We use plain AutoCAD. Typically we design small structures like platforms, walkways, stairs and pipe trestles. Once in a while it gets a bit more involved. We've designed bases for two cooling towers and the framing for a three story addition to a process building. Most all of this has been done utilizing small structural members (mostly tube shape, channel and angle) but our latest project, a roof extension over a waste drum storage pad, involves "W shapes" ranging in size from W18x60, W16x40, W14x22 to W12x26, W12x19 and W6x12. The columns are a combination of W10x39 and HSS12x12. We're covering this with galvanized steel decking.