| Tower crane is the vital equipment for lifting materials in the working sites. The working reliability of the tower crane is the guideline of ensuring the safety of all the condition. But nowadays, there are more and more higher or plate type construction needed to be built, so tower crane are very busy to lift goods. The static stress in the steel structure of tower crane is higher than before. The Previous design method can't ensure tower crane to work safely. There are many accidents occurred when tower crane is working. After analysis, this paper found that most of the accidents of tower crane are due to the fatigue damage in the steel structure working under circular loads. So this paper presented a new method which is based on finite element method and fatigue software—msc.fatigue to estimate the fatigue life of tower crane's steel structure. The method not only can estimate the residual fatigue life of tower crane that is in working, but also can effectively guide the engineer to design new type tower crane. The new method improved the design level of tower crane. The research work is given as follows. This paper studied the actual working condition of tower crane. By the terms of fatigue theory, it is obvious that the tower crane's fatigue is mechanical, high cycle and breadth changing. According to the fatigue type, use safe-life design method to study tower crane's fatigue, and choose nominal stress approach to estimate the life of tower crane. Presented the approach to simplify the steel structure of tower crane, which based on the theory of finite element method. The finite element model of tower crane is established in msc.patran software. The new method defined a working condition when the rating loads acting on the intersection of two strides, and calculated the static stress of steel structure under every working condition by msc.nastran software. And the calculating result from the model supplied the geometry condition to estimate the life of tower crane by MSC.FATIGUE software. After analysis we found there are two main types fatigue loads acting on tower crane, the load due to the dolly to changing the range and the load due to the impact. Presented a method with local observation and statistical knowledge to gain moving rule of the dolly. First found the frequency of the dolly slipping the stride on the orbit and the beam's coordinate obey normal distributions, and gained the normal probability density function. Then formatted the times history of the load due to the dolly to changing the range. Established the dynamics finite element model, and do transient response analysis with msc.nastran software to gain the force varied with time, then formatted the times history of the load due to the impact. This paper calculated the fatigue life of QTZ4010 type tower crane as a example, and illuminated the idiographic process to estimate the fatigue life with the new method. By the terms of the calculated result we found a rule that all this type tower crane don't need to estimate the fatigue life of balance beam. At the end, this paper presented a optimization scheme for this type tower crane.
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