structural drawings

huangyhg

structural drawings
according to a recent publication by aisc, "when the engineer turns the structural drawings over to the fabricator the connections discussions start. these take a lot of time that could be greatly reduced if the engineer would indicate actual end reactions on the members." has anyone been doing this? we usually leave connections up to fabricator,to develop full capacity of member at connection.
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my work is mainly with special structures and bridges, we rarely ever leave connection design up to the fabricator.  most of the time this is something that is driven by the owner, who, in most instances, is an engineer as well.  for example we do most of our work for state dots, army coe, federal gsa etc.  they simply want to know what they are getting and that all of the coordination issues are resolved before other parties begin work.
in more than 30 years of practising in a design/construct contractors office and as a sole practitioner consultant, including work on large industrial buildings, heavy plant structures (coal washeries, major conveyors etc), mining structures, steel bridges of various sizes and major temporary work, i have never seen connection design left to the fabricator.

unless the connections are wierd and wonderful, with the exception of splice details where moment and shear are required, i usually leave the connection to the fabricator just specify that connection must develop 50% or web shear or something of that ilk, min of 2 bolts, a325 grade 1, etc... and then check to see if there's not something that's the exception...
i agree with dik.  for simple shear connections, i usually just show the end reactions on the drawings and let the fabricator do it, and include a note like dik said.
it depends where you are working too. here in botswana we have inherited normal british practice which is to give no connection design information to the fabricator and let him design them. unfortunately i don't think there are any fabricators here who employ structural engineers. what i tend to do is fully design the connections so there is no doubt. but what mostly happens is that the fabricator shows something on his shop drawing and this then gets checked by the engineer. it's kind of like designing connection by guesswork for the fabricator and then passing it to the engineer for approval. i agree with the aisc that connections should be thought through before they get to the fabricator. if you have a really good fabricator then i would discuss them with the fabricator to help with buildability but then that applies to the whole structure and not just the connections.
carl bauer
carl:
not so much with steel, but with other materials where the project is located 'out of the way', perhaps like botswana, even for simple projects, i tend to 'overdetail' because the control or skill isn't there... saves a pile of questions afterwards...
in the u.s. there is a variety of practices, depending on the type of clients and the general size of the project.  per austim and qshake above, many projects like bridges and power plants necessitate the full detailing of each and every connection.  
some firms have taken upon themselves the task of connection design in all instances, probably out of concern for liability in the wake of the hyatt regency collapse, etc.
the firms i have been associated with have progressed from not showing anything to creating a full connection schedule.  in cases of unique, odd, or skewed connections, we always detail and design it all.  in the case of typical beam/column beam/beam connections we use a standard schedule through a spreadsheet and require our engineers to check each and every connection against the calculated capacity.
for standard connections, there isn't anything wrong with allowing the fabricator to design it, as long as you, the engineer of record, are satisfied with the process and result (checking their shops to spot check the more typical connections and fully verify the complex ones).  after all....you are ultimately responsible for the connection...not the fabricator.
the tendency in the uk for structural steelwork connections design is to leave them for the fabricators. member reaction forces are noted on the design drawings by the original designer who then "checks and reviews" the fabricators connection design and details before approving them for construction. the original designer remains in overall charge of the "design".
having worked for a fabrictor in the past, i found that they prefer to do the connections in-house so that they can utilise their "standard cleats and endplates", for faster fabrication in the automated modern workshops.
this split works well as the consultant make a saving on his fee by not having to carry out this part of the design, and the fabricator is happy as he can design and detail the connection to suit his workshop. a win-win solution.
for structural concrete detailing however the recent tendency in the uk is to leave the reinforcement detailing to the contractor .....once again the consultant passing on a labour intensive element of the design work onto the contractor. in this case the reinforcement detailing is rarely checked in thorough detail.  
is australia on its own in having promulgated a set of standardized structural steel connections?  we have been doing that for about twenty years or more.
for most straight forward connections, we can simply go to our aisc (ie australian isc) connections reference, check the number of bolts needed to provide the required capacity, and fully specify the connection (cleat dimensions, bolt diameter and spacing, coping details, weld quality etc) by means of a simple reference to the aisc publication.
the range of connections covered includes welded or bolted splices or end connections and five different types of flexible end connections, plus purlin cleats and base plates.
this practice avoids the need to consider each fabricator's 'special cleats and end plates' since all fabricators are set up for the standard sizes, whether automated or not.
thus i would suggest that we have a real win/win situation.  the fabricators are not faced with too many idiosyncratic connection details, and the engineers have full control over one of the most vital aspects of their designs.
as for leaving reinforcement detailing to a contractor ('unchecked in thorough detail'), my  stomach churns at the very thought.  the uk lawyers must be rubbing their hand in glee.
the american isc asd and lrfd have tables upon tables of connection capacities for different lengths and number of bolts, single shear, double shear, eccentric bolt loading, etc.  we also specify that fabricators and erectors be aisc certified.  so i don't see much of a problem letting the fabricator do the connection detail (unless it's an unusual connection).  besides, you get shop drawings to review, so you can check their connections then.  also, ask for a connection capacity chart with your shop drawings.