Lines exist in electric hoist gantry crane

Crack exists in electric hoist gantry crane on beams, cracks are mainly concentrated in beams and girders connection parts and beam connected to the leg on the parts of the parent bridge gantry crane or weld. 2 causes the crack part stress state is complex, such as bending stress and shear stress and welding stress, both to carry hoisting load and dead weight load overhead gantry crane by the bending stress and shear stress, and at the same time, the operation of the lateral load, big, the car braking inertia load and wind load, and so on. Stress is larger, therefore, the local synthesis with cantilever crane, the load on the cross and cantilever end beam weld on both sides there are alternating stress and angular distortion in the opposite direction, combined with structural reason is easy to produce stress concentration, and therefore part of weld and parent metal under alternating stress and stress concentration susceptible to fatigue damage. Design flaws in the side of the leg on the top of the beam by two independent small box girder (or i-steel) structure, as shown in figure 1. Causes of crack for stress concentration, uneven force and stiffness. 8 of this type of crane in our city in the cracks without exception, the shortest using only 3 ~ 4 months appeared crack, crack of the other in a test cycle. Beams on the independent structure crack distribution material crack, crack on weld beam bending crack.