The Fatigue Life Prediction Of Tower Cranes Technology Research

Tower crane is the main lifting equipment of Construction, its safety running timeis an important index of the evaluation of fatigue life. Along with the fast developmentof Construction industry, the load factor of tower cranes have increased, in recentyears, the crane accidents have happened more and more frequently. Through analysis,the thesis find that the majority of those accidents are caused by Structural fatigue. Taketower crane QTZ4510as an example, the thesis have conducted a research to predictionits fatigue life. The main research work is as follows.By studying The fatigue status of the tower cranes at home and abroad.The loadcharacteristics and frequency of use of the tower crane, we get that the kind of fatigue ofthe tower crane is of high cycle.According to the fatigue type, we choose the virtualfatigue experiment,based on nominal stress method, to predict fatigue life of the metalstructure of the tower crane QTZ4510. We have studied the basic theory of analysismethod of the finite element; through the result of statics analysis and the actualstatistics of the operating frequency of the conditions within the a week, we haveprepared for the stress spectrum of its stress history and have extropolated its stressspectrum, we analyze the rain-flow statistics in the nSoft fatigue analysis software.According to the life curve assumptions,like Goodman,we have converted theasymmetrical stress cycling of the stress spectrum to the stress cycle--its mean is0,andhave compiled the statistics of the numbers of times of the stress cycles of all levels.According to the actual concentration conditions and load of the stress, we havecalculated the double logarithmic coordinates P—S—N(stress—life)curve of towercrane material Q235. Along with the stress spectrum,we have analyzed various factorsthat affects its fatigue life in the nSoft. According to the prepared stressspectrumwe,we have used the predicting method of gray system to test the fatigue life of the tower crane,and verified the accuracy of its forecast.Finally, we have predictedthe propagation life of arm fatigue crack of the tower crane,and have proposed thesafety testing cycle of the fatigue crack of its lifting arm.