function deltak = mrptstmt(K_u,M_u,phi_d,Freq_d)
%
%
% Function: mrptstmt
% 
% Usage:  deltak = mrptstmt(K_u,M_u,phi_d,Freq_d)
% 
% Description:
%    Computes the perturbation to the global stiffness matrix
%
%

% Version SWD970109
%
% Author(s): Scott W. Doebling, doebling@lanl.gov
%
% Institution: Los Alamos National Laboratory, ESA-EA
%
% Copyright (c) 1997, The Regents of the University
%     	of California.

Lambda_d = diag((Freq_d*2*pi).^2);

dvecs = K_u * phi_d - M_u * phi_d * Lambda_d;

H = inv(dvecs.' * phi_d);

deltak = dvecs * H * dvecs.' * 100;

return