一、概况桥式吊车在使用一段时间之后,其主梁上拱度逐渐消失而产生下挠,这种塑性变形是逐渐产生和发展的。特别是安装在热加工车间或经常超载的吊车,下挠的发展更为迅速。下挠发展的后果,主要表现在起吊负荷后主梁总下挠量很大,使小车自中部朝两头运行困难,在两头停不住车,会自行滑向中部,因而影响工艺上的特定操作(如浇注时钢包对不准浇口等),甚至还会发生事故;另外,下挠过大将引起主梁截面焊缝开裂或主、端梁间节点开裂,因此当吊车下挠严重时必须尽快处理,使主梁恢复上拱。以往处理吊车下挠常用的方法是火焰矫正和电焊加固。采用这种办法施工复杂,吊车停产时间较长,而且对主梁的承载能力还有所减低,虽然当时恢复了上拱,但过了不很长的时 First, an overview of the bridge crane in use for some time, the camber gradually disappear on the main beam and produce the next scratch, this plastic deformation is the gradual generation and development. Especially in the thermal processing plant or often overloaded cranes, the next development of the more rapid deflection. The consequences of the development of flexing are mainly manifested in the fact that the total deflection of the main girder after the lifting load is very large, making it difficult for the car to run toward the two ends from the middle part. The car can not be stopped at both ends and slides to the middle by itself, thus affecting the specific operation on the process (Such as pouring ladle on the gate is not allowed, etc.), and even accidents; In addition, the greater deflection will lead to the main beam cross-section of the weld cracks or cracks between the main beam and end beam, so when the cranes serious deflection must be as soon as possible Processing, so that the main beam restored arch. In the past, the commonly used methods for handling crane crooks were flame straightening and electric welding reinforcement. In this way, the construction is complicated, the crane stopped production for a long time, and the carrying capacity of the main beam was reduced. Although the upper arch was restored at that time,