Abstract: In order to study the influence of multiple presences of heavy vehicles on the reliability of medium and small span bridges, the measured heavy load data based on the most adverse effect was extracted. The parallel probability of all vehicles and the parallel probability of heavy load were compared and calculated, and a real-time simulation method of multiple presences of heavy vehicles based on random fleet flow was proposed. Furthermore, the finite element models of T-girder bridge, box-girder bridge and hollow slab beam bridge were established respectively. Considering the influence of the random variability of material properties and section geometric dimension on structural resistance, JC method was used to calculate the reliability index of each main beam under the action of different multiple presences of heavy loads and single heavy loading in the main lane, respectively. The research results show that: the reliability indexes of girder component significantly decrease under multiple presences of heavy loads and even decrease by 40% at maximum, compared with single heavy loading, which is only 50% of the target reliability index specified in the code. Meanwhile, the multiple presences of heavy vehicles have the greatest impact on the reliability of box girder bridges. The calculated reliability index of each component is 2.3~3.7, which is 23%~40% lower than that of single vehicle.

Key words: bridge engineering, heavy traffic loads, multiple presences of heavy vehicles, medium and small span bridges, reliability index

摘要： 为研究重载并行作用对中小跨径梁桥可靠度的影响，基于最不利效应提取实测重载数据，对比计算了所有车辆并行概率与重载并行概率，提出了基于随机车队流的重载并行实况模拟方法，分别建立了T梁桥、箱梁桥和空心板梁桥有限元模型，考虑材料性能及截面几何尺寸随机变异性对结构抗力的影响，采用JC法分别计算不同重载并行和主车道单车作用下各主梁的可靠度指标。研究结果表明：重载并行时主梁构件的可靠度指标显著降低，与单车作用相比，可靠度指标最大降低了40%，仅达到规范目标可靠度的50%左右；同时，重载并行对箱型梁桥可靠度的影响最大，各构件的计算可靠度指标为2.3~3.7，相对单车作用降低了23%~40%。

关键词: 桥梁工程, 重载交通, 重载车辆并行, 中小跨径梁桥, 可靠度指标