Fatigue life and fatigue reliability assessment for long-span spatial structure based on long-term health monitoring data

Abstract

Based on the structural health monitoring system of long-span cantilevered spatial structure in Taiyuan Botanical Garden, the welded details strain of the main truss welded tubular joints is monitored for a long time, and the massive monitoring data processing method and the structural fatigue performance evaluation method are studied. First, the key component of the structure is determined through using the measured data, to propose the empirical mode decomposition (EMD) method to compress the load time history, and the rain-flow counting method to extract the stress cycle to obtain the standard daily stress spectrum. Next, through the Palmgren-Miner linear cumulative damage criterion and the S-N curve, the fatigue damage analysis and fatigue life estimation method are established. Consequently, the Monte-Carlo method is used to analyze the fatigue reliability of the key component, on which basis, the influence of considering the load growth effect on the fatigue life and fatigue reliability index is analyzed. The study shows that the weld fatigue damage is mainly caused by the small number of medium amplitude strain cycles. When the load growth effect is considered, the fatigue damage development rate of the weld is significantly accelerated, resulting in a significant decrease in the fatigue life and fatigue reliability index of the weld.