Static structures (e.g. – buildings) – With component having discrete prestressing means – Anchorage
Reexamination Certificate
1999-02-04
2001-04-17
Friedman, Carl D. (Department: 3635)
Static structures (e.g., buildings)
With component having discrete prestressing means
Anchorage
C052S223140, C052S295000, C052S576000, C052S577000, C052S742100, C052S742140, C052S745210
Reexamination Certificate
active
06216403
ABSTRACT:
This invention relates to anchoring apparatus used in civil engineering, especially so-called blind anchoring devices accessible from only one side, and more particularly to a method of constructing such a device of the type having more than one tendon, as well as to an anchor member for constructing such a device. The invention further relates to a tendon of the type having one end intended to be inserted into an anchoring cavity of such an anchoring device.
BACKGROUND OF THE ART
For certain anchoring devices having an anchor head with a tendon, prestressed or not, it is not possible to gain access to the anchoring device from the rear. This situation is encountered particularly in the case of a buried anchoring device where access is possible only from the surface of the ground, or when fluid-tightness or anticorrosion protection must be especially meticulous, so that the rear side of the device must be closed. This requirement prevents the use of a conventional anchor plate where the attachment of the tendon to the plate, e.g., with the aid of anchoring cones, calls for the development of new types of anchoring.
U.S. Pat. No. 5,056,284 shows an anchoring device accessible from only one side, the drawback of the device described there being that each tendon, hence the tube in which they are inserted, is held solely by longitudinal adhesion, thus greatly limiting the tractive stress which such an anchoring device can withstand and leading to a very great anchoring length to obtain a sufficient adhesion surface.
Likewise, U.S. Pat. No. 4,043,133 provides a tendon sheathing held solely by longitudinal adhesion to the surrounding earth. The tendons extend from the bottom end of the sheathing and are all attached to an anchor plate; the way in which this plate is inserted in the cavity, and the way in which the tendons are fastened to the plate, are not described. In case this embodiment can be produced, the transmission of the anchor force to the ends of the tendons in the surrounding earth through the injected sheathing is produced solely by longitudinal adhesion, without benefiting from the wedge effect as described below in connection with the present invention.
It is an object of this invention to provide a method of constructing an anchoring device accessible from only one side which does not encounter the mentioned drawbacks of prior art anchoring devices, i.e., an anchoring device wherein the tendons are held so that the tractive stress on each of them at the level of the anchoring device is taken over by adhesion, this adhesion being appreciably favored by the confinement induced by the overall shape of the anchoring device, and by longitudinal mechanical blocking of the ends of the tendons due to the particular shape of these ends and their arrangement in a cavity of substantially tapering shape.
A further object of the invention is to provide an anchor member of a particular shape which, associated with a plurality of tendons also having a particular shape, makes it possible to construct such an anchoring device.
Still another object of the invention is to enable the construction of such an anchoring device without the direct use of an anchor member.
SUMMARY OF THE INVENTION
To this end, the method of constructing an anchoring device according to the present invention, of the type initially mentioned, includes the steps of making a cavity in a surrounding structure, this cavity having a substantially oblong, tapering shape and having two ends, the area of the cross-section of the end disposed on the accessible side of the anchoring device being less than the area of the cross-section of another portion of the cavity, the cavity comprising an opening on the accessible side of the anchoring device; successively inserting through the opening of one end of each of the tendons, each of these tendons being made up of a traction rod having a first cross-sectional area and an end portion having a second cross-sectional area larger than the first cross-sectional area; and filling the cavity with an embedding material.
The anchor member according to the present invention is of a substantially oblong, tapering shape and has two ends, the area of the cross-section of a first end being less than the area of the cross-section of another portion of the anchor member, the anchor member being made up substantially of a wall bounding a cavity of a shape substantially similar to that of the anchor member and provided with an opening having a first cross-sectional area at the first end of the anchor member and comprising a bottom wall at the second end, another cross-section of the cavity having another area larger than the first area.
The tendon according to the present invention, of the type initially mentioned, is made up of a traction rod provided at the end thereof intended to be inserted in the cavity with an end portion, the area of the cross-section of which is larger than the area of the cross-section of the traction rod.
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A Phi Dieu Tran
Friedman Carl D.
Oldham & Oldham Co. LPA
VSL International AG
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