Here are some pics of the polytunnel in my earlier thread

[kindlett]

we have now put a walkway down the middle still holds 540 nets .

[Gillsgardening]

Wait until the wind gets hold of it! I bought two both wrecked within 9 months

[Sussex Groundie]

Sadly Polly Tunnels can have mishaps, but as you have a lot of air running through it should do better, this was sited next to a hedge with about a foot of soil holding down the poly sides. Used for 200+ tomatoe plants. One night in January and poof

[cornish wood burner]

Sadly Polly Tunnels can have mishaps, but as you have a lot of air running through it should do better, this was sited next to a hedge with about a foot of soil holding down the poly sides. Used for 200+ tomatoe plants. One night in January and poof

These is a few things to do to vastly improve the strength of this one Sussex . 3x3 cross members at the ends. Even a short length above the door spreads the load on the hoop via the p clips.

Most important is a brace from the ridge bar to the cross member We use a vertical from the cross bar to the top of the hoop then brace from the cross bar to the ridge to make a triangle.

Wrap your poly tighter around the end hoop and batten tight to the door posts. Posts are needed the other end too, fasten them to the underside of your cross bar. Also brace from the ground diagonally to halfway uo the hoop. It looks like your failure was the end hoop bending in because of no braces. Polythene could be a bit tighter along the sides and ends as well. When you fit the poly put a little soil over it in the trench and go along and lift and flap as you go. Fold the polythene back over the soil in the trench to help it grip then fully fill. A tunnel should last at least 5 years even in the most windy site. Low and sheltered like yours longer. I hope that will help.