Simulation Of Fatigue Load Spectrum And Fatigue Life Estimation Of Space Grid With Bolt Sphere Joint

At present,China is in the midst of large-scale infrastructure construction stage,the development of space grid with bolt sphere joint is still thriving.And the suspension crane is often set up as a hoisting equipment for the space grid with bolt sphere joint in the industrial buildings due to the need of production.At the same time,the grid is subjected to moving loads due to the operation of the crane,the own weight and lifting weight of hanging crane.Which makes the space grid with suspension crane more prone to fatigue problems.But at present,researchers at home and abroad have less reports on the fatigue problems of space grid with bolt sphere joint.And the research mainly focused on "resistance",there are few studies on "load".The fatigue load spectrum is an important basis for the fatigue strength test and fatigue damage study of grid structure.Therefore,according to a structural laboratory example,to design the space grid with bolt sphere joint with suspension crane.To complete the static analysis of the grid strcuture and fatigue performance analysis with crane with different weight of lifting and different routes.And combined with fatigue experimentalresearch results of Taiyuan University of Technology,the fatigue load spectrum theory of the connecting bolts and the fatigue life estimate were carried out.The research contents,research methods and research results of this paper are as follows:1.According to a structural laboratory example,the design of the space grid with bolt sphere joint is carried out.The static analysis and fatigue performance analysis with crane with different weight of lifting(0.5t?3t?5t?7t?10tand11t)and different routes was completed by MIDAS the finite element analysis software.And the law of the force of the connecting bolts of all kinds of bars of the space grid with bolt sphere joint is obtained.Screening the bolts with large changes in stress,to explore the weak connection bolts that may cause fatigue damage,which are bar 50(the bottom chord of the grid along the short span)?bar 62(the bottom chord of the grid along the long span)and bar 262(the diagonal bar).2.Combined with the actual operation of the crane,the fatigue load spectrum and corresponding frequency histogram of the control bolts was compiled.The results are as follows:(1)The range of stress amplitude from large to small in order are:the diagonal bar(0—150MPa)? the lifting point(0—130MPa)?the bottom chord of the grid along the short span(0—90MPa)?the bottom chord of the grid along the long span(0—50MPa);(2)The stress cycle frequency of each bar is relatively concentrated in:10—30MPa(the bottom chord of the grid along the short span)?0—30MPa(the bottom chord of the gridalong the long span)?10—50MPa and 60—80MPa(the diagonal bar)?10—40MPa and 50—70MPa(lifting point);(3)Compare the difference between the crane and the hoist,the following conclusions are found:most of the smaller stress amplitude are mainly caused by the running of the hoist,most of the larger stress amplitude are mainly caused by the running of the crane.3.Combined with the exponentiation regression curve of the fatigue experiment data of the Institute of Steel Structure and Space Structure of Taiyuan University of Technology,the influence of the weight of lifting,different routes of crane and different routes of hoist on the fatigue damage of the bolt is explored.The results are as follows:(1)The fatigue damage of each connecting bolt is mostly due to the operation of the crane running on path 1 and path 2;(2)The fatigue damage of each connecting bolt is mostly due to the operation of the crane in interval 4 and interval 5;(3)The fatigue damage to the connecting bolts from large to small are:7T?10T?5T ? 3T,Occasionally overloading and smaller lifting weights are not significant for fatigue damage.4.According to fatigue calculation method of high strength bolt for space grid with bolt sphere joint proposed by Professor Lei Honggang in ? The Theoretical and Experimental Research on Fatigue Performance of High Strength Bolt Connection in Grid Structure with Bolt Sphere Joint ?: The fatigue strength was evaluated for the connecting bolts of the following bars,which are most susceptible to fatigue damage: the bottom chord of the grid along the short span as bar 48?49?50;the bottom chord of the grid along thelong span as bar 62;the diagonal bar as 212?257?258?259?260?261?262?312?387?412 and the lifting point.It was found that the connecting bolts of diagonal bar(e.g,bar 257 and 262)and all the hanging bolts designed in the section 2.2 do not meet the fatigue strength.These connection bolts were targeted optimization,and a certain basis for the directional monitoring of the key connecting bolts after the grid is built were provided.