APPENDIX D FOR NONSTRUCTURAL COMPONENT IN SEISMIC CATEGORY E

[vvs9770]

IBC 2009 section 1908.1.9 modifies the ACI 318 Appendix D as follows:

"Section D.3.3. Modify ACI 318, Sections D.3.3.4 and D.3.3.5 to read as follows:

D.3.3.4 - Anchors shall be designed to be governed by the steel strength of a ductile steel element as determined in accordance with D.5.1 and D.6.1, unless either D.3.3.5 or D.3.3.6 is satisfied.

Exceptions:

1. Anchors in concrete designed to support non- structural components in accordance with ASCE 7 Section 13.4.2 need not satisfy Section D.3.3.4.

2. Anchors designed to resist wall out-of-plane forces with design strengths equal to or greater than the force determined in accordance with ASCE 7 Equation 12.11-1 or 12.14-10 need not satisfy Section D.3.3.4."


If I understand this correctly, we can neglect the requirements of D.3.3.4 (i.e. neglect ductile failure requirements)for non-structural components, i.e .air filters, cooling towers, blowers, pumps, etc..

What are your thoughts on this? Do we not need to assure the functionality and position retention for these items during and after a severe earthquake?


vvs

 

[jdgengineer]

I agree with your interpretation, ductile failure of the anchorage or the 2.5 overstrength factor is not required for the anchorage of non-structural components. This was newly added in the 2009 IBC and I don't think occured in the 2006 (except 2007 CBC had it in the "A" chapters).

What's the reasoning for this? I'd imagine it has to do with the fact that building design in high seismic areas is all about capacity design approach and limiting the failure mechanisms to ductile areas so in the event that an earthquake occurs that is larger than anticipated there is sufficient ductility for the earthquake to have some "reserve" capacity. I believe this logic is the reasoning they do not allow Ordinary Moment Frames in high-seismic areas (outside of some limitations) even though they could be designed for the higher forces and lower R. It's all about life-safety and having as much reserve capacity as possible.

Now with non-structural components, I think largely the impact of a failure of a non-structural component is not as critical. A failure of a non-structural component will not result in the collapse of the building, so the need for that extra "reserve" capacity is not as great. Now, the building code provides MINIMUM design loads. If for some reason, you feel that the failure of your component could have larger impacts, then I would decided on a case-by-case basis if I wanted to include it.