## 1 Introduction  
### Background  
A Bailey Bridge is a prefabricated truss bridge type whose symmetrically bending moments vary from maximum to zero from the center span to the end posts. This aspect is fundamental during their design because the end bays are not entirely used, exposing the center bays to maximum stress [1]. Bailey Bridges were initially meant for military use. However, their benefits have been diversified from temporary to semi-permanent or permanent due to their ease of transportation, low cost, flexible structural form, onsite fabrication, and versatility in accommodating various loading requirements [2]. The panel elements are interchangeable, making them easy to assemble by pinning the components under different configurations. It takes at least 40 min for a simple combination of double truss employing the cantilever launching method short of falsework [3]. Structural degradation due to loss of parts is expected; primarily, loose pins that readjust during the dynamic movement of traffic have been reported. Additionally, they are subject to maintenance issues and lack of historical data [4], such as the bearing capacity. Therefore, it is advisable to assess their structural integrity. To verify the load-bearing performance of an actual Bailey Bridge, [PERSON] et al. [4] [PERSON] et al. [5] and [PERSON] et al. [2, 6] are hereafter worth mentioning. The authors [2, 4, 6] exploited the Diagnostic load test using Dynamic and Static Loading (DSL) to certify the bearing capacity for both in-service [2, 6] and out-of-service bridges [4]. Diagnostic load testing is meant to assess the structural response of a bridge, and update or calibrate an analytical model for decision-making. The calibrated model is then deployed to evaluate the load rating factors, particularly to determine load rating and safety. Conventionally, the loads applied are below the bridge's capacity--similar to serviceability limit state conditions; hence larger loads are extrapolated. Consequently, [PERSON] et al. established that the design drawing was unavailable during the load rating of the 'Engineers Bridge' pinned arch bridge. Three targets were selected, 1/4 span, mid-span, and 3/4 span, to establish deflection using a total station with an accuracy of 0.2 mm. The author modeled the bridge using existing onsite geometry for the bridge to be analytically examined and compared the deflection results with field measurements. The author went further and established the load rating based on the serviceability and ultimate limit of the bridge using the current codes, demonstrating an approach for establishing the bearing capacity [4]. On the other hand, [PERSON] et al. found that to evaluate the structural response of a Bailey-type Bridge, actual loading conditions should be tested, and a numerical model employed to examine the nonlinear response. Under laboratory testing the author used a 130-t Universal dynamic Servo-hydraulic Tester to simulate various loading conditions and Linear Variable Differential Transformer (LVDT) displacement sensor to monitor deflections [5]. Further, [PERSON] et al. determined the Bailey Bridge response through onsite experimentations and structural analysis of a bridge in Laos [6]. The author acquired on-site data statically by displacement transducers and total station, and dynamically using an accelerometer positioned at optimum locations along the girders for maximum deflection. In each of these studies, the evaluation of load-bearing performance by linear or nonlinear finite element analysis of digital twins is based on actual and on-site member measurements. Therefore, it is thought that appropriate maintenance and management of a permanent bridge can be performed by clarifying the bearing capacity and ensuring the conversion from a temporary bridge to a permanent bridge. The present study aims to assess a Bailey Bridge's condition and investigate its adaptation as a permanent structure. The Sukumo bridge was targeted, the only Bailey Bridge type in Uchiko Town, Shikoku Island, Japan.