Squirrels. They’re the worst vermin. From them the garden required complete protection. So, I built a small Garden House.
I’ve long been fascinated by arches and so decided to incorporate them as a design element. The canopy of the Garden House is constructed of 3’ x 10’ sections of 3/4” thick-wall PVC framed poultry netting and garden stakes for cross members to hold up the netting. The garden stakes are insufficient to restrain a load of snow, and last weekend the canopy of my garden collapsed.
The nature of arches is that they carry the load downwards into their supports, but also distribute force outwards as well. To counter this I’ve used 14 gage galvanized wire to restrain the lateral forces on the side walls of the garden. The packaging of the wire stated a working load of 75 lb. Several inches of heavy, wet, sticky snow fell last weekend. It is reasonable that the load on the canopy was 1/2 ton. Possibly more.
I believe the structural failure was due to the garden stakes not being able to hold the weight upon them and bending downward causing the PVC began to be bent inward and the arches failed to be in compression and were not able to restrain the forces allowing the structural collapse.
I fear however that the failure may be with the wire. Evidence shows that these wires are now loose. They may have rusted through. They may have broken under tension. They may just be loose because they are no longer under a load. I will have to dig down to the anchors and assess their condition but the ground is still frozen. Usually, I start planting outside by the last week of March. This winter has been unusually wet, cold and long here in Minnesota. Still, I have the itch to get started. Beet and pepper plants are ready and tomatoes should germinate soon. Planting the garden can be delayed only a few more weeks. Argh!
Last fall I began strengthening with wooden crossmembers. I only had time for this one. It also failed. You may notice in the picture that the wood is on the wrong side of the netting. I believe that when the others fell away this one also failed because because the PVC was then free to rotate in the elbows allowing the arches to be inverted.
I have two other projects which I wish to incorporate structural elements in tension. Now I’m nervous about why the Garden House canopy failed. I have yet to verify that the failure was not in the wires. All would be much worse if it had been a large aquarium. Consider the load on the center brace of a large aquarium.
I’ve long been fascinated by arches and so decided to incorporate them as a design element. The canopy of the Garden House is constructed of 3’ x 10’ sections of 3/4” thick-wall PVC framed poultry netting and garden stakes for cross members to hold up the netting. The garden stakes are insufficient to restrain a load of snow, and last weekend the canopy of my garden collapsed.
The nature of arches is that they carry the load downwards into their supports, but also distribute force outwards as well. To counter this I’ve used 14 gage galvanized wire to restrain the lateral forces on the side walls of the garden. The packaging of the wire stated a working load of 75 lb. Several inches of heavy, wet, sticky snow fell last weekend. It is reasonable that the load on the canopy was 1/2 ton. Possibly more.
I believe the structural failure was due to the garden stakes not being able to hold the weight upon them and bending downward causing the PVC began to be bent inward and the arches failed to be in compression and were not able to restrain the forces allowing the structural collapse.
I fear however that the failure may be with the wire. Evidence shows that these wires are now loose. They may have rusted through. They may have broken under tension. They may just be loose because they are no longer under a load. I will have to dig down to the anchors and assess their condition but the ground is still frozen. Usually, I start planting outside by the last week of March. This winter has been unusually wet, cold and long here in Minnesota. Still, I have the itch to get started. Beet and pepper plants are ready and tomatoes should germinate soon. Planting the garden can be delayed only a few more weeks. Argh!
Last fall I began strengthening with wooden crossmembers. I only had time for this one. It also failed. You may notice in the picture that the wood is on the wrong side of the netting. I believe that when the others fell away this one also failed because because the PVC was then free to rotate in the elbows allowing the arches to be inverted.
I have two other projects which I wish to incorporate structural elements in tension. Now I’m nervous about why the Garden House canopy failed. I have yet to verify that the failure was not in the wires. All would be much worse if it had been a large aquarium. Consider the load on the center brace of a large aquarium.
