Thermodynamic and Fluid Dynamic Analysis of Clamping Force Variability in High-Strength Bolts Across Temperature Extremes in Northern China

This study investigates the thermodynamic and fluid dynamic influences on the clamping force of high-strength bolts (HSBs) within a temperature range of -20 to 60, reflective of the climatic conditions prevalent in northern China.Eight HSB specimens were subjected to focused experimental investigations to quantify the effects of thermal expansion and the dynamics of clamping force relaxation under varying thermal environments.It was determined that initial clamping force relaxation, significantly influenced by thermal dynamics, was completed within seven hours at a controlled temperature of 24, with observed losses ranging from 1.01% to 3.44%.Furthermore, a substantial degradation of clamping force was recorded, attributed to a thermal gradient, where losses increased up to 19.02% as temperatures rose from 20 to 60.The findings culminated in the development of a thermofluid model, which effectively estimates clamping force behaviour across the studied temperature spectrum.To mitigate the adverse effects of thermal relaxation, a recommendation was made to increase the standard tightening force by 5%, thereby providing critical guidelines for optimising the mechanical integrity of steel connections under thermal stress.These insights are expected to enhance the understanding of clamping force stability in high-strength bolted joints within extreme thermal environments, contributing to the advancement of structural integrity assessments in engineering applications.