The ornamental design for a loadbarsecuringmechanism, as shown and described.
FIG. 1 is a left side view for a load bar securing mechanism showing my new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a top side view thereof; pos FIG. 4 is a bottom side view thereof;
FIG. 5 is a back side view thereof; and,
FIG. 6 is a front side view thereof.
The broken lines in FIG. 3 and FIG. 6 depict environmental subject matter of load bar(s) for the invention only and form no part of the claimed design.