Patent Application
20180282993
The present invention relates to precast concrete building elements, such as precast concrete columns, and more particularly, to assemblies made from such building elements and related methods of assembly.
The use of reinforced concrete for structural elements of buildings is well known. The loads in concrete structures are transferred by both the concrete and the reinforcement within the structural elements. For many building applications, formwork for the concrete is assembled in situ, reinforcement is placed (typically in the form of steel rebar, often pre-stressed), and the concrete is poured and allowed to cure.
Alternately, precast concrete building elements are sometimes used, with the reinforcement already located therein and often extending out from one or more surfaces thereof. The use of precast elements can offer several advantages, including simplifying and speeding construction, reducing susceptibility to weather and environmental conditions on site, affording greater consistency and quality control for precast elements made in a more controlled, factory setting, etc. Examples of the advantageous use of precast concrete structural elements can be found in the inventor's prior U.S. Pat. No. 4,505,087, the contents of which are herein incorporated by reference in their entirety.
A conventional downside of the precast building elements is the complexity that can be involved when structurally tying one such element into other structural elements. Often, the reinforcement from adjacent elements are bolted or welded together, which can be very time consuming, require highly skilled laborers and special equipment. Sometimes the connection problem is largely avoided in low-rise structures by al the precast elements tall enough for the full height of the structure.
Referring to
While this appears, on the face of it, to be a rather simple solution, the problem is that engineering concerns and code requirements will often require a splice length 176 so considerable that it becomes impractical to accommodate the space needed between the precast elements 114, 124. Although the particular equations used to calculate the required splice length can be rather complex, a good approximation for illustrative purposes is that the splice length must be 40 times the diameter of reinforcement for splices in tension and 30 times the diameter of reinforcement for splices in compression.
In view of the foregoing, it is an object of the present invention to provide improved precast concrete building elements, assemblies thereof and related methods.
According to an embodiment of the present invention, an assembly of concrete structural elements includes a precast concrete lower column, a precast concrete column capital supported on an upper end of the lower column, at least one precast concrete beam supported by the precast column capital, at least one slab supported by the at least one beam, an upper column extending above the lower column, and a poured concrete lap splice connecting the lower and upper columns, a volume of the lap splice being at least partially defined by the lower column, the column capital, the beam, the slab and the upper column.
According to a method aspect, a lap splice is made between opposed ends of adjacent concrete structural elements having structural reinforcement extending therethrough and out the opposed ends thereof. The method comprises embedding splice reinforcement in each of the opposed ends such that the splice reinforcement extends out of each approximately as far as the structural reinforcement and overlaps the structural reinforcement within the opposed ends, and bringing the structural elements together such that the ends of the structural reinforcement and the splice reinforcement extending from the opposed ends overlap.
These and other objects, aspects and advantages of the present invention will be better appreciated in view of the drawings and following detailed description of preferred embodiments.
According to an embodiment of the present invention, referring to
The precast concrete structural elements include a lower column 14, a column capital 16, beams 20, slabs 22 and upper column 24. A poured footing 26 supports a lower end of the lower column 14. With reference to
Referring to
Referring to
To support the column capital 16 before it is permanently tied to the lower column 14 and the rest of the assembly 10, support blocks 42 are glued or otherwise secured around an upper end of the lower column 14. The support blocks 42 can be made of polystyrene or other suitable material. When no longer needed, the support blocks 42 can be removed, or alternately, left in place with some finish applied thereto. To facilitate visibility, the support blocks 42 are shown extending to the edges of the column capital 16; however, this is not a design requirement. The support blocks 42 can be much smaller than the footprint of the column capital 16. Strengthening the holding power of the support blocks 42 can be performed by wrapping cellophane or other substance acting as a belt around them.
Referring to
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The upper column 24 is arranged above the lower column 14, with upper column reinforcing 60 extending downwardly therefrom. From the foregoing, it will be appreciated that the lower column 14, column capital 16, beams 20 and slabs 22 both offer support for the upper column 24 and serve as a form for the space that needs to be poured to complete a lap splice between the respective reinforcement 32, 60. Thus, little or no additional formwork need be added, and the upper column 24 need only be lowered into the location shown in
For clarity of the illustrations, the reinforcement 32, 60 of the upper and lower columns 14, 24 is not shown in detail and every reinforcement element is not necessarily shown. Referring to
Each element of splice reinforcement 72, 74 overlaps its respective column reinforcement 32, 60 by the entire required splice length 76. Approximately one-half 80 of the overlap is within the respective column 14, 24, and one-half 82 of the overlap is outside. Thus, the effective exposed distance over which the column reinforcement 32, 60 and splice reinforcement 72, 74 is approximately one-half the full required splice length 76. An approximately 50% reduction in the required spacing for the lap splice 70 is achieved. Further reductions could be achieved by using larger diameter rebar for the splice reinforcement 72, 74 and/or by employing additional, shorter splice reinforcement sections 78 in the space 82 between the columns 14, 16. Preferably, an element of splice reinforcement 72, 74, 78 is supplied for each element of column reinforcement 32, 60.
The substantial reduction in effective lap splice 70 length achieved by the present invention can work synergistically with the assembly 10. In particular, the height of the column capital 16, beams 20 and/or slabs 22 can readily be adjusted to closely match the effective lap splice 70 length, making tying together of structural elements via a lap splice much simpler.
While the present invention can significantly reduce the required splice length, and allow other structural elements to serve as formwork for the lap splice, it may still be desirable to provide additional stability to the upper column 24 while the lap splice 70 is being poured. Referring to
Only two pairs of connectors 84 are shown in
In general, the foregoing description is provided for exemplary and illustrative purposes; the present invention is not necessarily limited thereto. Rather, those skilled in the art will appreciate that additional modifications, as well as adaptations for particular circumstances, will fall within the scope of the invention as herein shown and described and the claims appended hereto.
