code, but also according to the ACI prediction model, the predicted value can be adjusted. (2) through the analysis of the model, in the short term, under the maximum cantilever state in construction, The vertical deformation caused by concrete creep is the most close to the total deformation, which is the primary consideration factor in setting the pre-arch degree of construction. (3) in the long run, concrete creep is still the main cause of long-term deflection of beam bridge. The deflection of the bridge will increase with the development of time. Among them, the humidity that causes concrete creep, temperature also can have an effect on downwarping. The greater the relative humidity, the smaller the deflection, and the lower the relative temperature, the higher the deflection. Therefore, it is necessary to establish a model consistent with the construction environment, and to improve the long-term reliability of the bridge by taking into account the factors affecting creep. (4) for other factors, such as longitudinal prestress loss and vehicle load, It is also an important factor affecting the pre-arch of the bridge. The deflection caused by the longitudinal prestressing loss of the roof is larger than that by the prestressing loss of the bottom slab. Therefore, in the setting of pre-arch, we also need to take full account to make the prediction of pre-arch more accurate.
【学位授予单位】：河北工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U445.466

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