We propose a novel representative power spectrum density as a specific characteristic for showing responses of spans during a long operational period. The idea behind this method is to use the representative power spectrum density as a powerful tool to evaluate the stiffness decline of spans during their operation period. In addition, a new measurement method has been introduced to replace the traditional method of monitoring the health conditions of bridges through a periodic measurement technique. This helps to reduce costs when carrying out testing bridges. Besides, the proposed approach can be widely applied not only in Vietnam but also in many other underprivileged countries around the world. Obtained results show that, during the operational process of spans, there is not only a pure vibration evaluation such as bending vibration and torsion vibration tests but also a combination of various vibration types including bending-torsion vibration or high-level vibrations like first-mode bending and first-mode torsion. Depending on each type of structure and material properties, different types of vibrations will appear more or less during the operational process of spans under a random moving load. Furthermore, the representative power spectrum density is also suitable for evaluating and determining many different fundamental vibrations through the same measurement time as well as various measurement times.

中文翻译：

---

随机运动载荷作用下跨度振动特性的新认识-以越南胡志明市的38座桥梁为例

我们提出了一种新颖的代表性功率谱密度，作为在较长的运行周期内显示跨度响应的特定特征。该方法背后的思想是使用代表性功率谱密度作为评估跨度在运行期间的刚度下降的有力工具。另外，已经引入了一种新的测量方法，以代替通过定期测量技术来监视桥梁健康状况的传统方法。这有助于降低执行测试桥时的成本。此外，建议的方法不仅可以在越南广泛应用，而且可以在世界许多其他贫困国家中广泛应用。所得结果表明，在跨度的操作过程中，不仅存在诸如弯曲振动和扭转振动测试之类的纯振动评估，而且还存在包括弯曲扭转振动或第一模式弯曲和第一模式扭转之类的高水平振动在内的各种振动类型的组合。根据每种类型的结构和材料特性，在跨度的操作过程中，在随机移动载荷下，或多或少会出现不同类型的振动。此外，代表性的功率谱密度还适合于通过相同的测量时间以及不同的测量时间来评估和确定许多不同的基本振动。根据每种类型的结构和材料特性，在跨度的操作过程中，在随机移动载荷下，或多或少会出现不同类型的振动。此外，代表性的功率谱密度还适合于通过相同的测量时间以及不同的测量时间来评估和确定许多不同的基本振动。根据每种类型的结构和材料特性，在跨度的操作过程中，在随机移动载荷下，或多或少会出现不同类型的振动。此外，代表性的功率谱密度还适合于通过相同的测量时间以及不同的测量时间来评估和确定许多不同的基本振动。