EC8spectrumElastic.m

function [ Se,Td,tc ] = EC8spectrumElastic(ag,soil,Td,damp)

% Function to generate the EC8 (EN1998-1-2004) spectrum

if size(ag,2)>size(ag,1)
   ag = ag'; 
end

if strcmp(soil,'A')
    tb = 0.15;
    tc = 0.40;
    td = 2.5;
    S = 1.0;    
elseif strcmp(soil,'B')
    tb=0.15;
    tc=0.50;
    td=2.50;
    S = 1.2;
elseif strcmp(soil,'C')
    tb=0.20;
    tc=0.60;
    td=2.50;
    S = 1.15;
elseif strcmp(soil,'D')
    tb=0.20;
    tc=0.80;
    td =2.5;
    S = 1.35;
elseif strcmp(soil,'E')
    tb=0.15;
    tc=0.50;
    td=2.50;
    S = 1.4;
end

if ~exist('damp','var')
    damp = 5;
end


if damp > 1
    eta=sqrt(10./(5+damp));
else
    eta=sqrt(0.1/(0.05+damp));
end

i1 = find(Td<=tb);
i2 = find(Td>tb & Td <=tc);
i3 = find(Td>=tc & Td <=td);
i4 = find(Td>td);

Se(i1) = ag*S*(1 +(Td(i1)/tb)*(eta*2.5 - 1));
Se(i2) = ag*S*2.5*eta;
Se(i3) = (ag*S*2.5*eta).*(tc./Td(i3));
Se(i4) = (ag*S*2.5*eta).*(tc*td)./(Td(i4).^2);

end