Change of use to DIV-88 Building

[Adamian]

A previously DIV-88 retrofitted West Los Angeles building was undergoing a change of use that would require an occupant load greater than 100. The building was previously thought to have URM walls. However, the test by a specialized company revealed that the brick wall has reinforcement bars at 12’’ horizontal and 14’’ vertical, 5’’ deep from the exterior face of the wall. In addition, a 5’’ thick layer of high-strength concert (no rebars) is applied on the inside face of the 13’’ thick brick wall. Questions:

1. Does this new discovery change the URM wall to a different structure?

2. If yes, does the DIV-88 retrofit completed in 1990 become absolute?

If not, is any new retrofitting required to the building to allow an occupant load greater than 100?

 

[Harbringer80]

Is your risk category changing? To determine if a retrofit is required you need to go through the extensive checks in ASCE 41.

 

[Adamian]

A previously DIV-88 retrofitted West Los Angeles building was undergoing a change of use that would require an occupant load greater than 100. The building was previously thought to have URM walls. However, the test by a specialized company revealed that the brick wall has reinforcement bars at 12’’ horizontal and 14’’ vertical, 5’’ deep from the exterior face of the wall. In addition, a 5’’ thick layer of high-strength concert (no rebars) is applied on the inside face of the 13’’ thick brick wall. Questions:

1. Does this new discovery change the URM wall to a different structure?

2. If yes, does the DIV-88 retrofit completed in 1990 become absolute?

If not, is any new retrofitting required to the building to allow an occupant load greater than 100?

Is your risk category changing? To determine if a retrofit is required you need to go through the extensive checks in ASCE 41.

The previous use was a movie theater. The new use is retail and banquet hall. I think the risk category is the same for both uses. The note from the plan-check states:

YOUR OCC LOAD IS >100 NOT PUTTING YOU AT A RATING CLASSIFICATION OF HIGH RISK (TABLE 88-A), SHOW COMPLIANCE WITH A1 FOR NEW BUILDING

 

[Harbringer80]

What is your role, architect or structural engineer? The architect would be determining the occupancy category. The engineer needs to determine the risk category of existing and new. Structurally all I care about is the risk category. Occupancy sometimes effects the risk category (ie. assembly) but otherwise I leave occupancy to the arch to determine. 100 occupancy is not a magic number for SE's that I know of.

 

[Adamian]

Thanks for sharing your thoughts.
I am hired as a structural engineer to handle the comment "show compliance with A1 for new building". Since the walls have reinforcement, does it make any difference? Do you think ASCE 41 still applies?

 

[Harbringer80]

A1 is assembly. You need to address accessibly, fire rating, in addition to structural. If were not an assembly before (Ie=1.0) then you are now (Ie=1.25). You need to review ASCE 41. That document will help you to proceed with the shear wall evaluation.

 

[Adamian]

Thanks again! I think I got it.
Movie theaters should have the same importance factor with banquet halls.
However, I now realize this structure must be evaluated as a new building, regardless of the previous uses and retrofits.
In the result, the DIV-88 URM building classification may change to Type-III construction or something similar.
Can you point me to a section in ASCE 41 that is most relevant to brick walls with reinforcement?
I appreciate your help.

 

[Harbringer80]

...However, I now realize this structure must be evaluated as a new building, regardless of the previous uses and retrofits....

I don't think I agree with that statement at all. The whole purpose of ASCE 41 is to evaluate existing buildings which are undergoing modifications.

You will need to conduct your own determination if a rehabilitation/retrofit (which is specifically defined in ASCE 41) is required.

Harbringer: "...To determine if a retrofit is required you need to go through the extensive checks in ASCE 41."