钢桥面铺装车辙预估有限元分析

2018-05-14 13:54马雪城李国芬赵康
森林工程 2018年5期
关键词:车辙有限元

马雪城 李国芬 赵康

摘 要:为得到荷位、轴载、大气温度以及计算方法各因素对钢桥面铺装车辙的影响,本文以上层高弹改性沥青混合料(35 mm)+下层浇筑式沥青混合料(40 mm)复合铺装结构为研究对象,并建立钢桥面铺装模型,通过单轴贯入试验获取材料的蠕变参数,利用ABAQUS计算钢桥面铺装车辙。分析表明:车辙主要发生在下层的浇筑式沥青混合料;横向荷位变化对车辙的影响远大于纵向荷位;车辙值总体与温度呈正相关性,与季节的温度变化相一致;连续变温下铺装车辙的计算方法比恒温下的要准确,车辙深度随着接地压力的增加而不断增大。研究结论对钢桥面铺装设计和车辙预估有一定的意义。

关键词:车辙;蠕变试验;钢桥面铺装;有限元

中图分类号:U443.33 文献标识码:A 文章编号:1006-8023(2018)05-0077-06

Abstract: In order to get the influence of load location, axle load, atmospheric temperature and calculation method on rutting of steel bridge deck pavement. The composite pavement structure of high elastic modified asphalt mixture (35mm) and under layer pouring asphalt mixture (40mm) as research object in this paper, and a steel bridge deck pavement model was established, through a single axis penetration test to obtain the material creep Variable parameters, using ABAQUS to calculate the steel deck pavement. The analysis shows that rutting mainly occurs in the under layer of asphalt mixture; the effect of lateral load change on the rutting is much greater than that of the longitudinal load; the rutting value is positively correlated with temperature, which is consistent with seasonal temperature change; the calculation method of the pavement at the continuous temperature change is more accurate than at the constant temperature, and the depth of the rut increases with the increase of the ground pressure. The research conclusion is of significance for the design and rutting prediction of steel bridge deck pavement.

Keywords: Rutting; creep test; steel bridge deck pavement; finite element

0 引言

目前我国多数大跨径钢桥面铺装出现了不同程度的破坏,其中车辙病害日益严重,大大降低了钢桥面铺装的使用性能[1-2],因而需要对车辙进行深入研究分析。课题组对比分析了基于浇筑式沥青混合料的复合铺装结构高温性能[3],并基于修正Burgers模型进行了车辙预估分析[4-6]。汤文[7]采用多参数得到车辙预估模型,杨军、钱振东[8-10]等采用Bailey-Norton模型,龙尧[11]采用Burgers模型,Al-Qadi I L[12]采用广义的Maxwell模型对混凝土材料参数进行获取并进行车辙预估,但是未对连续变温下的铺装进行准确考虑,本文以南京长江四桥的铺装为分析对象,通过ABAQUS建立局部箱梁模型,通过不同的荷位、温度等因素对车辙的影响分析。

1 钢桥面铺装分析模型

1.1 有限元模型参数

本文采取的计算模型具体参数参照南京长江四桥,见表1。铺装为两层结构,上层高弹改性沥青混合料(35 mm)+下层浇筑式沥青混合料(40 mm),有限元模型如图1所示。

1.2 材料参数

混合料的蠕变模型采用Bailey-Norton[13-14]模型,其表达式为:

式中:为应变速率;σ为应力;t 为荷载累计作用时间;A、m、n为系数,主要与温度和应力大小有关。

为了使获得的参数更接近钢桥面铺装的真实受力状态,实验制作300 mm×300 mm×50 mm的标准车辙板试件,分别为高弹改性沥青混合料试件和浇筑式沥青混合料试件,共有4种温度水平,分别为30、40、50、60℃,每种温度水平共用3组试件,对混合料的蠕变参数分别拟合,拟合结果见表2。

1.3 荷载参数

根据李凌林[15-18]等研究,轮胎接地压力与轮胎的内压处于不平衡的关系,参照经验公式计算不同轴载作用下的接地压力,公式如下:

p=0.290×pt+0.0042×P+0.1448。 (2)

式中:p為轮胎接地压力,MPa;Pt为轮胎充气压力,MPa;P为轴载,kN。

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