Project overview

Shenzhen Chuangye Interchange is located at the intersection of National Road 107 and Chuangye Road, Bao'an District, Shenzhen. It is a fully interoperable hub and was opened to traffic in 1997. The overpass is composed of 10 directional ramps, all of which are bridges, with a total of 20 links and 96 spans, each with 2-8 spans. Each ramp bridge has a radius of 70-250 m, a length of 40.4-174.4 m, and a total length of 1,992.58 m. The upper structure of the ramp bridge is a 30m standard span prestressed concrete continuous box girder structure with a single box and a single room. The bridge deck is 7.5-17.2 m wide and the beam height is 1.30 m. The substructure piers are pile-column piers, the foundation is bored piles, and the abutments are gravity abutments or side cap beams. Most ramps are equipped with 1-2 single-pillar piers and beam-consolidated piers with a diameter of 1.2 or 1.5m. . The design load of the bridge is car-over 20 and trailer-120.

Bridge disease

After testing and on-site investigation, the diseases of Chuangye Overpass mainly manifested as the lateral movement and longitudinal slip of the end of the curved beam, the damage of the limit stop at the beam end, the failure of the expansion joint, and the misalignment of the bridge deck between the two bridges. Some pier tops, cap beams and corbels have cracks. Some ramps need to rely on tension bearings to maintain the status quo of operation. The technical status of the bridge is rated as Category 3

Maintenance reinforcement plan and technological innovation

The principle of the reinforcement design of the Chuangye Overpass is to maintain the current highway level unchanged, and use reinforcement methods to limit the deviation of the main girder and further aggravate other diseases. The remaining common diseases shall be repaired and reinforced in accordance with the principle of "what are the current problems and what are the problems to be solved" to ensure the safe operation of the bridge.

The scope of maintenance and reinforcement covers the entire overpass bridge. A total of 14 bridge spans need to be reinforced to varying degrees. The length of the bridge reinforcement is 1531.

Main reinforcement design plan

1) Consolidation pier reinforcement technology

After the pier body is reinforced, the original foundation bears a new and larger load, so the original foundation needs to be reinforced at the same time. Due to the complex site conditions under Qianqiao Bridge, the clearance under the bridge limits the construction of traditional bored pile foundations of the bridge. Therefore, in view of the characteristics of construction under the bridge, the foundation adopts micro-pile.

2) Strengthening technology of bridge pier cap beam

Considering that the joint piers are all cap beams, the reinforcement design uses a steel-concrete composite structure cap beam under the original cap beam to be re-made, and concrete is poured in to make it bear the load together with the original cap beam.

3) Limiting device at the end of the main beam

A limit device is added at the girder end of the main girder, which works together with the fixed pier of the middle pier and the abutment cover girder block to prevent the further development of the main girder deviation.

4) Articulated pier, corbel reinforcement

For articulated piers and corbels that have obvious diseases and need to be reinforced after calculation and analysis, they are reinforced and repaired by externally bonding Horse carbon fiber method and  externally bonding steel plate method respectively.

Experience conclusion

Summarizing the reinforcement design experience of the Chuangye Interchange Bridge, the following points should be noted for the reinforcement design of the overpass and curve bridges:

1) Bridge reinforcement should avoid or minimize new damage to the structure.

2) Foundation reinforcement should focus on improving rigidity. In view of the characteristics of the construction clearance under the overpass bridge, the foundation reinforcement should be given priority to choose the micro pile foundation.

3) Under conditions, the installation of strong consolidation piers can effectively restrain the torsion deformation and deflection of the upper main beam of the curved beam.

4) Steel-concrete composite cover beams are added to strengthen the sub-junction pier cover beams. By increasing the effective height of the section, the purpose of improving the bending, shearing, and punching resistance of the section is achieved; at the same time, the use of steel components has a large strength reserve and can ensure structural safety.

5) Take the steel pin method to set the limit device. At present, limit devices are installed in the newly built curved bridges. Although they are different in appearance, the principle of action is the same. All are through the joint end to set the transverse bridge direction restraint to effectively reduce the torque of the car's centrifugal force on the pier.