structure and the end portions of main beams 13 are longer in the preferred embodiment by u00bc of module and by u00be of module than the main beams 13 of the remainder of the structure a similar solution that does not involve any remarkable constructive complication and at the same time solves the problem of the parking places for the disabled makes it possible to realize at the upper level as shown in fig7 a structure with the sides perfectly orthogonal so that the available area may be exploited at best for the construction of the parking structure fig7 also o shows schematically the position of an access ramp 2 but it is clear that the number and the position of such ramps that in any case are preferably two in order to be used one way will vary depending on the design requirements of each case fig8 schematically shows an overall view of a parking structure according to the invention with both levels but limited to a partial section which does not include the sites where the ramps 2 are placed the upper level of the structure is partially sectioned to show the position of the columns 3 and of the stalls 17 at the lower level it is evident that at the higher level since the bracing hindrance is not present the stalls distribution may be designed in the most various way in accordance with the design choice of each case the demountable parking structure according to the invention finally may comprise bases 4 for resting on the ground having a hinged foot means for adjusting the columns length such ad threaded joints 5 node elements 12 of the same kind as those provided by ep 0364414 and schematically illustrated for instance in fig2 elements as pedestrian stairs.