Odd part to ID

In one of the clearouts I am doing we found around 10 of these arcs. Another guy came and had a look and was certain it was aircraft, but had not been used as there were no holes anywhere. More the intriguing thing is the sheer size of them. They had been in the place for over 40 years, and to give you an idea of the size, the height of the fence is 7ft. The other guy and myself both thought possibly B29 but are not 100%. Its must have been a pretty big aircraft though !

Anyone able to help? I’ve got plenty more odd parts to ID coming up….:rolleyes: