Removing load bearing wall - shoring issues
Removing load bearing wall - shoring issues
(OP)
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?






RE: Removing load bearing wall - shoring issues
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.
RE: Removing load bearing wall - shoring issues
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.
RE: Removing load bearing wall - shoring issues
RE: Removing load bearing wall - shoring issues
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.
RE: Removing load bearing wall - shoring issues
Also, X-bridging between joists is required along the shoring length.
RE: Removing load bearing wall - shoring issues
RE: Removing load bearing wall - shoring issues
RE: Removing load bearing wall - shoring issues
RE: Removing load bearing wall - shoring issues
RE: Removing load bearing wall - shoring issues
"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.
RE: Removing load bearing wall - shoring issues
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.
RE: Removing load bearing wall - shoring issues
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?
RE: Removing load bearing wall - shoring issues
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.
RE: Removing load bearing wall - shoring issues
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
RE: Removing load bearing wall - shoring issues
RE: Removing load bearing wall - shoring issues
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
RE: Removing load bearing wall - shoring issues
RE: Removing load bearing wall - shoring issues
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.
RE: Removing load bearing wall - shoring issues
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?
RE: Removing load bearing wall - shoring issues
JAE that is a good point and another reason that I wonder if by reviewing a shoring submittal we may be sticking our feet into something we shouldn't be altogether. What do you think?
I did find a case here:
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Where it seems to imply that since the EOR asked for a shoring submittal he was in the right.
See under "Unreinforced masonry wall collapse"
RE: Removing load bearing wall - shoring issues
Let's review quickly. MikeE55 stated: "...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?"
As I stated earlier, I believe that the Standard of Care owed to a project like this is to insure that the structure is adequate from the time that the first modification is made to the existing structure, completely through to the completion of the new + madified structure. Particularly since you know that you are specifying the removal of a shear wall.
Should your plans include a shoring design? I'd say not necessarily, but they should (at a minimum) include the loads that the contractor-designed shoring is expected to sustain.
Now, is the entire 100' of shear wall going to be removed in its entirety before anything new is constructed? In my NTBH opinion this should be evaluated with the contractor's input. It may be wiser to construct as much of the new portion as possible (before removing the old wall) to prepare for a rapid connection between the two. This way your final design can be realized quicker and safer.
From JAE: "We don't have the statistical data nor the knowledge that the contractor has." Just because a contractor has experience with these kinds of situations doesn't mean he has a clue about the loads or the hazards. He could simply be lucky. Further, his crew on one project may only have one individual (or possibly no one) who has done this kind of work before. Much of the labor force can be local hires for the job, lacking in the accumulated wisdom that you think the contractor should have.
I do not mean to insult contractors. They have a tremendous wealth of experience with regard to how to put something together. They know how to get large pieces of building components from the truck to the proper place in the structure. But they do not always know the effect of their processes on the structural integrity of an individual component or a partially completed assembly. Haven't you ever heard the line "But we've always done it that way, and it works"? That "way" may have eaten up every safety factor that we engineers rely on, and all it takes is one stupid act or mis-step to precipitate a disaster.
The contractor who built L'Abiance Plaza had experience with lift-slab construction ...
Ralph
Structures Consulting
RE: Removing load bearing wall - shoring issues
I have a dumb question: what is NTBH mean? And to the rest of the forum, thanks for the input. I realized that I should have posted my question in another thread, but luckily the issue discussed was somewhat part of the original thread.
RE: Removing load bearing wall - shoring issues
CCB1 -
NTBH opinion = Never to be humble opinion.
Ralph
Structures Consulting
RE: Removing load bearing wall - shoring issues
Also, in section 7.10, it states that the EOR should designate on the plans how the lateral-load resisting system works, what portions of the structure contribute to that stability, and recommend areas of shoring that may be necessary. The EOR does not design that shoring, nor does it suggest that the EOR must review it. It does suggest in the commentary to 7.10.3 that the EOR may require an erection bracing drawing if desired.
In 7.10.3 the Erector is responsible to "determine, furnish and install all temporary supports..."
So from an AISC/steel viewpoint, the EOR clearly should communicate/educate the contractor in how the structure works, both laterally and vertically, and provide any necessary shoring loading that is anticipated on the shoring points (per ASCE 37).
The Erector determines and designs the temporary shoring necessary for the steel erection and the EOR should provide any special loads that are non-steel that might apply.
The General Contractor would oversee the temp shoring as well.
RE: Removing load bearing wall - shoring issues
The engineer's involvement is needed more in remodelling works than new constructions though.
RE: Removing load bearing wall - shoring issues
In response to your question about my post, I would say for a simple strucure, esp. one that has no live load, I would probably calulate that myself. For a portion of a shear wall in a basement that might have several floors framing into it, that may be a different story. The EOR has probably spent a lot of time researching and modeling the structure to determine loads. As the contractor's engineer, we generally do not get all the information, have a resticted time frame to develop the design, will probably run some numbers on loads anyway, but it is good to see the struct eng numbers. As I said, despite what the contract says, we are all in this together and the beast way to win a lawsuit is to avoid it.