考虑车道荷载差异的多车道桥梁横向折减系数

Transverse Reduction Factor of Multi-lane Bridges Considering Lane Load Disparity

为考虑车道荷载差异对多车道桥梁横向折减系数的影响,提出横向折减系数的多系数表达模式,并改进基于独立重复试验的相遇车道荷载方法以进行系数校核。首先,引入反映车道荷载差异性的车道修正系数和体现多车道荷载相遇概率的车道组合系数,形成横向折减系数的多系数表达模式。其次,改进目前常用的基于独立重复试验的相遇车道荷载方法,将车道交通流量及荷载分布的差异性涵盖进来。随后,参数化研究横向折减系数的关键影响参量,包括货车通过控制断面的平均时间、荷载重现期、车道交通量和车道荷载分布等。最后,基于某高速公路实测动态称重数据,给出采用该方法校核横向折减系数的详细过程,并与传统方法及JTG D60—2015规范方法所得结果进行对比。研究表明:所提出的改进相遇车道荷载方法,摈弃了传统方法中车重正态分布、车道荷载同分布、最大观测车重与均值3.5倍偏差关系等备受质疑的假设,是更一般性的解答。参数化分析表明:货车通过控制断面的平均时间和荷载重现期对结果影响很小,货车荷载模型及其在车道间差异性则影响很显著,说明对车道荷载分布规律进行准确建模的重要性。实测车道货车荷载数据统计发现:货车的交通量和荷载分布在车道之间具有明显的差异,传统方法和规范方法给出的横向折减系数均高估了实际情况,最大达19%,可能造成设计与管养资源的浪费;而基于该方法校核的横向折减系数,更能深入揭示各车道荷载的贡献规律,准确反映不同车道组合作用下的荷载横向折减规律,具有显著的工程应用价值。

To consider the influence of lane load disparity on the transverse reduction factor of multi-lane bridges,a novel multi-coefficient model of the transverse reduction factor was proposed,and lane-load meeting approach based on the independent repeated trials was improved to calibrate these coefficients.First,a lane load correction coefficient that reflects the lane load disparity and a multi-lane combination coefficient that reveals the occurrence probability of laneload meeting events were introduced.These shaped the multi-coefficient model of the transverse reduction factor. Then,the commonly known lane-load meeting approach based on the independent repeated trials was improved to consider the differences in truck volume and truck load over multiple traffic lanes.In addition,critical parameters that influence the calibration of the transverse reduction factor were studied.These included the average time for a truck to pass through a control cross-section,the return period of the traffic load,lane truck volume,and lane load distribution.Finally,measured weigh-in-motion data from a freeway were used to calibrate the transverse reduction factor,and the results were compared with those derived from the conventional approach and bridge design specification JTG D60—2015.The research shows the improved lane-load meeting approach is a general solution that allows the questionable assumptions used in the conventional approach(e.g.,normal distribution of truck weight,identical truck weight distribution to different lanes,and 3.5-times standard deviation between the maximum and mean truck weights)to be discarded.Parametric studies indicate the average time of a truck passing through the control cross-section and the return period of the traffic load have slight effects on the results,whereas the truck weight feature and its distribution over multiple lanes have the most significant effects.This highlights the importance of precise modeling of lane loads.Statistics of truck loads show the truck volume and distribution of truck loads are obviously different in various traffic lanes,and the transverse reduction factors given by the conventional approach and the design code overestimate the realistic condition,which is as much as 19% and thus may lead to waste of design and management resources.However,the transverse reduction factor calibrated by the proposed approach and model form may clearly reveal the contribution of truck loads in each lane and accurately reflect the transverse reduction raw of lane load under the combined loading of different numbers of traffic lanes.This would have wide engineering applications.