Most structural engineers would be able to come up with a suitable design approach once you provide them with the configuration and functioning of the davit. You can look up Dennis R.Moss, "Pressure Vessel Design Manual", Chapter 6. Related equipment, for some guidance on Davit Design...
Can't tell you where to find it, but I happen to have an old data sheet of WEL-TEN 80 that states the following. WEL-TEN 80 is a high strength steel for welded structures. It is a low carbon (0.18%), quenched and tempered, low alloy steel. Chemical and mech. properties are equivalent to...
