# Flexural Behavior of a 30-Meter Full-Scale Simply Supported Prestressed Concrete Box Girder
## 1 Introduction  
Many civil infrastructures are operated under adverse service conditions [1], such as corrosion [2; 3; 4], vibration [5; 6], overload [7; 8], and impact [9], which may cause structural damages at different levels, including loosened connections [10], cracks [11; 12], reduced bending stiffness [13; 14], and decreased or even lost load carrying capacity [15; 16]. Structural damages have received much attention in recent years from different directions [17; 18]. On one hand, structural health monitoring (SHM) [19; 20; 21] and damage detection technologies [22; 23] have been developed to report structural health status and damage situations by using various integrated sensors [24; 25; 26] and advanced algorithms with the goal of issuing early warnings in the presence of structural damage. On the other hand, destructive tests are conducted on various structures to better understand the structural behavior under failure [27; 28]. However, civil infrastructures often involve large-sized structural components, making destructivetests of such large components difficult. A good example is the prestressed concrete (PC) box girder, which has the advantage of long span capacity at relatively low cost. A large number of studies have been conducted on the mechanical behavior and failure mode of PC box girders using small-scale models [29; 30]. It is known that full-scale experiments, without the influence of size effects, are more intuitive and reliable. However, due to them consuming a lot of human, financial, and material resources, only very few studies have been carried out with full-scale model tests on the flexural behavior of PC box girders from decommissioned bridges around the world. [PERSON], [PERSON] and West, H.H. conducted a full-scale experiment on a segmental PC box girder bridge with a length of 36.88 meters (m) [31]. They found that the structure was 15% more stiff than theoretical predictions suggested. The failure mode was that a wide crack occurred at a segmental joint and the strand was broken in the tensile zone, while the concrete was crushed in the compression area. [PERSON] and [PERSON] carried out a destruction experiment on two PC box girders removed from a 27-year-old bridge with a span length of 16.5 m [32]. It was illustrated that the PC girders were ductile and behaved as predicted. The load-deflection curve performance was as anticipated, while the flexural strength was more than that required. [PERSON] and [PERSON] carried out a destructive experiment on a deteriorated PC girder with a length of 21.32 m [33; 34]. The tested PC girder failed suddenly just after the yielding of the prestressing strand. The cracking moment could be predicted using the American Association of State Highway and Transportation Officials (AASHTO) Standard, while the specification was not suitable for the ultimate moment. [PERSON], [PERSON] et al. tested two PC box girders with a length of 21.34 m [35]. Due to a low amount of prestress, both PC girders experienced an unexpected brittle failure. [PERSON], [PERSON] and [PERSON], [PERSON] tested the static and dynamic behavior of a 20 m PC box girder subjected to four-point bending load until failure with an fibre Bragg grating (FBG) sensing system [36]. It was observed that at the failure stage, the bending moment of the girder was lost abruptly after the prestressing tendon yielded. [PERSON], [PERSON] conducted destructive testing of a three-span PC box girder bridge to determine the mechanical behavior of the bridge under varying magnitudes of damage [37]. The bridge behaved well as a system, and the shear keys and transverse tie rods were able to transfer load to adjacent beams. [PERSON], [PERSON] et al. tested a 30 m span prestressed ultra-high-performance concrete (UHPC) box girder until failure with four-point bending [38]. Based on the test and parametric analyses, a verified strain-stress diagram for cross-sectional analysis and a simplified calculation formula for the prestressed UHPC box girder were proposed.