###### Abstract  
The accuracy of bridge performance monitoring and evaluation is easily affected by unfavorable factors such as vehicle coupling and test noise. In order to accurately evaluate the dynamic response and health monitoring threshold of the bridge under different operating conditions, a time-varying dynamic vehicle group model including the main uniform mass and the coupling mass was established, and the influence of road roughness was considered in the coupling equation. A bridge monitoring strategy considering signal noise ratio and vehicle-bridge interaction was proposed, and the effectiveness of the monitoring strategy was verified by taking a simple supported beam as an example. The results showed that the proposed time-varying dynamic vehicle group model could accurately consider the influence of road roughness and estimate the threshold of health monitoring, and the proposed bridge monitoring strategy could filter out a large amount of low signal-to-noise ratio or meaningless data, thus saving computing resources and realizing the lightweight safety monitoring of bridges. b +
Footnote †: journal: Applied sciences  
today  
Axle dynamics theory is the basic framework for calculating the dynamic response of bridges, and it is the basic way to accurately calculate and understand the dynamic performance of bridge structure. When a vehicle passes across a bridge deck, a dynamic response amplification occurs, necessitating consideration in response analysis and performance assessment [4; 5; 6; 7]. With the growth of China's economy and traffic transportation, the widespread use of heavy trucks places a significant burden on bridges. The increased dynamic loads contribute to a continuous decline in bridge reliability, underscoring the increasing need for regular maintenance and monitoring [8; 9]. As a result, the dynamic analysis of coupled vehicle-bridge systems has attracted significant attention in recent years [10; 11; 12; 13; 14; 15]. The aim of these studies is to investigate and simulate the structural behavior of bridges subjected to moving vehicles, as well as the ride comfort of vehicles crossing bridges [16; 17; 18]. The predominant focus in the study of vehicle-bridge interaction lies in closed-form or analytical expressions, especially in simplified cases such as the consideration of a simply supported Euler-Bernoulli beam model for the bridge and a moving load model for the vehicle. When representing the vehicle as a moving mass or oscillator, the vehicle-bridge interaction problem requires the simultaneous solution of a set of coupled partial differential equations governing the motion of both the bridge and the vehicle [17; 19]. In contrast to the modal superposition technique, the finite element method provides a more versatile approach for handling complex bridge-vehicle models in the dynamic interaction analysis [20; 21]. It was found that the most important parameters influencing the separation are the sliding speed and the mass ratio between the moving mass and the beam [22]. On the other hand, the road roughness of the bridge deck is an inherent physical phenomenon present in almost all bridges, due to construction quality and maintenance capacity. Several scholars have observed that road roughness amplifies the dynamic response due to the moving action of the mass, potentially compromising the safety and serviceability of the structure [23; 24]. Existing studies exhibit certain deficiencies, primarily in the assumption that vehicles on the bridge are typically regarded as one or several separate moving load models. However, in reality, especially in high-traffic scenarios for busy bridges, actual traffic vehicles should be conceptualized as a continuous group. Hence, it is important to establish a coupled bridge-vehicle group model that accurately represents the interaction under conditions of intensive traffic flow.