MOTOR-VEHICLE STRUCTURE HAVING A HOLDING ELEMENT FOR HOLDING A SPARE WHEEL OR OTHER COMPONENT ON A FLOOR PORTION MADE OF PLASTIC MATERIAL

A motor-vehicle structure includes an underbody portion (14) of sheet-metal defining an aperture (12) with within there is mounted a floor portion (10) of plastic material or composite material, for housing a spare wheel (R) or other component (C) of a vehicle, such as an electric or electronic component and/or for example a unit (ESS) for accumulating electric energy. To said floor portion (10) of plastic material or composite material there is associated a holding element (16) having at least a first part anchored to the underbody portion (14) of sheet-metal and at least a second part which can be anchored to said spare wheel (R) or said other component, so that in case of an accident, said holding element prevents said spare wheel (R) or said other component (C) from being projected far away from the underbody structure, by constraining it instead to remain within a distance corresponding to one dimension of said holding element.