My buddy wants to build some ramps to load a skid steer onto the back of a flatbed. He plans to build 2 ramps, each of which is built like a ladder. The side rails will be steel channel and the cross pieces will be steel angle, all hot rolled, welded. He has asked my help in figuring how light he can build it. I figure his Bobcat weighs around 4000 pounds. I own a Ryerson Steel data book which has allowable uniform loads for steel channels but it doesn't go down to the 4" or 3" channel he's considering. I can't find any useful specs online, not because I haven't googled, but because I get way too much wrong information or because I can't think of the smart way to limit or phrase the search string.
In particular, I want to know the allowable uniform load in ksi of 4" and3" channel, each the lightest channel made (approximately 3/16") with a span of eight feet.
Grant Erwin Kirkland, Washington