bldg;				% you need to have bldg.m in the same directory as this m-file
% bldg.m evaluates the natural frequencies and mode shapes of the 
% 16 story building
p=size(M);				% M is the mass matrix from bldg.m
e=ones(p(1),1);     	% vector with the same size as M and entries of 1
xi=0.02;					% A damping ratio of xi is assumed for all the modes
							% by setting xi=0, the undamped system will be modeled
A=[zeros(p(1))  diag(ones(1,p(1)));-om2  -2*xi*om];% with damping
B=[zeros(p(1)); Phi']*M*e;      %earthquake input matrix
% note that earthquake signals are normally collected by accelerometers
% and in simulation acceleration at the base of the building is viewed as
% the input to the system.  Acceleration at the base can be changed by forces
% on each mass with the magnitude of m_of_each_floor*acceleration_of_the_base

% to simulate the response of the building to a single force acting on one of the 
% floors, say 10th floor, change B to the following (comment the above B) and
% uncomment the B, below
%B=[zeros(p(1),1); (Phi(10,:))'];

C=[Phi(16,:) zeros(1,16)];			% displacement is the output
D=zeros(1);				%control input D matrix
w=logspace(0,2,100);
bode(A,B,C,D,1,w);	% bode plot for the 16th floor
title('bode plot for the 16th floor')