Temporary work platform

[tmalik3156]

Good day.
Just wondering if anyone can give me some suggestions on putting up a temporary work platform for the situation shown in the two photos.
The big watermain pipe needs to be replaced. The work platform can not hang below the bottom of the exterior girder due to clearance restrictions for the train track below. Working from ground using a boom (e.g., Genie lift) is also ruled out. A mobile access platform (e.g., Bridgemaster) parked on the deck above can not be used because of traffic. The Girder is about 3 feet 4 inches deep.
Would it be a good idea to attach plywood to the bottom of the cantilevering brackets?

 

[BridgeSmith]

The first step, I would think, would be to calculate the capacity of the brackets that support the edge beam (angle?) and the capacity of the connections between the edge beam and the concrete deck above, if they exist, so that you know whether the platform can be supported by the edge beam, or whether you'll need to add anchors into the concrete parapet to support the platform.

If you can't go below the girders at all, it's going to make connecting the platform to the girders more difficult, and make for very cramped and difficult working conditions. Our bridges are typically 24' clear of the top of the rails (23.5' is minimum permanent clearance), but the railroad typically only requires 21.5' vertical clearance for rehabilitation activities. There may be some negotiating room, for someone who has experience in how to go about it.

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

 

[PEinc]

Did you check the vertical clearance between the bottom of the water pipe and the top of the facia girder's bottom flange to see if there is sufficient room for some planks?

http://www.PeirceEngineering.com

 

[3DDave]

What is the pipe made of?

 

[bridgebuster]

Safe Span decking might be a good option. Thin and lightweight.

Link

 

[PEinc]

bridgebuster, the platform cannot hang below the facia girder. Therefore, probably cannot use Safe Span.

http://www.PeirceEngineering.com

 

[bridgebuster]

PEinc the cables would be below the floorbeams but the decking would be above. Hard to tell if the bottom of the brackets are flush with the fascia. This poor fellow has too many restrictions on his work.

 

[PEinc]

bridgebuster, wouldn't the platform need to pass under at least the first two longitudinal girders? If so, the platform would need to be below the lower or lowest girder which, I believe, the OP said was not allowed.

http://www.PeirceEngineering.com

 

[SlideRuleEra]

tmalik3156 - As a bridge contractor, we did a number of bridge projects over railroads. We always had a full-time, on-site, railroad employee who was in continuous radio contact with his dispatchers. This RR employee's job was to coordinate, in real time, train traffic under our overpass with our necessary construction work. Sometimes he would tell us to stop work and get out the way. Other times the RR company would slightly adjust there schedule to accommodate our work (such as a certain concrete placement).

Contact the RR company to see if they can help in this way. This full-time RR employee is not "cheap" (the DOT paid on our projects) but it can overcome seemingly impossible restrictions.

 

[tmalik3156]

Thank you very much all for your replies.
1. The inner part of the platform (made of plywood / lumber) may be supported on the top of the bottom flange of the girder, as suggested by PEinc. This is shown as A.
2. The outer part of the platform may be suspended from the parapet above, as suggested by BridgeSmith. This is shown as C1. The edge stringer is a Channel; it might be possible to attach clips to the bottom flange of this channel and hang the platform. This is shown as C2. The platform might also be suspended from top chord of the bracket (shown as C3), as there is a gap between the top chord and the soffit above.
3. We could also attach the platform to the bottom chord of the bracket truss (Shown as B).

All these depends on structural analysis of the members for adequacy.

Still, the lack of space will make it difficult to work.

3DDave - pipe is made of PVC
bridgebuster - I don't know about Safe Span (will Google), but as PEinc said the gondola / platform can not hang below the girder.
SlideRuleEra - I fully agree. But cost issue will drive the contractor to try other options like this. Also, there are frequent trains as this is an urban transit.