公路桥梁长加载区间的多车道车辆荷载概念模型

高速公路多车道荷载及其响应的差异一直是桥梁设计与研究关注的重点,目前的多车道荷载模型对这种差异表述不合理,特别是长加载区间效应.选取2009~2013年实测的2车道和4车道28d自由通行的WIM(Weigh-in-motion)数据,研究车辆的车道选择和荷载的空间分布特性,分析长加载区间的多车道荷载响应,提出了考虑多车道荷载模型的新思路,并校核了该概念模型的系数取值.研究表明,应选用至少3周以上数据进行车辆及荷载分析才具有统计意义,多车道中各分车道的车辆及荷载分布具有显著差异,我国规范基于车道荷载同分布的假定不成立.车道荷载分位值差别显著,而最大值却大致相同,说明多车道荷载模型无法兼顾不同加载区间的修正要求.长加载区间上分车道荷载响应之间的比值趋于稳定数量关系,表明各车道不仅不能达到相同水平极值,且不能同时达到.推荐的多车道概念模型能科学考虑长加载区间上分车道及总车道响应极值的关系,更具工程意义,校核的系数表明推荐模型合理可用.

Conceptual Traffic Load Model for Multi lane Highway Bridges with Long Loading Length

Differences in vehicle load and its response on multi-lane highway bridges are crucial to bridge design and related research. These differences, especially the load effects with long loading length, are poorly illustrated by the current multi-lane traffic load models. In this paper, 28-day free flow WIM (weigh in motion) data on a two-lane highway and a four-lane highway is offered. The data was obtained from 2009 to 2013. Based on the data, characteristics in the vehicle lane selection and spatial load distribution are studied. Multi-lane load response with long loading length is analyzed. A new multi-lane load model is proposed, based on which model coefficients values are calibrated. The results suggest that statistical stability of the vehicle and load analysis can only be ensured with a data length over 3 weeks. Vehicle and load distribution in each lane is of significant difference, indicating that the equal distribution assumption of vehicle lane load in current Chinese code is in need of modification. Variation of the vehicle load is substantial while the maximum load values are of not much difference, which suggests that the current multi-lane load model can no longer satisfy the modification requirements raised by varied loading lengths. The load response ratios of different lanes with long loading length roughly remain as constants, indicating that extreme load responses in different lanes are different and will not appear simultaneously. The recommended conceptual multi-lane load model provides a reasonable and scientific elaboration on the relationship of extreme load responses among different lanes and all lanes with long loading length. The model is proved to be reasonable and of more engineering application value by the coefficient calibration.