I don't directly account for the weight of the connections I mean. If you were to compare the actual weight of the connections to the total weight of the member being connected, it's likely negligible
I use 5% because that's just what's done at my firm. The actual weight is pretty small, and when you account for the fact that beams are actually shorter than the gridline to gridline distance and coped usually, zero is probably pretty damn close. But 5% of beam selfweight is pretty damn close to zero relative to the other loads on the structure, so I don't think it's a practice worth changing.
We have used 5% in the past as well for just that reason. Probably actually underestimates the costs somewhat because you are typically looking at a lot of labor to fabricate, plus many of the materials (bolts, nuts, etc.) are obviously some of the more expensive items per pound.
Delagina:
This is a question you should be asking some of your fabricating friends, or fabricators who have worked on your last few jobs. Different fabricators will have developed slightly different numbers for estimating lbs. of connection material/steel per ton of major materials involved on the job. This will also be highly dependant upon the type and complexity of the job. 14' deep plate girders and complex architecturally exposed steel details or trusses, etc. are just radically different in terms of gross tons of steel vs. connection costs. Probably more important than the lbs. of connection material is the estimator’s sharp eye as involves things like the complexity of the details, how well are the details and connections defined on the construction documents, how will are the connection loads shown, are they going to be responsible for the design of the connections, etc., etc. Keeping it clean and simple, on your part, will always buy you some more material, and save many fabrication hours and designing/detailing time on their part, and buy you a less expensive job. Ask some of those fabricators how each one of these types of things figures into the total cost. On large repetitive jobs, we would sometimes go back to the owner or EoR with our own (equal or better) detail, which was more amenable to our fab. methods and equipment set up, if we thought we could save them money, or make life easier for ourselves without any detriment to the quality of the finished project.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
