p1=1.71;
p2=1.71;
p3=5.90;
Ei=30000000*0.00023976
l1=8;
l2=16;
l3=24;

EQ1=Ei v1''''[x]==-p1;
EQ2=Ei v2''''[x]==-p2;
EQ3=Ei v3''''[x]==-p3;

sol=DSolve[{EQ1,EQ2, EQ3},{v1[x],v2[x],v3[x]},x];

v1[x_]=v1[x]/.sol[[1]];
v2[x_]=v2[x]/.sol[[1]];
v3[x_]=v3[x]/.sol[[1]];

φ1[x_]=v1'[x];
φ2[x_]=v2'[x];
φ3[x_]=v3'[x];

M1[x_]=Ei v1''[x];
M2[x_]=Ei v2''[x];
M3[x_]=Ei v3''[x];

T1[x_]=-Ei v1'''[x];
T2[x_]=-Ei v2'''[x];
T3[x_]=-Ei v3'''[x];

cc1=v1[0]==0;
cc2=-Ei v1''[0]==298.13;
cc3=v1[l1]==0;
cc4=v2[l1]==0;
cc5=v1'[l1]-v2'[l1]==0;
cc6=v1''[l1]-v2''[l1]==0;
cc7=v2[l2]==0;
cc8=v3[l2]==0;
cc9=v2'[l2]-v3'[l2]==0;
cc10=v2''[l2]-v3''[l2]==0;
cc11=v3[l3]==0;
cc12=-Ei v3''[l3]==226.5;

sol1=Solve[{cc1,cc2,cc3,cc4,cc5,cc6,cc7,cc8,cc9,cc10,cc11,cc12},{C[1],C[2],C[3],C[4],C[5],C[6],C[7],C[8],C[9],C[10],C[11],C[12]}]

v1[x_]=v1[x]/.sol1[[1]];
v2[x_]=v2[x]/.sol1[[1]];
v3[x_]=v3[x]/.sol1[[1]];

v1[x];

v2[x];

v3[x];

g1=Plot[-Ei v1''[x],{x,0,l1},PlotRange-> All];

g2=Plot[ -Ei v2''[x],{x,l1,l2},PlotRange->All];

g3=Plot[-Ei v3''[x],{x,l2,l3},PlotRange->All];

Show[g1,g2,g3] (*MOMENTO FLETTENTE*)

Ei v1''[0]

Ei v1''[l1]

Ei v2''[l2]

Ei v3''[l3]

g1=Plot[Ei v1'''[x],{x,0,l1},PlotRange-> All];

g2=Plot[ Ei v2'''[x],{x,l1,l2},PlotRange->All];

g3=Plot[ Ei v3'''[x],{x,l2,l3},PlotRange->All];

Show[g1,g2,g3] (*TAGLIO*)

-Ei v1'''[0]

-Ei v1'''[l1]

-Ei v2'''[l1]

-Ei v2'''[l2]

-Ei v3'''[l2]

-Ei v3'''[l3]