| Tower cranes become more and more important lifting equipment in modern construction, its'safe and reliable operation is an important indicator to ensure the safety of the whole construction site. Load factor of tower crane is increasing, lifting frequency is in aggravation, many tower cranes are working under high stress in most working time, accidents of them is not absolute in a few. In this paper, some analysis and study have been done about the accidents, I found that a considerable portion of these accidents are due to structural damage caused by fatigue. Therefore, this paper choose a WQ6 flat top tower craneto estimate its fatigue life. Mainly conducted the following studies:Study the status of fatigue researched at home and aboard, according to the mechanical characteristic of tower cranes and frequency of their using, fatigue type of tower crane is high-cycle fatigue. According to the fatigue type, choose the nominal stress method to estimate the fatigue life of WQ6 roof flat top tower crane's metal structure. Study the basic theory of the finite element method,obtained the crane's stress-time history curves in its'amplitude movement and under the impact loads. Choose rain flow counting method,establishment stress spectuum of the stress history,based on life curve of the Goodman assumption,change the asymmetrical stress cycling to the stress cycle with mean O,count the number of the stress cycle at all levels. Analysis the double logarithmic coordinates stress-life curve of Q235 steel,combined with the stress spectrum,obtained the damage degree of cycle at all levels,calculate its' fatigue life by Miner Theorem.Finally, based on the fatigue calculation in crane design standard GB/T 3811-2008,calculate it's fatigue life in a reversed way,this verified the correctness of calculation for fatigue life by nominal stress method.
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