Strengthening the concrete bridge

Project introduction

• Name of the project: bridge reinforcement

• Prestressed CFRP laminate specifications: 2.0mm thick, 10cm wide first grade prestressed CFRP laminate

• Project scale: 206 40mm prestressed CFRP plates, 27 prestressing carbon plates on each floor,12 carbon plates arranged on the flange plate

  
  

Difficulties in Construction:

• Fengyi bridge is a cast-in-place continuous concrete box girder structure. The uneven layout of the floor steel bars has a great influence on the orientation of the prestressed carbon plate bearing.

• Fengyi bridge project is a municipal bridge maintenance project in Beijing. It only allows night construction, with great difficulty and short construction period.

• 1.46M long prestressed carbon plate, requiring rapid and accurate construction.

Fengyi bridge is a separate span bridge, which is divided into right and left span, each of which is 3 span. The cross diameter is composed of (13.15 16 13.15) m ordinary concrete continuous slab beams with a height of 85CM, and the lower structure adopts concrete column piers and lightweight concrete abutment.

The cracks in the web, floor and flange plate of the left and right beam of the bridge have been cracked by field test. The vertical crack of the web is 0.40mm, the crack width at the center of the steel bar is 0.30mm, the width of the transverse crack in the floor is 0.37mm, and the larger width of the flange plate is 1.0mm. Due to the tight connection between the girder and the abutment, the flange plate near the abutment at the front and third span faces different oblique cracks, and the crack width is 0.30mm. There are transverse cracks at the flange plates near the top of the piers near each pier. The width of the cracks is 0.6mm.

Reinforcement scheme

There are a lot of transverse cracks in the bridge floor and the flange plate, the stiffness of the bridge is insufficient and the safety reserve is insufficient, and the prestressed carbon plate reinforcement system is used to reinforce the bridge. Each floor has 27 prestressing carbon plates, 12 flange plates and 206 prestressing carbon plates. The prestressed CFRP Strengthened with 2.0mm thick and 10cm wide prestressed carbon plate has a tensile stress of 1000MPa and a controlled strain of 7 per thousand.

Tensioning monitoring of prestressed carbon plate

The tensioning process of the prestressed carbon fiber sheet is monitored for the tensile force values and deflection values of each carbon sheet. The deflection monitoring of the bridge consists of 6 points for each span, 1 for each flange span, 2 for the bottom plate, and 1 for 1/4 span and 3/4 span.

3 days after the completion of the whole bridge carbon plate, the deflection value of the span plate and the bottom plate of each span is reduced by 2mm, and the whole bridge beam and plate are arched upward, indicating that the prestressed carbon plate has been well involved in the force of the structure.