Anchor bolts too short 9

[jamie2000]

I visited a building construction site yesterday and was shown that the anchor bolts in a column baseplate do not extend through the baseplate enough to set the nut. Actually, some of them do not extend through the baseplate at all. The problem appears to be that the contractor set the top of the pier too low (it would not be a problem if they were consistently low). For some reason this was not brought to my attention when the problem was discovered, and now the rest of the framing has been installed. This is a serious problem because these columns 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, either by welding the anchor bolts to the baseplate or by welding studs to the bolts and extending them through the top of the baseplate a sufficient distance to secure a nut. What should I suggest that he do?

 

[Qshake]

Seems like a precarious place to weld...no room and little chance of inspecting a weld. Not to mention that this is critical for a moment connection and fatigue as well.

Assuming that the pier is oversized, is it possible to jack up the column and slip a new, oversized plate undeneath the base plate which can be bolted down by drilling into the new steel plate and concrete pier and using expansion anchors or an appropriate concrete anchor. The new, oversized plate can be welded to the existing base plate.

Another alternate, in case the pier cannot accept a larger plate and bolts, may be to collar the existing pier with a steel plate. The collar would be affixed to the pier by anchorages in the side. The plate could then have appendages welded on the sides to accomondate new vertical anchor bolts.

Interesting problem...waiting to see what other solutions are recommended.

 

[MikeMilburn]

Sounds like you've got youself in a mess, not being an engineer type myself so I don't know if this would be an approved method, here goes.
I wouldn't recommend butt weldng the studs to the anchor, sounds like it would be a difficult position to get into and being able to produce a good consistant weld could be a problem.
Presuming the anchor bolts are protruding a small amount what about making a base plate from say 1" plate and drilling holes to match the existing anchor bolt pattern, thru these holes the plate could be plug welded to the anchor bolts. This would require a welder with experience not to mention the correct documentation, cover thy a$% so they say.
Before these plates are welded into place, plug weld studs so they protrude upward thru the plate and will give you sufficient length to do your bolting.
Just my 2 cents worth...Mike

 

[Ginger]

I think that Q has two good workable ideas there. The option of sliding a larger plate with new hole positions below the existing plate is probably the best one, but the new plate will need to be thicker than the old one to carry the larger moment and prying forces generated in the new plate.

As another approach, how about welding triangular gusset plates to the column base in both directions. The gussets would come wih their own base plates attached which carry new bolt hole positions.

Another option (although I'm not convinced about this) is to grout in the existing bolts to ensure they can't move and then diamond drill out all of the existing bolts. Then grout in new ones in the same position.

I agree that you must nott attempt to weld extra lengths onto the existing bolts.

Regards

Andy Machon
Andy@machona.freeserve.co.uk

 

[Ron]

A variation on Andy's gusset plate idea is to use a "bolt box" which is essentially an open faced box welded to the side of the column, 12 to 18 inches high through which a new bolt is inserted (all this after drilling through the base plate and coring into the concrete a sufficient distance to achieve necessary load capacity. Use structural epoxy to bond bolt to concrete) and nut placed at top plate. Technique is commonly used in tanks to spread load off the base plate and into the tank wall.

I like Q's collar idea also. This puts the fasteners in shear rather than tension. Make sure the fastener depth picks up the rebar influence or you'll just shear a chunk of concrete off though.

Welding to the anchor bolts can be done but it requires several considerations. One, the "joint" is not a pre-qualified procedure and would have to be "qualified" through testing a similar setup in order to comply with AWS (in US), CWS (in Canada) and likely other welding code bodies. Secondly, the "joint" would be a variation on a plug weld but would require tapered removal of the top of the bolt to affect proper weld access and provide some combined tension and shear mobilization in the weld. Nondestructive testing would then need to be done (angle probe ultrasonics)to verify weld integrity. Third, in welding, the filler metal and weld deposition technique should be selected such that piping porosity and other outgassing weld anomalies are reduced while still achieving adequate penetration and fusion. Lastly, due to the thickness of the base plate and the anchor bolt, pre-heating and post-heating are likely necessary, particularly since the base plate is in contact with a huge heat sink (the concrete).

Wish I had a nickel (well, OK maybe a buck...inflation, you know) for every time this has happened!

 

[Riz]

Jamie2000,
Hi!
The problem is a function of support depth or base type.

If you have the stanchion sitting on a column plinth and size of the plinth say about 350mm max. than you can drill through at sufficient depth and put in dowels of suitable diameter laterally. This dowel has to be checked for both shear and bearing. At plinth faces allow for cleats that can reach upto the stanchion. Use suitable gusset plates to weld the stanchion and the cleats. Ofcourse cleats, gussets and weld length and thickness has to be designed.

If it is resting on a base than it would be easier to use rawl bolts drilled and set in epoxy. Check bolt dia. for tension and anchorage. These bolts are to hold cleats maybe in 2 directions or all around depending on the pull out forces. Again allow suitable gussets welded to both stanchion and cleats.

Note the gusset shape is important for aesthetic purposes.

Hope this is useful.
Riz

 

[MOEIT]

why the heck don't general contractors bring these things to our attention sooner? then they expect us to dig them out of the hole they put themselves into and want an answer asap. i say have them go buy a new column or repour the pier. the building is not what you designed or intended. who's paying for your time to fix the mistake? if i sound a bit to bitter, please excuse me. but i'm tired of having GC's coming to me to fix mistakes that shouldn't have happened if they would just do the job they're supposed to...coordinating the subcontractors and keeping an eye on the job instead of sitting in the job trailer drinking coffee and eating donuts. i've only been in the business for 4 years and i feel i'm bitchin like some old grumpy SE. (or maybe just whining like a baby...

 

[Ginger]

The latter I think.

Andy Machon
Andy@machona.freeserve.co.uk

 

[Qshake]

MOEIT,

General contractors, for ages, have tried the patience of many engineers. Yes, they should be qualified to do the work and yes they should do the work as depicted on the plans but our industry mandates a quick and appropriate repsonse from the engineer in situations like this no matter what the cause. Usually, the general contractor's fix is based on convienence or expedience for that situation and ignores what function the designer meant for that detail to play in overall scheme of the structure. As such, I am glad to have the opportunity to review those proposals and determine just what is appropriate rather than perpetuate the problem.

 

[MOEIT]

but it seems to happen more often than not. is it approriate for me to tell them to make it right? to build it the way it was intended? My reason being, is that i usually do not have the time to deal with these screw ups when i have 50 other things to do. I don't feel comfortable just giving them the 'quick fix solution' they're always asking for. it's my boss' seal that's on the line, and my credibility as an engineer. i don't like being walked all over and i hate it when they tell me, 'you're holding up the job.'>:-<

When do they take the responsibilty? It always seems to be my fault for not being out there to supervise them, my fault for not responding soon enough, my fault for not doing enough site visits, my fault for not catching it on the shops, i'm not the GC! %-(

i'm sorry if my venting is inappropriate. i just want to know i'm not the only one. and that as my career goes along it's not always going to be this way.

 

[Ron]

Well said, Q.

The construction process is not an easy one, just as design is not easy. Having experience on both sides of this table, I can say that we all bear responsibility for communication....communication of design intent (which is sometimes lacking), communication of lack of understanding of the design intent (just a simple question will sometimes suffice...the trick is knowing when you need to ask the question!), and communication of intolerance.

Most engineers are not &quot;in your face&quot; personality types and the result is a grizzled construction superintendent holding the high hand. In my experience, construction people respect clarity. When engineers respond to questions, all too often the answer is equivocal. If you want a contractor to tear something out and start over, tell him exactly that. Just be sure you're right! If you screwed up and didn't make your intent clear, work out a solution and don't complain about the question. I get a bit wary when I DON'T get questions. That means they think they know what I want.

And MOEIT, contractors are not slovenly idiots (well...there are some exceptions!). In another 10 or 15 years, look back and see how much they taught you, either through overt competence or through inadvertent screw-ups. You might be surprised.

 

[Ginger]

Ron - excellent tip

In reply to MOEIT, before laying into the contractor too early, it may be worth asking yourself a question: If this is happening more often than not, then are you designing details which are not buildable?

The contractor is no more likely to understand the ideosyncracies of your design than you are to know his in-depth construction and erection knowledge. You have both been employsed on the project in order to bring your particular expertise to the scheme. Was the contractor involved at the design stage so that you can work together to improve the buildability of your design. if not, did you meet to go through the design and explain how the structure works.

If the drawings are not explicit then the contractor has a right to apply his/her own expertise as a construction professional in order to interpret what your drawings show.

I have a recent case in point where, what I considered to be the definitive work of art drawing of a structural detail, which I had painstakingly notated and shown from several angles, came back from a number of fabricators with a range of queries and their own interpretations of my thoughts included in their prices.

Clarity of thought and its presentation to others is not as strightforward as one might imagine.

Regards

Andy Machon
Andy@machona.freeserve.co.uk

 

[Ron]

To Jamie2000...my apologies for monopolizing your thread but I think you have your answer and MOEIT has raised several good philosophical points that Qshake, Ginger, and I just cannot pass up!!!

To MOEIT...you have received the benefit of well over 50 years of collective experience in this thread, dealing with exactly the situations and concerns you have described. Your frustration is apparent, but be assured...you are not alone. We have all dealt with these issues from time to time and each wishes he would never have to face them again, but that is not to be in the design/construction world.

Andy put it quite nicely when he said &quot;Clarity of thought and its presentation to others is not as strightforward as one might imagine.&quot; We all fall into the trap of being overly familiar with our own intent, only to fall short in conveying that to others. After all, it is intuitively obvious to us, so why is it not so to others?

As Q said, expedience doesn't equate to quality or understanding of the consequences...to a contractor it is just a means to an end...the end...the schedule.

I applaud your sense of honor in protecting your supervising engineer and your recognition that your response and decisions reflect upon your own credibility. That is what mentoring is about, and you have apparently had some appropriate mentoring along the way. You will soon change from &quot;MOEIT&quot; to &quot;MOPE&quot;, as you have indicated about 4 years of experience and you seem likely to pursue registration. While you might quickly get a bit more respect on the jobsite, that will only last a short time if your actions are not consistent, responsive, and competent. Remember...if you have adequately conveyed your design intent, capable of ready interpretation, it is not you who is &quot;holding the job up&quot;...it is your contractor. Don't be shy about telling him, after all, he won't be shy with you!

Good construction is truly a group/team effort...ask any design/build contractor, as they get to keep their fight inside the house and live with each other from project to project.

Good luck.

 

[jamie2000]

Thank you all for your responses to the question. I understand MOEIT's position on the issue as I have been frustrated by the contractor on two other occasions on this same project. The first problem came when he placed some footings in the wrong location, and then had the anchor bolt pattern wrong on some other footings.

On the other hand, I have worked with contractor's that have pointed out errors on my drawings early in the construction process, thereby avoiding costly &quot;fixes&quot; later.

Therefore, in this particular case, I am working with the contractor to resolve the anchor bolt problem, without becoming antagonistic.

I take this position also for another reason. We only have a part time site representative. This situation results in having the contractor in constant contact with the client, and us with only partial contact with the client. When problems arise on the job site, regardless of who's responsible, we have to react without &quot;finger pointing&quot; as this would potentially lead to &quot;pissing off&quot; the contractor who then may indicate to the client that the problems are all my fault, even if they were not. Also, they may indicate to the client that we are slowing down the project.

So for the interest of trying to keep a good client relationship, my personal feeling is that we need to work with the contractor on these problems to keep the project going, so that the client remains satisfied with our committment to the project.

Jamie.

PS. The solution that I have proposed to the contractor for the &quot;short anchor bolt&quot; problem, is to jack up the column, cut the existing baseplate flush with the column, and weld a new baseplate with the original bolt pattern, to the existing baseplate. This new baseplate should be low enough to allow sufficient bolt threads to protrude through to install the nut.

 

[MOEIT]

I thank everyone for thier responses on this thread, and i also apologize to jamie2000 for taking over the thread.

I'm glad to have the views of other engineers out there. My company is small with only two engineers (my boss and i) and a handfull of architects and draftspeople. My boss is a good mentor, a competant engineer, but, as principal of the company, has passed mostly all of the engineering reponsibilities to me while he runs the company. Sometimes i feel, with only one other engineer here with me, that i'm not getting the best mentoring i may have recieved at a much bigger company. But, thanks to the internet, i can readily get many opinions from all over the world. So thanks, again, for your continued support.

 

[knarf]

It's probably too late, but if the mounting holes are sufficiently oversize or can be bored out, you might want to consider turning down one end of a stainless coupling bolt so that part of the threaded length extends below the plate surface (t-shaped like a tee nut without the prongs, or a castle nut without the slots). The exposed portion can be made to look like an ordinary bolt, and a short stud could be added for esthetic purposes. Of course you would need to consider the load requirements etc. to determine the required minimum wall thickness. A washer would probably be a good idea too.

 

[asdf]

If the anchor bolts are not extending up throught the concrete as intended, there is a good chance they were set deeper into the foundation. That being the case, here is what you do.
1. Center a core drill over the bolts, and use the bit to cut a ring around the bolts to an appropriate depth. Remove waste material, clean threads, etc...
2. Install a threaded coupler on the embedded bolt, as well as an extension. Grout around the couplers.
3. Increase the bolt hole in the base plate, and add another plate on top of it, thick enough to extend past the couplers.
4. Install washers and nuts. Move on to next problem...

 

[IJR]

I have been following this discussion pretty well. And I thank all of you guys who went through it . Is there a way we can put it in a FAQ area in this forum?

Thanks

 

[dpa]

MOEIT,

While I agree with all the other engineers who stated that the reality is we must fix the contractor screw ups there are a lot of idiots out there. I have a friend who specializes in fixing those kind of problems. He says he loves stupid contractors because they keep him busy, especially when it comes to concrete.

A couple of days ago a building inspector told me that his experience with residential contractors is that they only glance at the plans. He said when he points out missing anchor bolts in a foundation they usually did not even realize that the detail was on the drawing. They are used to 4 foot spacing and that's what they use.

Like you, I do resent the pressure of "you're holding up the job". Other clients whose jobs are already in progress deserve your attention too.

DPA

 

[trainguy]

MOEIT,

I hear you, and I've often felt the same way. It's a shame that we have to put our professional liability on the line while at the same time giving a quick solution to the contractor's screw-up.

However, I'll share with you my recent (5 years) rationalization with respect to our profession. I spent many years dreading the phone calls from the site, or shop floor, etc. because it meant my design was questionable.

Now I realize that if you issue drawings and do not receive any calls, it must mean the phone line is dead...

Actually, what I mean is this:
Any engineer can design a building or other structure (railcar ...) and issue drawings assuming that all will go as planned and anticipated. There is not much problem solving here, usually.

The real problems to solve arise when a CHANGE is required due to unforeseen circumstances. This is when your REAL WORLD PROBLEM SOLVING SKILLS ARE REQUIRED. If you can be of assistance at this time, you have saved the contractor's a$$, and in doing so, you add some real worth to the project. The world needs real engineers at these times. When you do manage to respond effectively in these circumstances, you have saved the day, and you can bask in that glory. After that, anything's possible : free hockey tickets, who knows...

Some of the best compliments that I have received from shop floor foremen were not related to my high factors of safety and elegant designs, they were 100% impressed with how able and willing I was to help them through a design modification or at providing a clarification.

tg