Multistrand Post-Tensioning System
DYWIDAG-Systems International utilizes two different methods to insert strands into ducts. The installation method depends on the access conditions of the structure and the job site.
Method 1: Pushing
Pushing strands into the duct on the job site is very economical and can be done either before or after casting the concrete. The pushing equipment can be installed remotely and a flexible pipe connected to the insertion point. DSI strand pushers provide relatively high speeds of up to 25 ft/s (8 m/s) and require minimal operating personnel. These advantages make pushing the preferred method for strand installation.
Method 2: Pulling
To install strands while pulling them into the duct can be very efficient in special structures, for example where the loop anchorage is used. In most cases the entire bundle of strands is pulled through the duct using a winch with a steel cable.
Method 3: Pre-Assembled Tendons
The prefabrication of tendons either in the shop or in the field can be very economical when the tendons are short and the location of the job site is close. Special uncoilers and hydraulic winches are usually required to properly install the tendons in the structure.