The ornamental design for the structural strut joint, as shown.
FIG. 1 is a perspective view of a structural strut joint which has been
sectioned through one quadrant thereof showing my new design;
FIG. 2 shows a midline sectional view of the outer portion of the
structural strut joint with the inner portion having a partially
fragmented midline sectioned view in the upper portion thereof; and,
FIG. 3 shows an upright elevation view of the entire structural strut joint
.