I think you meant to use:
get_template_directory()
Codex: Absolute path to the directory of the current theme (without the
trailing slash). (link)
instead of:
get_template_directory_uri()
Codex: Retrieve template directory URI for the current theme. Checks for SSL. (link)
if you’re using include() for PHP code.
But you should rather consider using:
get_page_template()
Codex: Retrieve path of page template in current or parent template.
(link)
The function get_template_part() is also handy when want to resuse template parts.