The Theory And Test On Variable Amplitude Fatigue Behavior Of Grid Structure With Steel-Pipe-Welded Hollow Spherical Joints

In the suspension crane under the action of welded hollow spherical joints grid in the domestic is more and more widely application, but the global engineers begin to think about it which the fatigue problem of suspension crane. Particularly there aren't rules on the fatigue in《Specification for Design and Construction of Grid Structure》(JGJ7-91), so designers don't have references in fatigue design. That verily impacts the grid structure's application in the design method of fatigue.Based on fatigue test of grid structure with welded hollow spherical joints, the paper carries out the test on variable amplitude fatigue behavior of grid structure with welded hollow spherical joints and works out the following conclusions:1,To set up a effective,stable and reliable test device, through this device can better finish all the works of the fatigue test.2,The paper has acquired six pipe-welded hollow spherical joint's variable amplitude fatigue test dates under program block through test research on variable amplitude fatigue behavior.3,To analyze the stress of steel-pipe—Welded hollow spherical joints.4,Based on the fatigue test, get 15 datas on the constant fatigue and 6 dates on the variable fatigue of steel-pipe—welded hollow spherical joints. make the full and systemic analysis, get the normal S-N curve of joints.5,To analyze the fatigue feature of fracture and the uncertain function which effect the fatigue test datas. 6,To make the method which design the fatigue strength.The research results in the paper make up for the shortage of the test studies on fatigue performance of grid structure with welded hollow spherical joints. The research results also can supply some pipe-welded hollow spherical joint's variable amplitude fatigue test dates to consult for the modification of《Specification for design and construction of grid structure》.