EXPERIMENTAL STUDY OF MECHANICAL BEHAVIOUR OF ANGLES IN TRANSMISSION TOWERS UNDER FREEZING TEMPERATURE

摘要

Compared with the lower-grade steel members, the application of steel angles made of Q420 greatly reduces the self-weight of lattice transmission tower and further leads to the saving of foundation cost. However, unlike the conventional transmission towers, the strength and brittleness of the towers using higher-grade steel are more sensitive to freezing temperature, especially in cold regions. It is noted that the studies on transmission line tower at cold region are limited in literature. In this paper, a series of tests such as Charpy impact test, uniaxial tensile test and tensile notch test were carried out at low temperatures to investigate the mechanical properties and toughness of steel angles made of Q235B, Q345B and Q420C as well as welded joints using Q420C. The results show that the toughness of steel angles decreases with the lowing temperature while the strength increases with the decreasing temperature. The heat affected zone in welded joints is more susceptible to fracture than the parent material. A strength reduction method is proposed for the design of transmission tower in cold regions with rich experimental data provided. The influence of stress concentration at low temperatures was also investigated for fracture resistant design.