%EXE17_04 Solves Exercise 17.4, A simple bridge - animation.
%EXER17_4 Movie of bending moment produced by a moving load.
F = 700; % travelling man's weight, N
l = 4; % bridge span, m
% Generate a reference frame
a = 1; % man's distance from left support, m
x = 0: l/8: l; % axis along bridge, m
B = x.*(1 - a/l)*F; % bending moment, Nm
for k = 1: length(x)
if x(k) > a
moment = B(k) - F*(x(k) - a);
B(k) = moment;
end
end
plot(x, B)
Mmax = F*l/4; % Maximum-maximorum moment, Nm
axis([ 0 l 0 Mmax ])
pause
% generate movie
a = 0: 0.5: l;
M = moviein(length(a));
for m = 1: length(a)
B = x.*(1 - a(m)/l)*F; % bending moment, Nm
for k = 1: length(x)
if x(k) > a(m)
moment = B(k) - F*(x(k) - a(m));
B(k) = moment;
end
end
plot(x, B), axis([ 0 l 0 Mmax ])
M(:, m) = getframe;
end
disp('Now try, for instance, MOVIE(M, 3, 5)}.
