Question: Warning, solutions may have been lost

I am trying to plot the shearforce of a hollow section circular beam along the hight of the cross section.

I don't seem to be able to solve the equation. I get the message:"Warning, solutions may have been lost"
Can anyone help?

The tricky part is the distance of the "point of grafity of the area above y' to the 'point of grafity of the cross section (y=0)'. This distance is a function of y and is called y_

this is de code: M_V_as_function_of_hight_cc__temporary.mw

restart: with(LinearAlgebra): with(plots, textplot, display): #Digits :=5: evalf(%): with(RealDomain):
Rout:=168.3/2:
Rin :=Rout-12.5:

T:=V*Q/(II*b):
Q:=A_*y_:
bout:=2*sqrt(Rout**2 - y**2):
bin:=piecewise( y<Rin,2*sqrt(Rin**2 - y**2)  ,  y>=Rin,0):
#bin:=Re(2*sqrt(Rin**2 - y**2)):
b:=bout-bin;
A_ :=piecewise(  y<=0,0   ,    y<Rin,evalf( int(b ,  y=y..Rout ) ) ,    y>=Rin,int(bout , y=y..Rout)    ,    y>=Rout,0);
y:=y_: AA_:=A_;
y:='y':
eq1:=2*AA_ = A_:
sol1:=solve(eq1, y_ );
y_ := sol1:
y_;
#plot(y_,y=0..Rout);