Beam Jacking

[OSUCivlEng]

I have a project involving some bearing replacements on an overpass over a very busy highway. Another engineer in our office suggested using a carrier beam like in the attached PDF. It would certainly help alleviate any problems with constructing falsework next to busy traffic by closing down a lane. We would be removing part of the deck as part of the rehabilitation anyway.

Does anyone have any experience using a system like this? Any lessons learned or something like that.

Thanks

 

[DDBPE]

If the bridge is under traffic, wouldn't the carrier beam or beams be in the way?
I have heard of using hydraulic jacks just in front of each bearing pad location underneath hooked to a manifold so when the pump is turned on and pressure is applied all the jacks move at the same rate and pick up the entire side at once. One of my previous mentors used this method to replace bearings on a bridge 20 years ago.
This hydraulic jacking method is similar to the way they lift houses or structures to move them on a trailer from one location to the other.

 

[bridgebuster]

I've used a carrier beam to support damaged stringers but not for jacking. Although I recall a job from 30+ years ago, my squad leader used a carrier beam perpendicular to the girders to replace the bearings but there were two other beams also. I can't quite visualize it. The bridge was over Amtrak and they wouldn't allow any falsework. I don't think I have a drawing - back then PDF were letters of the alphabet and CAD was a disreputable guy.

How close are you to traffic? Can you jack against the end diaphragms - you may have to reinforce them - or can you put a column in front? Your idea works but you may need a robust section to prevent buckling.

 

[BridgeEI]

I do it all the time for beam repairs. Not much to it really. We have a standard detail that we always use as a schematic and leave the design up to the contractor. They pretty well follow the detail, just a large beam capable of the loads, add locations for them to jack at, and give a kicker angle from the beam top flange to the deck.

It works nice since the footprint is a few feet plus barrier if needed. Can't really think of any pointers per se other than size the beam appropriately (or if the contractor has something in their yard) and brace it.

I have also made a saddle around the pier cap and jacked from there. Easiest to do with equal spans.

Also, EFFO makes a little support that bolts through and has a lot of capacity. It works well.

 

[OSUCivlEng]

I can block off the area where the carrier beam will be with portable barrier. If we are removing the deck we'll need the portable barrier anyway. Again the busier road is underneath, so I would rather not use falsework next to it.

I don't think I can fit a jack in front of the bearing, the gap between the bottom of the beam and the pier cap or seat is maybe 3.5". Do they make pancake jacks that slim?

I am worried about jacking against the diaphragms. They are concrete and "attached" to Type III and II beams. They are attached to the deck, but I would worry about damaging them or the deck.

BridgeEI when you say kicker angle, do you mean some kind of brace to prevent twisting or lateral buckling? How do you attach the end of the angle to the deck? I like you idea about a saddle, but I'm not sure it would work with a 60' Type III on one side and a 40' Type II on the other. Do you mean EFCO or EFFO?

 

[BridgeEI]

I meant EFCO. The kicker angle is an additional measure to brace for lateral torsional buckling, but I'll design the carrier beam assuming it's unbraced the full length. For the most part I'll never get anywhere near the capacity of the beam so the angle bracing is more of a feel good measure.

With those spans it would be hard to do a saddle. I haven't come across any low profile cylinders in the 3-4 inch range.

 

[3Fan]

Can you mount jack brackets to the face of the abutment seat with expansion anchors, then run a W section between the jack brackets to place your jack on the W section?

Attached are a couple details from our office.

Enerpac makes some very low profile jacks. Can you get one thin enough to slide under the bottom beam flange and sit directly on the beam seat?

 

[OSUCivlEng]

Thanks for the suggestions 3Fan.

This is pretty amazing. A 30 ton jack with a collapsed height of 2.31". There is about 3.5" between the seat and the bottom of the beam so that would work. Thanks!

http://www.enerpac.com/en-us/indust...rsm-rcs-series-low-height-hydraulic-cylinders