Are Concrete Moment Frames Reusable/Re-Occupiable? 1

[Respawn]

I have been wondering if concrete moment frames, like the special moment frame, are reusable? Can the yielded rebar be replaced or is it just an analysis procedure to deem the structure occupiable? What about mild steel in precast hybrid moment frames? Can they be replaced?

 

[WARose]

Just because it's a moment frame doesn't mean it has seen forces that has made the rebar yield. But to answer your question: yes, very reusable.

 

[Respawn]

@WARose Do you mean it undergo more cycles or it is repairable?

 

[dik]

As long as the frame is in good condition, there is no reason not to reuse it. You might look to see if there have been any significant changes in the codes.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[WARose]

Do you mean it undergo more cycles or it is repairable?

Just to be clear: apparently the moment frame you are talking about has seen some sort of big seismic event....yes?

But in any case, I agree with dik.....if it's in good shape....no reason not to use it.

 

[Respawn]

@WARose Yes, a MF after a big seismic event. Essentially, there are going to be yielded rebar. Can they be replaced? How do you determine if they are in good shape? I know of assessments found in P58 and ASCE 41. I also know of taking core samples too.

 

[WARose]

You named the written material I am aware of. There are a few nondestructive tests that can (IIRC) determine the strain that the rebar has seen. (Ultrasonic being one of them.)

But probably the best of all would be to recreate the event (via time-history in something like STAAD; assuming that data is available) and seeing how many cycles it has gone through.

 

[HTURKAK]

The structure is repaired if feasible and the rebars are not replaced ..

If you write seismic performance levels and search , one of the outcomes FEMA 273 performance levels..

The picture depicts also replacement , repair cost vs performance levels..

You know P58 and ASCE 41..

I will suggest you to look ACI 369 and NIST GCR 16-917-40

https://nvlpubs.nist.gov/nistpubs/gcr/2016/NIST.GCR.16-917-40.pdf

When a RC special moment frame , subject to seismic event, the expected mechanism SHALL BE at least Intermediate mechanism (Figure 3-1. Design of special moment frames aims to avoid the story mechanism ..) and if plastic hinges develop at all probable beams , the structure is around collapse prevention level and the option is , demolish and construct new..
If ( say for the fist three storey beams of a ten storey frame ) 10 % of beams yield and hinge develops, still 90 % still elastic and the bldg could be occupied after small repairs , so the full potential is not exhausted..