Mechanized Bridge Construction
Gantry cranes (or Launching Gantry, LG) are movable cranes which will be assembled at site on the bridge deck and columns and help to erect the pre-fabricated bridge segments in place to complete a deck. Gantry cranes have many types among which LG Overhead and Under-Slung LG are very common. In Under-Slung LG, hydraulic units hold the segments in place but in Overhead LG, PT Bars hold the segments in their locations.
In general, the way LG’s work is that all prefabricated LG’s are brought to the location and LG lifts them up. Each segments is held in its place by a monobars which is connected to the LG. All the segments are aligned. The next step is to pass the post tensioning strands through the internal ducts and stressed. At this stage the segments form a complete unit which is then put on its place on the columns.
Payab Zamzam Company has been the provider of 4 LG’s used in SADR Multilevel Highway. In addition to providing trainings and spare parts, half of the whole route (3200m in 4 lanes) was erected and constructed by PZ Company.