State evaluation of transmission towers based on loosening of key position bolts

This study investigates the detrimental effects of bolt loosening at critical positions on transmission tower structural integrity. A three-dimensional tower model was established, incorporating static analysis, modal analysis, and wind-induced fluid-structure coupling analysis to identify vulnerable bolt connections. The Analytic Hierarchy Process and Fuzzy Comprehensive Evaluation Method were employed to quantify the structural impacts of different bolt-loosening scenarios. Results demonstrate that increasing looseness of key bolts leads to progressive growth in maximum tower deformation. Large-sized bolts exhibit the most pronounced effect, causing deformations up to 7.071 cm, followed by key position bolts. Small-sized and non-critical bolts show a relatively minor influence on structural deformation. In addition, the influence weights of different bolt types on the status of transmission towers are as follows: 58.68% for key position bolts, 24.38% for large-sized bolts, 11.77% for small-sized bolts, and 5.17% for non-critical bolts. According to the influence weight, the degree of influence of bolt types is sorted by size as follows: key position bolts>large-sized bolts>small-sized bolts> non-critical bolts.