Converting abutment in bridge to pier for future purposes

[Sam1993]

Hello All:

I am designing a one span 90 ft bridge and width is 40 ft with prestressed concrete girders
But I should take in consideration while designing the abutment that this bridge will expand in the future to be 270 ft (3 spans, each one = 90ft)
Another two spans will be added in the future

I am designing the two abutment on piles for the 90 ft and we do not have piers right now
According to the future bridge Widening, I should take in consideration about the load coming to the abutment it will be doubled ant it may convent to a pier

My question is: in the future, How they will convert the abutment to be a pier and what is the type of the abutment that I should design?
if we have wing walls with the abutment, how the will demolish it in the future when they expand the bridge?
Any helpful resources as well??

picture is attached for clarification

Thank you

 

[BridgeSmith]

If you can excavate down to the future groundline, you'd just design a concrete pier for the future condition, and then it'll get buried until the expansion.

If you can't do that, I'd suggest driving steel piles with enough axial capacity below the future groundline for the loads it will see as a pile bent, plus the weight of a concrete wall/jacket around the piles. Then, predrill holes for the piles down to the future groundline, to keep the piles straight and plumb. In the future, they'll excavate out, form up a concrete encasement/pier wall that will brace the piles against buckling.

Don't forget to size the cap for bearing of the girders for both spans.

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

 

[SlideRuleEra]

Don't be overly concerned. Just incorporate a few basic features into the design (see below for some suggestions). As a former bridge contractor, we widened several bridges that were never intended to be widened. Not the same as lengthening a bridge, but a contractor's approach would be similar.

1) Of course, the abutment should be designed for loading as both a (current) abutment and a (future) pier.

2) I would install anchor bolts for future girders, just make sure they are embedded enough to be suitable when top or cap elevation is reduced for (future) girders.

3) Thread these anchor bolts for girders (shown in green, below). Make sure the steel used for these anchor bolts is weldable in case they have to be cut off and replacement short, threaded bolts installed in the future, because of damage during demolition for future girders.

4) Use a construction joint (shown in red) to raise top of pier for current use, and give a good "surface" as a guide for where to stop future demolition.

5) Wing walls are not a problem, a good impact or two with a small wrecking ball, followed by clean-up with a pavement breaker will take care of wing walls.

A qualified bridge contractor can perform what appears to be uncontrolled demolition and create a modified reinforced concrete structure that looks and performs as it should. This type work is relatively expensive compared to new bridge construction and there are fewer bridge contractor willing to do it.

 

[BridgeSmith]

Wing walls are not a problem, a good impact or two with a small wrecking ball, followed by clean-up with a pavement breaker will take care of wing walls.

Yeah, I forgot to comment on that. I agree, except for the wrecking ball - last widening I was on-site for, they just grabbed each of the the wingwalls with the slab crab on the trackhoe, and just ripped it right off whole.

Just be sure to have them construct it with a (non-optional) cold joint at the wingwall.

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

 

[SlideRuleEra]

BridgeSmith - Notice that I said a "small wrecking ball"... there is a reason. After excavating around the wingwall, a low velocity "impact or two" with a small wrecking ball does not shatter the wingwall, it knocks the wall off fairly cleanly and mostly intact.
Means and methods adjusted to make use of available equipment (crawler crane, on our jobs).