haven't tried it but a shelter made of electrical conduit and reinforced plastic like this (http://hardware.hardwarestore.com/27...lm-630556.aspx
) could be made easily. Have built a lot of winter shelter on construction sites with the stuff and it holds up well. Construction site shelter uses scaffolding and a clip to hold plastic in place., I'm thinking you could use conduit and bend to form a half circle hoop and cover with the plastic using split plastic pipe used for exterior conduit(the gray stuff)-just make sure the plastic is very secure, not using enough attachment points will cause it to be slack and wear out much quicker than you want. Nice thing is , could be taken down if you want and stored until next winter.
kinda like these car shelters: