Under some conditions, ZZHZ cuts main girder upper cover plate of gantry crane by use of the influence that main girder self-weight has on the camber, thus reduce bending box girder gantry cranemodulus of main girder section at cutting position, weaken bending resistance of main girder, generate a mechanical deformation caused by main girder self-weight, then reduce upper camber value at mid-span and increase up-warp value at cantilever end. It is easier to control the whole correction process and deformation degree by using the method, but we should mention that main and auxiliary web plates around cutting parts will cause a web plate wave out of tolerance caused by main girder axle rotary deformation vertical to web plate direction, which should be avoided.

 

Practices prove that cutting method features simple operation and easy control, can keep preferably original technical data after permanent deformation of main girder and won’t cause a larger change of technical parameters for aging reason after internal stress or thermal deformation releasing. So cutting method is a better way to correct main girder with over-proof camber as well as correct over-top cantilever (qualified span part), over-top span part (qualified cantilever) or other up-warp defects. Expected purpose can be achieved only by choosing different support position and cutting parts as supporting main girder in the air. It must be mentioned that some technological measures should be taken to avoid web plate deformation with a larger correction scope.