Static structures (e.g. – buildings) – Crossed reinforcing rods with connector
Reexamination Certificate
2000-08-11
2001-12-11
Stephan, Beth A. (Department: 3635)
Static structures (e.g., buildings)
Crossed reinforcing rods with connector
C052S719000, C052S251000, C052S260000, C052S414000, C052S334000, C052S742100
Reexamination Certificate
active
06327832
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a shearing reinforcement for flat ceilings comprising several dowel strips arranged in a substantially radial position in the bearing area and each consisting of a dowel rail and a plurality of vertical, parallel dowels attached thereto at a distance from one another, whereby said dowels are provided with an elongated dowel shank and an enlarged dowel head on at least one end opposite said rail. The invention relates also to a dowel strip for such a shearing reinforcement.
Shearing reinforcements of this type are used in the transmission of vertical forces occurring in the bearing area of flat ceilings made of reinforced concrete or similar stressed concrete slabs (DE 27 27159 C3). The dowels, which are arranged perpendicular to the plane of the slab, absorb shearing forces that occur in the bearing area. The dowel shanks are thereby substantially stressed by a tensile load.
In addition to the especially favorable arrangement, as seen from a technical manufacturing viewpoint, of placing the dowels at equal distances apart along a dowel strip, it is also known to arrange the dowels at various distances from one another on the dowel strip. In particular, a closely spaced dowel configuration may be chosen for the highly stressed region in the immediate vicinity of the ceiling support of stay. A dowel spacing may be selected that is further apart in the zone away from the stay where there is less stress; however, exceeding the upper deviation value of a given dowel spacing is not permitted since an uneven shearing force distribution could possibly result thereby.
In practice, this leads to the fact that this shearing reinforcement is dimensioned according to stress conditions in the immediate vicinity of the stay and it is over-dimensioned at the region further away from the stay.
It is therefore the object of the invention to provide a shearing reinforcement of the type mentioned at the beginning so that an improved adaptation to the respective occurring stress is obtained.
SUMMARY OF THE INVENTION
This object is achieved according to the invention in that the shank diameter of the dowels near the ceiling support is greater than the shank diameter of dowels disposed further away.
This shearing reinforcement configuration fulfills static requirements to absorb the same vertical load in the region near the stay as in the outer and clearly larger region without experiencing over-sizing of the shearing reinforcement in the outer region and whereby the widest allowable spacing of the dowels, determined especially from static values, is not exceeded.
The selection of a smaller shank diameter for dowels further away from the stay makes possible a more even stress on the dowels corresponding to the actual load distribution. More dowels with smaller shank diameters are better in their load bearing performance than fewer dowels with larger shaft diameters.
Since the dowels have at least on one end, but preferably on both ends, an upsetted (flattened) dowel head (formed while the metal was hot) and said dowel head is about three times larger than the shaft diameter, the amount of energy necessary for manufacturing the dowel head by upsetting shanks with smaller diameters is considerably lower. Production is thereby faster and ecologically better.
Consumption of material and the weight of the dowel strip is reduced by the use of dowels with smaller shank diameters in a substantial part along the length of the dowel strip; this simplifies and makes easier the transportation and assembly at the building site. Since the dowel strips are installed together with an upper and lower ceiling reinforcement that is normally very close on one another, a large dowel head diameter is a hindrance during installation since the space between the two neighboring reinforcement rods is often times very small. A smaller dowel head diameter is therefore better for installation. Furthermore, the insertion of the reinforcement is made easier with smaller shank diameters.
According to a preferred embodiment of the invention it is proposed that in the zone near the stay, dowels are arranged with a diameter that is greater than the diameter of the remaining dowels disposed at the zone away from the stay. The stay reinforcement corresponds thereby to the given static load conditions whereby in the zone near the stay, for example, the same load has to be carried as in the larger zone away from the stay.
The zone near the stay and the zone away from the stay are preferably adjacent to one another whereby each zone is arranged substantially annular and concentric around the stay and whereby the diameter of the zone away from the stay is preferably at least twice as large as the diameter of the zone near the stay.
In addition to the configuration within the scope of the embodiment of the invention wherein the dowels have continuously decreasing diameters from the stay toward the outside, which admittedly makes possible a wide adaptation to the load conditions, but which would require substantial production expenditures, it has been shown to be very beneficial—under consideration of the technical manufacturing conditions—to divide the area around the stay into two zones, namely a highly stressed zone near the stay and a lower stressed zone further away from the stay and to select various shank diameters for the dowels in these two zones. Since so far only two different shank diameters have been proposed, the manufacturing requirements are only slightly higher relative to a version with equal shank diameters; however, at the same time a very favorable adaptation to occurring load conditions is achieved.
According to another preferred embodiment of the invention it is proposed that in the zones near and away from the stay there are disposed separate inner or outer dowel strips. Preferably there is arranged for each inner dowel strip in the zone near the stay an outer dowel strip in the zone away from the stay, both being aligned with one another. This separation into a respective inner and outer dowel strip makes possible to manufacture these two types of dowel strips separately and to separate them from the longer dowel strips, which are equipped with equally designed dowels. In particular, various configurations may be selected for the inner and outer dowel strips, which are not only different in regard to the shank diameter but also in regard to the function of the dowel strip itself carrying the dowels.
Preferably it is proposed that the dowels of the inner dowel strip are welded at one end of their shank to an inner dowel strip and are provided with a dowel head on the other end. The dowels of the outer dowel strip are designed as double-headed dowels, which are attached to an outer dowel strip.
The more costly welding of the dowel to the dowel strip during manufacturing is thereby only used for the inner dowel strip because it is more advantageous for static reasons and which is often times even necessary to pull the dowel strip against the surrounding concrete material for transmission of forces. In the zone way from the stay, where the increased static requirement does not exist, dowel strips are used to only to secure positioning of the dowels so that a more simple type of connection may be selected in view of manufacturing technology. Costly and environment-impacting welding processes may be avoided thereby. These outer dowel strips may be manufactured by having less weight, which results in advantages for production and assembly.
Under consideration of static requirements and assembly, it is furthermore advantageous to arrange the inner dowel strips with the lower dowel rail and the outer dowel strips with the upper dowel rail.
In an additional configuration of the embodiment according to the invention, there is a one-piece dowel strip for such a shearing reinforcement, characterized in that at least two groups of vertical dowels are attached on the dowel strip parallel and at a distance from one another. The dowels have each an elongated shank and an enlarged
Ernst Peter
Schrader Gerhard
Burns Doane Swecker & Mathis L.L.P.
DEHA Ankersysteme GmbH & Co. KG
Dorsey Dennis L.
Stephan Beth A.
LandOfFree
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