Additive genetic variance components from LMER in R
From what I understood of your code and what you are asking I am guessing that you do the following:

Generating a virtual set of 40 individuals (lines) of which you have 200 measurements (repetitions). You say that they are full siblings, so they share both parents. Then you use the lmer function (which I am not familiar with) to give you the total variance, within-group variance and between-group variance, ($V_{T}, V_W, V_B$ respectively). What you call $V_L$ would be the $V_W$. 

We know that $V_P=V_A+V_D+V_E$ 

In full siblings we also know that $V(A,A')=\frac{1}2V_A+\frac{1}4V_D$ where $A$ is the additive value and $D$ is the dominance value because they share a quarter of their gene combinations.  

If you are treating with full siblings the $V_W$ should be then the $V_E$ and the $V_B$ would be the $\frac{1}2V_A+\frac{1}4V_D$ as you are seeing the variance between siblings. 

So no, you are not calculating correctly the $V_A$ because you are missing your $V_D$ on your counting. The code itself looks fine for what I understood, but maybe you should take that to corssvalidated with the R tag