Introduction  The existing angle steel transmission tower has been running for many years, and the structural damage leads to the reduction of service performance. At the same time, the design bearing capacity of the old transmission tower ceases to meet the design requirements of the existing specifications. In order to address the insufficient bearing capacity of the old transmission tower, a parallel reinforcement method of angle steel fitted with channel steel is proposed. The bearing capacity of the reinforced structure is obtained through experimental research and finite element analysis (FEM), and the critical buckling load is proposed based on elastic analysis.

  Method  In order to obtain the bearing capacity of members, two groups of axial compression tests on test specimens were set up. Two kinds of finite element numerical simulation include unreinforced angle steel and angle steel fitted with channel steel were conducted under axial compression. According to the failure mode, the calculation formula of buckling load of thin plate based on elastic analysis was deduced.

  Result  The axial compression test results show the bending failure of the unreinforced angle steel specimen and the local buckling failure of the angle steel fitted with channel steel. The results also show that the bearing capacity of the reinforced members could be effectively improved.

  Conclusion  Angle steel fitted with channel steel changes the instability failure state of the original angle steel and improves the bearing capacity of the angle steel. The established FEM can reflect the true failure state of the reinforced members, and the theoretical calculation formula can accurately calculate the axial compression bearing capacity of the reinforced members.