# Bridge Substructure Component Inelastic resistance



## Layman (Jan 27, 2012)

Under AASHTO Article 3.10.9.4.3a regarding Inelastic Hinging Forces, the second paragraph indicates: "...Inelastic flexural resistance of substructure components shall be determined in accordance with the provisions of Sections 5 and 6." Anybody can pinpoint which provisions in Secion 5 or 6 it talks about? Or share your understanding about this provision at all please.

Layman


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## Layman (Jan 27, 2012)

For steel structural members, I identify the location of the plastic neutral axis of the critical cross-section and go from there. I am kind of OK with this.

But I am not sure about reinforced concrete members. As an example, for tension controlled section, rebars on the tension side of neutral axis should reach yield stress first. I understand rebar may harden and then offer a strength significantly higher their yield strength. I just had trouble locating relevant codes in AASHTO to calculate out this Inelastic Flexural strength.

Layman


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## McEngr (Jan 27, 2012)

I believe this is similar to the hinge concepts for special moment frames of ACI 318 chapter 21 for determining the anticipated plastic moment. You basically take the average of the moments and then determine your shears in the member by Sigma (Mpr)/L.

For a substructure, I believe you force the hinge at the midpoint of the column bent heights and determine your moments and shears from there. I will double check when I get a chance with chapter 5 and 6.


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## McEngr (Jan 31, 2012)

Layman: I may have struck a goldmine! Message me if you're interested in some information that I've found. I can make some copies for you!

Be sure to use the overstrength factor to determine Mpr. The overstrength factor can be found in section 3.10.9.4.3b as 1.3 for concrete and 1.25 for steel. Mpr = Overstrength factor x Mn.


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## ADB (Apr 11, 2012)

McEngr: sorry I am just now reading this. What information did you find in regards to Layman's question?


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