Static structures (e.g. – buildings) – Machine or implement
Reexamination Certificate
1999-04-15
2001-02-27
Redman, Jerry (Department: 3634)
Static structures (e.g., buildings)
Machine or implement
C052S583100, C052S295000
Reexamination Certificate
active
06192647
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a high strength grouted pipe coupler by which pairs of spaced axially aligned steel reinforcement bars (i.e. rebars) are reliably spliced to one another for the purpose of connecting together and providing continuous support for contiguous precast or cast-in-place columns, walls, beams, and similar concrete structures to enable buildings, parking structures, bridges, subways, airports, and the like, to be better able to survive a seismic event.
2. Background Art
It is common in the construction industry, during the erection and retrofitting of buildings, parking structures, bridges, subways, airports, etc., to add a new contiguous concrete structure to an existing precast concrete structure. Care must be taken during construction to ensure that the contiguous structures are interconnected so that they will not shift relative to one another, particularly as a consequence of a seismic event. The foregoing has typically been accomplished by means of splicing together steel reinforcement bars (commonly known as rebars) that are embedded in and project from the existing and new structures so as to provide continuous reinforcement between the structures, whereby the structures will be capable of withstanding shear forces as well as tensile and compressive loads.
It has been known to use cement grout filled pipe couplers to splice together opposing rebar upstands that are embedded in the existing and new concrete structures. Such pipe couplers are usually made from steel by means of a casting process which increases the cost of construction, especially when large numbers of couplers are used in a project. In addition, the conventional pipe coupler requires a relatively long cylindrical pipe so as to prevent a separation of the rebars from their couplers in response to strong pulling forces.
In this same regard, the majority of stress experienced by conventional cement grout filled pipe couplers are concentrated along the interface of the reinforcement bar with the cement grout with which the cylindrical pipe of the coupler is filled. Consequently, the reinforcement bars can be undesirably loosened from or pulled out of their pipe couplers under compression and tension forces, such as those generated during an earthquake. To overcome this problem, the rebar has been provided with pronounced ribs along the length thereof to enhance the bond between the reinforcement bar and the cement core which fills the cylindrical pipe of the coupler. In other cases, a special, high strength cement grout has been used to preserve the integrity of the pipe coupler. In both of these solutions, the cost and complexity of manufacturing and/or installing known conventional grouted pipe couplers are increased which leads to an overall inefficient and possibly unreliable construction effort.
Accordingly, it would be desirable to have a relatively low cost, high strength and readily available cement grouted pipe coupler that will overcome the problems associated with conventional pipe couplers so as to be capable of reliably splicing together a pair of opposing embedded reinforcement bars and withstanding decoupling under tension and compression loads like those generated during an earthquake.
Reference may be made to the following application and patents for examples of conventional grouted pipe couplers:
European Application 92117276.3 published Jun. 23, 1993
U.S. Pat. No. 3,540,763 issued Nov. 17, 1970
U.S. Pat. No. 4,627,212 issued Dec. 9, 1986
U.S. Pat. No. 5,366,672 issued Nov. 22, 1994
SUMMARY OF THE INVENTION
In general terms, a high strength grouted pipe coupler is disclosed by which pairs of spaced, axially aligned steel reinforcement bars (i.e. rebars) are spliced to one another for connecting together contiguous precast and cast-in-place columns, walls, beams, etc. during the construction or retrofitting of a building, parking structure, bridge, subway, airport, or the like. A precast concrete structure has a first reinforcement bar embedded therewithin and projecting upwardly therefrom. The top or free end of the first reinforcement bar is first upset so as to have a relatively wide head.
Next, the pipe coupler is installed by positioning a hollow cylindrical steel pipe around the first reinforcement bar so that the cylindrical pipe rests upon a seal which lies against the concrete structure from which the bar projects. Located within the hollow cylindrical pipe is a spiral reinforcement wire that surrounds the reinforcement bar in coaxial alignment therewith. An opposing reinforcement bar having a relatively wide upset head formed thereon is coupled to the cylindrical pipe by means of threaded male and female collar and anchor members which engage the upset end of the opposing reinforcement bar. The upset heads of the first and opposing reinforcement bars are arranged in spaced axial alignment with one another at the interior of the hollow cylindrical pipe.
The interior of the hollow pipe of the pipe coupler is then filled with cement grout via a grout inlet port so as to envelop the spiral reinforcement wire therewithin. By virtue of the spiral reinforcement wire, the stresses that are applied to the first reinforcement bar during an earthquake are uniformly spread out and distributed away from the upset head thereof so as to improve the bond between the reinforcement bar and the cement core at the interior of the pipe coupler. In addition, the combination of the spiral reinforcement wire and the upset heads of the first and opposing reinforcement bars cooperate to anchor the cement core within the pipe coupler in order to impede a removal of the cement core from the coupler and prevent the first reinforcement bar from pulling loose of the core. Accordingly, continuous and reliable reinforcement between contiguous concrete structures is provided by means of the grouted pipe coupler of this invention splicing together a pair of opposing reinforcement bars that project from such structures.
REFERENCES:
patent: 4627212 (1986-12-01), Yee
patent: 5308184 (1994-05-01), Bernard
patent: 5366672 (1994-11-01), Albrigo et al.
patent: 5383740 (1995-01-01), Lancelot
patent: 5606839 (1997-03-01), Baumann
patent: 5732525 (1998-03-01), Mochizuki et al.
patent: 2034857 (1980-06-01), None
Fischer Morland C.
Redman Jerry
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