# Load Testing and Analysis of a Large Span Through Simply-Supported Steel Box Arch Bridge
## 1 Introduction  
Transportation infrastructure serves as an essential prerequisite for urban development, with bridges, as a vital component of the transportation system, experiencing significant advancements alongside the rapid growth of the transportation industry. Simply supported steel box arch bridges constitute a substantial portion of current bridge construction projects. These bridges are characterized by their excellent stability, high bending and torsional stiffness, lighter self-weight compared to concrete arch bridges, and superior load-bearing capacity [1]. They also excel in aesthetic appeal, construction maintenance, and economic benefits [2]. In recent years, the number of simply supported steel box arch bridges being constructed has consistently increased, along with an expansion in their maximum spans and diversification in structural designs. This has provided extensive engineering experience for the construction of such bridges [3, 4, 5]. However, it has also resulted in increasingly complex stress conditions within the bridges. Therefore, accurately and effectively assessing the condition of existing bridges to determine their load-bearing capacity and reliability levels has become particularly crucial [6]. Conducting load testing research to evaluate the safe load-bearing capacity and operational quality of bridge structures is essential for ensuring their reliability and stability. It is also the most effective and direct method for understanding the actual working conditions of bridge structures under test loads [7]. Theinitial purpose of load testing was to demonstrate the safe usage of bridges [8]. The task of load testing typically is not to determine the load-bearing capacity of bridge structures but to prove the sufficient safety of their impact resistance [9]. Bridge load testing involves applying test loads equivalent to the design loads on the bridge structure, thereby inducing displacements and vibrations to measure stress, deflection, acceleration, and other parameters at specified locations. This directly assesses the structural characteristics of the bridge and provides fundamental evaluation indicators for its maintenance. Dynamic load testing is one of the key methods for calibrating reliable numerical models. It provides valuable information about structural properties such as frequency, mode shapes, and damping, which are crucial for verifying and optimizing the accuracy of the numerical model. The dynamic response data obtained through vibration testing can effectively assess and model the structural performance without the need for additional loading or interrupting the structure's operation [10]. Static load testing is more sensitive to detecting local defects and deformations. In particular, measurements of strain and displacement can effectively reveal the elastic behavior of a bridge under static loads. This makes static testing particularly useful for identifying local damage or deformations that dynamic tests might not detect [11]. Currently, scholars and engineers have conducted extensive experimental and theoretical research on bridge load testing and achieved certain research results. [PERSON] et al. [12] determined and described the relationship between the natural frequencies of bridges and their damage through modal analysis and identification of bridge characteristics. [PERSON] et al. [13] provided a detailed description of the roles and classifications of load testing for highway bridges and summarized the basic principles of bridge load testing. [PERSON] et al. [14] established a finite element model updating method for continuous box girder bridges based on static load testing to evaluate bridge structural performance. [PERSON] et al. [15] conducted static and dynamic load tests on a steel-concrete composite box girder bridge and analyzed and evaluated its performance and load-bearing capacity. [PERSON] et al.