Countersunk Bolts with oversized/ slotted bolt holes? 1

[msit]

Hi everyone,

I am designing a crossover steel plate with countersunk bolt anchors anhcored the plate into the deck on each side of the crossover.
Due to expansion and contraction concern, I want to use oversized/ slotted bolt holes for the countersunk bolt anchors.
However I could not find any information in AASHTO Bridge Specification or AISC steel manual to determine if countersunk bolt with oversized/slotted bolt hole is allowed.
Anyone know where I can find the related information??


-Sit

 

[dvd]

I think you would have better luck using a counterbore approach with socket head cap screws or button head cap screws over a heavy washer in stepped slots. Don't know the codes...

 

[dvd]

Actually a T-nut in a stepped slot in conjunction with a shoulder bolt inserted from the backside would a great way to accommodate expansion without needing a tight connection.

 

[MikeHalloran]

Slotted countersinks are such bad practice that I doubt you'd find any mention of such a thing in any standard. I've fired people for less egregiously poor designs, and I don't even do bridges.

I suppose you could sort of invert the T-slot suggestion, and use flat head screws in countersunk washers ~half as thick as the plate you're trying to anchor, with the washers having a squarish periphery sliding in a milled stepped slot. You'd probably want to use some sort of threadlocker on the threads, grease the slots regularly, and install the bolts 'tight minus {some fraction of a turn}'.

Both details are too complex, corrosion-susceptible, dirt- susceptible, and infrequent maintenance- susceptible, in my inexpert opinion, for bridge service.

Can't you get those interposed finger edged expansion joint plates in the size you need? Or laser or waterjet cut a custom size?


Mike Halloran
Pembroke Pines, FL, USA

 

[bridgebuster]

By crossover plate do you mean a cover plate over an expansion joint? Typically for bridge and transit platform work, it's always been a countersunk bolt in a standard hole on one side only.

If you want to bolt both sides, go with dvd's recommendation to counterbore the plate for the bolt head then drill a second hole larger than your bolt.

 

[msit]

Thanks for all the responses!

This is actually a temporary crossover steel plate spans between a new deck and an existing deck. We called the countersunk bolt manufacturer about the countersunk bolt with slotted/oversized hole solution and he advise us not to do that. We finalized our design with TC bolt with counterbore slotted hole on one side and countersunk bolt with standard hole on the other side.

-Sit