United States Patent
`
`[19]
`
`[11]
`
`.Patent Number:
`
`5,044,139
`
`[45] Date of Patent:
`Mills
`Sep. 3, 1991
`
`[54] METHOD OF REPLACING POST
`TENSIONED BEAMS
`
`[75]
`
`Inventor:
`
`Tyrone T. Mills, Ramsey, Minn.
`
`[73] Assignee:
`
`D. H. Blattner & Sons, Inc., Avon,
`Minn.
`
`[21] App]. No.: 554,966
`
`[22] Filed:
`
`Jul. 20, 1990
`
`Related US. Application Data
`
`[63]
`
`Continuation of Ser. No. 355,923, May 23. 1989, aban-
`doned.
`
`
`[51]
`Int. Cl.5 .. ................... E04C 5/08
`
`[52] US. Cl. ............................. 52/741; 52/223 R
`[58] Field of Search ................. 52/744, 743, 741, 230,
`52/226, 223 R
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`3,785.617
`1/1974 Friedrich.
`4,574,545
`3/1986 Reigstad ................................ 52/223
`4,616,458 10/1986 Davis et a1.
`.
`4,621,943 11/1986 Swanson .
`
`OTHER PUBLICATIONS
`
`Progressive Architecture, Aug. 1959, pp. 139—140.
`“A Stable Post Pensioning"; Building Design & Con-
`struction, Jun. 1974, pp. 64—65.
`G. M. Roberts, “Report on I—59 St. Clair/Etowah
`County Bridge Deck Deterioration”, Jul. 16, 1982.
`Interoffice Memorandum of Stresssteel Corporation
`from E. Schechter, “Strand Failures at Watergate
`Apartment Complex”, 12/1/71.
`Daily Log Books of “Chuck” of VSL Corp. of Spring-
`field, VA dated, Jul. 1970.
`“Interim Report of Tendon Distress of the Roof Level
`at the East Medical Campus Parking Structure”, Univer-
`sity of Michigan, Sep. 17, 1979, by Wiss, Janney, Elst-
`ner & Associates, Inc.
`“Post Tensioned Less Expensive, Faster than Renovat-
`ing by Shoring” article in Journal of American Con-
`crete (Proceedings vol. 72.
`PCI Design Handbook (1971 Edition).
`“Preliminary Investigation of Deterioration of East
`
`Medical” by Carl Peterson and Joan Riordan, Aug. 22,
`1979.
`
`“Correction of Mislocated Tendons in Denver Parking
`Structure” from Post Tensioning Institute Journal,
`Nov. 1981, by Ib Falk Jorgensen.
`“Specification for the Repair and Restoration of Co-
`lumbia Mall Parking Garage”, Sep. 17, 1982 prepared
`by Wiss, Janney, Elstner and Assoc.
`Blueprint of 6/27/83 by Raths, Raths, and Johnson, Inc.
`“Combating Ravages of Climate on Parking Ramps
`Requires Remedies Involving Design, Construction and '
`Operation” by Edward Wicklund, 9/7/84.
`“Problems Encountered with Post—Tensioned. Un-
`
`bonded Tendons” By Donald A. Erickson, from Build-
`ing Official and Code Admin., pp. 12-15.
`“Repair of Prestressed Concrete—Restressing of Re-
`placed Prestressed Concrete," by Philip Mohr, FIP
`Notes, (Jan. 1984).
`Pp. 355—356 of Post Tensioning Manual, published
`1985.
`“Corrosion Resistance of Unbonded Post—Tensioned
`Slabs" by Carl Peterson, from U of M, Extension Cen-
`ter, Mar. 11, 1987.
`“Epoxy Plastics in Architecture” by Guy G. Rothen-
`stein. Aug., 1959 issue.
`
`Primaty Examiner—JohnE. Murtagh
`Attorney, Agent, or Firm—Vidas & Arrett
`
`[57]
`
`ABSTRACT
`
`A method for repairing damaged post-tensioned or
`pre-tensioned concrete structures by removing steel
`tendons and forming new concrete post-tensioned
`beams in their place. The method includes the steps of
`removing concrete above the tendon to be replaced
`while leaving concrete under the tendon, releasing any
`remaining tension in the tendon and removing same,
`preparing the concrete surface for a pour of new con-
`crete,
`installing rebars perpendicular to the tendon,
`installing new tendon and anchorages, pouring concrete
`and post-tensioning the new tendon in the new beam
`formed.
`
`11 Claims, 3 Drawing Sheets
`
`
`
`Metromont Ex-1006, p.1
`
`Metromont Ex-1006, p.1
`
`

`

`US. Patent
`
`Sep.3, 1991
`
`Sheet 1 of3 _
`
`5,044,139
`
`
`
`Metromont Ex-1006, p.2
`
`Metromont Ex-1006, p.2
`
`

`

`US. Patent
`
`Sep. 3, 1991
`
`Sheet 2 of 3
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`5,044,139
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`4
`7 9/"- ‘
`lg.
`W 7
`12
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`k
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`Metromont Ex-1006, p.3
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`Metromont Ex-1006, p.3
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`

`

`US. Patent
`
`Sep. 3, 1991
`
`Sheet 3 of 3
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`5,044,139
`
`=E‘
`
`gqpf— 5-..- 1— - —I-u—‘!!:
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`Metromont Ex-1006, p.4
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`Metromont Ex-1006, p.4
`
`

`

`1
`
`5,044,139
`
`2
`
`METHOD OF REPLACING POST TENSIONED
`BEAMS
`
`This is a continuation of copending application Ser.
`No. 07/355,923 filed on May 23, 1989, now abandoned.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`This invention relates to a method for repairing post
`and pre-tensioned concrete structures such as parking
`ramps whose beams are damaged. More particularly,
`the method involves the creation of a new post-ten-
`sioned beam in a trench where the old tendon and en-
`casing concrete were present.
`2. Description of the Related Art
`Post-tensioned concrete structures depend on the
`spaced beams of concrete in which a post-tensioned
`tendon is positioned. Pre-tensioned structures apply
`tension to the tendon prior to the concrete pour. 'With
`time, salt and other detrimental chemicals tend to break
`down the concrete and contacts the tendons. Damage
`to the tendons may severely weaken the integrity of the
`post-tensioned structure requiring repair. In some cases
`damage is so severe that the entire deck must be re-
`placed which is extremely expensive and effectively
`puts the structure out of use until repairs are completed.
`An alternative method of repairing such post-ten-
`sioned structures is described in Reigstad et al, US. Pat.
`No. 4,574,545, the disclosure of which is incorporated
`herein by reference. In Reigstad, concrete is repaired
`either by pulling the individual strands of the steel ten-
`don out and replacing the tendon after reaming the
`bore, or by releasing tension in the tendon and exposing
`the tendon from above at its ends and beneath through
`its central span. After the tendon is removed, new con-
`crete is applied to cover the new tendon. Plywood must
`be applied to the underside of the slab and be supported
`overhead by shoring from the slab below as a form for
`the new concrete placed on the ceiling of the slab.
`The Reigstad process involves the use of jackham-
`mers and overhead jackhammer stands from below
`which remove concrete from the ceiling. The method
`necessitates the closing of both the floor being worked
`on and the lower floor where' jackhammers must be
`used and forming must be supported by shoring. The
`Reigstad process leaves much more than half of the
`original concrete untouched around the tendon being‘
`replaced, for fear that excessive removal of concrete C
`will cause slab deformation. Thus, a large amount of
`concrete above the tendon, which may have chloride
`ions present,
`is left in place. The new tendon in the
`Reigstad process is coated to prevent corrosion by this
`and other sources of chloride ions.
`The Reigstad process is particularly inappropriate
`when the slab being repaired functions as a ceiling for
`office or retail store space, since such spaces would
`need to be closed down during the repair process. Un-
`fortunately, complete slab replacement or complete
`removal of the. post—tensioned beams also require the
`shutdown of any underlying businesses.
`Reigstad describes repair methods in which the entire
`beam is removed by cutting completely through the
`slab. This method‘was characterized as being unwork-
`able. The Reigstad process had been known and prac-
`ticed in the United States since at least as early as 1970.
`
`SUMMARY OF THE INVENTION
`
`S
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`The present invention provides a method in which
`the deteriorated beam, complete with tendon and sur-
`rounding concrete,
`is replaced to form a new beam.
`Enough concrete is left below the original tendon dur-
`ing the process to provide a form for positioning the
`new tendon and concrete. The concrete with the high-
`est chloride ion concentration is completely removed in
`the process. The old concrete under the new beams thus
`formed functions aesthetically and contributes little, if
`any, structural strength.
`The method of the invention involves the formation
`of a trench down to the original tendon to completely
`expose the tendon from above, except adjacent the end
`anchors. The tension in the tendon is maintained until
`the concrete is substantially removed, which greatly
`aids the removal of old concrete because of the upward
`force of the tendon. Also, the tendon under tension acts
`as a shield to ensure that a jackhammer does not acci-
`dentally break through the ceiling of the lower floor.
`The exposed tendon is then cut to release any further
`tension which has not been relieved by the removal of
`overlying concrete and is removed.
`The remaining concrete above the ends adjacent the
`anchors is removed and a profile groove for the new
`tendon is cut. The bonding surfaces of the entire trench
`to which the new beam must be attached is then pre-
`pared. The trench is then built up if needed to present
`the desired tendon profile grade.
`Tendon profile rebar retainers are then positioned
`across the trench to connect
`the opposing concrete
`surfaces, prevent spalling, facilitate bonding of the new
`concrete and retain'the position of the new tendon
`therebelow. The rebar retainers consist of coated rebar
`which are placed in bores drilled into the trench sides.
`The rebar are then bonded in place with epoxy or the
`like and are bent to the desired elevation. Generally, the
`rebar retainers are placed from the midpoint of the new
`beam toward the anchors. The retainers are usually to
`be used during the concave drape region of the new
`tendon.
`
`The new tendon (preferably coated or sheathed) is
`woven into the tendon profile groove. It
`is then at-
`tached to new end anchors which preferably include
`the addition of coated bars anchored into the old con-
`crete perpendicular to the new tendon in a manner
`similar to that used in installing the rebar retainers.
`Angled hook bars are also preferably used in the an-
`chorage and are placed parallel with the tendon extend-
`ing from the new anchor.
`In order to improve bonding and corrosion resistance
`the entire bonding surface of the trench is preferably
`coated with an epoxy compound, after which concrete
`is poured. After the new concrete has reached the re-
`.quired strength the new beam is post-tensioned to the
`specified design load. Protective caps are then placed
`over the tendon ends at the anchors. The end anchor
`region pocket is then filled with concrete to complete
`the new post-tensioned beam.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The detailed description of the invention including its
`preferred embodiment
`is hereinafter described with
`specific reference being made to the drawings in which:
`FIG. 1 is a perspective view of a portion of a typical
`post-tensioned slab showing existing tendons and tem-
`perature tendons in phantom;'
`
`Metromont Ex-1006, p.5
`
`Metromont Ex-1006, p.5
`
`

`

`3
`FIG. 2 is a perspective view similar to FIG. 1 in
`which the old concrete has been removed to form a
`trench for the new beam;
`FIG. 3 is a cross-sectional view through lines 3—3 of
`FIG. 2 showing the trench profile for the new beam;
`FIG. 4 is a cross-sectional view through lines 4—4 of
`- FIG. 3 showing the cuts made to expose the tendon at
`its deepest point in the old slab;
`FIG. 5 is a sectional view similar to FIG. 4 showing
`an alternate method to expose the tendon;
`FIG. 6 is a perspective view of the slab and cut trench
`to show the position of the anchors and new tendons;
`FIG. 7 is a sectional View taken along line 7—7 in
`FIG. 6 showing the tendon profile rebar retainers rela-
`tive to the new untensioned tendons;
`FIG. 8 is a top View of the trench showing the rebar,
`new tendons and anchor plates;
`FIG. 9 is an illustration of one form in which the new
`beam may be made;
`FIG. 10 is an alternative design to the new beam
`shown in FIG. 9;
`FIG. 11 is an illustration of a means to repair break-
`through regions showing the suspended form in phan-
`tom; and
`FIG. 12 is an illustration of an alternative means to
`repair breakthrough regions.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`With reference to the drawings in which like refer-
`ence numerals are used throughout to designate identi-
`cal or corresponding elements, the process will be seen
`as involving a slab 10 supported upon beams 12. Slab 10
`is a post-tensioned structure having primary tendons 20
`extending in one direction and temperature tendons 24
`(which may also be post-tensioned) extending perpen-
`dicular to the primary tendons 20. Although the de-
`scription of the invention will refer to repairing post-
`tensioned structures,
`it
`is also applicable to repair of
`pre-tensioned structures. In these cases,
`the pre-ten-
`sioned tendon is replaced with a post-tensioned tendon
`in a new beam.
`
`After testing has been conducted to determine which
`tendons need replacement, the tendons are located by a
`metal detector. Preferably, the tendons are located with
`a Rebar Hunter ® brand instrument from Matcor, Inc.
`of Doylestown, PA. Such an instrument locates metal in
`concrete and displays information on depth. The ends
`of the tendons 20 to be replaced are exposed by jack-
`hammer to confirm their profile, course and location.
`Saw cuts are then formed on both sides of the tendon
`to establish a trench about six (6) to seven (7) inches in
`width. The saw depth is set to ensure that any tempera-
`. ture tendons 24 are not cut. Usually, this entails a saw
`depth of two (2) inches or less. It is preferable to make
`the saw cuts only about four (4) to six (6) feet in length.
`Opening this short length of trench allows one to follow
`the course of the old tendons. Existing tendons may not
`have been installed in a straight line or at original design
`depth or elevation.
`After the trench has been outlined by the parallel saw
`cuts, the concrete between the saw cuts is removed until
`the top of the old tendon is exposed. Removal of con-
`crete may be made by the use of jackhammers. Prefera-
`bly, a heavier jackhammer is utilized initially to remove
`the first several inches of concrete, followed by a ligh-
`ter weight chipping jackhammer. The remaining ten-
`sion in the tendon assists the removal of concrete by
`
`5,044,139
`
`4
`
`.
`
`imparting an upward force to the concrete chunks in the
`trench. Also, the uncut tendon assists in preventing the
`jackhammers from cutting completely through the old
`concrete.
`
`The process of concrete removal continues with
`short lengths of saw cuts and removal of concrete until
`all but about five (5) feet on both ends of the tendon are
`exposed. At that time, any remaining tension in the »
`tendon is released by cutting the tendon which is usu-
`ally cut with a torch. The removal of concrete may
`release some tension on the tendon.
`Tension in the tendon is utilized to assist the concrete
`
`removal process. Also, release of tension from stressed
`tendons by cutting off button heads in end anchors 28 is
`not preferred, since shim plates may let go.
`The tendon thus exposed is then removed from the
`trench. Preferably, the tendon is cut between tempera-
`ture tendons and pulled in sections from the trench.
`The removal of concrete down to the top of the old
`tendon preserves the old tendon’s profile groove for
`installation of the new beam. After the remaining con-
`crete at the tendon ends is removed, a vee-shaped pro—
`file groove is formed at the bottom of the trench for
`placement ofthe new tendon. The vee-shaped groove is
`formed by saw cutting to the bottom of the old tendon
`profile groove. It is sawn to the width needed for the
`number of new tendons to be installed.
`Jackhammers with (l-fi inch wide) chisel bits may be
`used to remove concrete between the saw cuts to define
`
`the vee-shaped groove 30. A11 rubble and debris is then
`removed from the trench. Enough concrete remains to'
`function as a form for the new concrete pour which will
`form the new beam. Structurally, this retained concrete
`contributes little strength to the new beam formed.
`Any breakthrough regions 48 caused by the concrete
`removal step are repaired. Breakthroughs may occur
`due to poor placement ofthe original tendon which was
`too close to the bottom of the concrete slab. With refer-
`ence to FIGS. 11 and 12, a repair method is shown in
`which a plywood form 50 is held beneath the hole 48 by
`cable 52 which may be attached to a piece of rebar 54.
`After the concrete is cured, the cable may be cut to
`remove the rebar 54. Alternatively as shown in FIG. 12,
`the rebar 54 may be embedded beneath the surface of
`the beam by securing one or both ends to walls of the
`old concrete trench.
`
`The entire trench is then prepared for formation of
`the new beam. All bonding surfaces of the trench are
`cleared of loose concrete, aggregate or other deletori-
`ous materials. Sand or water blasting are suitable clean-
`ing methods. The trench is then vacuumed or blown
`out.
`
`The tendon profile groove for the new beam is then
`built up, if needed, in areas where the old tendon was
`originally too deep or the trench was over-excavated.
`As shown in the drawings, the tendon's profile drape
`creates a concave area in relation to the horizontal plane
`ofthe slab surface over a significant length of the ten-
`don. In those areas, the tendons must be retained below
`the horizontal midpoint of the slab to ensure that the
`post-tension of the tendon provides the required struc-
`tural lift and support the beam is to provide. To accom-
`plish this, prevent spalling of concrete, and facilitate the
`bonding of the new beam to the existing slab a plurality
`of tendon profile rebar retainers 60 are utilized.
`Rebar retainers 60, as best shown in FIGS. 6 and 7.
`are placed into angled drill holes 70 in walls 74. 76 of
`the trench. The rebar retainers 60 are preferably epoxy
`
`Metromont Ex-1006, p.6
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`Metromont Ex-1006, p.6
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`

`

`5,044,139
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`6
`While this invention may be embodied in many differ-
`ent forms, there are shown in the drawings and de-
`scribed in detail herein specific preferred embodiments
`of the invention. The present disclosure is an exemplifi-
`cation of the principles of the invention and is not in-
`tended to limit the invention to the particular embodi-
`ments illustrated.
`
`5
`coated rebar. The drill holes 70 should be close to the
`bottom of the trench and must be cleared of debris. The
`rebar retainers 70 are then epoxied in position. The
`rebar retainers are needed from the midpoint between
`beams 12 and may be placed at one (1) to two (2) foot
`centers. The portions of the tendon’s concave profile
`drape which will require retention below the horizontal
`midpoint of the slab may be about fifteen (15) feet. The
`length of the concave profile drape and number of rebar
`retainers 60 required may vary depending on the appli-
`cation.
`New tendons 80 are woven into the profile groove
`positioned under the rebar retainers 60 and temperature
`tendons 24. Preferably,
`the tendons are coated or
`sheathed, such as with polyurethane, for corrosion re-
`sistance. Suitable tendons include % inch, low relaxation
`7-wire stress-relieved strand in accordance with ASTM
`A416. Such tendons have a breaking load of about
`42,000 pounds. New end anchors 90 are constructed as
`best shown in FIG. 6. In addition to the standard anchor
`plates 90, it is preferable to include reinforcing bars 92
`to strengthen the anchorage. Standard anchor plates are
`available from many sources, including VSL Corp. of
`Los Gatos, California. A suitable anchor plate 90 is
`described in US. Pat. No. 4,616,458, the disclosure of
`which is incorporated herein by reference.
`The anchor plate 90 is preferably attached to a plural-
`ity of bars 92 perpendicular to the tendon. The bars 92
`are anchored to the walls 74, 76 of the trench in much
`the same manneras the rebar retainer. The bars 92 are
`epoxied into holes in walls 74, 76 of the trench. Hook
`bars 94 are positioned over the anchor plate 90 so as to
`run parallel with the tendons as shown. Hook bars 94
`may be on the order of about three (3) feet in length.
`Both bar 92 and hook bars 94 are preferably coated with
`epoxy or other corrosion resistant material. The ends of
`the hook bars are preferably inserted into drill holes in
`the concrete beam and epoxied in place.
`The entire surface of the trench is then preferably
`coated with an epoxy compound to improve the adher-
`ence of the new beam to the original slab. A suitable
`epoxy is the high modulus, high strength epoxy bon-
`ding/grouting adhesive Sikadur® 32 from Sika Corp.
`of Lyndhurst, New Jersey. The epoxy may also be used
`to set the rebar retainers.
`Concrete is then poured into the trench to complete
`the'new beam 100. The new beam 100 is shown in
`FIGS. 9_ and 10. It may range from a single rectangular
`box to the version of FIG. 10. Preferably, the upper
`surface is coated with a concrete curing compound.
`The concrete may include a plasticizing, water-reduc-
`ing and extended slump-life concrete admixture such as
`Sikament @320 from Sika Corp. of Lyndhurst, New
`Jersey. Such admixtures are usually added at the ratio of
`6-18 fluid ounces per sack of concrete. The concrete
`may be a Type 111 Portland mix such as Minnesota
`Department of Transportation specification 3U18,
`available from Twin City Concrete, Minnesota.
`After the concrete has reached a strength of at least
`above 5,000 pounds per square inch, the tendons are
`post-tensioned to the specified design load, which is
`typically in the range of 27—35 kips. Any cable grease on
`the cable should not be removed since it makes for
`easier installation of a cap and since it adds corrosion
`protection. A protective cap may be placed on the pro-
`truding tendon beyond the anchor plate. The stressing
`pocket area is then filled with a non-shrink concrete to
`complete the beam replacement.
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`This completes the description of the preferred and
`alternate embodiments of the invention. Those skilled in
`the art may recognize other equivalents to the specific
`embodiment described herein which equivalents are
`intended to be encompassed by the claims attached
`hereto.
`What is claimed is:
`l. A method for repairing a defective post or preten-
`sioned concrete slab comprising the steps of:
`(a) removing all original above said original defective
`tendon expose at least the upper surface of said
`original tendon while leaving an underlying por-
`tion of the original concrete along the length of the
`defective tendon;
`(b) relieving any remaining tension in said exposed
`tendon and removing said tendon from the trench
`so formed;
`I
`(c) installing at least one tendon profile rebar retainer
`into said original solid concrete in the sidewall of
`said trench so as to extend at least partially across
`said trench adjacent the middle region of the length
`of the trench;
`(d) constructing end anchorages where needed to
`replace defective original anchorages for the new
`tendon or tendons;
`(e) weaving a new tendon or tendons into said trench,
`said tendon or tendons being supported by said at
`least one tendon profile rebar retainer, operatively
`positioning the ends of said tendon or tendons to
`said end anchorages
`(t) coating the bonding surface of said trench with a
`curable epoxy bonding compound;
`(g) filling the trench with new concrete to completely
`encase said new tendon in concrete, thereby form-
`ing a new concrete beam; and
`(h) post-tensioning said tendon or tendons.
`2. A method for replacing beams consisting of post or'
`pre-tensioned tendons in concrete, said method com-
`prising the steps of:
`(a) removing all original concrete directly above an
`original tendon to be replaced along substantially
`the length of said tendon between its original end
`anchorages, thereby forming'a trench;
`‘
`(b) releasing any remaining tension in said original
`tendon, exposing the remainder of the tendon at
`each end anchorage and removing said tendon;
`(c) constructing new end anchorages where needed
`- to replace defective anchorages for a new tendon
`or tendons in a new beam to be formed in said
`trench;
`(d) installing at least one new tendon in said trench
`between said end anchorages;
`(e) placing concrete into said trench to encase said
`new tendon or tendons, in concrete, thereby form-
`ing a replacement beam; and
`.
`(f) post-tensioning said tendon or tendons.
`3. The method of claim 2 further including the steps
`of installing rebar retainers into said original solid con-
`crete so as to extend at least partially across said trench
`prior to placing new concrete into said trench.
`
`Metromont Ex-1006, p.7
`
`Metromont Ex-1006, p.7
`
`

`

`5,044,139
`
`8
`further including the installation of bars secured to said
`anchor plates, said bars being generally parallel to the
`new tendon and within said trench.
`9. The method of claim 8 wherein said bars are se—
`cured into holes bored in the original concrete at the
`end of said bars adjacent said anchor plates.
`10. The method of claim 2 wherein the removal of
`
`7
`4. The method of claim 2 further including the step of
`coating the bonding surface of said trench with a cur-
`able epoxy bonding compound prior to placing new
`concrete in said trench.
`5. The method of claim 2 wherein said trench is built
`up with concrete to the desired grade and elevation for
`- said new tendon or tendons along their length prior to
`installation of said new tendon or tendons in said trench.
`6. The method of claim 2 wherein step (a) includes
`the step of cutting a trench on either side of said original
`tendon.
`7. The method of claim 2 further including the step of
`installing at least one tendon profile rebar retainer into
`said original solid concrete so as to extend at least par-
`tially across said trench adjacent
`the middle of the
`length of the trench.
`8. The method of claim 2 wherein step (c) includes
`the installation of rebars parallel to each end anchor
`plate adjacent said anchor plates, said rebars being se—
`cured into bores formed in walls of said trench; said step
`
`concrete in step (a) involves the formation of saw cuts
`on either side of the original tendon, removal of con-
`crete between the cuts with hammers until the top of
`the tendon is exposed, forming saw cuts on each side of
`said tendon to the bottom of said tendon and breaking
`said tendon free from the remaining concrete.
`11. The method of claim 2 wherein repairs of open-
`ings accidentally cut completely through said slab in
`step (a) are repaired by suspended flat form members
`below said openings from wire attached to rebar se-
`cured to the sides of the trench such that said form
`members close off each said opening.
`=0!
`*
`*
`*
`*
`
`10
`
`15
`
`20
`
`25
`
`30
`
`4O
`
`45
`
`50
`
`55
`
`60
`
`65
`
`Metromont Ex-1006, p.8
`
`Metromont Ex-1006, p.8
`
`