| 实测车流作用下大跨桥梁荷载效应极值外推法 |
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| 引用本文： | 鲁乃唯,刘扬,肖新辉.实测车流作用下大跨桥梁荷载效应极值外推法[J].交通运输工程学报,2018,18(5):47-55. |
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| 作者姓名： | 鲁乃唯 刘扬 肖新辉 |
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| 作者单位： | 1.长沙理工大学土木工程学院, 湖南 长沙 4101142.汉诺威莱布尼茨大学风险与可靠度研究所, 下萨克森 汉诺威 301673.长沙理工大学桥梁结构安全控制湖南省工程实验室, 湖南 长沙 410114 |
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| 基金项目： | 国家重点基础研究发展计划项目2015CB057705国家自然科学基金项目51378081国家自然科学基金项目51878072湖南省自然科学基金项目2018JJ3540桥梁结构安全控制湖南省工程实验室开放基金项目18KD02 |
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| 摘 要： | 提出多种密度随机车流作用效应极值的概率叠加方法, 外推了公路实测车流作用下大跨桥梁的车载效应极值; 阐述了基于Rice公式的界限跨阈率叠加原理, 并验证了其正确性; 基于中国某高速公路长期监测车流数据模拟了稀疏、一般和密集3种状态的随机车流, 应用界限跨阈率叠加模型估算了某混凝土斜拉桥主梁的最大弯矩。研究结果表明: 根据某高速公路实测车流数据, 稀疏、一般、密集车流密度分别约为1.7、5.0、8.3veh·min-1;在数值算例中, 车辆质量为45t车型占有率由0增加至80%导致最大车辆质量仅下降1.2%, 而车辆质量为50t的车型占有率由0增加到20%导致最大车辆质量增加14.4%, 说明多个平稳随机过程组合而成的非平稳随机过程的极值主要是由数值较大的随机过程决定; 采用跨阈率叠加方法对某混合车流车辆最大质量的外推误差为2.55%, 验证了将实际混合车流数据进行“车流离散”和“极值概率叠加”后得到的车载效应极值的方法的可行性; 密集车流占有率从0逐渐增加至5%导致斜拉桥主梁弯矩极值增幅为33.45%;某斜拉桥设计年限内的年均交通量增长率为2.8%, 对应的主梁跨中正弯矩极值超越设计标准值的概率为0.83, 高于设计要求, 需对桥梁车流量采取管控措施。
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| 关 键 词： | 桥梁工程 车辆荷载 荷载效应极值 随机车流 动态称重 外推法 |
| 收稿时间： | 2018-05-20 |
Extrapolating method of extreme load effects on long-span bridge under actual traffic loads |
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| LU Nai-wei,LIU Yang,XIAO Xin-hui.Extrapolating method of extreme load effects on long-span bridge under actual traffic loads[J].Journal of Traffic and Transportation Engineering,2018,18(5):47-55. |
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| Authors: | LU Nai-wei LIU Yang XIAO Xin-hui |
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| Affiliation: | 1.School of Civil Engineering, Changsha University of Science and Technology, Changsha 410114, Hunan, China2.Institute for Risk and Reliability, Leibniz University Hannover, Lower Saxony, Germany3.Hunan Province Engineering Laboratory of Bridge Structure, Changsha University of Science and Technology, Changsha 410114, Hunan, China |
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| Abstract: | A probabilistic superposition approach was proposed for investigating the extreme load effects of stochastic traffic flows with multiple densities.The approach was utilized to extrapolate the extreme values of vehicle load effects on the long-span bridges using the measured traffic data.The principle of superposing level-crossing rate based on the Rice's formula was explained, and its validity was proved.Three types of stochastic traffic flows, including the sparse flow, normal flow and dense flow, were simulated based on the long-term monitored traffic data of a highway bridge in China, and the maximum bending moment of a concrete cable-stayed bridge was analyzed based on the level-crossing superposition model.Analysis result shows that basedon the measured traffic data of a highway, the densities of free flow, normal flow and busy flow are 1.7, 5.0 and 8.3 veh·min-1, respectively.In the numerical example, when the occupancy of 45 t-vehicles increases from 0 to 80%, the maximum vehicle mass decreases by only 1.2%.But when the occupancy of 50 t-vehicles increases from 0 to 20%, the maximum vehicle mass decreases by 14.4%.This phenomenon indicates that the extreme value of a non-equilibrium random process composed by some stationary random processes is mostly depended on the random processes with higher values.The maximum extrapolating error of the maximum vehicle mass is2.55%for the mixed traffic flow using the level-crossing superposition approach, which explains that the extrapolating approach of extreme load effects on long-span bridges based on the principle of vehicle dispersion and superposition of extreme value probability is feasible.The increase of occupancy of dense traffic flow from 0 to 5%leads to an amplification of 33.45%for the maximum bending moment of the girder of a cable-stayed bridge.When the annual traffic growth rate of a cable-stayed bridge is 2.8%in the design lifetime, the probability that the midspan extreme bending moment of the bridge girder exceeds the design standard value is 0.83 and higher than the design requirements, therefore, it is deserved to take some measures to control the traffic flow. |
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