plot_design_spectrum

% Function to calculate and plot of the design spectrum
% Inputs:
% Ss: The mapped MCER spectral response acceleration parameter at short 
%     periods as determined in accordance with ASCE 7-26 Section 11.4.2
% S1: The mapped MCER spectral response acceleration parameter at a period 
%     of 1 s as determined in accordance with ASCE 7-26 Section 11.4.2
% Fa: Site coefficient, see ASCE 7-26 Ch 11
% Fv: Site coefficient, see ASCE 7-26 Ch 11
% TL: Long-period transition period(s) shown in ASCE 7-26 Figs. 22-14 
%     through 22-17.
% maxT: Controls the upper limit in the x axis 
% maxY: Controls the upper limit in the y axis 
% Outputs:
% t: time vector
% Sa: acceleration vector [g]
function [t, Sa] = plot_design_spectrum(Ss,S1,Fa,Fv,TL,maxT,maxY)
% Previous calculations
SMS = Fa*Ss;
SM1 = Fv*S1;
SDS = 2/3*SMS;
SD1 = 2/3*SM1;
T0 = 0.2*(SD1/SDS);
TS = SD1/SDS;
% Create time vectors
t1 = linspace(0,T0)';
t2 = linspace(T0,TS)';
t3 = linspace(TS,TL)';
t4 = linspace(TL,1.25*TL)';
% Calculate parts
Sa1 = SDS.*(0.4+0.6*t1/T0);
Sa2 = SDS.*(1+0*t2);
Sa3 = SD1./t3;
Sa4 = SD1*TL./(t4.^2);
% Total spectrum
t = [t1;t2;t3;t4];
Sa = [Sa1;Sa2;Sa3;Sa4];
% Plot
figure()
plot(t,Sa,'Color','k')
xlim([0 maxT])
ylim([0 maxY])
xlabel('T [s]')
ylabel('Sa [g]')
title("Design response spectrum")
end