A job that will soon reach the top of the pile is making a cattle grid, primarily to stop the dog from wandering down the drive and on to the road. It needs to be 4-5m wide and about 2m front-back. I'll probably cast a concrete trough to put it in, with one side open to an adjacent dingle so water and hedgehogs can escape, and so it can be hosed-out. I'm only just starting to think about how to do it, but the current thought is to get four 2m lengths of I-section for the main supports and use scaffold pipes for the top surface. The I-sections would sit on concrete piers to get sufficient depth. I'd weld the pipework in four sections so it's removable.
Does this sound sensible?
How can I calculate what load a scaffold pipe can take without permanently deforming?
The scaffold pipes will be galvanised so I'll be grinding the joint areas clean before welding, and then spraying with a zinc-rich paint. How can I protect the I-sections from rust?
Any other thoughts, ideas, considerations?