PREDAM（Prefabricated Steel-shell Cofferdam）Method
A new method for the simpler and more efficient earthquake-resistant reinforcement of bridge piers and repair of underwater structures
There are increasing needs for repair of bridge piers and other structures constructed in the sea and rivers because of their deterioration or for earthquake-resistant reinforcement because of the revision of the Seismic Design Code. It is vital for reinforcement and repair works on these underwater structures to have dry work space without water around the structures, which is required for ensuring the quality and safety of the work. The conventional method is to construct a cofferdam by driving steel sheet piles and constructing cut-off walls around a structure. However, the shortcomings of this method are the difficulty in driving sheet piles and, consequently, the longer time required for the work when it is used in places with limited overhead clearance such as bridge piers.
PREDAM has overcome the height constraint during execution by the use of caissons which can be towed afloat.
PREDAM can be used for construction near navigational routes because it does not require heavy equipment.
PREDAM reduces the size of caissons and costs associated with the use of caissons made of assemblable / disassemblable buoyant parts.
Adoption of pre-fabricated caissons has shortened the work period and increased the applicability.