Supporting structure for play yard

A supporting structure adapted to construct with a boundary shelter to form a play yard, comprising:

• a ring-shaped top frame which comprises at least three head joints and three top construction posts, each of said head joints comprising two connecting ends and a tubular head sleeve integrally connecting between said two connecting ends and having a bottom opening, wherein each of said top construction posts is connected between two of said head joints by respectively connecting two ends of each of said top construction posts to said respective connecting ends of said respective two head joints;
• a ring-shaped bottom frame which comprises at least three holding joints and three bottom construction posts, each of said holding joints having an axial threaded adjusting hole and two connector ends integrally and oppositely extended therefrom, wherein each of said bottom construction posts is connected between two of said holding joints by respectively connecting two ends of said bottom construction post to said respective connector ends of said two holding joints;
• and
• at least three identical support posts mounted between said top frame and said bottom frame to define an interior cavity, each of said support posts comprising a tubular frame post having a predetermined length, and an adjustment base axially affixed to a bottom end of said frame post, wherein said bottom end is axially inserted into said adjustment base and secured by rivets and each of said adjustment bases has a threaded upper shank and a base turner adapted for steadily sitting on ground to support said supporting structure and facilitating the rotation of said support post, wherein each of said threaded upper shanks has an outer diameter equal to an inner diameter of said threaded adjusting hole of each of said holding joints, wherein said support posts are respectively penetrated through said threaded adjusting holes of said respective holding joints until top ends of said frame posts of said support posts rotatably insert into said head sleeves through said bottom openings thereof respectively, and then by rotating each of said base turners, said threaded upper shanks of said support posts are respectively rotated and screwed in said threaded adjusting holes of said holding joints, so as to adjust a distance between said top frame and said bottom frame for tensing said boundary shelter which is mounted between said top frame and said bottom frame to form said play yard.