Study on the Mechanical Performance of the Xiuzhen River Bridge Strengthened Using K-brace Composite Trusses

In this study, a finite element (FE) model of the Xiuzhen River bridge was developed, and the validity of the model was verified using monitoring results, load tests and theoretical calculations. Subsequently, a series of FE simulations were conducted on a model of the Xiuzhen River Bridge strengthened using K-brace composite trusses (K-BCTs). Static, eigenvalue and response spectrum analyses were carried out for 16 prestressed concrete box-girder (PCB) bridge strengthening models with different K-BCT stiffness and spacing. The results revealed that K-BCTs could reduce the girder deflection, improve the load distribution, and reduce the distortion stress. A slightly better-strengthening effect in the K-BCTs with higher stiffness and smaller spacing. The dynamic analysis revealed that the K-BCT stiffness and spacing influenced the higher vibration modes but had little effect on the lower modes. Furthermore, the K-BCT had no significant effect on the maximum internal force of the model under different seismic waves, and the maximum deviation was within 5%. Finally, two K-BCTs made of concrete-filled steel tubes, with a spacing of 3 m and an elastic modulus of 50 GPa, were used to strengthen the existing bridge. The experiment results indicated that the strain and deflection in the Xiuzhen River Bridge were reduced by 53.6% and 20.6%, respectively.