Generally, the connection of reinforcing cages in road and bridge pile foundations is use threaded rebar couplers and upsetting forged rebar coupler.

When using threaded rebar couplers, one end of the steel bar needs to be processed into a threaded end that is longer than the coupler length. The coupler and lock nut are then screwed onto the extended threads. After aligning two reinforcing cages, the coupler is rotated downward to connect the two cages. The advantage of this connection method is that it is easy to construct, but the disadvantage is that there are exposed threaded ends.

Another connection method is using upsetting forged rebar coupler. In this method, the end of the steel bar is first enlarged using a steel bar enlarging machine and then threaded using a steel bar threading machine. This method requires a larger investment and much labor, but provides a better connection effect.