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起重机主梁的自振,对起升机构零部件的动载冲击和对主梁结构的裂纹产生与扩展有不利影响。由于司机室一般悬挂在主梁上,主梁的自振对司机会产生影响,人体器官对于低频振动比较敏感,低于2Hz的振动会引起司机的恐慌感,从而有可能导致事故,故要求主梁自振频率在一定范围内。尤其要着重说明的是:主梁若存在较大裂纹(这些裂纹一般产生于下盖板,不易被发现),将削弱主梁受力截面,进而造成断梁的重大事故。主梁截面被削弱,主梁自振频
The natural vibration of the main girder of the crane adversely affects the dynamic impact of components of the hoisting mechanism and the generation and expansion of cracks in the main girder structure. As the driver’s cab is generally hung on the main beam, the natural vibration of the main girder will affect the driver. The human organs are sensitive to the low-frequency vibration. The vibration lower than 2Hz will cause the driver’s sense of panic, which may lead to accidents. Therefore, The natural frequency of the beam is within a certain range. In particular, it is important to note that if there is a large crack in the main girder (these cracks are generally produced in the lower cover and are not easily found), the main girder stressed section will be weakened, resulting in a serious accident of the broken girder. The main beam section is weakened, the main beam self-vibration frequency