Plate at end of anchor bolt in concrete
Plate at end of anchor bolt in concrete
(OP)
I was notice by the special inspector at the construction site yesterday that the anchor bolts in a column baseplate does not included the plate washer at the end of the bolt in cocrete. For some reason this was not brought to my attention when the problem was discovered, and now the footing has been pour. This is a serious problem because these anchor bolts are part of a moment frame and the bolts are subjected to pull-out forces. He has asked me what he can do the resolve the problem. What should I suggest that he do? Thank you ahead for your reply
RE: Plate at end of anchor bolt in concrete
Good luck!
RE: Plate at end of anchor bolt in concrete
Take for instance, a typical headed anchor. It has only a nominal head (no big plate washer) but it is enough to engage the concrete and develop the shear cone mechanism that anchor bolt capcities are based on. If there is at least a nut or head at the end, there should be enough to provide your capacity, assuming the embedment and other checks have been performed. If you use a nut, it should be tack welded to avoid turning of the bolt during tightening operations above.
You might also try AISC technical personnel if you need further substantiation.
RE: Plate at end of anchor bolt in concrete
RE: Plate at end of anchor bolt in concrete
Make sure that there is in fact a head or nut at the end of the rod, though. If not, you will be drilling or chipping.
RE: Plate at end of anchor bolt in concrete
1. Check the calculation for any redundancy. Can the design still work?
2. Test the anchors to something like 1.5 x working load.
3. Can you drill in longer anchor bars or extra anchors bars?
4. Breaking out? The last resort.
nb
RE: Plate at end of anchor bolt in concrete
RE: Plate at end of anchor bolt in concrete
To continually compensate for contractor error by re-analysis and compromise in an effort of expedience and cooperation implies that our original analyses are flawed and that we just use the premise "when in doubt, make it stout!".
We all realize that construction is difficult and sometimes screw-ups occur, but the responsibility lies with the contractor and the liability and pressure should not then be reverted to the designer.
RE: Plate at end of anchor bolt in concrete
Speaking as a person who has been on all sides of the fence I believe
that completing the Client's project as a team is the main objective. It portrays
a professional image to our employers.
Engineers should accept that mistakes occur both in the design office and
on the site. A reputable contractor should be able to assist the Engineer
by offering solutions to construction errors.
A viable solution is to review the design and should not be dismissed
if a solution is found in a short time. Designers will know whether their
designs can take a little more etc. I know a few occasions
where this has helped the designer escape from awkward situations.
I am sure that all parties acknowledge their contractual liabilities and the Client will
be even more assured if the team he has employed has worked through their problems together.
I strongly dislike the "it's your problem attitude" which goes against the
modern partnering concept. The old adversarial system is for dinosaurs.
Let's use our brains before reaching for our Contracts chaps!
NB
RE: Plate at end of anchor bolt in concrete
In some cases, going back to the original design to analyze the effects of the modified structure is unavoidable (your spread footing is 6' lower than plan elevation as rock was not where it was anticipated, so several columns are 6 feet longer etc).
I am not against partnering nor do I believe that the contractor alone should bear the sole responsibility of originating the appropriate fix but I do beleive that the problem must be approached with good sense.
RE: Plate at end of anchor bolt in concrete
It is so easy for the engineer in a nice warm dry office with Autocad to draw 50 different baseplates with different diameters and lengths of bolts in each, but a different matter on a cold wet building site to put the right set in the right base.
With the steelwork manufacturing methods employed in the UK it is no more expensive to make 50 baseplates identical ( even if 49 are bigger than really required ) than to make 50 different. This is because labour is expensive and steel comparatively cheap - the cost of the extra steel in making all the baseplates the same is outweighed by the supervision and other labour costs in matching different sized baseplates to different columns in the fabrication shop and similar costs on site.
In practice this means that there is a degree of redundancy which can be "dipped into" when problems occurr on site. Back check the design first, identify the areas of concern and design an appropriate solution.
If the steelwork erector puts some temporary "X" bracing in the frame then erection can proceed ignoring the base fixity of the columns whilst a solution to the problem is devised - time is money and delays in getting the main frame up can be very expensive.
In situations like this I have retro-fitted resin anchor holding down bolts using high tensile allthread bar. Use a mix-in-the-nozzle resin with low shrinkage and some moisture tolerance whilst liquid and proof load-test every one after curing. I do this after the main frame has been lined, levelled, plumbed and the baseplates grouted. This gives the foundation concrete time to cure and reach its full strength.
RE: Plate at end of anchor bolt in concrete
But when it comes to the issue of sorting through all of that information a year or two later with all of the correspondance, legalities, and proper protocal etc., it is, in my opinion, to provide a "fix" to the satisfaction of the contractor, engineer, and owner.
Regarding your commentary, let me point out that while it one thing to acknowledge that mistakes happen in the field, it is quite another to make excuses for them. Contractors and or inspectors are professionals just like us, and are expected to read the plans and build/insure that what has been detailed is built properly.
RE: Plate at end of anchor bolt in concrete
RE: Plate at end of anchor bolt in concrete