How many ways to construct a bridge?

To construct a bridge, there are about 3 ways:

1. using one launching girder which is a professional bridge construction equipment, its support equipment has girder carrier and gantry crane for lifting girders. The launching girder is applicable for almost all bridges, but it costs much.

launching girder

2. using gantry cranes crossing the bridge, service conditions: ?there has roadbed underbridge which can lay rail tracks for gantry cranes. It is better to use two sets gantry cranes for a long bridge construction project, one sets gantry cranes lift and move precast girder, and the other set install girders. Gantry cranes crossing the bridge has a faster speed to install girders and cheaper, but there are some limits to use them.

3. using truck cranes, two truck cranes can lift and install one girder synchronously at one time, but still a girder carrier is necessary. ?service condition: the track crane can move under the bridge and the bridge is not very high.?Truck cranes has a faster speed to install girders, but there are some limits to use them.