Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Appendix D 3
- Thread starter FeSE
- Start date
Sure it's tougher than older ways. Anybody's welcome to come up with a better alternative and argue for its adoption.
There are those around here who are VERY vocal wrt App. D, but when asked for specific examples of unreasonable results, we hear crickets.
There are those around here who are VERY vocal wrt App. D, but when asked for specific examples of unreasonable results, we hear crickets.
Spreadsheet is the obvious way to go for this. I haven't gotten unreasonable results, but it is just the fact that in order to design a couple of bolts embedded in concrete I must to go to a spreadsheet -unless I want to spend a couple of hours to make sure it is exactly correct according to App. D for anything but a simple bolt pattern. .... seems a little unreasonable.
Agreed haynewp, but this is true for many things. Wood connection design with all those crazy factors comes to mind. Heck, calculating phiMn for an unbraced steel beam takes a good while without tables or a program.
What I'm still waiting for (and maybe it does exist) is for someone to come up with a connection for which App. D gives irrational results as compared to the old ways.
What I'm still waiting for (and maybe it does exist) is for someone to come up with a connection for which App. D gives irrational results as compared to the old ways.
JedClampett
Structural
Let's turn it around:
Who has experienced a problem (failure) based on the way we used to do it? i.e. ICBO reports, PCA Methods, UBC Anchor bolt allowables, etc?
Who has experienced a problem (failure) based on the way we used to do it? i.e. ICBO reports, PCA Methods, UBC Anchor bolt allowables, etc?
I respectfully disagree, Jed. There are factors of safety and the low probability of the worst case design load being on there. No failures doesn't prove anything. Matching up test results with the equations is the way to go IMO. Honestly, I haven't done this with App. D, so don't know whether it's better or not. I assume it is because that's what the ACI folks were probably looking at when they adopted it.
Ok a few thoughts.
In the old method, by just using guides in the manufacturer's catalog, there were factors of safety, and all sorts of reductions due to edge clearance and bolt spacing.
In the new method, we are using results which more closely relate to the actual failure point, for a PERFECTLY installed anchor.
This last point is the part that scares me. How many times have anchors been installed incorrectly on your job? Are the holes really cleaned with compressed air and wire brushed out? What if they aren't? How does that affect the values you get? With the old method, it appears to be safer. And really, most jobs that use post-installed anchors, cost of the bolts/plates aren't going to make/break a job. I don't understand why we need to be so exact on these anchors...
Just my 2 cents even though we're being forced in App. D now.
RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke
In the old method, by just using guides in the manufacturer's catalog, there were factors of safety, and all sorts of reductions due to edge clearance and bolt spacing.
In the new method, we are using results which more closely relate to the actual failure point, for a PERFECTLY installed anchor.
This last point is the part that scares me. How many times have anchors been installed incorrectly on your job? Are the holes really cleaned with compressed air and wire brushed out? What if they aren't? How does that affect the values you get? With the old method, it appears to be safer. And really, most jobs that use post-installed anchors, cost of the bolts/plates aren't going to make/break a job. I don't understand why we need to be so exact on these anchors...
Just my 2 cents even though we're being forced in App. D now.
RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke
JedClampett and RCraine:
I couldn't agree more! Appendix D has always looked like a solution in search of a problem to me. The old method did work. And it kept us out of trouble.
Its easy to calculate exactly how many anchors and what size to use when your in a testing lab, and the installation is being constructed by grad stutdents in a very controlled enviroment, and it won't every be used in a real building anyway. Its a lot harder to go to the very edge with your design when you know its going to be installed by a worker on a real job site in the rain, or cold or heat, and he is in a foul mood, and its getting close to quitting time on Fridaym and he's not following every instruction to the letter. And if he screws up, and it falls down, You might have just lost your company and everything you spent 20 years building.
I don't mind that there was a little bit extra factor of saftey built into the old way. Don't mind it one bit!
The n
I couldn't agree more! Appendix D has always looked like a solution in search of a problem to me. The old method did work. And it kept us out of trouble.
Its easy to calculate exactly how many anchors and what size to use when your in a testing lab, and the installation is being constructed by grad stutdents in a very controlled enviroment, and it won't every be used in a real building anyway. Its a lot harder to go to the very edge with your design when you know its going to be installed by a worker on a real job site in the rain, or cold or heat, and he is in a foul mood, and its getting close to quitting time on Fridaym and he's not following every instruction to the letter. And if he screws up, and it falls down, You might have just lost your company and everything you spent 20 years building.
I don't mind that there was a little bit extra factor of saftey built into the old way. Don't mind it one bit!
The n
RCrane, you have some good points.
The last time I checked, though, App. D wasn't used for adhesive anchors, so that leaves only expansion anchors and embedded studs or rods. The issues you mentioned don't exist for most of those.
Right or wrong, "ease of manual calculation" will NEVER be a criterion for deciding if an equation is used. There are LOTS of examples of modern provisions that are inconvenient (or worse) for manual calcs. Almost anybody regularly using App. D, the wood connection heinous equations, AISC Ch. F, AISC stability design provisions, etc. will use either a program or a table. I really don't like some of this, but that's obviously the way it's gonna be from here on.
The last time I checked, though, App. D wasn't used for adhesive anchors, so that leaves only expansion anchors and embedded studs or rods. The issues you mentioned don't exist for most of those.
Right or wrong, "ease of manual calculation" will NEVER be a criterion for deciding if an equation is used. There are LOTS of examples of modern provisions that are inconvenient (or worse) for manual calcs. Almost anybody regularly using App. D, the wood connection heinous equations, AISC Ch. F, AISC stability design provisions, etc. will use either a program or a table. I really don't like some of this, but that's obviously the way it's gonna be from here on.
Similiar problems do exist with mechanical anchors. The holes for Undercut and Expansion anchors are supposed to be cleaned out with compressed air according to Hilti.
I've seen expansion anchors without nuts on them, or nuts that did not come in contact with the surface.
Problems do exist with the installation of mechanical anchors. Thats why a bit more factor of saftey was never a bad thing in my mind.
I've seen expansion anchors without nuts on them, or nuts that did not come in contact with the surface.
Problems do exist with the installation of mechanical anchors. Thats why a bit more factor of saftey was never a bad thing in my mind.
271828,
Expansion anchors can be installed wrong. If they aren't tightened to the correct torque or the hole isn't cleaned out correctly. I have no problem with the amount of work, its the thought of why do we need to design so tight on items that could use a factor of safety anyways.
RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke
Expansion anchors can be installed wrong. If they aren't tightened to the correct torque or the hole isn't cleaned out correctly. I have no problem with the amount of work, its the thought of why do we need to design so tight on items that could use a factor of safety anyways.
RC
All that is necessary for the triumph of evil is that good men do nothing.
Edmund Burke
JedClampett
Structural
Thank you all for covering my back. I have no doubt that Appendix D more accurately simulates anchor behavior. But part of code writing is translating the test data into usable code guidance. There are a lot more accurate simulations for bending moments, torsion, corbel design, redistribution of moments, etc. But someone decided that the models needed to be simplified or they wouldn't be used. If a code is too onerous, it won't be used and then what has been accomplished?
![[deadhorse]](/data/assets/smilies/deadhorse.gif "[deadhorse] [deadhorse]")
Acutally, one of the big changes with this code is that mechanical and adhesive anchors must now be tested with the anchor installed incorrectly on purpose. This is a major upgrade over the old method which assumed the anchor was installed perfectly. You get a different phi factor depending on how well the anchor works installed correctly vs. incorrectly and get a rating 1 through 3 which again corresponds to different phi factors. If your anchor works good installed correctly but performs like crap when installed incorrectly you get nailed on the phi factor. This testing never existed before. Manufactures are now going to highlight anchors with a category 1 rating, the best possible/least sensitive to installation.
- Status
Similar threads
- Question
- Locked
- Question
- Locked
- Question
