The geometrical shape of the steel Scroll case/spiral case of a hydro-turbine is a complex one which is mostly supported by reinforcement concrete surrounding it. Due to its complicated shape and loading pattern, the stresses at different locations become un-assessable by conventional methods, for which design of substructure is done mostly by the empirical principles based on engineering judgments with 2D theories. But the problems are basically three dimensional. A 3-D model is considered as per the dimensions of the physical model tested by Nigam [1]. Nigam's study revealed only the normal stresses in the concrete. But in the present study in addition to the above, deformations along different axes and shear stresses in separate planes subjected to static loads of the generators and other structures above it are also computed using Finite Element Method (FEM). The ANSYS CAE software is used in conjunction with 3D CAD solid geometry for simulation. Total static load acting on the spiral case is considered uniformly on the concrete surface spreading over an annular area encircling the turbine pit, to determine the stresses and deformations in the concrete. It is found that the normal stresses and total deformations in all axes are higher towards the inner face of concrete. The shear stresses along all the planes are well within the safe limit.

Keywords: Hydro-turbine, Scroll case, Stresses in concrete, FEM.