Bridge pier failure mode.

[yakpol]

I work on bridge seismic retrofit. The pier in question is very short, only 10 feet from top of pilecap to the soffit of superstructure. Cross-sectional dimensions 8'x9', almost a cube. In dynamic analysis the pier was modeled as a beam element and assessed as a such show that plastic hinge has a significant ductility demand governed by stresses in reinforcement. Shear reinforcement is adequate for shear but does not satisfy confinement requirements.
What will be a reasonable way to assess this pier? By proportions it's not qualified to be treated as flexural element.

Thank you for responses!

 

[jayrod12]

Given the dimensions you might be better of modelling it as a plate as it's more of a rigid body then anything else. I would bet if you were to check it for overturning the dead load alone would counteract any overturning force and so there would be next to no tensile stresses acting on the concrete.

But that's just a thought.

 

[VoyageofDiscovery]

I think you hit the nail on the head, the stiffness of the stubby pier will attract load so if you need it to function for plastic design, it needs to be able to dissipate energy and therefore good confinement is necessary. I suggest wrapping the column for additional confinement.

VoD

 

[CELinOttawa]

Strut and Tie.

 

[Qshake]

Hi Yakpol -

For this stubby pier, a rigid link would be applicable in the analysis, with the resulting shears then applied to a dimensionally correct plate element. Strut and tie would be a good method to determine the reinforcing.

Regards,
Qshake

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