Lifting and handling of 220 tons (english units) Railroad Bridge 4

[mayur]

Hi,
I have a question regarding the lifting of 220 tons railroad bridge (110' long , 21' wide)
Made of two main plate girders (9' high, with 40 mm flange thk, 20 mm web thik.)
Floor beams of 2' high, 21' long connected with main girders with 20 mm High strength bolts with 152mm 152 mm by 9.2 mm angles on both sides of floor beams with 50 mm clear distance from the edge of the angles to the bolt holes
There is stringers between two floor beams and it is also bolted connection.

NOW, I AM THINKING THAT WHETHER THIS WHOLE ASSEMBLY CAN BE LIFTED IN ONE PIECE WITH THE FLOOR BEAMS OR NOT.

I REALLY APPRECIATE YOUR REPLY.

Thanks,
Mayur

 

[evelrod]

The Ironworkers in Los Angeles set the Queensway bridge sections (two sections eace weighing 660 tons) in one piece. Don't see any problems for you if access is available for your cranes. After all , it's only time and money and picking a qualified contractor.
The biggest single pick that I made was relocating an old RR bridge in the Chevron refinery @ approx. 190 tons. but that was back in the 60's. Did set some pretty big sections on the Vincent Thomas Bridge (suspension) but I don't recall what they weighed.

Rod

 

[dik]

have to do your 'sums'... although not unreasonable. When they refurbished the bearings on the Arlington Bridge in Winnipeg, I was helping the steel fabricator, and my calcs showed that it was possible to lift one of the four supports by jacking one one of the cross purlins that was over the abutment.

 

[mayur]

Thanks, dik and everlrod for your comments.
Basically my question was that the whole
assembly can be lifted by tieing the lifters
at the floor beams not by the main girders.
So, my concern is with the shear at the floor
beam and main girder connection. Does it possible to
run any calculation for the safe load transfer through
the floorbeam to main girder.
IF possible please reply of this comment.
Thanks,
mayur

 

[Qshake]

Your floorbeams have to carry the loads to the main girders. The allowable shear for the floorbeam can be calculated using the AREA (if US) allowable shear stress times the web area. knowing this as a limit you can determine how many pick points you need for the whole section. Many of the frames for picking girders usually have four picking points for two girder picks but I'm sure you can modify them as necessary or make your own. If you can work with the main girders its best to do that, as the standard picking frames can be used.

Of course for single girder picks one uses the old "girder dogs"...arf! arf!

 

[evelrod]

Sorry , this is a bit long, but I feel it necessary!!!


In '95 I removed an old shiploader that the best engineering minds estimated to be 7000 lbs. No problem, just a small job. Well it turned out to be 17000 lbs.---PROBLEM!!! All came out ok ---this time!

The old RR bridge was estimated at 200 tons approx. and set for 4 pick points. When we saw the setup ready to go, all became a bit nervous and converted to 8 pick points thereby cutting the static load at each point to half. All went well.

My point here is that it is hard to determine what type of stresses an old bridge has been subjected to and the buck beams were never disigned to handle the shear applied as a pick point for the entire bridge. Just proceed with extra care on this type of pick. A good safe pick is worth the extra expense.

Work safe-----Rod

 

[Hariharan]

Mayur,

We are used to REALLY Heavy lifts in the offshore industry,
and 200 tons is very small by our standards. Here are a few
suggestions.
1. Check adequacy of crane(s), clearances for lifting i.e., no
obstructions during lifting and shifting.
2. We normally do not accept more than four-point lifting for
a single crane lift. Reason is, the inaccuracy in sling lengths
can change the load pattern significantly. From that point, it
would be better if you lift by the main beams. If you are
lifting by the secondary beams, the shear capacity of the joint
at the main beam should be at least 1.5 times the theoretical
shear. This accounts for sling length tolerance. We consider
one diagonal pair of slings to carry 75% of the load and the
other pair 25%, instead of 50% each. If you have
lifting beams, and the arrangement is statically determinate,
the magnification is not required. For onshore lifts, a minimum
dynamic load factor of 1.15 is provided, and lifting points and
accessories are designed for a DLF of 1.5.(Quantifies what Rod
stated). Of course, in your case primarily two main beams need
to be lifted, and more number of lifting points, sling length
variations etc would not be critical.
3. If your slings are inclined to the axis of the secondary beam,
you would get out of plane loading in the beam, and its strength
should be checked.
4. Lifting eyes (also known as padeyes) should be properly
designed and detailed to suit the proposed size of shackle.

One last point, unless absolutely unavoidable, I would not lift the
assembly with the floor beams, which are bolted to the main
girders. It is far easier and safer to lift by the main girders.

M. Hariharan

 

[evelrod]

To Hariharan:

Back in '80 or'81 the 660 ton picks on the Queensway Bridge were a pretty big deal around here. Each section was picked using Bigge's Marine Boss barge crane.
Just wondering if you know what the largest single crane pick is. Just curious.

P.S.>>>On some large picks I have made I used very large chain falls or "come-a-longs" to equalize the load. I like BIG safety factors, too.

Rod

 

[Hariharan]

Rod,

The largest single crane lift we have had in India was about
2100 tonnes, and double crane lift was about 4500 tonnes.
At other locations, with some other barges, higher lifts
would have been executed. I don't have the details.
There are a few floating crane barges with twin
cranes. The highest crane capacity is 2 X 7000 tons. The
heaviest lift weight with twin cranes is around 11000 tonnes.
(Piper B Platform topsides, North Sea)
The heaviest my company (includes me) designed is 6400
tonnes. The standard crane barges available in this region
have capacities upto 2500 short tons. Offshore process
platforms are quite heavy. They are divided into modules
for installation, and we target for lift weights of about 2000
tonnes.

Incidentally, such crane barges cost a lot. The hiring charge
for a 2000 ton range barge could be about $100,000 per day,
and the twin crane barges could cost upto $500,000 per day!

This is too expensive for onshore infrastructure projects. Only
the Oilmen can afford it! For onshore erection probably the
600 ton region seems to be reasonable.

We have used massive counterweights to move the COG to
the desired region. In one case the counterweight weighed
over 100 tonnes!

M. Hariharan

 

[Ginger]

I have lifted a railway bridge of a similar weight but smaller span. We didn't use a crane but hired in a jacked platform which has about 25 axles on it. It drove in under the bridge and then jacked itself up under the main beams in order to lift the deck off the bearings. The rig then rotated through 90 degrees thanks to its independent steering system and drove away along the road. No problem with lifting eyes etc.

Regards Andy Machon