Equipment Added at a later date.

[Brooklyn2012]

I have a building that was designed 30+ years ago for two reactors. Only one was installed. The owner wants to install the second reactor. Does the building need to be seismically evaluated for the current building code?

IBC Section 102.6.1
A building or portion of a building that has not been previously occupied or used for its intended purpose in accordance with the laws in existence at the time of its completion shall comply with the provisions of this code or the IRC, as applicable, for new construction or with any current permit for such occupancy.

Has anyone encountered this situation before?
Is this clause relevant to this topic?

How did your project handle the situation?

 

[phamENG]

I haven't dealt with it, but it certainly sounds like it applies directly to your situation.

It makes sense. The reason we can keep using things that have been around for a while that 'don't meet code' is because they've proven themselves already. Structurally speaking, the building code is concerned first and foremost with reliability. Can we rely on these materials to do a job if they are arranged in this way? Because we're installing new, untested materials, we take certain measure to ensure they will work through testing and inspections and safety factors. Well...if a building has been doing a job for 50 years, we don't have to be as rigorous in our statistics. We already know that this material is above a certain threshold regarding strength, so it changes the calculation a little. The IBC/IEBC doesn't do a great job of dealing with this directly, but accomplishes it circuitously.

Now, if the building was never used for the purpose...we don't have that history of knowing that it can do it. Sure, the building hasn't collapsed, so that's something, but it hasn't not collapsed while also loaded with the second reactor. Since we don't know, we fall back on the 'new construction' reliability requirements. To meet that, we have to treat it as if it were a new building.

 

[TLHS]

Just saw this, sorry. I've been in this exact situation and I've generally informed clients that they need to meet the current code, or at least the reduced seismic level that we use as a point after which seismic upgrade is required. They don't love it, but what else are you going to do?

People sometimes provide extra capacity to add floors to buildings. If you did that back in 1960 and then decided to add the floors now, you would have to validate it against current code. This is the same situation.

There's obviously play with regards to meeting mandatory system or detailing requirements that didn't exist at the time. Those have to be looked at case by case.

That being said, there are lots of ways to sharpen pencils on seismic designs. 30 years ago is in the range where you can likely make it work if they weren't being too aggressive with things in the original design. You can also likely use the provisions of the International Existing Building Code to reduce your seismic load for evaluation. The fact that it was built with this in mind would likely give you justification to be a little more permissive when you go through and establish what kind of alteration this is as defined by the IEBC. You can likely justify it not being a change in use/occupancy given that it was part of the original design basis.

 

[Brooklyn2012]

Below is an excerpt from the Code Opinion that I received from ICC.

Section 102.6, as referenced in your e-mail, deals with the legal occupancy of a structure. Buildings that exist legally at the time the code is adopted are allowed to have their existing use and occupancy continued if the use of the structure was also legally in existence. As such, the building was legally in existence even though only one of the two process systems was installed.

Although the existing building may have been designed to have two identical process systems, the second process system was never installed. Your e-mail indicates that the second process system is equal to or less than the weight of the originally designed, but never installed, process system. As such, the designer / structural engineer must substantiate to the building official that the original design of the building was sufficient for both process systems and that the “new” process system would not contain any additional weight. If such information can be provided, then, in my opinion, redesigning the building to comply with current code requirements would not be necessary. Final approval, however, would still be subject to the building official.

A couple of items to note. The Opinion cautions that it is ultimately up to the AHJ to agree or not.

Also, this is a building built in the 1900s. So, it is not the same as something built before seismic detailing became part of the code.

If this becomes a project, I will obtain a copy of the appropriate BOCA code and perform a high-level seismic analysis to make sure that the original design was done correctly.

I would also perform a visual observation of the connections in the LFRS to make sure they are robust and ductile connections.

 

[MotorCity]

Without diving into nuances of the code, I think the prudent thing to do is to update per the code. Alot of changes in our knowledge of seismic design have occurred over the last 30 years. Its not like were debating IBC 2018 vs IBC 2021. That said, you can expect the owner to disagree on the updates "because its worked for 30 years".

However, there have also been other updates to the code in the last 30 years and other loopholes that you may be able to take advantage of and soften the blow.....like live load reduction.