A purlin connection assembly including a purlin, a frame segment and a spring. The purlin has a protrusion that is receivable in a first end of a slot of the frame segment. The purlin is slidable to a smaller second end of the frame segment. Locking engagement is achieved in a direction parallel to the frame segment by a pair of push buttons projecting from the frame segment that flank the purlin when in the second end, and in a direction perpendicular to the frame segment by constraining of a flared head of the protrusion in an interior of the frame segment when in the second end. The push buttons are part of a spring compressingly disposed in the interior of the frame segment, wherein the first button and the second button are biased to extend outwardly through button holes of the frame segment.