The greater than Math node returns 1 (greater than) or 0 (smaller or equal).
You probably want the Maximum option instead of the Greater than:
note that clamping a sine wave will not give you half circles, for that you will need other formula:
$$ \begin{cases} 0 & \texttt{if } M> 2r \\ \sqrt{r^{2}-\left ( M-r \right )^{2}} & \texttt{if } M \leq 2r \end{cases} $$ $$$$
$$\mathbf{M}=\operatorname{mod}\left(x+r,\ 2r+s\right)\\ \mathbf{r}=\text{radius}\\ \mathbf{s}=\text{spacing}$$
- $\mathbf{M}=\operatorname{mod}\left(x+r,\ 2r+s\right)$
- $\mathbf{r}=\text{radius}$
- $\mathbf{s}=\text{spacing}$
Or since you know the cirlce radius and the spacing between, you can put vertices in optimal positions: