In state-of-the-art building codes, the traffic loads for the design or assessment of bridges should derive from a probabilistic characterization. However, because traffic depends on the vehicle flow peculiar to the transportation infrastructure of interest, the frequency of exceedance of code-assigned loads is factually unknown. This study presents a methodology to probabilistically characterize the traffic loads on bridges based on network-level traffic micro-simulation and its application to the A56, that is, the urban highway connecting Naples’ (Italy) districts. One year of traffic simulations, in conjunction with structural modeling of the bridges featured in the infrastructure, enabled the probabilistic characterization of the traffic-induced structural demand and the determination of the bridge-specific safety margins along the highway. The results of the study and of the application to A56 ultimately show that: (i) traffic micro-simulation appears to be a suitable approach to bridge-specific structural safety assessment; (ii) structural actions deriving from code-assigned loads tend to be conservative with respect to their traffic-simulation-derived counterparts; and (iii) structural demand induced by traffic loads can vary along the same transportation infrastructure.

中文翻译：

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用于桥梁荷载概率分析的基础设施级交通微观模拟

在最先进的建筑规范中，桥梁设计或评估的交通载荷应来自概率特征。然而，由于交通取决于相关交通基础设施特有的车辆流量，因此超出代码指定负载的频率实际上是未知的。本研究提出了一种基于网络级交通微仿真及其在 A56（即连接那不勒斯（意大利）地区的城市高速公路）中的应用来概率表征桥梁交通载荷的方法。一年的交通模拟，结合基础设施中桥梁的结构建模，能够对交通引起的结构需求进行概率表征，并确定高速公路沿线特定桥梁的安全裕度。研究结果和对 A56 的应用最终表明：(i) 交通微观模拟似乎是一种适用于特定桥梁结构安全评估的方法；(ii) 源自代码指定载荷的结构作用相对于其交通模拟衍生的对应物往往是保守的；(iii) 由交通负荷引起的结构性需求可能因同一交通基础设施而异。