should the designer consider the construction process

huangyhg

should the designer consider the construction process
aggieyank asked in "contractor calls about construction loading" what responsibility does the structural engineer have to check the suitibilty of the structure for the contractors equipment. the subsequent discussion has brought me to ask the following question: how much should the engineer consider the construction practice in his design, and what should he communicate to the contractors about the construction loads and sequence to the bidders and contractors.
my take is that although the designer can not consider exactly how the structure will be built, some consideration of the construction process and communication of those thoughts will go a long way in achieving more constructable projects that will go more smoothly and more profitably for everyone. what does everyone else think?
over time, it becomes second nature to think about how a contractor will build something... becomes a matter of detailing for constructability.
dik
i've worked for several clients where the finished engineered product is value engineered by the contractor wherein the client pays for us to review the contractors design and construction.  that is the only way i would consider the contractors point of view unless the project were db.  when the client pays for an engineering review and it's in the scope i have no problems with it.
regards,
qshake
eng-tips forums:real solutions for real problems really quick.
some one has to build the structure, that you design.  as dik mentioned with experience an engineer develops an understanding of how a contractor will construct the building.  
means and methods are not something an eor should specify, however an engineer should have a basic understanding of how buildings are constructed.  a designer looks really foolish if  his or her design is not buildable.  
i dealt with a project where once the beams and columns were in place it was not physically possible to place the roof rafters.  in this case a modification in the design solved the problem.
there was a way that the building could be built.  it would have required placing the rafters providing temporary support for them, sliding the 70' long supporting beam in horizontally under the rafters.  holding the beam in place while placing the support columns for the beam.  this would have required at least two cranes, probably three and a large number of man hours to complete.
the argument,that when the contractor submitted a bid on the job, he was agreeing that the building could be built: only goes so far.  in a case like the one i described above a large contractor will refuse to construct the building until design changes are made.   smaller contractors might walk away from the job, figuring that the loss incurred would be less then the loss if he or she actually tried to complete the project with no changes.
   
i call contractors all the time asking on how they are going to build certain things.  then i put it on paper.  many times though our client is the owner/archictect not the contractor so we have no idea who will build it.   
the bottom line is that if you design in ways which cannot be constructed, it will eventually get back to your clients and make you look bad.
i have given guidance on the drawings the stages by which something is to be constructed if it is critical for the design to actually work. but 99% of the time i do not give instructions and leave it to the contractor, unless i notice when something may not be buildable by ordinary methods or if the ordinay methods adversely affect the capacity of my design. there is also something called staged construction analysis that might be of interest to you.
isn鈥檛 one of our responsibilities to design for economy and also for constructability? are you going to tell your client 鈥渂y the way, i鈥檓 not sure if you can build this and didn鈥檛 even verify if there is a more economical way.鈥?of course you have to consider how it is going to be built 鈥?you don鈥檛 have to specify it on the drawings, unless is critical like haynewp mentioned. in concrete construction, for example, labor and formwork are more expensive than the actual concrete. so, don鈥檛 design a slab with drop panels that cannot be easily or economically formed with actual lumber sizes or pre-fabricated forms just to save 0.5鈥?in concrete.
i agree with the other posts that the engineers should be aware of standard construction processes and reflect them in the details.  occassional extraordinary cases requiring special sequencing may warrant additional notes for the contractor's benefit which they may use or they may use alternate methods of their own.
the bottom line is: documents must be buildable.
depends.  the owner will be pissed if you make a heavy building just to make it easy on the contractor, but will be happy if you design something that gets built on schedule.  you gotta balance the two, and i guess that just comes with experience of knowing what things are commonplace.
you should design a structure that 'can' be built in an efficient and safe manner.
you should not specify 'how' it is to be built as the contractor usually has far more knowledge and experience at this than the designer.
calling up a specific construction method may in fact cost the client more money as the contractor may have put in a better tender if they were allowed to do it their way.
the exception to this rule is when the project involves demolition or underpinning. in these cases i always call up where shoring is required even if i dont call up a capacity.
this is most certainly an interesting thread.
the posts i have read in this thread, buttress the widely held view that, the pratice of strucural engineering, depends amongst other things on: the region/area one is located, insurance and litigation concerns, client, nature of project,.....