結ぶ and 縛る: tying a cord and binding an object
Compare tying with the focus on binding an object securely. The two descriptions may overlap in one action using the same cord.
Tie with a cord
結ぶ, read むすぶ, means tie or form. 箱を閉じて赤い紐で結ぶ。 says that someone closes the box and ties it with a red cord.
赤い紐で identifies the cord used for tying. Preserve the nonpast description rather than changing closing and tying into completed past actions.
Bind an object securely
縛る, read しばる, means tie or bind. 荷物が崩れないよう、ひもでしっかり縛った。 says that the luggage was tied securely with cord so it would not collapse.
崩れないよう supplies the purpose, not an event in which the luggage already collapsed. Tying the cord and securing the object can be overlapping descriptions.
Read uses beyond physical objects
二つの町は文化交流の約束を結んだ。 says that the two towns made a promise to engage in cultural exchange. 結ぶ here is not physical tying.
古い慣習に縛られず、新しい方法を試したい。 says that someone wants to try a new method without being bound by old customs. The desire does not report an already completed attempt.
Can 結ぶ and 縛る describe the same action of tying luggage with a cord?
Show the answer and why
They can overlap in context. Read tying the cord versus securing the object without requiring different events for the two verbs.