Bridge Widening And Reconstruction

A municipal bridge was built and put into operation in 2002. Considering the increasing traffic volume of the bridge, the existing traffic capacity of the bridge can no longer meet the needs of normal traffic, so the bridge must be widened and rebuilt. At the same time, part of the bridge structure should be reinforced to meet the requirements of bridge deck widening and load level upgrade.

Reinforcement plan

According to the requirements for the widening of the municipal bridge and the bridge reliability test report provided by the testing party, the structural stability check is carried out for the upper and lower structures of the bridge due to load lifting and new dead load changes. The checking results show that the original bridge foundation and piers meet the load change requirements after the bridge is widened. However, the bearing capacity of the bridge deck girder, T girder, bridge deck supporting cover girder, etc. is insufficient to meet the new load requirements of the original bridge after widening, and the bridge structure must be strengthened.

After the comparison and selection of the plan, it was decided to adopt the reinforcement technology of pasting carbon fiber cloth. Specifically, 40cm-wide carbon fiber cloth was pasted along the longitudinal direction of the beam bottom in the midspan of the plate beam and the T beam, and 25cm-wide L-shaped carbon fiber hoops were pasted at both ends of the support, as shown in Figure 1. A carbon fiber U-shaped hoop is pasted on both sides of the cover beam, and a ribbon-shaped carbon fiber cloth pressure strip is added on the top of the cover beam. The size of carbon fiber cloth and carbon fiber hoop and the number of pasting layers are determined according to the degree of lack of cross-sectional area of steel bars in the beam structure to be reinforced.

Carbon fiber cloth is used to strengthen the widening structure of this municipal bridge, using Horse's carbon fiber and glue. The indoor test results show that the tensile strength of this type of carbon fiber material is 4110MPa, the elastic modulus is 260GPa, the elongation is 1.8%, and the positive tensile value of the bond strength is 3.8MPa. The material strength fully meets the bridge structural reinforcement requirements.

In the process of pasting carbon fiber cloth, the cutting length of the material should be controlled at about 3.0m to avoid damage to the components due to excessive length during reinforcement construction. Ventilation space should also be reserved to ensure good ventilation after pasting and reinforcement, so as to speed up the consolidation of the glue. The overlapping width of the carbon fiber cloth should be controlled at about 20cm, and the air bubbles in the bonded carbon fiber cloth should be removed in time, and finally wrapped with tape to fix it.

After the bonded carbon fiber material is reinforced in the municipal bridge construction project, the fireproof layer should also be coated. The construction personnel should apply a fireproof layer before curing the carbon fiber cloth to enhance the sufficient bonding and durability of the fireproof coating and the adhesive glue.

Evaluation of reinforcement effect

The carbon fiber reinforcement construction of concrete structures of municipal bridge projects requires high reinforcement materials and construction techniques. Any failure to meet the design requirements will lead to the failure of reinforcement construction. Therefore, it is necessary to strengthen the indoor test of reinforcement materials and the on-site inspection of construction technology.

The construction process of carbon fiber reinforcement in municipal construction projects is not complicated, and the effect test of bridge concrete structure reinforcement also shows that compared with other reinforcement technologies, carbon fiber reinforcement technology has very significant advantages.