Bar, barrier, barricade mean something which hinders or obstructs.
Both bar and barrier apply to something that prevents free communication or passage; more specifically, bar frequently suggests a restriction of ingress or egress, while barrier suggests an obstacle to advance, progress, or attack; bar also may suggest a simple structure and barrier a more extensive or elaborate one.
Barricade is chiefly used in the sense of an obstruction thrown across a street or way to check a hostile advance.