The temperature-induced response of long-span steel bridges can be more significant than the structural responses associated with operational loads or structural damage. These responses depend on the spatio-temporal temperature variation in bridge members, including the effective temperature and temperature difference within members. Bridges are designed to withstand the extreme temperature variations predicted for a given site. Hence, numerous studies have employed statistical analysis techniques to provide critical information for the design and maintenance of bridges during life cycles. However, the correlation between the effective temperature and temperature difference is usually ignored, which can result in inaccurate assessment of the extreme temperatures in members. In this work, the joint probability distribution for the temperature variation in a long-span steel truss arch bridge is investigated based on field monitoring data. The extreme temperature variations are mapped on contours with relevant return periods; the results show that the probability distribution of the effective temperature can be described using the normal distribution; the weighted sum of two lognormal distributions can describe the distribution of temperature difference. Moreover, extreme values of the effective temperature and temperature difference do not occur concurrently. The effective temperature and temperature difference in the structural member directly exposed to solar radiation vary significantly, while the temperature of the shaded member can be assumed uniform, which is mainly affected by air temperature. The study leads to more accurate estimation of the temperature extremes in long-span steel truss arch bridges, which is of great importance for proper design and maintenance of bridges.

大跨度钢桥的温度响应可能比与运行载荷或结构破坏相关的结构响应更重要。这些响应取决于桥构件中的时空温度变化，包括有效温度和构件内的温度差。桥梁的设计可承受给定站点预测的极端温度变化。因此，许多研究已经采用统计分析技术来为生命周期内桥梁的设计和维护提供关键信息。但是，通常会忽略有效温度和温差之间的相关性，这可能导致对构件中的极端温度进行不正确的评估。在这项工作中，基于现场监测数据，研究了大跨度钢桁架拱桥温度变化的联合概率分布。将极端温度变化映射到具有相关返回周期的轮廓上；结果表明，可以用正态分布描述有效温度的概率分布。两个对数正态分布的加权和可以描述温度差的分布。此外，有效温度和温度差的极端值不会同时出现。直接暴露在太阳辐射下的结构构件中的有效温度和温差变化很大，而阴影构件的温度可以认为是均匀的，这主要受空气温度的影响。