The ornamental design for a trampolineframe, as shown and described.
FIG. 1 is a perspective view.
FIG. 2 is a front view.
FIG. 3 is a rear view.
FIG. 4 is a left side view.
FIG. 5 is a right side view.
FIG. 6 is a top view; and,
FIG. 7 is a bottom view.
The claimed design is shown with a symbolic break in its length. The appearance of any portion of the article between the brake lines forms no part of the claimed design. The dotted line disclosure forms no part of the claimed design.