(l) Internal water pressure.
(2) The axial force caused by the water pressure at the change of pipe diameter and turning of the steel pipe.
(3) The metal structure of the penstock is self weight, the weight of the water in the steel pipe and the weight of the pier and support pier.
(4) Frictional resistance generated along the piers and expansion joints as well as the friction generated by the water against the pipe wall when axial displacement of the penstock occurs.
(5) Centrifugal force caused by water flow in the pipe at the turning point of the pipe.
(6) Force due to deformation of steel pipe due to temperature changes.
(7) The axial force caused by the deformation in the diameter direction under the action of the water pressure in the steel pipe.
(8) Active earth pressure when the soil acts on the pier or support pier.
(9) The force generated when the middle pier is unevenly subsided