Seismic upgrade of old buildings

[dcceecy]

I am looking at a drawing for the seismic upgrade of an old warehouse (tilt-up concrete wall+plywood roof)

One structural note says: "This structure does not conform to present Earquake codes requirements. It has been reinforced in accordance with Section 3403 of the Uniform Building Code and is within the current practice for the renovation of existing building of this age and type of construction."

What does this statement mean?
Does that mean it is impossible to make the building meet current codes or it is ok for this building does not meet current code?

 

[jdgengineer]

There's different approaches for seismic retrofits. Assuming that it is a voluntary seismic retrofit, (i.e. not a change in occupancy or something else that may require a more stringent retrofit) the retrofit level is largely left up to the owner's discretion. Unless there is a change to the building like an addition, change of occupancy, or something similar there is no requirement to meet current code levels.

Most seismic retrofits I have designed have used either ASCE 41, IEBC, or the California Historical Building Code. Each of these documents has a different approach, but the intent (depending on the performance level that is chosen i.e. Basic Safety Objective in ASCE 41) is to retrofit the building to a level that is approximately on par to new construction. However, existing buildings have a lot of complications that limit their performance, most notably in that you do not have control over the detailing that was used at the construction. Therefore, the shearwalls may not have boundary elements, the moment frames may have weak columns, etc. The retrofit guidelines give guidance on how to handle these items since you are inheriting a building that has them, but this type of construction may not meet current building codes.

The idea is to provide a building that is "safe" while taking into account the economics of retrofitting a building.

I'd say the statement is largely a CYA statement so it's plain and clear to the reviewer, building, owner, whoever what the engineer's intent was in their design.