You need to use a full-bridge 1 equation. (If you do not know about a full-bridge 1 equation, please refer to this site: Full-Bridge Type 1
.) The equation of full-bridge 1 considers the tensile force and compressive force. As measuring strain for torque is also needed tensile force and compressive force, you can use the below equation about full-bridge.
If you want to know how to attach sensors, please refer to Additional Information.