How to determine the Bending Moment Diagram for simply supported beam with UDL and two point loads???

Hi all,

I was to prepare the Shear force diagram and bending moment diagram for simply supported beam with UDL acting throughout the beam and two Point Loads anywhere on the beam. I was able to determine the Shear Force Diagram, but currently I'm struggling with the Bending moment diagram. I'm not too familiar with the Matlab I have to say, so if someone could assist me I will be grateful.

In this file user inputs the values for: Span UDl Point Load 1 Point Load 1 distance from LHS Point Load 2 Point Load 2 distance from LHS

I have it worked out on paper, but I cannot do it in Matlab.

Regards, Borys Szewczyk

PLEASE HELP

%This code will solve for simply supported beam with UDL and up to two
%point loads.

clear all, clc

%Data Input
Span=input('Please enter the length of the beam in meteres: ');
UDL=input('Please specify the magniture of UDL in kN/m: ');
P1=input('Please enter a magnitude of the Point Load 1 in kN: ');
PL1=input('Please enter the distance at which Point load 1 is acting from left hand side in meteres: ');
P2=input('Please enter a magnitude of the Point Load 2 in kN: ');
PL2=input('Please enter the distance at which Point load 2 is acting from left hand side in meteres: ');
PL3=(Span-PL2)/2;
%Calculate the Reactions
R1 = (P1*(Span-PL1)/Span)+(P2*(Span-PL2)/Span)+(UDL*Span/2) %Left Support Reaction
R2 = ((P1*PL1)+(P2*PL2)+(UDL*Span*(Span/2)))/10 %Right Support Reaction

%Create Beam array
n = 1000;                %Number of discretization of x-axis.
D=Span/n;        %Increment for discretization of x-axis.
x = (0:D:Span);  %Generate column array for x-axis.

SF = zeros(size(x,1),1);    %Shear force function of x.
BM = zeros(size(x,1),1);    %Bending Moment function of x.

%Shear Force Calculations
for i=1:n+1

      if x(i)<PL1 %Region 1
          SF(i)=R1-(UDL*D*(i));
          SFO(i)=0;

      elseif x(i)<PL2 %Region 2
          SF(i)=R1-(UDL*D*(i))-P1;
          SFO(i)=0;
          else SF(i)=R1-(UDL*D*(i))-P1-(UDL*(PL2-PL1))-(UDL*(Span-PL2))+R2;
              SFO(i)=0;
      end
  end

%Bending Moment Calculations

for i=1:n+1

      if x(i)<PL1 %Region 1
          BM(i)=R1*x(i) ;
          BMO(i)=0;

      elseif x(i)<PL2 %Region 2
          BMO(i)=R1*x(i)-UDL*((x(i)-PL1)^2)/2; ;
          BMO(i)=0;
          else BM(i)=(R1*D*(i))-(UDL*D*(i))-P1-(UDL*(PL2-PL1))-(UDL*(Span-PL2))+R2;
              BMO(i)=0;
      end
  end

%SFD AND BMD PLOTTING

subplot(3,1,1)
plot(x,UDL,'b.-')
grid
title('Span of the Beam')
xlabel('Span (m)') %x-axis label
ylabel('UDL (kN/m)') %y-axis label

subplot(3,1,2)
plot(x,SF,'m',x,SFO,'b','linewidth',1.5)
grid
title('Shear Force Diagram')
xlabel('Span (m)') %x-axis label
ylabel('Shear Force (kN)') %y-axis label

subplot(3,1,3)
plot(x,BM,'m',x,BMO,'b','linewidth',1.5)
grid
title('Bending Moment Diagram')
xlabel('Span (m)') %x-axis label
ylabel('Bending Moment (kN-m)') %y-axis label

[Shadi Fakher]

thing just doesnt make sense, the user cannot enter the length of the Uniform Distributed Load... the program allows him to enter the magnitude only , so how is this compatible to find the moments ? another question, what does the reaction equations be if i want to make the code also allow the user to enter the location of the supports?