Removing load bearing wall - shoring issues 3

[MikeE55]

I am designing an addition which requires removing about 100 feet of load bearing wall (also serves as shear wall for a single story bldg). I'm replacing it with posts and beams and making frames rigid to handle the lateral loads. This wall supports bar joists spanning about 25 feet. My past procedure is to state on the plans "provide shoring as required". Should the plans include shoring design? I think this is part of the contractor's means and methods, and I don't want to design it. But should I ask for the shoring design to be submitted for approval, and sealed by a PE, etc. What's your standard practice?

 

[swivel63]

shoring calcs/drawings signed and sealed provided to EOR. but i don't think you're going to be going through a detailed check of it, either.

i wouldn't do it unless it's in your scope of work. if you're just doing the addition, i don't think that would include shoring. technically, this is means and method and thus the contractor's responsibility to get a specialty engineer to design it and provide drawings for it.

 

[JAE]

What you can do is at least indicate a required shoring load and locate where on the joist (i.e. panel point) the shoring should occur.

The loading on the roof or floor used to determine this shoring load should be based upon ASCE 37.

I'd agree that a shoring plan should be a required submittal.

 

[PEinc]

Shoring the bar joists may be tricky. They aren't designed to be supported except at their ends. A supporting compression load could damage the joists' diagonals. Are you leaving any of the existing wall in place which could support the joists while you remove only a lower portion of the wall? If so, possibly the wall under the joist ends could be supported rather than the joists. I think you should give as much information as possible to the contractor so that he can intelligently design the shoring. Give him loads and information on the joists. You need to make sure your addition design is buildable.

 

[nuche1973]

MikeE55,
Did 5 years of this; the "shoring as required" note will work. You'll also need to note the imposed loads: dead, live and lateral. The general contractor will take your plans to a shoring contractor, that may have in-house engineers, the national companies like Patent, EFCo, Aluma usually do, or at least a regional engineering office. They will be the ones that will design the shoring. The tricky part may be the lateral loads and their load paths. That might require a conference call. As for the bar joist, "cribbing" is usually added at the closest panel point to the end. This consist of either steel or wood mini-columns that connect the top and bottom chord at that first panel point. The shoring engineer will also design this. Just remember to clearly state any concerns or load requirements you may have and you should get a sealed set of drawings. Good luck.

 

[JAE]

PEinc is right - if you do shore up bar joists, the shoring needs to go at the panel point, unless you add vertical angles to send the shoring point support reaction up to the upper panel point.

Also, X-bridging between joists is required along the shoring length.

 

[PEinc]

Even if you shore at the panel points, you need to watch that you don't buckle a diagonal tension member with a compression shoring load.

 

[JAE]

True

 

[nuche1973]

My experience was on the "other side" in the field working with seal drawings and inspecting shoring: the issue with the diagonal tenion member did not come up. We just erected what was on the plans. So, now that I have switch sides, my question would be: who is responsible for checking buckling? I know from experience that the shoring contractor/engineer would put this issue back in the hands of the Structural Engineer, but since MikeE55 is not the original EOR (an assumption since this is an addition) is this his responsibility? I am interested in anyone's opinion on this, since I have only been in design work for two years and this is the first shoring issue I've seen from this side.

 

[kslee1000]

Yes, he has to ensure the project can be done asfely, since he is the EOR for this particular task.

 

[haynewp]

This is kind of interesting because I don't think I have ever seen shoring being required as a submittal to the EOR.

"But should I ask for the shoring design to be submitted for approval, and sealed by a PE, etc. "

If we see a drawing from another engineer as a submittal we have taken on a much larger responsibility I feel. If I see a shoring submittal, now I have to make sure they know what they are doing and that is not normally in our scope. This could impact the existing structure if the shoring is not designed correclty so I would also feel obligated to get involved in checking that too, specifically for the shoring design.

We normally have left the "shoring as required to be designed by contractor's hired engineer...." note and not required a submittal. I would give loads for their shoring design though.

I am interested to hear more on shoring submittal reviews and EOR responsibility. It seems that reviewing shoring submittals is getting into means and methods and could become very involved, and not something usually in our contract.

 

[kslee1000]

In general, you are correct that the design firms usually don't require, and won't review the shoring design as it is the contractor's responsibility. However, if the shoring has significant weight on project excution and success, then a courtesy review (on the concept) should be in the order, though the contractor is still carrying the ultimate responsibility.

For the case under discussion, the shoring is to support the existing structure, for which, the designer shall provide specific load information, and point out feasible support locations, because the contractor has no business to analyze the existing structure, and make own decisions.

 

[JAE]

You may have written your scope in a way that you think you aren't responsible for the shoring. And I would generally agree with that as means and methods are the responsibility of the contractor and our designs are indicated to be "in a completed state".

However, if something fails, its probable that you will get sucked into being sued. Whether that means we should, as good professionals, review the shoring plan or not is a good question. Anyone here been sued for a shoring collapse?

 

[haynewp]

"However, if something fails, its probable that you will get sucked into being sued." I agree. And if it is a special case, I think the Standard of Care would be seen as to review the shoring submittal.

And again, when I review a submittal, then I think as the EOR I end up being highly responsible from that point on for the performance of that item whether it was sealed by someone else or not. No matter what your shop drawing stamp may say.

 

[DTGT2002]

As a P.E. designing temporary structures (Concrete formwork and Shoring), I do not expect thorough review for my formwork/shoring designs. I do expect to submit a copy of my plan For Record, and hope a cursory review occurs to make sure the design professional responsible for the project does not see anything that indicates a severe deviation or lack of consistency shoring concept.

That said, those are my thoughts for standard operating procedure on new construction, when any anomolous shoring requirements have been presented to me to indicate the desired performance I am responsible for the means to achieve that performance.


In such a case as a remodel or in distinctly atypical cases in new construction, a thorough effort at coordnation from the EOR is needed. Whether this effort is in providing the necessary or allowable performance criteria, or performing a thorough review of the execution plans, ensuring the right design is put in place is part of being a design professional.

That certainly doesn't mean the EOR has to do the work of the specialty engineer and it shouldn't mean you take on extra responsibility - the final performance of the structure is unquestionably affected by the construction activities.


On the other hand, finding a qualified shoring company with staff licensed engineers or an independant shoring engineer is not always easy and many contractors will claim to have missed or will igonre your requirements for the seal if not boldly and explicity required.

It's hard to compete on projects requiring sealed shoring calcs when my company carries me and others in house and some of the competition "forgets" to get those pesky sealed drawings and can get away with it.


Enough of my ranting.

While you should expect to see an RIF verifying assumptions of design or at very worst assumption stated in a document for review, providing appropriate or conservative design criteria for such a project is very reasonable and could prevent future RFI or other actions that may very well become billable events. While many RFIs are justified for lack of information, providing information to support the process you need to occur is reasonable and necessary.

Rant off for real.


Thanks,

Daniel

 

[MikeE55]

This discussion has been very helpful to me and I appreciate everyone's input. I had no problem locating a company who specializes in shoring of this type, and who is able to seal and submit their plans. I'm leaning toward not asking for a submittal, but at least asking the contractor to allow me to do an informal review. Thanks.

 

[RHTPE]

Ah, one of my pet shoring challenges.

As a 40+ year veteran of the shoring & temporary structures arena, I feel compelled to comment.

If an EoR's drawings call for modification of an existing structure, he has a Duty of Care to insure the stability of the original structure and its transformation into the final design.

Do any of you realize how many times I have seen a section showing a new beam inserted to replace an existing wall with the notation "Shore existing beams (joists) as required". No loads, no clue about lateral stability, etc. Problem is, the EoR's drawings do not show me enough about the existing structure to even begin to evaluate loads, never mind lateral stability. And all my customer sends me is a fax showing only the section and proceeds to get irritated when I push for more information. Then there's the question about about the existing use (most important for a floor) - is the existing still expected to remain in service. Trust me, I've seen it.

Early in my career I detailed open web steel joists. I learned enough about their design to know that most bar joists cannot easily be supported from their bottom chord. Yes, you can insert temporary struts to the top chord - in theory - ever try to build one that will work as intended? Ideally, if you can ensure that compression members remain compression members after the shoring carries the joists, the members are probably going to be okay. But, as JAE says, you must install bridging/blocking/x-bracing between the shored joists.

Now, back to the shoring issue. Most shoring companies will design for gravity loading only. I have worked for them, and they have worked for my former employer (a formwork & shoring contractor), and they do not want the responsibility. Most will simply tell you (the EoR) what the safe working load of the equipment is and expect you to go from there. When it comes to lateral loads, the shoring supplier will tend to dump that back on the contractor. For the amount of rent they get for the equipment, it just isn't cost-effective to assume that responsibilty.

As a licensed professional engineer, it is my NTBH opinion that the EoR should provide all loads that must be carried by the shoring. Further, the EoR should follow that load path to the ground to ensure that no component in the path would be damaged by the loads.

There. I've added my rant to the thread.


Ralph
Structures Consulting

 

[kslee1000]

One vote for ralph.

 

[DRC1]

Even the hot dog vendor at the leAmbiace Plaza failure had to pay into the settlement fund. so we are all in this together, regardless of what the plans and contract says. In a collapse the extent of ones responsbility is on par with the depths of his pockets. So clearly the best insurance is to spend a little time reviewing the drawing to be sure there are no blantent errors.
That said I do a lot of temporary work and nearly always need to submit stamped drawings and calculations. If stamped drawings are required by contract, I would, if I were the EOR be sure that they were submitted. The contractor is responsible for the contract, and if stamped drawings are required, not seeing that in the spec is no excuse. If the EOR approves an unstamped submittal that the contract requires to be stamped, it might be argued that the EOR has taken on that liability. I am not saying that is the case, but in a case a good attorney could win that point.
Finally, I think there is a division of responsibility. The EOR should provide losding information. He has modeled the structure and has a much better understanding of what those loads will be. These loads should be broken down. The engineer may carry a 20 psf snow load for the strucure, but if the strucure is to be shored for 2 weeks in the summer, you may not see the snow load. The contractor's engineer is then responsible for safely supporting the building while keeping stresses in the existing strucure with in code. The EOR then needs to review the design to insure that it does not interfere with the construction of the final work, and that when the loads are transfered to the new support, the deflections and stress are what are anticipated. Along this line, unshoring the work can be as important as shoring, and the EOR should be on board with how the loads are transfered to the neww supports.

 

[JAE]

DRC1 - your quote: [red]The EOR should provide losding information. He has modeled the structure and has a much better understanding of what those loads will be.[/red]

I'd maybe question that a bit. The loading that we use as EOR's is much different than anything seen during construction.

ASCE 37 outlines different load safety factors for structures during construction. Wind loads are based upon statistical occurances that are for a life of a building, not the 3 to 12 months construction period. Snow loads are the same.

We EOR's many times do NOT have a good handle on loads applied to a shored floor during construction. We don't have the statistical data nor the knowledge that the contractor has.

What do you think? Does that make sense?