contractor using screw instead of bolt for connector

huangyhg

contractor using screw instead of bolt for connector
i am dealing with a contractor that has placed screw instead of bolt for simpson connector; he is telling me that it has enough capacity for the applied load.
i am not sure what should i respond to contractor, does he have any leg to stand on? if contractor does not follow the plan, is engineer still liable?
i assume here that you do not support what the contractor wants to do.  have you considered bringing this non-compliance issue to the attention of the building inspector assigned to cover the project?
can't you simply compair the specs of the screw with that of the bolt. if it falls short, show the contractor this.
it's always better to argue someone's "opinion" with with facts on your side.
and if you find that it is equivilant, then you have an ace up your sleve for the next time.
wes c.
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there are no engineers in the hottest parts of hell, because the existence of a 'hottest part' implies a temperature difference, and any marginally competent engineer would immediately use this to run a heat engine and make some other part of hell comfortably cool.  this is obviously impossible.
how does he know what the applied load is?  is he an engineer?  if the bolt was a through bolt, it is unlikely that the screw could develop the same strength as the bolt.  however, if the load is low enough, the screw could possibly be strong enough.  check the 2005 nds - they have all the info you need to calculate the screw and bolt capacity.
does the simpson connector allow the use of either bolts or screws?  if so, are the allowable loads for each type of fastener (from the simpson catalog) greater than the applied load?
liability issue:
if you know that construction was not done according to plans.  you have an obligation to check construction for adequacy or have construction corrected to what is shown on plans.
check the adequacy of the as-built construction.  if not adequate insist that contractor make changes.  if as-built construction is adequate, inform owner (& building inspector) that the contractor made a field change to the plans and that you have checked the adequacy of field change.
if the contractor is telling you that his deviation has enough capacity, tell him to prove it to you.  you already designed it once, so if you have to check out this deviation, you should also get paid to do it.  why should you have to do free engineering for someone elses screw up? i would inform your client of what the contractor did, letting it be known that what happened was an unauthorized change by the contractor.  let your client know how much your fee will be to either check the adequacy of the change or to review any "proof" provided by the contractor.  if your client (the architect?) seems willinig to let the matter drop i would let the code official know.  
if the simpson connector provided by the contractor has been fabricated for bolts (large holes), i don't think there's any way the connector assembly is going to be adequate by substituting screws for bolts.  i would never approve it.  again, why should you accept the liability for something the contractor did that is not in conformance with your design?  if this thing fails and someone gets hurt or killed you could be in for a lot of trouble.
it is the contractor's job to build the structure, not to re-engineer it.  if the contractor wanted to substitute a different connector than the one you specified, the contractor should have requested the substitution in writing to you before building it.  to sum up my wordy response, in my opinion the contractor doesn't have a leg to stand on. when i am made aware of an unauthorized substitution, i always make them remove it and furnish and install what i specified.  if it's not feasible to do that, then i make sure that i get paid to engineer a fix for the problem the contractor created.  the costs to implement the fix should also be the responsibility of the contractor.
things like simpson connectors are tested in a certain configuration that is then published with load values.  if you change anything in that configuration, simpson will tell you their load value no longer applies and you are on your own for whether the thing works.  how do you know what the failure mode was that resulted in that published connector value?  maybe it was the bolt, or the yielding of the steel, fracture at the net section, and so on.  
bottom line, if he didn't install the thing correctly and there is nothing in the simpson literature that supports what he did, i wouldn't except it.
i agree with what ucfse said.  the capacity of most simpson connectors is based on test data. if the connector is installed in any way that varies from the requirements given in the simpson catalog, its unclear what capacity you actually have. as-built capacity might be roughly estimated using the nds and your noggin as stated in the other posts above, but in the end not sure that approach would be defendable if something went wrong.  make sure you get compensated for spending your valuable time on this issue!
   
calc1 - i gather from your question you are rather new at this.  it's a good question and one that comes up routinely in construction.  
as others have noted, particularly sperlingpe and ucfse, there are practical and liability issues associated with such a review, evaluation, and response to the contractor.
if you are the structural engineer of record, the you have already stated in the design what you want to see from the contractor.  contractors often substitute systems they deem to be "equivalent".  such "equivalence" must be proved by the contractor at his expense.  this is probably covered in the construction contract.  he's trying to substitute something that is less expensive for him and get you to approve its "equivalence" at no cost to him.  don't buy it.
have him prove, through a licensed professional engineer and test data that the substitution is equivalent to your design.  if he does so, then you can accept it with some level of reliance on the other engineer (that helps your liability).  if he does not do so, stick to your guns.
ron
thanks everyone, how about even if you tell the contractor follow the cd and still does what ever he wants and city inspection approve it and the owner is noted of the problem, am i still liable and what are my options, how can i protect myself?