Replacing footbridge decking - ideas for making connections into prestressed girders

[Tabaluga]

Hi there,

As per the subject line, I am looking to replace a footbridge deck with a temporary decking system (thinking GRP grating panels?) but struggling to think of sensible options of making connections into the pre-stressed concrete girders as decking is at the bottom of the section so adjacent to the tendons and so need to avoid drilling in that area.

At the moment I was thinking hangers of some sort if they could be anchored in the girder section but above the tendons.

Also a clamping system to the bottom of girders to support tie-rods across - but never come across such a solution on a bridge and so doubt it would be allowed.

Someone has also mentioned chemical or adhesive bonded connections to me, but never seen one for concrete, let alone on a bridge. Not even sure they would be allowed on a footbridge.

Note this is will be a temporary design until they find $ to replace with a new bridge, thus working on the assumption it would need to last say 2yrs max.

Loading is crowd loading 5kN/m2, decking to span 4.5' wide across x 50' long.

Any ideas/suggestions/thoughts much appreciated.

Sketch attached.

 

[bugbus]

Got a sketch?

 

[AS_PEng]

A sketch or photo would help.

Also, just be careful, there is nothing more permanent than a temporary bridge.

 

[LittleInch]

I HATE the word temporary. Implies all sorts of lower levels of design, construction and strength.

I've seen "temporary" stuff older than me...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Tabaluga]

Take 2 to attach a sketch as did not work last time...
Your file's link is:

https://files.engineering.com/getfi...a9-88fc-9e6e0f04f7f0&file=proposed_redeck.jpg

 

[bugbus]

What about something like this? Some combination of bent and/or welded plates.

 

[Tabaluga]

Thanks gussmur, I am actually considering this as an option as cannot think of anything better at the moment, unless there was guidance on drilling near pre-stressing tendons as got over 4" cover, or if chemical bonding of some sort that could be allowed (never seen it done)...

 

[bridgebuster]

Are you able to put the decking at the level of the top flange? Drilling into a prestressed beam is risky and will be difficult to avoid cutting rebars. Are any strands draped? You would have to avoid them also.

 

[Tabaluga]

Thanks, bridgebuster... but cannot change level of decking... there are some existing bolted connections inbetween the strands but we are not removing those so cannot reuse the opennings - that option would have been neat...

 

[bridgebuster]

You're welcome Tabaluga, good luck with your project

 

[AS_PEng]

What about something like this? Suspended angle or bent plate at 8' or 6' spans?

 

[ACtrafficengr]

I've seen "temporary" stuff older than me...

I think the saying you are reaching for is "It is only temporary if it doesn't work."

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -

http://xkcd.com/319/