Work with me on this … I’ll tell you all I know, see if you can come up with a reasonable answer.
There is a 6 floor city owned parking garage next to one ofmy buildings. About a year ago some of the brick veneer began falling off, the city investigated and found the brick ties were defective, and stripped off all the brick. Today I was talking with one of the tenants in the building, a partner in a law firm so he’s no dummy. (enough with the jokes already). He said they were talking with the mayor about the garage cuz he and his employees park there, and asked the mayor about the repair process.
Mayor says that they have now determined that there is some problem with the cables in the vertical wall panels. Problem is actually that the end caps of the cables are rusting out and need to be replaced. So I’m thinking that it is some kind of prestressed precast panel and the wedge anchors are going bad. Does that sound feasible?
And then I’m thinking that they are going to have a tough time replaceing the anchors, cuz when they try to replace one it will release the tension in the cable, which will suddenly un-stretch. And anyway wouldn’t they need a foot of excess cable on the end to grip and apply tension?
“Put your creed in your deed.” Emerson
“When asked if you can do something, tell’em “Why certainly I can”, then get busy and find a way to do it.” T. Roosevelt
Replies
Q1. Yes the wedge anchors could be rusting and losing their grip, the whole socket could fill with water and leak past the wedge anchor and rust out the cable and cause it to break, or the water could leak into the cable path and cause rust and since rust is usually larger in volume than the unoxidized steel it can bust the concrete from the inside and cause spauling of the concrete. Another possibility is that the de-icing salt water and leak into the cables and really cause them to deteriorate. I'm guessing their are other conditions that could cause problems as well.
Normally the the cables are left long and then the compressive force is applied and the cable is stretched, the wedge anchors seat themselves and the excess cable is trimmed off. So if the cable breaks and/or the wedges lose their grip the cable has already shortened and there will be no place to apply the jacks to re-stretch the cables. In some cases you might be able to pull new cable in as you pull the old cable out. But that is probably not a realistic option.
I.E. Replace the panels if the cables lose their pre or post stress.
Jim
You're telling me exactly what I thought. I don't know enough about concrete structures, so I didn't want to say anything to the lawyer, and of course I sure didn't want to contradict something hizzoner was saying. I think they have bigger problems than they want to admit. Glad it's not my building."Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
most post tension have safety build into hem just for this reason. the end cap is not the lock, it just the end cap. things like this is common. post tenstion are used alot around saltwater.
This sounds like a big problem. If it is old style post-tensioned concrete, the cable would be in a grouted conduit. These can be removed and replaced with some difficulty. Newer structures use sleeved cable for post-tensioning, which could not be replaced. Prestressed concrete has the cable cast into the panel, which could not be replaced. Someone wasn't checking the wedge caps and regreasing as they should have been over the years.