A frame structure comprising a plurality of leg members, a plurality of top-corner fittings, a plurality of slide fittings and a plurality of flexible-pole members. Each leg member comprises a first end and a second end. A top-corner fitting is attached to the first end of each leg member. A slide fitting is coupled to each leg member and is adjustably movable along a length of the leg member between the first end and the second end of the leg member. Each flexible-pole member corresponds to a leg member, and each flexible-pole member comprises a first end and a second end. The first end of each flexible-pole member is coupled to a slide fitting, and a second end of each flexible-pole member is coupled to a central hub member. Each flexible-pole member forms an arching shape when the frame structure is in an erect, unfolded position.