Working with Existing Concrete Structures
Working with Existing Concrete Structures
(OP)
How do you guys approach modifying/adding load to existing concrete construction where existing drawings aren't available? Is it common practice to assume the beams and girders have at least the minimum amount of reinforcement in them or do you get them X-rayed? X-raying seems overkill, but who know's how over or under reinforced the members are.






RE: Working with Existing Concrete Structures
RE: Working with Existing Concrete Structures
RE: Working with Existing Concrete Structures
You can then check the stresses of the existing use versus the proposed use.
The one catch is that if loads increase by more than 5% then the IBC says that they need to be brought up to current code standards.
Be careful of cracking due to changed support/load conditions. I will try and warn the client that some minor cracks/additional deflection may result.
In particular be mindful that old slabs rarely have compression steel at mid span.
Fire rating may be an issue depending on the typical cover at the time of construction - check the relevant code for that time.
It is not an easy task, and is more detective work than engineering.
After doing all this, if there are still a few critical members that you are concerned about, then by all means get thes X-ray tested. One job is not worth the liability of making assumptions.
RE: Working with Existing Concrete Structures
RE: Working with Existing Concrete Structures
RE: Working with Existing Concrete Structures
SteveMort, I'm not sure using the term "responsible engineer" is correct.....maybe "conservative engineer"? I cant see the footing. I cant see the column reinforcement. I cant see the concrete strength. Carbon sheeting isn't going to provide connection rigidity..etc
Will definitely try to check out those books.
thanks guys
RE: Working with Existing Concrete Structures
RE: Working with Existing Concrete Structures
If it helps, I also agree with csd72. The change in use is the main thing. If it is being changed from an office building to a residential building or a parking garage, no problem as long as you don't add too much dead load. But if it is being changed from office to storage, it would be a no go unless you can prove it somehow, and that would be unlikely.
RE: Working with Existing Concrete Structures