Joints and connections – Molded joint – Socket or open cup for bonding material
Reexamination Certificate
1997-09-15
2001-01-23
Kim, Harry C. (Department: 3629)
Joints and connections
Molded joint
Socket or open cup for bonding material
C403S267000, C403S408100, C405S259500, C052S698000
Reexamination Certificate
active
06176638
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to anchor systems for joining structural members, methods of making and using those systems and combinations of structural parts joined by the anchor systems. More particularly, the invention relates to tensioned anchor systems that give an indication that the system is under the appropriate tension, mold parts used to adapt poured concrete structural members for use with the anchor systems and joined structural members, such as columns and road barriers, employing the anchoring systems of the invention.
Threaded anchors that are secured with a securing agent in a hole into which the anchor is inserted are well known. In an improved anchoring system a fast setting polymer resin is introduced into the hole to fill the bottom portion of the hole, and a significantly slower setting resin securing agent fills the remaining upper portion of the hole. Then, once the faster setting securing agent has set, the anchor is tensioned by turning down a retaining nut on the exterior end. The torque induced tension to which the anchor is drawn is calculated to be higher than any subsequent forces the anchor will subsequently receive when loaded. The tension is maintained in the anchor portion extending from the quick-setting securing agent to the nut as the slower setting securing agent hardens. The load transfer via the resins to the surrounding concrete structure is accomplished on a molecularly bonded radially distributed basis over the height of the now adhesively secured, strained steel anchor. The bonded, extended anchor thus has its torquing energy distributed to the concrete causing compression within the structure. The stored energy in these systems is available to react to subsequent loads. The molecular bonding provides much more efficient load transfer than a mere mechanical action from commonly used non-shrink cementitious grouts.
In the improved systems as just described it was not evident if subsequently the anchor had loosened, for example, by elongation due to creep. Nor was there a means for continuing to apply tension to an elongated anchor member.
Structural members such as columns supporting bridges or freeways have utilized adjoining openings between which extend an anchor member that may have been grouted in at least one of the openings, but that was itself passive or free of loading. During earthquakes, these joined structural members have been known to fail at such junctions. Typically the rebars joining the members are not pre-loaded, nor bonded to the concrete. Thus, they have very little capacity to resist enormous multi-directed lateral and vertical seismic forces.
A means for quickly readily forming a structural member to accept chemically secured-in-place anchors without leaving behind a residue of release agent in the freshly poured concrete has been needed to assure that a liquid securing agent introduced into a hole molded in the concrete had purchase on the interior surface of the hole and readily transfer loads on a molecular basis by virtue of the bond anchor and the concrete. Known hole firming devices have acted as bond breakers to the concrete. The result has been mechanical load transfer from the anchor to the concrete rather than load transfer at a molecular level.
Road barriers have been joined end-to-end in the past, but have not been readily adapted for the introduction of grout into anchor receiving openings, and they have not been joined end-to-end with an anchor especially adapted to permit their being situated at an angle other than 180°.
BRIEF SUMMARY OF THE INVENTION
In accordance with this invention there is provided improved anchoring systems and their methods of use, whereby a deformable indicating member is located between a retaining member or nut and the surface into which the anchor protrudes. Upon tightening, the deformed member is resiliently deformed. However its elastic memory urges its return towards its previous, undeformed condition so that, should the anchoring system tend to loosen by virtue of elongation of the anchor, the tendency of the deformable member to return to its initial condition indicates this fact and continues to place the anchor in tension.
The use of a post-tensioned anchor system to join columns end-to-end by introduction of the anchor system into a diagonally formed hole opening through the side of one of the columns places the columns in compression at their adjoining faces unlike the passive anchors previously used and found to be vulnerable in earthquakes. The system is especially suitable for retro-fitting columns joined in the manner previously described. Because load transfer in these chemically secured anchors operate at the molecular level an extremely secure adherence of the anchor to the structural member is afforded, one that typically exceeds the tensile strength of the anchor.
In securing road barriers to road surfaces superior force resistance has been observed by use of a tensioning method similar to that mentioned above for joining columns. A hole in the road surface is filled or partially filled with a fast setting resinous cement or securing agent, and an anchor is introduced into the hole through an aligned hole in the barrier. After the fast setting cement has set, a slower setting grout or securing agent is introduced to fill or partially fill the aligned holes in the road surface and the barrier. Before the slower setting grout or securing agent sets, the anchor is tensioned as described above to bring the road surface and barrier into compression by turning down a nut on the protruding threaded end of the anchor. Again, a stored energy system is created that is very resistive to impact or other external forces. The dished washer can again serve as a visual indicator of the tensioned condition of the anchor.
Poured concrete structural elements such as columns, footings for lamp standards, and concrete highway barriers, to name just a few, need to have holes formed to receive hardening securing agent if a chemically secured-in-place anchor is to be used. These holes can be molded efficiently through the use of an inventive, tapered mold part threaded along its length and formed of a plastic that readily releases from the hardened concrete around it. The tapered or conical shape permits quick removal by just a few turns until the threads of the mold part are free of the threads it has formed in the concrete structural member, at which time the mold part and can be lifted out. The use of a rod-like mold part in communication with the tapered mold part readily defines passages from the exterior of the structural concrete member to the interior of the tapered, threaded hole formed by the tapered, threaded mold part. By that means liquid securing agent can be introduced through the passages left by the rod-like mold part.
Additional means for forming a hole for anchors subsequently to be bonded to the inside walls of the formed hole include:
1. a longitudinally slit non-adherent sheath or sleeve that covers a metal rod. Upon withdrawal of the rod, the sheath snaps inward to its relaxed condition and is easily withdrawn.
2. A hard mold part covered with a plastic or other chemically removed covering of sufficient thickness such that when the mold part is withdrawn following chemical destruction of the covering, there results an annular space between the mold part and the molded concrete structural member of sufficient width to permit the introduction of securing adjacent. The hard mold part may be the anchor itself.
3. A mold part covering of polystyrene foam or other material that is sufficiently resistive to compressive forces to withstand the unhardened concrete in which it is immersed, but that will crumble upon withdrawal of the mold part.
4. A plastic forming device particularly useful in elaborate molded passages and holes and filled with ice or another hardened material capable of being melted after the concrete structural member sets, whereupon easy withdrawal is effected.
Structural member combinations that are efficaciously formed
Jasien Leo
Kellison Roger C.
Baker & Botts L.L.P.
Kim Harry C.
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