Operating inside a structure during partial demo/renovation?

[gmoney731]

Hello,

I am working on the structural/architectural rehabilitation of an 80 year old 30'x60' building. CMU walls, and steel joists (from the 1930s) with some type of built-up roofing system that bears on the joists.

The roof is intended to be replaced. So, a full demo of the built-up roof, the steel joists, and other associated elements. They will need to fully-grout all non-grouted cells, and provide additional wall reinforcement too. As a result, the wall may also need to be partially demo'd for them to access open cells from the top.

The client needs to maintain Operations inside this structure. My question is, is it an established practice to continue Operations inside a structure if the roof/walls are being demo'd? Is there any temporary construction (I am thinking some type of metal "container" on the inside of the building that protects the workers while the work overhead happens. I know it sounds silly from a life safety standpoint, but I just want to know what options I have. We would need to ensure that the building is operable, weatherproof, and watertight, as demo goes on.

Thanks for your time.

 

[phamENG]

Generally, no - especially not in a building of that size. Risks are much higher. Most companies like this that "must maintain operations" have scheduled shutdowns to do maintenance and equipment overhauls. Any chance it can coincide with one of those?

Remember, your client needed to maintain their building. They didn't do that. So why do they need to maintain operations now? There might be a way around this, but without knowing specifics it's hard to say. Off the cuff, though, I think they need to vacate a building that is being almost completely rebuilt.

 

[3DDave]

They literally just went through this in Ohio - trying a fundamental structural repair with people in the building.

Don't do that.

Even small stuff can be a problem. A guy I worked with nearly got killed because a worker in a high-bay factory working on a catwalk dropped a large wrench through the suspended ceiling of a shop assembly area. It hit the floor hard enough that I still recall that from the first impact to the next was between 1 and 2 seconds. They should have cleared the assembly area with the drop ceiling and below whatever path was used to get there. The guy was still shaking 10 minutes later.

 

[BridgeSmith]

You'd basically need a complete building within the building, one with additional structure for safety against falling objects. It doesn't seem cost-effective for the client's operations or the contractor's ability to do the work. It would likely cost less for the client to move into a temporary workspace somewhere else.

 

[LuK13]

I am assuming the old joists will be replaced with new joists. Don't walk under a live load is like OSHA 101 that is in every tool box talk the day of any significant pick. I think at a minimum you have no choice but to shut down operations when placing the new joists.

Maybe you can come up with some type of protection that allows most of the work to be performed while maintaining operations. Then the owner can compare the cost of the extra protection and an extended construction schedule vs the cost of shutting down operations. Best case scenario is an unplanned shutdown is the more economical choice and they just give it to you.

 

[phamENG]

They literally just went through this in Ohio

Iowa? Yeah, don't do that. thread815-507372

 

[jerseyshore]

I would think the only possible way to do it without building a new structure inside and below the existing roof would be to do the demo and replacement in stages. Maybe 1/3 1/3 1/3 so that operations can continue in 2/3 of the building while any 1/3 is getting worked on. You'll never get something truly watertight when you take the roof off, but if you schedule it for a drier time of year that's the best shot you got.

 

[gmoney731]

Thank you all for your responses and support.

To give a little more context, the building is only 13' tall. Not big by any means, but based on what phamENG was saying, it's still a huge significant effort if Operations is to continue during the work. This work is for a Government facility. Shutdown of this facility would actually be a significant cost in itself as well.

The other piece of context is, cost is not really an issue. As BridgeSmith and jerseyshore are saying, if we were to really do this, the best case scenario is a "building within a building", with additional protection against any falling objects. However, are there any examples of this kind of work, or is this kind of work covered in codes/design guides?

Based on what everyone is saying, it seems like we shouldn't go down this route. But if anyone has further context or thoughts to add, I'd greatly appreciate it!

 

[phamENG]

What sort of operations are we talking about? Equipment maintenance? Storage? Clerical/office work? Relocating to a temporary facility is almost guaranteed to be easier and safer. Even if maintenance/repair that depends on specialized tools or machinery, repositioning and constantly changing workflows while dodging contractors as they move across the building is likely to be more disruptive than moving it all once into a temporary facility for 6 months and then moving it back. Even if they build the 'structure within the structure' it would have to be done at a time when the building is not in use. And How will it be supported? It's bound to get in the way somewhere. And that really only works if the work on the walls can be done from the exterior.

 

[gmoney731]

Thanks, phamENG. The building is the central control station for a Lock and Dam, so closures would essentially render the lock inoperable, and boats would not be able to cross throughout the duration of construction, which would be a huge issue.

I agree that the temporary structure is the best route, but the lock control equipment is extensive and difficult if not impossible to relocate. If we want to relocate it at this point, we might as well build a new structure entirely and relocate the equipment in one shot.

I will explore a temporary structure, with the option that we have new power/comms lines from the existing structure and they can somehow remotely operate the lock.

 

[phamENG]

Okay. That does change things. Sorry - "client needs to maintain operations" is an often used statement when you have some cheapskate who doesn't budget for building maintenance and, when the place is finally falling apart, they don't want to stop their work to fix it.

This is a bit different - but only just. I'd say the best way to approach this is with phased construction. Work with the ops manager to develop phases of wall repair that can be done without imperiling workers. Doing it from the exterior is probably going to be required. Can any of it be done with the roof still on? If so, do the wall work first. Then, work up a sort of panelized roofing system. Maybe 6 30'x10' segments? If you have room on the site, they could be built on the ground and staged. Then, shut down the lock for a day or two while the old roof is demolished and the new segments are put back in place. Once they are secured and safe, the building can be put back in operation and the rest of the work finished up.

Surely they have contingency plans for lock repairs and maintenance? Do they have planned shutdowns for the locks to do overhauls? Any chance one is coming up soon enough to align the projects?

 

[LittleInch]

Sounds to me like a large amount of scaffolding to both create your secure box under the ceiling and also externally to create what we call a "tin hat".

Not truly "water proof", but is usually pretty close.

I would go and start talking to some scaffolding companies on what they can do for you.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[gmoney731]

phamEng, sorry I wasn't clear on the scope before. I agree with you on the phased construction.

I know we can sawcut the exterior face shell of CMU to inject grout in open cells, but would they be able to also slide in and position rebar? Would they be able to sawcut the wall at the base from the exterior and epoxy dowels into the existing wall footing from the exterior as well? My instinct is yes, they can, but wanted to hear opinions of experienced engineers here. The lock does undergo maintenance, though I am not aware of the schedules. Will find out and try to phase construction to coincide with the maintenance.

I agree that phasing/sequencing of construction is my best bet. Your idea to fabricate roof "panels" on the ground first and then fabricate panel by panel is a great idea as well.

LittleInch, thanks for the recommendation. Will check it out.

 

[Aesur]

I'm of the opinion that you should not offer an opinion or means and methods of how to keep the building operation during construction. Normally structural engineers are hire to design the finished structure, not tell the contractor how to perform their job to get to the final structure. Let the contractor/owner figure it out. I suggest you read the post yesterday about claims: [URL unfurl="true"]https://www.eng-tips.com/viewthread.cfm?qid=507568[/url].

 

[phamENG]

This is a rare occasion where I'm going to have to disagree (sort of) with Aesur. I agree that you shouldn't dictate the means and methods, but you should absolutely be part of the conversation. Talk to your insurance broker to make sure you don't cross any lines you shouldn't, but this sounds like a scenario where collaboration between all stakeholders, contractors, and design professionals will be critical. Best case scenario: they can do this at the same time they shut the lock down for a maintenance overhaul. If not, your design may need to specifically accommodate whatever means and methods will be employed.

Biggest issue, though, may be the government entity's contracting rules. Depending on how the project is structured, they may not be able to bring a contractor on board until your design is done and it does out for a competitive bid. In that case, you may need to work with the owner (I'm going to guess USACE?) to develop something they are comfortable with that can go out for bid. Hopefully there can be some flexibility for selecting a qualified (not cheapest) contractor and some "redesign through RFI" if necessary to realign to their abilities in terms of means and methods.

 

[structSU10]

Without the particulars I am curious on a couple things:

you are removing the bar joists for some reason - are the damages? any way to reinforce the existing roof and keep the original joists?

when the roof is gone what keeps the walls stable? Do you need exterior bracing to hold them up while the roof work is being completed?

Can you reinforce the masonry by other means - cfrp or something less disruptive?

Again, I don't know much of what you need to do but I would start thinking about less invasive repair options that may permit operations to continue.

 

[milkshakelake]

Where I am (New York), there are filing procedures called "Tenant Protection Plans" that are submitted for doing operations while a building is in use. It's quite complicated, few people know how to do it properly, and it goes through an extensive review process. But it can be done. It needs coordinated structural and demolition sets here, though in other places, that might be combined (just hypothesizing).

-I'd put scaffolding inside the building that can take impact construction loads from the roof and will protect occupants below. Depending on your layout, this might be pretty damn complicated without causing egress issues.

-Removing the roof will remove the diaphragm and lateral stability. To avoid diagonal bracing that can potentially disrupt operations and cause all kinds of OSHA violations, you can build the new roof higher or lower and then take out the old roof. If it has to be exactly at the same elevation, you can replace the joists in kind, a few at a time, and use horizontal diagonal bracing; just have a nice procedure for it.

-Reinforce the masonry less intrusively with fiber reinforcement, or do it from the outside. Doing it from the outside still has issues because someone might accidently cut through the inner face of CMU when cutting the outer face to place rebar and grout. Though if you don't need rebar, you can just drill holes in CMU and fill it up.

-If for some reason you can't put scaffolding inside the building, you might consider building that new roof above or below the existing one and having a quick, time-critical removal of the old roof that would only shut down the lock for a few days instead of throughout the whole construction. Just make sure all the asbestos testing and removal is done beforehand, because if that roof has asbestos, removing it safely will take a very long time.

-I definitely recommend scaffolding and sidewalk sheds outside the building to protect pedestrians and give a way for workers to work on that CMU wall.

 

[Brad805]

There is no one answer to this question. This will depend upon your firms comfort level, the general contractor and the owner. If you can devise a safe working plan that all agree to, then it can be done in cases where there are no options. It is a ton more work for you.

 

[gmoney731]

Thank you all for your great feedback.

I apologize for not providing information upfront, but there are two additional caveats for your consideration. The structure needs to be missile-impact rated per ICC 500. Based on the NIST study, I understand that typically concrete walls, or fully-grouted CMU walls with additional joint reinforcement, would suffice to meet the missile impact requirements. So, they would have to at least work from the outside to inject grout, and then reinforce the wall with the FRP polymer.

The roof will also have to be missile impact rated. The joists are 80+ years old. I don't have visual access to see the joists, but there is water intrusion/roof damage, so I suspect the joists could be affected. Even if they are not, the joists are 80+ years old, and if we want the service life of this building extended by 100+ years, it doesn't make sense to leave the joists and allow them to be 150+ years old by the end of the new service life. The other issue is, per my calcs, the joists are okay if we were just putting a metal deck over it...but per ICC 500 the roof will need to be missile impact rated. I am thinking a 4" thick layer of concrete topping over the metal deck, which is what will do the joists in.

Thank you all once again for your recommendations. They are all helping me move forward.

 

[phamENG]

In that case, consider precast planks for your replacement roof.