demolition and removing existing bridge girders

[direct1way]

hello
i am new here and i want to say thanks about this forum,
how can we demolish and remove damaged bridge span (42m)long. contain (6)girders (3.5m depth) without using gantry crane (because of high cost).also this span is over the river.
note: the bridge contain 10 spans(42m.l) each. and our specific span is no.6 and river width is (250m). if any one have any ideas can help us.thanks

 

[LCruiser]

Sounds like an interesting challenge. This is span 6 of 6? How "damaged" is it? Is it over the actual river or the bank? How fast is the river? Is there access from underneath by land or water?

 

[Qshake]

Should provide more information. For example, at 42m, or about 120 feet, this is not outside the use of prestressed precast beams. So are the beams steel or concrete? Will the traffic be required to remain on the bridge and just repositioned by lane restrictions? Or will the traffic be re-routed?

LCruiser questions on the river are good ones. The width of the river 250m or 750feet give no information on reliable water depths for crane barges or pontoons. Is the river navagable? If so, is the span of note over the shipping channel? Are there restrictions placed on the channel by the appropriate shipping authorities?

Is there a limit on debris falling into the river? Can the span be felled and then salvaged out of the river?

If it is a steel span, it is likley you can cut joints in the concrete deck every so many meters (feet) and then look to torching off the steel girders near the inflection points and lifting the midspan of one girder at a time out. Of course, this needs to be reviewed by a structural/bridge engineer to insure it is safe.

If it is precast, then cutting the joints at the piers and lifting single girders out may be a possibility. That is a bit much of a span for a single crane, not weight but span and boom out distance.

In summary need more info.

Regards,
Qshake

Eng-Tips Forums:Real Solutions for Real Problems Really Quick.

 

[hokie66]

I assume you are going to replace the damaged span, so the lifting problem is not just for demolition, but for erection of the new girders. You would want to use the same system. If that is the case, installing a gantry crane running parallel to the bridge may not be a bad option, especially if barge craneage is not possible.

 

[Umassengr]

If the river is naviagable have you considered using SPMT (Self Propelled Modular Tansports) trailers on a barge? This method has been used sucessfully on several projects that I know of recently. There are some companies out there that use these machines quite effectively to solve problems like you describe where an overhead crane cannot be used.

 

[LCruiser]

SPMT's may not be suitable due to turbulence near the shore - this is span 6 of 6...

Too many questions about the situation though...

 

[davidbeach]

The OP states it is span 6 of 10. A bit of math also indicates that it takes only 6 spans to cross the river so there are also 4 approach spans. Depending on site conditions this span could be at the edge of the river or near the middle or somewhere in between.

 

[direct1way]

thanks for replays and i am sorry bcoz i late to write(net problem) this bridge damaged by direct hit by missile and make a hole over 3 girders (4m diameter) in span 6 and we must replace this span.no traffic over the bridge and the girders is prestressed precast concrete girders and this span is over the actual river water.the water depth in the river now is 4 to 6 m and no limit on debris falling into the river but we must clean the river from any debris when we finish and we can move freely in the river. i forget to say we will replace the damaged prestressed girders with steel girders. i will attach some photo if i can

 

[direct1way]

hi again this 2 pictures i hope it will explain the situation. the pipes over the bridge are temporary and removed

 

[direct1way]

picture no.2

 

[LCruiser]

I'd say set a couple of cranes diagonally on the other side at the piers, bust out the broken stuff, roll the new girders across far enough to support then lift with the crane from the far end, and just place them. I assume you are not really worried about a little concrete falling into the river...

What am I missing?

Cool thread by the way.

 

[itsmoked]

Can't just repair the immediate area? Seems like a lot of work just to make the bridge traffic worthy.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[VoyageofDiscovery]

It appears that the pipelines were diverted to maintain service, and there was no vehicular traffic when the pipes ran straight. In such a case, leave the bridge as is and run the pipes back over the hole and check the existing remainder of the bridge girders for traffic and finally barricade the hole from pedestrians and vehicles.

VOD

 

[LCruiser]

I suspect the pipes ran *under* the roadway and what is visible is just a temporary bypass.

 

[hokie66]

He said "the pipes over the bridge are temporary and removed".