| Tower crane, as a convenient construction equipment with high efficiency, hasbeen widely used in various kinds of engineering operations, so its safe reliability hasbecome an important indicator of construction safety. According to relevant statistics,most safety accidents of tower crane are caused by structural imperfection and overuse,which is bound to generate structural fatigue failure. However, due to the limitation ofeconomy, the majority tower cranes currently used in China were designed in the1960s and1970s, consequently, safety accident is inevitable if these old designedtower cranes are overused. In order to secure the safety of operating personnel andensure the successful construction, it is necessary to evaluate tower crane’s fatigue lifeand safety performance properly. In this paper, tower crane QTZ630is taken as aresearch object, and commercial finite element software ABAQUS and fatigue analysissoftware FE-SAFE are utilized to analyze tower crane’s fatigue life when operatingunder severe environment, as well as study the influence of different initialimperfection on tower crane’s life.Firstly, this paper combines fatigue theory with actual operating situation of towercrane, adopts nominal stress method from high-frequency fatigue theory to calculatethe fatigue life of tower crane, and simplifies tower crane’s structure reasonably.ABAQUS is used to conduct modeling on tower crane QTZ630, which is widely usedon Nanchang LianTai Riverside construction site. In addition, according to theoperation condition of tower crane, each cross-point’s rated load of jib loading boom isset to be a working condition, then28kinds of working conditions are established, andthe static stress of tower crane under each working condition is calculated for theanalysis of fatigue life later.Secondly, through observe and calculate the operation situation of tower cranetrolley, the knowledge of mathematical statistics is applied to analyze the statistics, thefrequency of trolley operates under different working condition is got, and the loadspectrum of tower crane is formulated out based on it. Then the fatigue analysissoftware FE-SAFE is used to combine the static stress of structure under differentworking condition got before with formulated load spectrum, thus get tower crane’sfatigue life.Finally, based on damage tolerance theory, initial imperfection is implanted to tower crane so as to analyze the crack growth life of it. And then through reasonablesimplification, transfer it to a plane problem, on this basis, the impact of differentinclusion and hole on crack with different initial angle is studied. The analysis showsthat the stress intensity factor of crack enlarges with the increase of initial angle;What’s more, to initial hole’s defect, with the enlarge of hole diameter, the stressintensity factor of crack growths; Furthermore, to different inclusion with differentmodulus of elasticity, with the increase of it, the stress intensity factor growths. Basedon the verification and analysis of plane crack, it illustrates that different initial crack,different hole diameter and inclusion with different intensity have significant influenceon tower crane’s crack propagation life, which provides essential reference for theanalysis of residual fatigue life of tower crane with initial defect. |
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