Test to determine lateral constraint stiffness of angle steel with in-situ nondestructive reinforcement for transmission tower

Abstract

As transmission lines expand and capacities increase, transmission towers are facing heavier loads. Older designs can't meet new standards. In addition, extreme weather increases the risk of tower collapse. Thus, enhancing the load-bearing capacity of existing towers is important. This paper proposed a new in-situ nondestructive reinforcement technology for strengthening the lateral constraint stiffness of angle steel in transmission tower. The proposed reinforcement method does not require drilling on the original material, making it easy to implement. Five specimens with different reinforcement length were fabricated and tested under out-plan loads. The failure mode, lateral constraint stiffness and strain development of the angle steel with in-situ nondestructive reinforcement were discussed. The effect of critical parameters (i.e., axial tension on steel, reinforcement length and connection method) on the lateral constraint stiffness of the reinforced angle was investigated. Finally, the reinforcement effect of the proposed in-situ nondestructive reinforcement was further discussed through comparing with the unreinforced angle. The results reveal that, the proposed reinforcement method is quite convenient to install. It can effectively strength the lateral constraint stiffness of steel angle, and has the same reinforcement effect on the bearing capacity of angle steel compared with the traditional welding reinforcement method. The lateral constraint stiffness of steel angle becomes larger as axial tension enlarges. The reinforcement effect evidently increases as the reinforcement length increases, and the lateral constraint stiffness can be increased up to 97.56% compared to the unreinforced angle.