Tie Rods and Pattress Plates

[neilmark]

Does anybody have any advice/guidance on how to estimate the tension force in a rod to be placed through a masonry bridge and secured with pattress plates? The rods will be placed perpendicular to the bridge span to holt lateral spreading of the side walls.

 

[desertfox]

Have a look at this:-

http://www.gobrick.com/portals/25/docs/technical notes/tn44.pdf

 

[dhengr]

Neilmark:
That’s kinda a tough problem, since you don’t really know if you are stressing the rod appreciably or if you are just pushing the masonry around. You could tension the rod with a hydraulic pulling device and then turn the nut down tight. Or, you could tighten the nut snug and then use the turn of the nut method to estimate the rod take-up. Either way, you probably want to stretch a couple piano wires from anchors 4 or 5' away so you can measure the elongation movement of the rod or the compressing movement of the masonry to monitor what you are accomplishing. You might use a sweeping laser plum plane to do this same thing. In fact, you are not really trying to tension the rod very much, just trying to take the sag and slack out of it and tighten it up, so it can prevent the masonry from moving laterally any further. It is not likely that you will move the masonry much, except locally around each bearing plate. And, you don’t really want to do that or you start to hurt the integrity of the entire wall. In fact you should study the strength of the wall so it can distribute these point loads in resisting any further lateral movement. This study will determine the tie rod spacing.