大跨度连续刚构桥施工阶段温度效应研究

发布时间：2018-05-10 15:09

本文选题：大跨度连续箱梁桥 + 温度效应　；参考：《中南大学》2014年硕士论文

【摘要】：国内外的调查资料表明,混凝土中的早期裂缝是大跨度连续箱梁桥施工实践中出现的普遍问题。其中,温度效应是早期裂缝产生的重要影响因素。本文以一大跨径连续刚构箱梁桥为工程背景,对箱梁桥施工阶段截面温度梯度和水化热效应进行分析研究,提出相应的温度控制措施,为防治大跨度箱梁桥的早期裂缝问题提供理论分析依据。文章利用ANSYS10.0的三维温度实体单元,考虑太阳辐射、大气温度、混凝土表面吸收与发散热辐射等参数,计算施工过程中无桥面铺装状况下的截面梯度温度场与实测温度进行对比分析,并根据温度场计算结果拟合适合于无桥面铺装箱梁温度梯度计算模式,进行施工及合龙后箱梁截面应力分析。同时,采用Midas civil2012的水化热计算模块,根据实际工程参数,计算箱梁悬浇过程中水化热在结构中的分布和时程变化规律,并将计算值与实测值对比,检验计算值的正确性。温度梯度及水化热计算结果表明：大跨度连续箱梁桥施工阶段的日照温度场与公路桥规的计算模式存在一定的差异,竖向及横向温度梯度比较符合指数曲线分布。由于悬臂板遮阳的效果不同,中间支点处梁段与跨中梁段应采用不同的温度模式。日照温度梯度作用下,箱梁在悬臂浇筑过程中产生了较大的纵横向拉应力,尤其是箱梁合龙后,由于温度自应力与次应力的共同作用,跨中截面的纵向拉应力尤为显著。箱梁悬浇过程中,水化热效应使得箱梁在节段交接位置及顶底板与腹板倒角处出现较大的拉应力,极易在施工过程中出现开裂现象。为了尽量降低施工过程中温度效应对箱梁的影响,可以采用选择浇筑时间,低水化热水泥,添加适量的缓凝剂,合理的养护及浇筑方案等温度控制措施。本文对大跨径预应力混凝土箱梁桥早期温度裂缝的防治进行了有益地探索,可为桥梁设计及施工提供参考。
[Abstract]:The investigation data at home and abroad show that the early crack in concrete is a common problem in the construction practice of long-span continuous box girder bridge. Among them, temperature effect is an important influence factor of early cracks. Taking a long-span continuous rigid frame box girder bridge as the engineering background, this paper analyzes and studies the temperature gradient and hydration heat effect of the section in the construction stage of the box girder bridge, and puts forward the corresponding temperature control measures. It provides theoretical basis for preventing and curing early crack of long span box girder bridge. In this paper, the three-dimensional temperature solid element of ANSYS10.0 is used to consider the parameters of solar radiation, atmospheric temperature, absorption and heat radiation of concrete surface, etc. The cross-section gradient temperature field under the condition of no bridge deck paving is compared with the measured temperature during the construction process, and the temperature gradient calculation model of box girder without bridge deck pavement is fitted according to the temperature field calculation results. The section stress analysis of box girder after construction and closure is carried out. At the same time, using the hydration heat calculation module of Midas civil2012, according to the actual engineering parameters, the distribution of hydration heat in the structure and the time history change law of the box girder are calculated, and the calculated values are compared with the measured values to verify the correctness of the calculated values. The results of temperature gradient and hydration heat calculation show that there are some differences between the temperature field of sunshine and the calculation model of highway bridge gauge in the construction stage of long-span continuous box girder bridge. The vertical and lateral temperature gradient are in accordance with the exponential curve distribution. Because of the different sunshade effect of the cantilever plate, different temperature modes should be adopted between the middle fulcrum and the middle span beam. Under the action of sunshine temperature gradient, the longitudinal and transverse tensile stress of box girder is produced in the process of cantilever pouring, especially after the closure of box girder, the longitudinal tensile stress of the mid-span section is especially obvious due to the interaction of temperature self-stress and secondary stress. During the casting process of box girder, the heat effect of hydration causes the large tensile stress at the joint position of the section and the chamfer between the top and bottom plate and the web, so it is easy to crack in the construction process. In order to reduce the influence of temperature effect on box girder during construction, temperature control measures such as selecting pouring time, low hydration heat cement, adding appropriate amount of retarder, reasonable maintenance and pouring scheme can be adopted. In this paper, the prevention and control of the early temperature cracks in the long span prestressed concrete box girder bridge are discussed, which can be used as a reference for the design and construction of the bridge.
【学位授予单位】：中南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U445.4;U441.5

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