为了对在役混凝土梁桥在未来服役期的承载力失效概率进行评估，本文首先基于实测随机车流数据，采用蒙特卡罗随机抽样的方法建立随机车流荷载模型；然后基于经典Rice公式，建立桥梁车致荷载效应极值的概率分布模型；最后，考虑桥梁抗力的逐年退化，基于结构可靠度理论，详细给出了在役混凝土梁桥在未来服役时间内的可靠度评估方法及步骤。实际工程的应用结果表明：（1）经典Rice公式对桥梁车致弯矩界限跨阈率的拟合效果很好，依此建立的桥梁车致弯矩极值概率分布模型有效可靠；本文给出的在役混凝土梁桥可靠度评估方法在实际工程中应用方便，可获取在役混凝土梁桥在未来服役期的承载力失效概率、承载力达到目标可靠指标的时间节点及桥梁可靠性能冗余度。（2）中小跨径混凝土梁桥在随机车流荷载作用下的弯矩界限跨阈率取决于过桥车辆数量，而受车辆间距的影响较小。（3）随着桥梁服役时间的增加，桥梁车致荷载效应极值的均值增大，标准差逐渐减小；桥梁抗力的均值和标准差随着桥梁服役时间的增加而逐渐减小。（4）混凝土梁桥中直接承受车辆荷载作用的主梁，其承载力失效概率大于非直接承受车辆荷载作用的主梁，其中边梁承载力失效概率最大。（5）混凝土梁桥的承载力失效概率随着抗力退化速度的增大而增大，抗力低速退化的承载力失效概率是抗力不退化承载力失效概率的4.88倍。（6）为保证在役混凝土梁桥的运营安全，建造时应该提高边梁的安全储备，管养时针对重型货车出现频率较高或恶劣使用环境的桥梁，可以因地制宜的采取相应的政策进行干预。
关键词：可靠度评估；经典Rice公式；随机车流；可靠指标；抗力退化
Abstract
In order to evaluate the bearing capacity failure probability of existing concrete beam bridge in the future service period. Firstly, this paper firstly established the random traffic load model based on the measured random traffic data by using Monte Carlo random sampling method. Then, based on the classical rice formula, the probability distribution model of the extreme value of vehicular load effect was established. Finally, considering the degradation of bridge resistance year by year, based on the structural reliability theory, the reliability evaluation method and steps of in-service concrete beam bridge in the future service time were given in detail. The application results of practical engineering show that: (1) The classical Rice formula has a good fitting effect on the threshold crossing rate of the bridge vehicular moment, and the extreme probability distribution model of the bridge vehicular moment is effective and reliable. The reliability evaluation method of in-service concrete girder bridge presented in this paper is easy to be applied in practical engineering. It can obtain the failure probability of the bearing capacity of the in-service concrete beam bridge in the future service period, the time node when the bearing capacity reaches the target reliability index and the redundancy of the reliability performance of the bridge. (2) The threshold crossing rate of moment limit of small and medium-span concrete beam bridge under random traffic flow load depends on the number of vehicles passing the bridge, but is less affected by vehicle spacing. (3) With the increase of bridge service time, the mean value of extreme value of vehicular load effect of bridge increases, and the standard deviation decreases gradually; The mean value and standard deviation of bridge resistance decrease with the increase of bridge service time. (4) In a concrete beam bridge, the failure probability of the bearing capacity of the main beam that directly bears the vehicle load is greater than that of the main beam that does not directly bear the vehicle load, and the failure probability of the bearing capacity of the side beam is the highest. (5) The failure probability of bearing capacity of concrete beam bridge increases with the increase of resistance degradation speed. The failure probability of bearing capacity with low-speed degradation is 4.88 times that of non-degradation. (6) In order to ensure the operation safety of concrete beam bridges in service, the safety reserve of side beams should be improved during construction. For bridge with high frequency of heavy trucks or harsh service environment, corresponding policies can be taken to intervene according to local conditions.
Key words: reliability assessment；classical Rice formula；random traffic flow；reliability index；resistance degradation
关键词
可靠度评估 /
经典Rice公式 /
随机车流 /
可靠指标 /
抗力退化
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Key words
reliability assessment /
classical Rice formula /
random traffic flow /
reliability index /
resistance degradation
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