Abstract: The plant comprises a carrier structure formed by a network of orthogonal paths (1,2) on which carriages to be stored (5) are capable to move in two directions (xy). The displacement along (y) is provided by a robot carriage (18) carried by a carrier carriage (23) moving on a side path (24,25). The displacement of carriages along (x) is provided by bars (11) provided with pneumatic fingers (17). The carriages are either provided with two wheel trains (8,9) with axles perpendicular between each other and of which the running planes are at different levels, or provided with pads allowing the carriages to move by sliding. When the carriages run on their high wheels (9), the low wheels (8) are free in clearing channels (10). The carrier structure may be completely full except for at least one transversal row (y). For the purpose of its withdrawal, a carriage is isolated in the free row, previously displaced if required by displacement along (x) of the neighbouring carriages.