If statement-intervals

Hello,

I had previously asked a question about my code. I have corrected the formulas but I still have a problem. My problem about this code is "a1" values. They are calculated correctly, except for the ones computed for x=Lb+d, 2Lb+d, ... 6Lb+d, which are limits of some if statements. For example, the 23th value of a1 (corresponds to x=Lb+d) should've been 12.35 but instead, somehow it is calculated zero. b1 show have been zero but instead, it is 12.35. I can't see what I am doing wrong. Any help is appriciated.

% MR-IL & Response

sp=7; % no of spans
d1=1.95; % distance between the unit load and point x
x1=zeros(sp*N+1,1); d_xs2=zeros(1,sp*N+1);
b1=zeros(sp*N+1,1); a1=zeros(sp*N+1,1); k1=226833; k2=226833; % [calculated-kN/m]
AAB=zeros(1,sp*N+1); % Area multiplication of AB triangle
ABC=zeros(1,sp*N+1); % Area multiplication of BC triangle
ACD=zeros(1,sp*N+1); % Area multiplication of CD triangle
d_xs1=zeros(1,sp*N+1); % Bending component of MR-IL
d_xs=zeros(1,sp*N+1); % Total MR-IL
resp_x=zeros(1,sp*N+1); % MR-IL Response
for i=1:sp*N+1
x1(i)=(i-1)*(Lb/N); 

if x1(i)<d1 % before load arrives
    b1(i)=0;
    a1(i)=0;
    d_xs2(1,i)=0; % support deflection component of MR-IL
    AAB(1,i)=0;
    ABC(1,i)=0;  
    ACD(1,i)=0;
    d_xs1(1,i)=0;
    d_xs(1,i)=0;
elseif x1(i)==d1 % when the load is on the first support
    b1(i)=0;
    a1(i)=0;
    d_xs2(1,i)=(Lb-x1(i))/(k1.*Lb);
    AAB(1,i)=0;
    ABC(1,i)=0;  
    ACD(1,i)=0;
    d_xs1(1,i)=0;
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); % total  MR-IL
elseif (d1<x1(i)) && (x1(i)<Lb) % load and x in the same span
    a1(i)=(i-4)*L;
    b1(i)=Lb-a1(i);
    if a1(i)<b1(i)
    d_xs2(1,i)=(a1(i)/(k1*Lb)) + (x1(i,1)*(b1(i)-a1(i))/(k1*Lb^2)); 
    elseif a1(i) > b1(i)
    d_xs2(1,i)=(b1(i)/(k1*Lb)) + (x1(i,1)*(a1(i)-b1(i))/(k1*Lb^2));
    end
    AAB(1,i)=(b1(i)*(b1(i)-d1)*a1(i)^3)/(3*Lb^2); 
    ABC(1,i)=d1*(2*a1(i).^2.*b1(i).*(b1(i)-d1) + a1(i).*b1(i).*(a1(i)+d1).*(b1(i)-d1)+(b1(i)-d1)^2.*a1(i).^2+2.*(b1(i)-d1).*2.*a1(i).*(a1(i)+d1))/(6*Lb^2);
    ACD(1,i)=(a1(i).*(a1(i)+d1).*(b1(i)-d1).^3)/(3*Lb^2);
    d_xs1(1,i) =(AAB(1,i)+ABC(1,i)+ACD(1,i))./(EI/1000); 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); % total  MR-IL
elseif (Lb<=x1(i)) && (x1(i)<=(Lb+d1)) %load is one span behind point x.
    a1(i)=(i-4)*L;
    b1(i)=Lb-a1(i);
    d_xs2(1,i) =(2*Lb-x1(i))*a1(i)/(k1*Lb^2);
    d_xs1(1,i)=0; % load is in the previous span so, no bending effect occurs in this span
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); % total  MR-IL
elseif (Lb+d1<x1(i)) && (x1(i)<2*Lb)
    a1(i)=(i-4)*L-Lb;
    b1(i)=Lb-a1(i);
    if a1(i)>b1(i)
    d_xs2(1,i)=(b1(i)/(k1*Lb)) + ((a1(i)-b1(i))*(x1(i)-Lb)/(k1*Lb^2));
    elseif a1(i)<b1(i)
    d_xs2(1,i)=(a1(i)/(k1*Lb)) + ((b1(i)-a1(i))*(x1(i)-Lb)/(k1*Lb^2));  
    end
    AAB(1,i)=(b1(i).*(b1(i)-d1).*a1(i).^3)/(3*Lb^2); 
    ABC(1,i)=d1*(2*a1(i).^2.*b1(i).*(b1(i)-d1) + a1(i).*b1(i).*(a1(i)+d1).*(b1(i)-d1)+(b1(i)-d1)^2.*a1(i).^2+2.*(b1(i)-d1).*2.*a1(i).*(a1(i)+d1))/(6*Lb^2);
    ACD(1,i)=(a1(i).*(a1(i)+d1).*(b1(i)-d1).^3)/(3*Lb^2);
    d_xs1(1,i) =(AAB(1,i)+ABC(1,i)+ACD(1,i))./(EI/1000); 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); % total  MR-IL
elseif (2*Lb<=x1(i)) && (x1(i)<=(2*Lb+d1)) 
    a1(i)=(i-4)*L-Lb;
    b1(i)=Lb-a1(i);
    d_xs2(1,i) = (3*Lb-x1(i)).*a1(i)./(k1*Lb^2);
    d_xs1(1,i)=0; % load is in the previous span so, no bending effect occurs
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); % total  MR-IL
elseif (2*Lb+d1<x1(i)) && (x1(i)<3*Lb) 
    a1(i)=(i-4)*L-2*Lb;
    b1(i)=Lb-a1(i);
    if a1(i) > b1(i)
    d_xs2(1,i)=(b1(i)/(k1*Lb)) + ((a1(i)-b1(i))*(x1(i)-2*Lb)/(k1*Lb^2));
    elseif a1(i)<b1(i)
    d_xs2(1,i)=(a1(i)/(k1*Lb)) + ((b1(i)-a1(i))*(x1(i)-2*Lb)/(k1*Lb^2));
    end
    AAB(1,i)=(b1(i).*(b1(i)-d1).*a1(i).^3)/(3*Lb^2); 
    ABC(1,i)=d1*(2*a1(i).^2.*b1(i).*(b1(i)-d1) + a1(i).*b1(i).*(a1(i)+d1).*(b1(i)-d1)+(b1(i)-d1)^2.*a1(i).^2+2.*(b1(i)-d1).*2.*a1(i).*(a1(i)+d1))/(6*Lb^2);
    ACD(1,i)=(a1(i).*(a1(i)+d1).*(b1(i)-d1).^3)/(3*Lb^2);
    d_xs1(1,i) =(AAB(1,i)+ABC(1,i)+ACD(1,i))./(EI/1000); 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); % total  MR-IL
elseif (3*Lb<=x1(i)) && (x1(i)<=(3*Lb+d1)) 
    a1(i)=(i-4)*L-2*Lb;
    b1(i)=Lb-a1(i);
    d_xs2(1,i) =(4*Lb-x1(i)).*a1(i)./(k1*Lb^2);
    d_xs1(1,i)=0; 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); 
elseif (3*Lb+d1<x1(i)) && (x1(i)<4*Lb) 
    a1(i)=(i-4)*L-3*Lb;
    b1(i)=Lb-a1(i);
    if a1(i)>b1(i)
    d_xs2(1,i)=(b1(i)/(k1*Lb)) + ((a1(i)-b1(i))*(x1(i)-3*Lb)/(k1*Lb^2));
    elseif a1(i)<b1(i)
    d_xs2(1,i)=(a1(i)/(k1*Lb)) + ((b1(i)-a1(i))*(x1(i)-3*Lb)/(k1*Lb^2)); 
    end
    AAB(1,i)=(b1(i).*(b1(i)-d1).*a1(i).^3)/(3*Lb^2); 
    ABC(1,i)=d1*(2*a1(i).^2.*b1(i).*(b1(i)-d1) + a1(i).*b1(i).*(a1(i)+d1).*(b1(i)-d1)+(b1(i)-d1)^2.*a1(i).^2+2.*(b1(i)-d1).*2.*a1(i).*(a1(i)+d1))/(6*Lb^2);
    ACD(1,i)=(a1(i).*(a1(i)+d1).*(b1(i)-d1).^3)/(3*Lb^2);
    d_xs1(1,i) =(AAB(1,i)+ABC(1,i)+ACD(1,i))./(EI/1000); 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); 
elseif (4*Lb<=x1(i)) && (x1(i)<=(4*Lb+d1)) 
    a1(i)=(i-4)*L-3*Lb;
    b1(i)=Lb-a1(i);
    d_xs2(1,i) = (5*Lb-x1(i)).*a1(i)./(k1*Lb^2);
    d_xs1(1,i)=0; 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); 
elseif (4*Lb+d1<x1(i)) && (x1(i)<5*Lb) 
    a1(i)=(i-4)*L-4*Lb;
    b1(i)=Lb-a1(i);
    if a1(i)>b1(i)
    d_xs2(1,i)=(b1(i)/(k1*Lb)) + ((a1(i)-b1(i))*(x1(i)-4*Lb)/(k1*Lb^2));
elseif a1(i)< b1(i)
    d_xs2(1,i)=(a1(i)/(k1*Lb)) + ((b1(i)-a1(i))*(x1(i)-4*Lb)/(k1*Lb^2)); 
    end
    AAB(1,i)=(b1(i).*(b1(i)-d1).*a1(i).^3)/(3*Lb^2); 
    ABC(1,i)=d1*(2*a1(i).^2.*b1(i).*(b1(i)-d1) + a1(i).*b1(i).*(a1(i)+d1).*(b1(i)-d1)+(b1(i)-d1)^2.*a1(i).^2+2.*(b1(i)-d1).*2.*a1(i).*(a1(i)+d1))/(6*Lb^2);
    ACD(1,i)=(a1(i).*(a1(i)+d1).*(b1(i)-d1).^3)/(3*Lb^2);
    d_xs1(1,i) =(AAB(1,i)+ABC(1,i)+ACD(1,i))./(EI/1000); 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); 
elseif (5*Lb<=x1(i)) && (x1(i)<=(5*Lb+d1)) 
    a1(i)=(i-4)*L-4*Lb;
    b1(i)=Lb-a1(i);
    d_xs2(1,i) = (6*Lb-x1(i)).*a1(i)./(k1*Lb^2); 
    d_xs1(1,i)=0; 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); 
elseif (5*Lb+d1<x1(i)) && (x1(i)<6*Lb) 
    a1(i)=(i-4)*L-5*Lb;
    b1(i)=Lb-a1(i);
     if a1(i)>b1(i)
    d_xs2(1,i)=(b1(i)/(k1*Lb)) + ((a1(i)-b1(i))*(x1(i)-5*Lb)/(k1*Lb^2));
    elseif a1(i)<b1(i)
    d_xs2(1,i)=(a1(i)/(k1*Lb)) + ((b1(i)-a1(i))*(x1(i)-5*Lb)/(k1*Lb^2)); 
    end
    AAB(1,i)=(b1(i).*(b1(i)-d1).*a1(i).^3)/(3*Lb^2); 
    ABC(1,i)=d1*(2*a1(i).^2.*b1(i).*(b1(i)-d1) + a1(i).*b1(i).*(a1(i)+d1).*(b1(i)-d1)+(b1(i)-d1)^2.*a1(i).^2+2.*(b1(i)-d1).*2.*a1(i).*(a1(i)+d1))/(6*Lb^2);
    ACD(1,i)=(a1(i).*(a1(i)+d1).*(b1(i)-d1).^3)/(3*Lb^2);
    d_xs1(1,i) =(AAB(1,i)+ABC(1,i)+ACD(1,i))./(EI/1000); 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); % total  MR-IL
elseif (6*Lb<=x1(i)) && (x1(i)<=(6*Lb+d1)) 
    a1(i)=(i-4)*L-5*Lb;
    b1(i)=Lb-a1(i);
    d_xs2(1,i) =(7*Lb-x1(i)).*a1(i)./(k1*Lb^2); 
    d_xs1(1,i)=0; 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); 
elseif (6*Lb+d1<x1(i)) && (x1(i)<=7*Lb) 
    a1(i)=(i-4)*L-6*Lb;
    b1(i)=Lb-a1(i);
    if a1(i)>b1(i)
    d_xs2(1,i)=(b1(i)/(k1*Lb)) + ((a1(i)-b1(i))*(x1(i)-6*Lb)/(k1*Lb^2));
    elseif a1(i)<b1(i)
    d_xs2(1,i)=(a1(i)/(k1*Lb)) + ((b1(i)-a1(i))*(x1(i)-6*Lb)/(k1*Lb^2)); 
    end
    AAB(1,i)=(b1(i).*(b1(i)-d1).*a1(i).^3)/(3*Lb^2); 
    ABC(1,i)=d1*(2*a1(i).^2.*b1(i).*(b1(i)-d1) + a1(i).*b1(i).*(a1(i)+d1).*(b1(i)-d1)+(b1(i)-d1)^2.*a1(i).^2+2.*(b1(i)-d1).*2.*a1(i).*(a1(i)+d1))/(6*Lb^2);
    ACD(1,i)=(a1(i).*(a1(i)+d1).*(b1(i)-d1).^3)/(3*Lb^2);
    d_xs1(1,i) =(AAB(1,i)+ABC(1,i)+ACD(1,i))./(EI/1000); 
    d_xs(1,i) =-(d_xs1(1,i)+d_xs2(1,i)); % total  MR-IL
    else
  disp('Error')
end

resp_x(i)= (Gvw/100).*d_xs(1,i); % response due to 1 axle

end

[Cris LaPierre]

"calculated dx_t values (resultant graph) are wrong for some intervals."

Which intervals?

[Torsten]

Maybe for both if-clauses you should include an

else
  disp('Error')
end

at the end in order to ensure that one of the cases has been used by MATLAB.

[Sinem Tola]

At least these ones:

(3*Lb+d1<=x1(i)) && (x1(i)<4*Lb)

(4*Lb+d1<=x1(i)) && (x1(i)<5*Lb)

(5*Lb+d1<=x1(i)) && (x1(i)<6*Lb)

(6*Lb+d1<=x1(i)) && (x1(i)<7*Lb)

Looks like the values jump up in these intervals. I cheked with an another program and results are close to the values one interval ahead of these above. For example:

(3*Lb<=x1(i)) && (x1(i)<3*Lb+d1)

(4*Lb<=x1(i)) && (x1(i)<4*Lb+d1)

(5*Lb<=x1(i)) && (x1(i)<5*Lb+d1)

(6*Lb<=x1(i)) && (x1(i)<6*Lb+d1)

[Torsten]

@Sinem Tola comment moved here:

Thank you Torsten, I did it and it did not result with the error. Maybe I should check my formulas one more time. Because the graph should be a concave curve.