CONCRETE BEAM ASSEMBLY
A concrete beam assembly has a concrete beam with two vertical webs spaced apart from one another that extend along the length of the beam. A horizontal first flange extends between the first edges of the webs, so that the webs and first flange define a channel extending along the length of the beam. Horizontal second and third flanges extend laterally outward in opposing directions from the second edges of the webs. A flat flooring structure is supported by the upper surfaces of the beam.
1. Field of the Invention
The present invention relates generally to the field of precast concrete construction. More specifically, the present invention discloses a reinforced concrete beam assembly having a cross-section with a lower flange extending between the lower edges of two vertical webs, and a two upper flanges extending laterally outward from the upper edges of the webs.
2. Statement of the Problem
A wide variety of precast concrete slabs and beams have used for many years. The simplest type of precast concrete beam has a generally rectangular cross-section and may include reinforcing strands embedded in the concrete to increase the tensile strength of the slab. This configuration has the disadvantage of being structurally inefficient. In other words, this asymmetrical beam cross-section is not proportioned to achieve its optimum load-bearing capacity.
First and foremost, the absence of a lower flange means that the neutral axis is relatively high in the cross-section of a double-T beam, which increases camber (i.e., bowing over the length of the beam). A degree of camber may be acceptable in some structures, such as bridges, walkways and parking garages. But, camber has been a major obstacle to use of precast concrete tees in other types of construction, particularly where a flat floor surface is required. One response to the problem of camber has been to construct a raised floor over double-T beams using a grid of variable-height risers to support the floor panels and compensate for variations in the elevation of the upper surfaces of the double-T beams. However, this approach increases construction costs by increasing the structural depth.
Nonetheless, hollow-core beams have a number of drawbacks. One of the most significant limitations is the difficulty in forming voids 28 within a concrete slab. Hollow-core beams can be made using an extrusion process, but this requires the use dry-cast concrete to minimize sagging and the risk of collapse of the voids as the concrete sets. The maximum length of extruded beams is also limited due to the difficulties in handling long beams and the limitations of dry-cast concrete. Another approach has been to suspend pieces of foam in the wet concrete as the beam is being cast to create voids. This is unexpectedly difficult due to the large amount of buoyancy associated with foam in wet concrete.
3. Solution to the Problem
Nothing in the prior art discussed above shows a concrete beam assembly having the structure of the present invention. In particular, the present invention employs a beam cross-section having two vertical webs with a horizontal first flange extending between one set of edges of the webs, and horizontal second and third flanges extending laterally outward from the other edges of the webs. For example, in one embodiment, the beam has a horizontal lower flange extending between the lower edges of the vertical webs and two horizontal upper flanges extending laterally outward from the upper edges of the webs. Reinforcing strands can be embedded in the lower flange. A flooring structure can be placed atop an assembly of the beams to provide a relatively flat floor surface.
The present beam cross-section has the advantage of approximating the structural properties of the a hollow-core beam, without the difficulties associated with forming voids in a hollow-core beam. More specifically, the present beam cross-section can also be viewed as a series of I-beams in parallel to one another, in the same manner this analogy can be applied to a hollow-core beam. The vertical webs are analogous to I-beam webs, and the upper and lower flanges of the present beam cross-section are analogous to the upper and lower flanges of the I-beams. This provides the present beam cross-section with superior structural properties. In addition, the location of the neutral axis in the beam cross-section can be readily adjusted to meet the needs of a particular job by changing the dimensions and spacing of the webs and flanges.
SUMMARY OF THE INVENTIONThis invention provides a concrete beam assembly having a concrete beam with two vertical webs spaced apart from one another that extend along the length of the beam. A horizontal first flange extends between the first edges of the webs, so that the webs and first flange define a channel extending along the length of the beam. Horizontal second and third flanges extend laterally outward in opposing directions from the second edges of the webs. A flat flooring structure is supported by the upper surfaces of the beam.
These and other advantages, features, and objects of the present invention will be more readily understood in view of the following detailed description and the drawings.
The present invention can be more readily understood in conjunction with the accompanying drawings, in which:
Turning to
The beam 40 can have any desired length and other dimensions, subject to structural limitations and job requirements. It should also be understood that the cross-sectional pattern of the beam 40 could be extended laterally for more than two vertical webs 42, 43 (and therefore the resulting beam would have more than one channel 48). For example, the beam could have four vertical webs and two channels.
Some types of construction require a relatively flat floor.
A thin concrete topping layer 55 can be poured on top of the assembly to create a relatively smooth, flat floor surface covering the concrete beam 40 and insert 50. The channel 48 can be used for carrying pipes 80, ducts or wiring that are concealed beneath the flooring structure, as shown in
It should be expressly understood that the various embodiments of the present invention can be generalized in the following terms. The vertical webs 42, 43 are spaced apart from one another and in a generally parallel relationship extending along the length of the concrete beam. Alternatively, the webs 42, 43 could be non-parallel or extend along only a portion of the length of the beam, although this may complicate manufacture. Each web 42, 43 has upper and lower edges extending along their lengths.
A horizontal first flange extends between either the upper or the lower edges of the vertical webs depending on the embodiment of the concrete beam. In the embodiment depicted in
It should also be noted that the webs and first flange define a channel 48, 68 extending along the length of the concrete beam. In
Horizontal second and third flanges extending laterally outward in opposing directions from the other edges of the webs. In
The horizontal flanges 44, 45 and 46 in
In addition to the channel 48, 68 formed between the vertical webs 42, 43 (or 62, 63 in
It is important to recognize the structural advantages of the present invention. As previously mentioned, the present beam cross-section emulates the structural properties of a hollow-core beam, which in turn can be viewed as a series of I-beams in parallel to one another. The vertical webs in the present beam are analogous to I-beam webs, and the upper and lower flanges of the present beam are analogous to the upper and lower flanges of the I-beams. Although the vertical alignment of the flanges and webs is different in the present cross-section, this is largely irrelevant for the purposes of structural analysis. In particular, the presence of lower flanges allows the present invention to offer structural properties similar to a hollow-core beam, but without its manufacturing difficulties. This provides a high span-to-depth ratio and a high moment of inertia for the beam cross-section. In addition, reinforcing strands 15 can be embedded in the lower flanges to increase the strength and stiffness of the concrete beam.
The location of the neutral axis in the beam cross-section can also be readily adjusted to meet the needs of a particular job by changing the dimensions and spacing of the webs and flanges. The dimensions of the flanges and webs, as well as the horizontal spacing between the webs can be used to adjust the neutral axis of the beam cross-section, and thereby control camber to meet the needs of a particular job. It should be noted that this camber adjustment can be made even without changing the overall area of the beam cross-section or its weight.
The present beam cross-section does have the disadvantage of creating an uneven upper surface for flooring. However, this can be addressed by using a flooring structure on top of the concrete beams, as shown for example in
The above disclosure sets forth a number of embodiments of the present invention described in detail with respect to the accompanying drawings. Those skilled in this art will appreciate that various changes, modifications, other structural arrangements, and other embodiments could be practiced under the teachings of the present invention without departing from the scope of this invention as set forth in the following claims.
Claims
1. A concrete beam assembly comprising:
- a concrete beam having:
- (a) at least two vertical webs spaced apart from one another extending along the length of the beam, said webs having first and second edges;
- (b) a horizontal first flange extending between the first edges of the webs, whereby the webs and the first flange define a channel extending along the length of the beam, and
- (c) horizontal second and third flanges extending laterally outward in opposing directions from the second edges of the webs, whereby said flanges define upper and lower surfaces of the beam; and
- a flat flooring structure supported by the upper surfaces of the beam.
2. The concrete beam assembly of claim 1 further comprising reinforcing strands extending through the lower portion of the concrete beam.
3. The concrete beam assembly of claim 1 wherein the flooring structure comprises:
- an insert covering the channel; and
- a concrete topping layer over the insert and the upper surface of the concrete beam.
4. The concrete beam assembly of claim 1 wherein the flooring structure further comprises an insert having a planar upper surface extending between the upper edges of the webs to create a flat upper surface for flooring.
5. The concrete beam assembly of claim 1 wherein the flooring structure comprises:
- a grid of risers supported on the upper surface of the concrete beam; and
- a grid of floor panels supported on the risers.
6. A concrete beam assembly comprising:
- a concrete beam having:
- (a) at least two vertical webs spaced apart from one another extending along the length of the beam, said webs having upper and lower edges;
- (b) a horizontal lower flange extending between the lower edges of the webs, whereby the webs and the first flange define a channel extending along the length of the beam; and
- (c) horizontal upper flanges extending laterally outward in opposing directions from the upper edges of the webs, whereby said flanges define upper and lower surfaces of the beam; and
- a flat flooring structure supported by the upper surfaces of the beam.
7. The concrete beam assembly of claim 6 wherein the flooring structure further comprises an insert having a planar upper surface extending between the upper edges of the webs to create a flat upper surface for flooring.
8. The concrete beam assembly of claim 6 wherein the flooring structure comprises:
- an insert covering the channel; and
- a concrete topping layer over the insert and the upper surface of the concrete beam.
9. The concrete beam assembly of claim 6 wherein the flooring structure comprises:
- a grid of risers supported on the upper surface of the concrete beam; and
- a grid of floor panels supported on the risers.
10. The concrete beam assembly of claim 6 further comprising reinforcing strands extending through the lower portion of the concrete beam.
11. The concrete beam assembly of claim 6 further comprising reinforcing strands extending along the lower flange.
12. A concrete beam assembly comprising:
- a concrete beam having:
- (a) at least two vertical webs spaced apart from one another extending along the length of the beam, said webs having upper and lower edges;
- (b) a horizontal upper flange extending between the upper edges of the webs, whereby the webs and the first flange define a channel extending along the length of the beam; and
- (c) horizontal lower flanges extending laterally outward in opposing directions from the lower edges of the webs, whereby said flanges define upper and lower surfaces of the beam; and
- a flat flooring structure supported by the upper surfaces of the beam.
13. The concrete beam assembly of claim 12 wherein the flooring structure comprises:
- a grid of risers supported on the upper surface of the concrete beam; and
- a grid of floor panels supported on the risers.
14. The concrete beam assembly of claim 12 further comprising reinforcing strands extending along the lower flanges.
Type: Application
Filed: May 18, 2009
Publication Date: Nov 18, 2010
Inventor: John W. Hanlon (Littleton, CO)
Application Number: 12/467,722
International Classification: E04C 5/08 (20060101); E04C 3/20 (20060101); E04B 5/04 (20060101);