On July 5, all circumferential welding work on the steel box girder of the Xintian Yangtze River Bridge was completed, marking that the bridge is about to enter the preparation stage for deck paving.

The Xintian Yangtze River Bridge has a main span of 1,020 meters and is currently the largest-span steel box girder suspension bridge under construction in Chongqing Municipality and the Three Gorges Reservoir area. The bridge crosses the river in a single span and has a total length of 1,770 meters. The entire bridge has 57 steel box girder segments and 56 welds. The circumferential welding of the steel box girder is an important milestone in the bridge construction project. The welds are symmetrically welded from the mid-span girder segment toward both ends of the girder, and through circumferential welding the 56 gaps are joined into a single "integral whole," thereby making the steel box girder deck more stable.

The circumferential welding of the steel box girder consists of inner and outer web butt joints, top plate butt joints, bottom plate butt joints, inclined bottom plate butt joints, wind fairing plate butt joints, and transverse diaphragm butt joints. The circumferential butt jointing of the steel box girder is particularly complex. Starting with gap measurement, the gaps are positioned and adjusted, positioning is carried out using fitting plates, and after the welds are leveled, back gouging and filling welding of the top plate and welding of the bottom plate are performed. At this time, 4 to 6 welders are needed to weld symmetrically in sections from the middle toward both sides simultaneously, while the cover pass of the top plate is welded by a semi-automatic submerged arc welding machine. This process requires both tacit cooperation among the welders and constant close monitoring of the machine. Non-destructive testing of the welds is carried out 24 hours after the welds are completed. After passing the test, third-party inspectors are invited to conduct 100% full-coverage flaw detection using ultrasonic testing and X-ray testing at the cross-shaped joints between the top and bottom plates of the steel box girder, so as to ensure that the welding quality of the steel box girder meets the design requirements, with a qualification rate of 100%.

Before the formal start of circumferential welding of the steel box girder, the project specially organized a circumferential welding skills examination. Welding operations could only begin after all personnel passed the examination, further ensuring the permanent welding quality of the steel box girder. When the steel box girder welding process began, it coincided with the plum rain season, and the steel box girder welding work was like "steaming buns"—muggy and hot. The project set up four mobile welding shelters on the bridge deck to protect against sun, rain, and wind, while also preventing welding sparks from splashing and endangering others, and was equipped with 18 blowers and exhaust fans to continuously supply fresh air into the steel box girder, ensuring personal safety and quality safety during circumferential welding.

With the completion of testing and repair of the last circumferential weld of the steel box girder, all circumferential welding of the Xintian Yangtze River Bridge has been completed. The ancillary work of full-bridge welding is expected to be completed in early August this year, laying a solid foundation for the next step of deck paving.