Heavy Industry Workshop Steel Crane Beam In Service Residual Fatigue Life Evaluation Method Research

China's modern industrial process is accelerating,the production capacity of heavy industrial plants is increasing,and the use of steel structure crane girder is more and more.Steel crane beam in service of heavy industry workshop often appears prematurely fatigue fracture,severe fatigue damage with the complex stress state,the load characteristic of large tonnage and repeatedly under fatigue loads.At present,the research methods on the problem of steel structure fatigue of ? the specification for design of steel structure?GB50017-2003 is S-N curve method,which focuses on steel structure design,but the evaluation results are often large difference with the actual situation in the test to assess the fatigue life of steel crane beam in design phase application.Therefore,it is of obvious practical value to study the evaluation method of residual fatigue life of steel structure crane girder in service with heavy industrial plant.Aiming at the characteristics of random fatigue load for steel crane beam in service in the heavy industry,the standard fatigue life,the confidence level and other parameters of detail fatigue rating method were corrected,and the theoretical derivation for detail fatigue rating method has been carried on.Secondly,the stress characteristics and cracking reasons of the steel structure crane beam were analyzed by field measurement,and the strain time analysis of crane beam in three states was carried out.Then,according to the stress cycle statistics of the measured strain time data,the cycle times corresponding to the stress cycles at all levels were obtained,and the corresponding life spans of stress amplitudes at all levels were fitted.Finally,the residual fatigue life of the steel crane beam in service for the heavy industrial plant wasassessed with application of detail fatigue rating method,and the evaluation results were compared between the method in this paper and the S-N curve method,gaining a higher accuracy of assessment method of fatigue life of steel crane beam.The main conclusions are as follows:(1)Through the analysis of the measured data research of steel crane beam fatigue for round steel bar rolling mills main factory building,fujian three steels fujian light steel limited company,the high incidence area of fatigue crack appears near the webs of the flange and the stiffening rib near the steel structure crane girder.(2)According to the life span of the crane girder D/34~35 and D/35~36 for fujian project,it shows that its life is not refused to obey the normal distribution.(3)The error of assessment results and the measured results is 3.6% with the application of the detail fatigue rating method for fujian project.The estimated of S-N curve method is a little bit worse than the estimated of Detail Fatigue Rating method in the use of the crane beam D / 34 ~ 35 when evaluating residual fatigue life,due to the differences of S-N curve model and the actual situation for steel structure materials and the ignorance of the effect of stress ratio.