Bridge weigh-in-motion systems use instrumented bridges or culverts to weigh vehicles as they pass over the structures. They also provide data to allow the calculation of several bridge performance indicators. The article starts with the basics of a bridge weigh-in-motion system and briefly describes two key bridge performance indicators, girder distribution factor and dynamic amplification factor, which are also derived from B-WIM measurements. The central part of the article focuses on monitoring of influence lines, the third key parameter that characterises the bridge performance under traffic loads. First, the method of calculating the bending moment influence lines from random heavy traffic is described. A coefficient of rotational stiffness is introduced, which defines the shape of influence lines around the supports as a linear combination of the ideal simply supported and fixed supported influence lines, to allow quantifying the influence line changes. Then the long-term monitoring of influence lines is investigated on four different single-span test bridges. The initial focus is given on the examination of the effect of temperature on the shape of influence lines. Finally, two sets of influence lines are compared on one test bridge, one from before and the other from after replacing the expansion joints and bearings. The work done so far confirms that calculating of influence lines from random vehicles with a B-WIM system is entirely feasible and that differences in their shape can be detected on single-span bridges. What remains to be investigated is the comparison of these differences to the actual damages and under which circumstances the proposed procedure can compete with or better the routine bridge inspection and the conventional monitoring techniques.

桥梁动态称重系统使用仪表化的桥梁或涵洞在车辆经过结构时对车辆进行称重。它们还提供数据以允许计算多个桥梁性能指标。本文从桥梁运动中称重系统的基础开始，简要介绍了两个关键的桥梁性能指标，即梁的分布系数和动态放大系数，这些指标也来自B-WIM测量。本文的中心部分集中于影响线的监视，这是表征交通负荷下桥梁性能的第三个关键参数。首先，描述根据随机繁忙交通计算弯矩影响线的方法。引入了旋转刚度系数，它定义了支撑周围的影响线的形状，将其作为理想的简单支撑和固定支撑影响线的线性组合，以量化影响线的变化。然后在四个不同的单跨试验桥上研究了影响线的长期监测。最初的重点是检查温度对影响线形状的影响。最后，在一个测试桥上比较了两组影响线，一组来自更换膨胀节和轴承之前，另一组来自更换膨胀缝和轴承之后。到目前为止所做的工作证实，使用B-WIM系统计算随机车辆的影响线是完全可行的，并且可以在单跨桥上检测出形状的差异。