# 2-D Truss Analysis

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Jillian Franke on 21 Oct 2020
Commented: Long Hoang Van on 20 Nov 2020
I have got my for loop to work which was my main issue but now when I try to display the unit vectors into command window using the fprintf my unit vectors all come out as zero. When I run my for loop they are not zero. I can't seem to figure out what is causing them to be zero in the fprintf
%.... Input problem data
nNodesP = 12;
nMembersP = 21;
NodeP = zeros(nNodesP, 3); %Initialize memory storage
MemberP = zeros(nMembersP, 2);
%.... Input node coordinates
NodeP(1,:) = [0,0,0];
NodeP(2,:) = [2,0,0];
NodeP(3,:) = [4,0,0];
NodeP(4,:) = [6,0,0];
NodeP(5,:) = [8,0,0];
NodeP(6,:) = [10,0,0];
NodeP(7,:) = [12,0,0];
NodeP(8,:) = [10,1.5,0];
NodeP(9,:) = [8,3,0];
NodeP(10,:) = [6,3,0];
NodeP(11,:) = [4,3,0];
NodeP(12,:) = [2,1.5,0];
%.... Input member connections
MemberP(1,:) = [1,2];
MemberP(2,:) = [2,3];
MemberP(3,:) = [3,4];
MemberP(4,:) = [4,5];
MemberP(5,:) = [5,6];
MemberP(6,:) = [6,7];
MemberP(7,:) = [7,8];
MemberP(8,:) = [8,9];
MemberP(9,:) = [9,10];
MemberP(10,:) = [10,11];
MemberP(11,:) = [11,12];
MemberP(12,:) = [1,12];
MemberP(13,:) = [2,12];
MemberP(14,:) = [2,11];
MemberP(15,:) = [3,11];
MemberP(16,:) = [3,10];
MemberP(17,:) = [4,10];
MemberP(18,:) = [5,10];
MemberP(19,:) = [5,9];
MemberP(20,:) = [6,9];
MemberP(21,:) = [6,8];
%% .. Use a for loop to compute the position vector between connected
%nodes, the distance between connected nodes, and to compute the unit
%vectors for the direction of every member. You can use the variable name
%"UnitVecP" for the unit vectors in the planar truss.
PosVecP = zeros(nMembersP, 3); %Initialize memory storage
UnitVecP = zeros(nMembersP, 3);
OppPosVecP = zeros(nMembersP, 3);
for j = 1 : nMembersP
SN = MemberP(j,1); %SN = start node
EN = MemberP(j,2); %EN = end node
PosVecP(j,:) = NodeP(EN,:)- NodeP(SN,:);
Length(j,:) = norm(PosVecP(j,:));
UniVecP(j,:) = PosVecP(j,:)/Length(j,:)
negUniVecP(j,:) = -UniVecP(j,:);
%Finish this section to compute the position vector, length, unit vector,
%and negative unit vector for each member in the truss.
end % for j (members)
%% .Create output for command window
fprintf('%s\n' , '----------------------------------------')
fprintf('%s\n' , '-------------Planar Truss---------------')
fprintf('%s\n' , '----------------------------------------')
for j = 1 : nNodesP
fprintf('%s%8i%8.3f%8.3f%8.3f\n',' Node: ',j, NodeP(j,:)')
end
fprintf('\n')
for j = 1 : nMembersP
fprintf('%s%8i%8.3f%8.3f%8.3f\n',' Unit Vector: ',j, UnitVecP(j,:)')
end
fprintf('\n\n\n')
##### 3 CommentsShowHide 2 older comments
Long Hoang Van on 20 Nov 2020
boolean matrix?

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### Answers (1)

Asad (Mehrzad) Khoddam on 21 Oct 2020
One t was missing in UniVctor:
%.... Input problem data
nNodesP = 12;
nMembersP = 21;
NodeP = zeros(nNodesP, 3); %Initialize memory storage
MemberP = zeros(nMembersP, 2);
%.... Input node coordinates
NodeP(1,:) = [0,0,0];
NodeP(2,:) = [2,0,0];
NodeP(3,:) = [4,0,0];
NodeP(4,:) = [6,0,0];
NodeP(5,:) = [8,0,0];
NodeP(6,:) = [10,0,0];
NodeP(7,:) = [12,0,0];
NodeP(8,:) = [10,1.5,0];
NodeP(9,:) = [8,3,0];
NodeP(10,:) = [6,3,0];
NodeP(11,:) = [4,3,0];
NodeP(12,:) = [2,1.5,0];
%.... Input member connections
MemberP(1,:) = [1,2];
MemberP(2,:) = [2,3];
MemberP(3,:) = [3,4];
MemberP(4,:) = [4,5];
MemberP(5,:) = [5,6];
MemberP(6,:) = [6,7];
MemberP(7,:) = [7,8];
MemberP(8,:) = [8,9];
MemberP(9,:) = [9,10];
MemberP(10,:) = [10,11];
MemberP(11,:) = [11,12];
MemberP(12,:) = [1,12];
MemberP(13,:) = [2,12];
MemberP(14,:) = [2,11];
MemberP(15,:) = [3,11];
MemberP(16,:) = [3,10];
MemberP(17,:) = [4,10];
MemberP(18,:) = [5,10];
MemberP(19,:) = [5,9];
MemberP(20,:) = [6,9];
MemberP(21,:) = [6,8];
%% .. Use a for loop to compute the position vector between connected
%nodes, the distance between connected nodes, and to compute the unit
%vectors for the direction of every member. You can use the variable name
%"UnitVecP" for the unit vectors in the planar truss.
PosVecP = zeros(nMembersP, 3); %Initialize memory storage
UnitVecP = zeros(nMembersP, 3);
OppPosVecP = zeros(nMembersP, 3);
for j = 1 : nMembersP
SN = MemberP(j,1); %SN = start node
EN = MemberP(j,2); %EN = end node
PosVecP(j,:) = NodeP(EN,:)- NodeP(SN,:);
Length(j,:) = norm(PosVecP(j,:));
UnitVecP(j,:) = PosVecP(j,:)/Length(j,:);
negUniVecP(j,:) = -UniVecP(j,:);
%Finish this section to compute the position vector, length, unit vector,
%and negative unit vector for each member in the truss.
end % for j (members)
%% .Create output for command window
fprintf('%s\n' , '----------------------------------------')
fprintf('%s\n' , '-------------Planar Truss---------------')
fprintf('%s\n' , '----------------------------------------')
for j = 1 : nNodesP
fprintf('%s%8i%8.3f%8.3f%8.3f\n',' Node: ',j, NodeP(j,:)')
end
fprintf('\n')
for j = 1 : nMembersP
fprintf('%s%8i%8.3f%8.3f%8.3f\n',' Unit Vector: ',j, UnitVecP(j,:)')
end
fprintf('\n\n\n')
##### 1 CommentShowHide None
Jillian Franke on 21 Oct 2020
Thank you!!

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