Patent ID: 8251637

Claim:
A method, comprising: determining an excitation frequency of a plurality of rotating turbine blades; determining a modal vibration frequency of an inner shroud, the inner shroud comprising: a body having a first end portion, a second end portion, an upper surface, and a lower surface, wherein the lower surface is adjacent to the plurality of rotating turbine blades; and at least two rails extending between the first end portion and the second end portion along a length of the body, wherein the at least two rails define an impingement cooling area on the upper surface and between the at least two rails; and modifying the modal vibration frequency of the inner shroud with at least one cross-member disposed on the upper surface in a direction transverse to the at least two rails, the at least one cross-member dimensioned to shift the modal vibration frequency of the inner shroud away from the excitation frequency of the plurality of rotating turbine blades.