Pier Cap Design for Overhead Sign Structures 1

[dlawrence529]

Hi,

I am looking into the design of drilled shaft foundations for overhead sign structures. I was wondering if anyone knows of a good reference for structural design of a "pier cap" that connects a pair of drilled shafts?

Attached is a sketch of what I am trying to describe.

Thanks for the help,
Dale

 

[jimstructures]

No attachment is visible.

Jim

 

[dlawrence529]

Sorry about that. I have attached it to this post.

 

[dlawrence529]

I should probably provide some more details...

This pier cap will have a moment of +/- 600 kip-ft, shear of +/- 30 kip, and column load of +/- 15 kip, applied at the base of the overhead sign structure. The drilled shafts will be 42" diameter with an 8 ft c-c spacing.

I briefly looked at the strut and tie model. It appears that the strut and tie model is better suited to handle a concentrated axial load which produces a moment in beam. Is this correct? Is there a strut and tie model that is tailored to applied moments rather than concentrated axial loads?

 

[KootK]

It appears that the strut and tie model is better suited to handle a concentrated axial load which produces a moment in beam. Is this correct?

Strut and tie would indeed be suitable approach given the typical proportions for these kind of things.

Is there a strut and tie model that is tailored to applied moments rather than concentrated axial loads?

To my knowledge, there is no such thing as explicit moment in a strut and tie model (as there would not be in a truss). Moments are typically decomposed into force couples.

I've made an STM suggestion below. I think that your first step should be to ditch those J-bolts and get yourself some real anchorage.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.