Reinforcement of Xinshu River Bridge

Bridge Overview

The Xinshu River Bridge was built in 2002, with a total length of 1,688 meters, and is located on the Fenguan Expressway in Lianyungang. The central pile number is K813+412, and the upper structure is an 8×(6×35)m pre-stressed concrete continuous box girder, which is composed of 5 small box girder transversely. Hole 13#28# crosses the Xinshu River, and the highest flood level is 9.68m. The lower structure is a pile-column pier, a ribbed platform, and a bored pile foundation.

Disease characteristics

During the health monitoring of the bridge structure in 2014, it was found that the pre-stressed concrete composite box girder webs of the Xinshu River Bridge generally had vertical cracks. According to the actual measurement, the crack width is about 0.10mm, mainly distributed in the position of 2L/5～3L/5, and it develops upward from the chamfer of the bottom plate and the web. During the inspection, it did not develop to the top edge of the cross section, and the bottom plate did not show any transverse cracks. Multiple beams have vertical cracks at the same position. After the cracks were closed in previous years, such cracks appeared in their vicinity.

Analyze according to the shape characteristics of the combined box girder:

① Consistent with the detailed analysis of the section, the normal tensile stress caused by the car load within the height of about 50 cm between the web and the bottom of the beam is relatively large; the normal tensile stress value is close to the cracking limit under the combined action of short-term effects, and the web is prone to cracks;

②The occurrence of vertical cracks in the web weakens the characteristics of the section, leading to the appearance and development of transverse cracks in the bottom plate. From the perspective of the crack development process, the vertical cracks in the web are generated before the transverse cracks in the bottom plate. It can be seen that such vertical cracks in the web are caused by excessive stress.

Reinforcement plan

CFRP plate has certain advantages in economy, and it also has the advantages of simple process, beautiful appearance, little damage to the beam body, and good anti-corrosion performance. Therefore, the pre-stressed CFRP plate reinforcement technology is adopted for this box girder reinforcement project.

It has been more than a year since the end of the construction, the structural force has been in a safe and stable state, and the beam cracks have not increased, which proves that the prestressed CFRP plate has a good effect in strengthening the highway bridge structure.