The classification of the gantry crane (divided into four types: (1) normal gantry crane: this kind of crane is the most widely use, can carry a variety of items and material, the weight below 100 tons, the span of 4 ~ 35 meters. Grab the general gantry crane work level is higher. (2) hydropower station gantry crane: mainly used for lifting and opening and closing valve, also can install operations. Weight of 80 ~ 500 tons, span is small, to 8 to 16 meters; Hoisting speed is low, for 1 ~ 5 m/min. This kind of crane, although not often lifting, once use work is very heavy, so to improve the working level appropriately. (3) shipbuilding gantry crane: slipway assembled hull, standing two lifting Trolley: there are two main hook, a the bridge frame flange orbit; Another has a main hook and a pair of hook, flange of the orbit under the bridge, to flip and hoisting large hull section. Lifting weight general for 100 ~ 100 tons; Span of 185 meters; Hoisting speed of 2 ~ 15 m/min, and motion of 0.1 ~ 0.5 m/min speed. (4) container gantry crane: for container terminals. Staying-time of quay wall container transport bridge are discharged from the ship after the container to the yard or rear, stacking up or direct loading away from container gantry crane, can accelerate the turnover of or other container transport Bridge crane. Can be stacked high 3 ~ 4 layer and 6 rows of container yard wide, generally use tyred, useful also trolley type. Container gantry crane compared with container straddle carrier, the span and height are larger on either side of the door frame. In order to meet the need of the transportation of port terminals, this kind of crane work level is higher. Hoisting speed of 8 ~ 10 m/min; Span across the number of container line according to need to decide, 60 meters corresponding to maximum 20 feet long, 30 feet, 40 feet container lifting weight respectively about 20 tons, 25 tons and 30 tons. (4) carrying bridge by the gantry crane, a greater span development and become a bridge type crane, also known as crane. For open storage yard, port and railway station. Common carrier bridge structure is similar to that of a large gantry crane. Features are: (1) mass of moving object is mainly material; (2) a span, generally in more than 30 meters, some 170 meters; (3) homework is frequent, high productivity, usually for 500 ~ 1500 t/a, high working speed, lifting speed is 60 ~ 70 m/min, the car speed is 100 ~ 350 m/min, job level is higher; (4) carrying bridge operation institutions only to adjust the work position, is a work item. When the span is larger, carrying bridge bridge abutment in a rigid leg and a flexible on the leg. Bridge with two leg bolt connection can be used; With the connection of flexible leg also can through the ball joint or column hinge, make flexible leg can be relative to the deflection of bridge has a certain scope. Bridge is composed of truss girder, lifting the car in its upper chord and bottom chord of the orbit. Some cars have rotary arm rest, be equivalent to a frame running in bridge crane boom type.