Torques can be added. 

Imagine a large horizontal wheel that turns a shaft. Now if one man applies a force to turn the wheel, the net torque will be some value. If two or three men join in and apply forces in the same direction (clockwise/anti-clockwise) then the net torque will increase.

This is commonly applied in machines such as human powered capstans...

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/XQX3g.gif