Architectural Bridge Pier

[STrctPono]

Most of the piers that I have experience with are more generic and not so rounded. This particular project has an architect providing guidance to the developer but is not part of the design team. They provided some rough guidance on pier geometry. This is what I came up with. Do you guys have any experience with architectural bridge piers? Are there any nuances with detailing or how to geometrically callout the radiuses.... etc. that I might overlook.

If my understanding is correct, this is considered a pier in the strong direction and a column in the weak direction. Seismic Zone 2. Because of how bulky it is, not only is the compression less than 0.1f'c but the pier remains elastic with no plastic hinging. I'm unsure if the horizontal tie bar I have shown (green) with the 90d and 135d hook is satisfactory from a detailing standpoint. It seems to satisfy the requirements of AASHTO 5.11.4.1.4.... although, technically I don't have to meet confinement requirements. What's your thoughts?

FYI, the triangular shaped wedges at the base (above the drilled shaft cap) are crash barriers that the impact attenuators connect to each side so you can ignore those.

 

[MIKE_311]

You will be doing some strut and tie modelling for the top.

I get that with architects is always form over function, but do you really need all the radii and large fillet edges? That going to make formwork a bit of a chore.

 

[STrctPono]

Duly noted on the strut and tie analysis.

I do not need all the radii but that is the guidance that is being provided by the Architect. The whole bridge and approach ramps are a big architectural piece so it's just one facet of the bigger picture. Developer has hired the Architect for consultation and other than me telling them that it is "going to cost you" I really don't have any other reason to shoot it down other than "I don't want to deal with it."

Quite frankly, I have a hard time imagining how they are actually going to build the formwork for this. I know it's done all the time with steel forms but this is only one pier. One of my coworkers, who is a Contractor, said it's possible to build out of plywood but will probably cost about $50,000 for the formwork alone. But I digress...

 

[Enable]

Just to provide one idea on how to do the formwork (or rather how I would probably do it as a contractor) would be to CNC the curved dimensions into successive plywood sheets (stacked on top of each other in thickness direction) and skin the face with a plastic sheet or thin / kerfed plywood sheet capable of making the radius. I have not done a bridge pier this way but I have done other architectural elements in a similar manner and they have all turned out decent. And CNC machining is surprisingly cheap these days.

I am of no help on call out details, however.

 

[BridgeSmith]

You can model the sections with concrete as rectangular, using the actual area, but reduced dimensions. It will be slightly conservative. I would calculate the effective depths of the reinforcing individually, and calculate the capacity as you would for multiple rows of bars.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dhengr]

STrctPono:
You say…, “other than me telling them that it is "going to cost you" I really don't have any other reason to shoot it down other than "I don't want to deal with it."

But, don’t worry, you will still get to deal with it again, after your initial design is done. They will come back asking if you can’t eliminate half the rebar and every other plate girder, to reduce the cost, which seems to have gone out of control. And, that’s all mostly your fault anyway.

Bridges are supposed to be functional, long lasting structures, they shouldn’t be out-n-out ugly. But, they don’t have to be architecturally stupid either, particularly when you aren’t spending your own money.

 

[STrctPono]

Sorry I missed responses on this one. Project is still under design and I will finalize next month.

Enable. I appreciate your advice from a Contractor's perspective. The sentiment that it can be done with wood mirrors what my Contractor colleague also told me.

BridgeSmith. Noted. Thanks. This is how I analyzed it for the initial design.

dhengr. Not sure who is going to be asking me to eliminate half the rebar. The State DOT? Already coordinated the design with them. They don't get their panties up in a bunch over a few hundred pounds of rebar. Are you used to working on jobs where the Contractor tells you (the EOR) what to do after bid? This is certainly not my experience. You also seem to be implying that I am unnecessarily adding girders just to accommodate the width of the top of the pier. Absolutely not. It was either this or design a pier wall with a corbel at the top.

I agree that bridges are supposed to be functional, first and foremost, but that does not preclude incorporating architectural features so long as it doesn't have a serious impact on the structural performance. This project is a public-private partnership which bridges the nearby metropolitan beach park from the surrounding ritzy high rise condos with 2 bedroom units selling for $3 million and penthouses for over $30$10 million. The developer is adamant on incorporating architectural features because the looks of this bridge affect their overall development plan of the surrounding property.

 

[PEinc]

Consider forming a regular, rectangular pier and then shotcrete to form the desired, curved surfaces?

http://www.PeirceEngineering.com