Bridge Expansion Joint/ Slotted Hole

[rummaan17]

Dear All,
I have designed the bridge between two building. Fixed at one end and roller at the other. The bridge at the roller end, rests on a concrete ledge. I have provided the expansion joint based on the formulation of ASCE for building separation. I have certain queries on it :
1- Is building separation formulation is appropriate to provide expansion/moment joint in my case?
2- I am trying to allow the movement through slotted holes in base plate. If my bridge required expansion is 300mm through formulation indicated in Point-1 above, should the slotted hole be twice of it i.e. 2x300mm = 600mm

I am still unsure as to what size the slotted hole should be ? and what governs the expansion joint of bridge over the ledge end.

I am relatively new to bridges. any help would be highly appreciated. Thanks in advance.

 

[bridgebuster]

I don't have my ASCE 7 handy at the moment, what Section are you reading? 300 mm is a LOT of movement.

 

[hokie66]

Guided slide bearings would be a better solution. No opinion on the amount of movement to allow.

 

[BUGGAR]

Built some access walkways between marine dolphins with similar movement. Used 3" diameter stainless steel guide pins welded to embedded stainless base plates. Stainless retainers were bolted to the pins. I think (old, poor memory) we used UHMWPE bearing pads because we could get the material in sheets to spread the load with low height requirements. The bridge ends could easily be jacked up to replace the plastic sheets.

 

[rummaan17]

Thanks all for your reponse.
@bridgebuster : Dear Bridgebuster, I am also thinking the same as this large movement is increasing my ledge size alot. As 300X2=600mm slotted hole.
The only reason I thought is that I worked out the building displacement at Ultimate LimitState i.e. with modifier.
I have used ASCE building separation formula δMT = SQRT[(δM )2 + (δM )2 ] to workout separation at ledge.

@hokie66 : Dear Hokie66 , even If i use guided slide bearing it should be atleast 600mm ? Right for 300mm expansion joint.

@BUGGAR: Dear BUGGAR, apart from the large movement joint I am getting which Is increasing my ledge size. Other concern I have is can I place one bolt per row of base plate along the ledge ? but problem again is the load dispersion ? would it be possible for a long and narrow base plate ?

 

[BUGGAR]

If I understand you, the base can be "relatively" narrow to it's width providing it is reinforced to spread the load considering that the UHWPE is a plastic. Overlap the material so your plate can't "dig in" to the plastic. Keep the stresses very low to slow down the wear rate. Consider UHMWPE to be a replacement item.

 

[rummaan17]

Dear Buggar, Do you have any calculation that you can share for such bridges. like you were mentioning for Marine Dolphin.
That would be really helpful.

 

[BUGGAR]

There were no special calculations. Just P/A and a low bearing pressure, I believe less than 100 psi (possible memory error 404 here). We didn't do any special sliding/shear calculations, we just made sure we had edge bars all around the UHMWPE pads to keep them in place. You can see these at Sabine Pass in TX. They're under the skinny bridges tying the mooring dolphins together just off shore there.

 

[rummaan17]

Thanks @BUGGAR for your help. Much Appreciated.

 

[daranguiz]

Hi. Are you counting only in the available space do design your expansion joint? Did you consider the effect of the vertical load?

 

[rummaan17]

@daranguiz Available space ? I am providing expansion joint based on lateral loads. What do you mean by vertical loads ? Can you explain. Thanks in advance.

 

[sandman21]

Members spanning between two structures falls under ASCE 7-10 12.12.4, not building separation.

 

[daranguiz]

@rummann17 When you say that you allow movement "through slotted holes in base plate" does it means that you will have a surface of vertical contact?
If it is the case you should account to the friction force resisting the movement given by the friction-factor*normal force.

 

[rummaan17]

@sandman21, thanks. I will look into it. do you have any example that you can share on similar problem that would be helpful.

@daranguiz . I am designing anchor bolts for shear force as you indicted. I am precisely concerned about what size slotted hole should be. what guidelines are used to calculate the expansion joint / slotted holes for bridges between building.

 

[rummaan17]

Dear Sandman21, daranguiz and other, Please find attached below the ledge detail we came up with. I am still unsure about the big slotted hole we are providing. Any comments would be highly appreciated. Thanks.