AASHTO Column Lateral Steel outside of Hinge Region

[JohnCE920]

I am curious how everyone applies the volumetric ratio for spirals in 5.7.4.6 in Seismic Zone 1 with SD1 > 0.10. In this scenario, I must meet the transverse steel requirements for a plastic hinges in 5.10.11.4.1d (which includes this equation) but between these regions, should I apply 5.7.4.6? Depending on concrete strength & steel grades & column diameter, 5.7.4.6 can be the controlling hinge equation for my spiral requirements and would essentially bring my hinge steel down through the entire column. Does that seem reasonable?

My understanding of the equation in 5.7.4.6 is to give a fully spalled concrete column the same axial capacity (via proper confinement) as the gross area column. Definitely a 'must have' in the hinge region but is that necessary where a plastic hinge will not form? And if so, why doesn't a hoop have similar requirements?

I'm probably missing something here and I appreciate any help in educating me on this.

 

[bridgebuster]

Maybe someday AASHTO will make things clear...don't hold your breath.

According to 5.10.11.2, you're in the high end of Zone 1, Sd>0.1, so 5.10.11.4.1d applies for the hinges. 5.10.11.4.1e applies to the rest of your column.

5.7.4.6 doesn't apply in your case because you are controlled by seismic requirements.

 

[JohnCE920]

I appreciate the response, I was beginning to think this was a dead thread. And no worries, I have no illusions that AASHTO will make this clear one day.

Regarding your answer, I feel that 5.10.11.4.1e is still only applicable to the entire hinge. For instance this section requires transverse steel spacing to not exceed 4". I've typically only seen that in a plastic hinge region.

My gut says that the volumetric equation of 5.7.4.6 shouldn't apply to the middle of the column. But this area also isn't necessarily controlled by seismic detailing requirements (if you agree with my earlier statements). My thought is that 5.10.6 should only apply to the middle of the column.

 

[bridgebuster]

In my haste and flipping back and forth in the PDF I overlooked 5.10.6. I agree with your assessment.