The Fatigue Analysis And Experimental Research On M22High Strength Bolt In Grid Structure With Bolt Sphere In Service

Relying on its comprehensive advantages,grid structure with bolt spherejoint has a wide range applications in long span buildings such as publicbuildings and industrial factory buildings.Grid structure with bolt sphere jointhanging crane will cause fatigue problems under the crane random alternatingload on and may occur fatigue damage.But relevant design specificiations codesin our country in the fatigue design of grid structure with bolt sphere joint is stillblank,which make designer has no principle to rest on and largely limits thedevelopment and application of grid structure with bolt sphere joint in thefuture.In this paper,based on The National Natural Science Foundation ofChina The further study on fatigue problem of space grid structure under theaction of the suspended crane (No.51178286,2012-2015),will do some relatedtheorical and experimental research on fatigue performance of M22highstrength bolt in grid structure with bolt sphere joint.The main content summedup as follows:1. Do static analysis and fatigue analysis on grid structure with bolt spherejoint in service by MIDAS software and estimate the fatigue life of gridstructure based on the cumulative damage.Arrival at a conclusion:high strengthbolt in hanging point is most easily to fail for fatigue,followed by webmember,third for bottom chord.Grid structure with bolt sphere is safe in the design reference period.2. Do verification test on M22high strength bolt fatigue performance ingrid structure with bolt sphere joint by using stable and reliable test device andAmsler fatigue test machine,obtain7equal amplitude fatigue test data and2varied amplitude fatigue test data,analysis the effect of age harding on highstrength bolt fatigue strength:age harding can reduce fatigue strength.3. Explain fatigue damage mechanism of high strength bolt in gridstructure with bolt sphere joint by analysis M22high strength bolt fatiguedamage fracture macroscopic and microscopic photos;The fatigue fracture of thehigh strength bolt can be divided into:the fatigue source area,fatigue extensionarea and transient breaking area.4. Analysis the influence of high strength bolt diameter size,thread form,theexposed screw thread number on high strength bolt stress concentration,designthe thread form which stress concentration factor is smallest;Calculate all thefatigue notch coefficient of high strength bolt diameter,interal:3.99to5.74,which provided a basis for establishing hot spot stress amplitude fatiguedesign method.Analysis shows that the stress concentration factor of the circulararc form thread is minimum.On the basis of this,puts forward improvementsuggestions for common thread form:the tooth type angle from the original60°to30°.