Method for installing or replacing tendons in prestressed concrete slabs

DETAILED DESCRIPTION The present invention is directed to a method for further reinforcing an existing prestressed slab or replacing a single damaged or deteriorated tendon without removing and replacing the entire slab.
In general, for repair the method comprises the steps of relieving substantially all stress in the original tendon before removing the original tendon from the slab.
A new tendon is then installed in the space from which the original tendon was removed.
New concrete is installed around the new tendon to replace any original concrete removed while removing the original tendon and the new tendon is stressed thereby again prestressing the slab.
For adding a tendon not previously present, a space is chipped into the concrete slab similar to the space created by a removed, damaged tendon, then the new tendon is installed.
More particularly, the present method specifies removing original concrete from nonfacing sides of the original end anchors and, for wire reinforcing systems, cutting the buttons or retaining mechanisms for each wire at the stressing end anchor.
With all stress in the original tendon relieved, additional original concrete may be removed in order to remove all original anchor mechanisms.
Next, original concrete is removed in locations over each beam down to the wire bundle of the tendon and the wire bundle is severed.
At this point removal and replacement of the wires may proceed in a couple of different ways.
First, a pulling mechanism such as a hydraulic jack may be anchored with respect to any particular section of the severed wire bundle.
One of the severed wires in the bundle is fastened to the pulling mechanism and pulled from the slab.
Each wire is thereafter pulled in a similar fashion.
With all wires pulled, a working strand is placed in the vacated passage and attached at one end to a broach and at a second end to the pulling mechanism.
The broach is pulled through the passage to clean and enlarge the passage.
Additional broaches of increasingly larger size may be pulled through the passage to shape and enlarge the passage as desired