MATLAB: Stopping a loop at the maximum value of y and finding the x from the maximum y

helpmaximum valuestopping a loop

Hi everyone,
How can i stop the loop when i get the maximum M(i) and how do i know what is the value of the x (phi) for the maximum value of M?
Thank You.
b=300;  %mm

d=400;  %mm
fc=40;  %Mpa



Ecm=22*(fc/10)^0.3*10^3;  %Mpa
Es=200000;  %Mpa
As=2400;  %mm^2
fy=400;  %Mpa
epsc1=min(2.8/1000,0.7*fc^0.31/1000);
epscu=3.5/1000;
k=1.05*Ecm*epsc1/fc;
epscmv = linspace(0.05, 3.5, 50)*1E-3;
for i=1:50(epscmv);
    epscm = epscmv(i);
    funC=@(epsc) (k*epsc/epsc1-(epsc/epsc1).^2)./(1+(k-2)*epsc/epsc1);
    compression=@(c) b*fc*c/epscm*integral(funC,0,epscm)/1000;
    tension=@(c) min(Es*(d-c)/c*epscm*As/1000,fy*As/1000);
    c(i)=fsolve(@(c) compression(c)-tension(c),1);
    funM=@(epsc)(k*epsc./epsc1-(epsc./epsc1).^2)./(1+(k-2)*epsc./epsc1).*(d-c(i)+(c(i)./epscm).*epsc); 
    M(i)=b*fc*c(i)/epscm*integral(funM,0,epscm)/1000000;
    phi(i)=epscm/c(i);
end
Mmax=max(M(i))
plot(phi, M)
grid on
xlabel('phi  [1/mm]')
ylabel('Moment  [kNm]')

Best Answer

b=300;  %mm

d=400;  %mm
fc=40;  %Mpa



Ecm=22*(fc/10)^0.3*10^3;  %Mpa
Es=200000;  %Mpa
As=2400;  %mm^2
fy=400;  %Mpa
epsc1=min(2.8/1000,0.7*fc^0.31/1000);
epscu=3.5/1000;
k=1.05*Ecm*epsc1/fc;
epscmv = linspace(0.05, 3.5, 50)*1E-3;
for i=1:50(epscmv);
    epscm = epscmv(i);
    funC=@(epsc) (k*epsc/epsc1-(epsc/epsc1).^2)./(1+(k-2)*epsc/epsc1);
    compression=@(c) b*fc*c/epscm*integral(funC,0,epscm)/1000;
    tension=@(c) min(Es*(d-c)/c*epscm*As/1000,fy*As/1000);
    c(i)=fsolve(@(c) compression(c)-tension(c),1);
    funM=@(epsc)(k*epsc./epsc1-(epsc./epsc1).^2)./(1+(k-2)*epsc./epsc1).*(d-c(i)+(c(i)./epscm).*epsc); 
    M(i)=b*fc*c(i)/epscm*integral(funM,0,epscm)/1000000;
    phi(i)=epscm/c(i);
end
[Mmax,idx]=max(M);%this is how you would get the max of M and the index at the maximum
phiAtmax=phi(idx);%using the index at maximum you can get the phi at the maximum
plot(phi, M)
grid on
xlabel('phi  [1/mm]')
ylabel('Moment  [kNm]')
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