Structure Collapse - Picking up the pieces 1

[curvbridger]

All,

A steel frame building collapsed during construction, has been redesigned, and is now being rebuilt.

During the collapse, the anchor bolts pulled out of the concrete caisson foundations.

My task is to verify that the damaged portion of the foundation has been removed, and that the caisson, when rebuilt, will be ready to receive the new structure.

Any thoughts regarding tests that should be conducted on the concrete after the broken portion is removed?

curvbridger

 

[evelrod]

I can't address the concrete problem but I can reccommend a pull test on the anchor bolts with certainty. I spent two months in hospital because someone skipped that little detail.

Rod

 

[jheidt2543]

evelrod,

What do you mean by a "pull test on the anchor bolts"? I've never seen one specified, only weld tests and torque tests for nuts. Are you suggesting that a pull out test be done on one or more anchor bolts? Please explain.

 

[sgdon]

For testing the integrity of concrete (existing), you can resort to dome NDT tests where some are quite crude while others have been quite established. Depending on the parameters you are interested in, you may consider, Ultrasonic tests, pull tests (e.g. the Capo test), etc etc etc. A book by Bungey and Millard is a good resource on this.

Hope this helps
sgdon

 

[evelrod]

Thanks sgdon, that about covers it.---It is not at all uncommon to pull test anchor bolts in SoCal and is mandatory for additions where new anchors are installed or replaced or repaired in schools and hospitals. The equiptment itself is simple enough, just a hydraulic pump (porta power type) and a guage to read the strain on the anchor bolt being tested.
I my particular case the job superintendant phonied the weld tests and the inspector trusted him. After the fact, the inspector had all the remaining bolts pull tested and several more failed. I was injured, the inspector was fired but, the super got off scot free! This was on a NAVY base, to boot. "Sometimes there just ain't no justice"!

Rod

 

[Ron]

I would agree with Rod about the pull tests on the anchor bolts. Whether you are leaving same in place or splicing, a test is appropriate. It is a relatively simple test that most testing laboratories should be able to do. You might even be able to get the anchor supplier to do it (Simpson will do it as will other anchor bolt suppliers).

Check the integrity of the concrete. This can be done with coring and correlated NDT such as ultrasonic pulse velocity or other NDT methods.

 

[curvbridger]

Thanks, all.

I am pretty sure that the anchor bolts will be replaced in total, not spliced or re-used, so I don't think pull out tests are in order. I will check on this. I was asked to conduct swiss hammer testing, but I don't expect to learn much, even if correlation with compressive strength tests can be made. It seems to me that the only issue is cracking of the concrete due to overstress during the failure, and this condition should be visible at the demolished surface.

Curvbridger