Bridge girder launchers, as a kind of construction hoisting machinery, are mainly used in the erection of highways, railways, bridges, etc. Being large-scale mechanical equipment, it will have a significantly adverse impact on national economy and personal safety once any accident occurs. The restoration ofbridge girder launchers not only requires muchtime and lots of money, but also severely affects the bridge erection progress. There are at present many cases of bridge girder launcher accidents in the market and therefore the causes are diversified. Nevertheless, the main causes can be summarized as follows:

1. Human factors: Poor quality, poor sense of responsibility and poor skills of the personnel of the construction unit; lack of safety awareness and failure to take command in strict accordance with the operating procedure of the leaders of the unit; moreover, violation of regulations or omission of certain necessary procedures or safety measures of the construction unit with the aim to meet the deadline or save troubles, etc.

2. Poor quality of subgrade and track: The subgrade on which the construction is performed is frequently not solidly filled and is therefore prone to accidents. With respect to poor track quality, a higher outer rail in the curved section will lead to tilting of the body and uneven tracks will cause the bridge girder launcher to slip and tilt.

3. Factors of the bridge girder launcher itself: Unreasonable design of the bridge girder launcher, such as long body, great dead load, great axle load, high center of gravity, absence of safety devices, etc., will lead to overturning accidents.

4. Improper maintenance of equipment: As the bridge girder launcher is large-scale hoisting equipment and involves many operating procedures, the problem in any component or procedure will cause breakdown of certain critical component of the bridge girder launcher or mis-operation of certain critical procedure, thus resulting in bridge girder launcher accidents.