先简支后结构连续梁桥徐变上拱对行车舒适性影响研究

发布时间：2018-04-22 07:07

本文选题：先简支后结构连续梁桥 + 徐变上拱　；参考：《重庆交通大学》2015年硕士论文

【摘要】：先简支后结构连续梁桥具有施工速度快、模板化制作、成品梁质量高、行车舒适性好等优点,目前在山区高速公路中小跨度梁式桥中被广泛采用。众所周知,中小跨度梁式桥活横载比较大,在预应力的作用下易产生较大的反拱。混凝土的徐变,对反拱有两方面的作用,一方面引起预应力损失使反拱得以减小;另一方面使构件混凝土截面应变增加,从而加大了负曲率,因此反拱增大。一般来说,后一项是主要的,以致尽管预应力减小,反拱却在不断增加。桥面上拱度过大将显著降低司乘人员的行车舒适性。对于行车舒适性的影响国内外专家在铁路方面作了较多的研究,而在公路方面研究较少。随着我国高速公路里程的增加和轿车家庭化趋势发展,国民乘坐汽车出行比例愈来愈高,高速行车的舒适性将受到司乘人员愈来愈多的关注。山区高速公路中桥梁占路线长度的比例高且绝大数为中小跨径预应力混凝土桥梁,其行车舒适性研究必将得到更多的重视。本文针对先简支后结构连续梁桥开展了混凝土徐变效应分析与计算、车桥耦合动力分析与计算、高速行车舒适性分析与评价、混凝土后期徐变上拱限值计算,从设计和施工两方面提出了控制混凝土徐变上拱度具体措施等系列研究,内容系统性强。首先从理论上给出了先简支后连续梁桥徐变计算公式,通过工程实例计算先简支后结构连续梁桥徐变效应发现混凝土徐变变形主要产生在简支梁预制存梁阶段,其徐变变形完成徐变总变形(先期徐变变形+后期徐变变形)的81%。其次介绍了动力反应数值解法,建立了车桥耦合振动方程,提出采用Newmark法求解动力反应方程,大大简化了计算且数值结果精度能满足工程实际要求。以加速度振动均方值作为行车舒适性的评价指标,得到了不同跨度、不同跨数、不同行车速度下的混凝土后期徐变上拱限值。最后为改善徐变过度上拱所形成的波浪形桥面,提出对于新建桥梁,应提倡采用部分预应力和精细化设计,降低预应力度,优化预应力束布置;对于预制梁拱度对桥面铺装厚度的影响,在常用跨度和跨数组合范围内,可采用减小跨中铺装厚度、加大墩顶铺装厚度的方法予以改善。综上所述,本文研究成果对于预防先简支后结构连续梁桥出现徐变上拱引起高速行车舒适性问题,以及降低维护成本有重要理论和实用价值。
[Abstract]:The continuous beam bridge with simple support and later structure has the advantages of fast construction speed, formwork making, high quality of finished beam, good driving comfort and so on. At present, it is widely used in medium and small span beam bridges of mountain expressway. As we all know, the small span girder bridge has a large live transverse load, and it is easy to produce a large reverse arch under the action of prestress. The creep of concrete has two effects on the reverse arch. On the one hand, the loss of prestressing force causes the reverse arch to be reduced; on the other hand, the strain of the concrete section of the member is increased, thus the negative curvature is increased, so the inverse arch increases. Generally speaking, the latter term is so important that, although the prestress decreases, the reverse arch is increasing. When the arch on the bridge deck passes, the ride comfort of the riders will be significantly reduced. Experts at home and abroad have done more research on the influence of driving comfort on railway, but less on highway. With the increase of highway mileage and the development of family passenger cars, the proportion of people travelling by car is becoming higher and higher, and the comfort of high-speed driving will be paid more and more attention by the riders. The proportion of bridges in route length in mountainous expressway is high and most of them are prestressed concrete bridges with medium and small span, so the study of driving comfort will be paid more attention to. In this paper, the analysis and calculation of concrete creep effect, vehicle-bridge coupling dynamic analysis and calculation, high-speed driving comfort analysis and evaluation, and the calculation of concrete creep upper arch limit are carried out for the continuous beam bridge with simple support and later structure. This paper puts forward some concrete measures to control concrete creep and arch from two aspects of design and construction, the content of which is systematic. In this paper, a formula for calculating creep of simple supported and then continuous beam bridges is given in theory, and the creep effect of continuous beam bridge with simple support and structure is calculated by engineering example. It is found that the creep deformation of concrete mainly occurs in the prefabricated beam storage stage of simply supported beam. Its creep deformation completes 81% of total creep deformation (early creep deformation late creep deformation). Secondly, the numerical solution of dynamic response is introduced, the coupled vibration equation of vehicle and bridge is established, and the Newmark method is proposed to solve the dynamic response equation, which greatly simplifies the calculation and the accuracy of the numerical results can meet the practical requirements of engineering. Taking the mean square value of acceleration vibration as the evaluation index of driving comfort, the upper arch limit value of concrete creep in later stage is obtained under different span, different span number and different driving speed. Finally, in order to improve the wavy deck formed by the overarch of creep, it is proposed that partial prestress and fine design should be adopted to reduce the degree of prestress and optimize the arrangement of prestressing tendons for the newly built bridges. For the influence of arch of precast beam on pavement thickness of bridge deck, in the range of common span and span number combination, the method of reducing the thickness of middle span pavement and increasing the thickness of pier top pavement can be adopted to improve it. To sum up, the research results of this paper have important theoretical and practical value for preventing the problem of high speed driving comfort caused by the creep uparch of simple support and then structure continuous beam bridge, and reducing the maintenance cost.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441

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