structure generally designated 7 which in cross section has a generally arch shape as best seen in fig2 a plurality of poles such as those designated 9 and 11 extend upwardly from the bottom points 13 and 15 of a terminal edge 17 over and completely across the vault a typical pole crossing is shown at 19 and is shown in detail in fig3 here a ring 21 has been fastened to the membrane 23 by means of an element which fits within the ring not illustrated in accordance with my co pending patent application ser no 825 410 ring 21 includes a loop 25 which passes over the poles 9 and 11 and holds them loosely together allowing each of the poles to slip within the loop 25 the poles themselves are held in tension by the fabric 23 and the method by which this is accomplished is best seen in fig2 here the fabric 23 acts as a geometric cord between arcuate segments of the poles 9 and 11 at first glance it would seem that the structure would flatten out because of the tension of the poles but it is obvious from fig2 how the arcuate poles are held in tension a plurality of the poles start at one bottom edge 27 and extend in arcuate form over the top of the vault structure and terminate at an opposite edge 29 other poles such as pole 31 and 33 may terminate at an edge other than the bottom edge as is shown at connector 35 this connector of course is connected to a terminal edge 37 of the membrane one peculiarity of the vault structure of the present invention is that if sufficient.