US3710526A

US3710526A - Annular compression beam

Info

Publication number: US3710526A
Application number: US00099053A
Authority: US
Inventors: C Parks
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-12-17
Filing date: 1970-12-17
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16

Abstract

A roof, floor and ceiling construction is disclosed wherein pre or post stressed, radially extending tendons are placed within an annular compression beam. In this construction a reinforced annular girder is precast. After the cement has set high tensile, radially extending tendons are prestressed. Concrete is than placed in areas defined as a web and annulus slab. After the concrete has set the tension is relieved and the beam is ready for use as floor or roof construction.

Description

PATENTEUJmsmn SHEET 1 OF 2 INVENTOR. CHARLES A. PARKS BY B2340 7 FIG. 4

ATTORNEY.

PATENTEUJM 16 :91:

SHEET 2 [IF 2 FIG.7

FIGS

r INVENTOR. CHARLES A. PARKS BY f/l m 7 1/4 ATTORNEY FIG.8

ANNULAR COMPRESSION BEAM BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to pre and post stressing of concrete slabs and more particularly to a method of construction of precast ceilings and floors for high rise buildings.

2. Description of the Prior Art There has always been a need for buildings having unobstructive,.open and expansive floor areas such as buildings which are used for civic auditoriums, aircraft hangers and the like. Numerous different structures have been proposed and numerous different materials have been tried in the construction of such buildings. Steel and concrete materials have been used largely because of their fire proof nature. However, long structural steel members create considerable shipping problems and they are expensive to move from one location to another.

In the prior art, concrete buildings have been principally constructed by pouring concrete in forms which have suitable reinforcement or by using precast and reinforced concrete slabs. This form of construction requires the repair and maintenance of pouring forms, their erection and disassembly and involves an appreciable shipping problem in moving the forms about.

Most reinforced concrete slabs which are produced in this manner have very good compression characteristics but they are relatively weak in tension. So, in order to compensate for such weakness a method in concrete construction has been introduced which is known as prestressed concrete. Prestress concrete may be classed as concrete having pretensioned steel inserts or post tension steel inserts. The steel used is a high tensile quality and may be in the form of wire ropes, strands or single length steel bars. In prestressing, the reinforcement is placed in tension before the concrete is poured and, subsequently, the release of the tension after the concrete has set, places the concrete itself in compression.

There is a second method of improving the tension characteristics of cement which is termed post stressing. In post stressing, the concrete is poured about the reinforcement-but it is not bonded thereto. Subsequently, after it is set, a tension force is applied to the steel reinforcements and is maintained to hold the concrete in compression.

Other particular methods of pre and post stressing concrete slabs are disclosed by the prior art patents such as:

U.S. Pat. No. 1,559,837

U.S. Pat. No. 3,153,302

U.S. Pat. No. 3,319,386

U.S. Pat. No. 1,559,837 discloses a reinforcing structure for ceilings and floors. In this device, a rectangular frame of reinforced concrete with an anchoring element at each corner is poured. After this outside frame has hardened, a wheellike frame which substantially touches the outside frame on the beam sides is disposed within the outside frame. The wheel has a centrally located hub from which radiates spoke like elements which extend to the rim portion of the wheel. These spoke like elements are, in this patent, shown to be rods which are screw threaded at both ends so as to be attached to the hub and the rim of the wheel. Attached to the peripheral edge of the wheel are stress rods which are attached to the anchoring elements referred to above. In this patent it is taught to stress, by means of a tensioning nut, these stress rods which radiate between the wheel rim and the various; anchoring elements. By this teaching then, as the tension nuts are drawn up the wheel as a whole is suspended in a condition of substantially uniform static stress. This patent further teaches that when the wheel frame has been secured and stressed in the manner described, concrete is applied and allowed to harden. Thus, it is taught that a force applied, either to a particular part or distributed over the whole area, is transmitted to the four anchors and from these four anchors in the direction of length of the outside frame elements.

In a second prior device, U.S. Pat. No. 3,319,386, another method of pre-stressing concrete is shown. In this patent, an inner tension frame and an outer compression frame member are spaced in a planar relationship to each other. A plurality of cables connect the two members and are secured with substantially no stress on these cables. Next, one of the frames is rotated relative to the second frame such that the distance between each cable connecting points is increased without altering the radial distance between the frame members. This action induces stresses in the inner frame member and the cables while induces compression stressed in the outer frame member. A fixed form is then constructed at the lower side of the assembly and a concrete slab is poured between the frame members, enclosing the cables. After the concrete has set, the form is removed and the exterior stress on the frame member is released. The stresses in the cables are thereby imparted to the concrete producing a slab of uniformly prestressed concrete with securely retained inner and outer peripheral rims.

In yet another prior art device, U.S. Pat. No. 3,153,302, another type of prestressed concrete roof structure is disclosed. In this patent, an umbrella form of roof is provided in which the entire dead load of the roof is carried by a central column. In this construction, a pair of concentrically disposed, annular rings are provided with high-tensile wire ropes between them. The inner annular ring is a tensile ring that is slidably mounted on the central column. This permits the roof to be fonned at the base of the column and to be later erected and tensioned on the column. The outer annular ring is a compression ring which also takes the form of a many sided irregular polygon. The roof tendons connect the inner and outer annular rings.

After the roof frame is wired and raised on the roof supporting central column, tension is applied to the peripheral edge of the outer annular ring by turning a turnbuckle on a plurality of tie down cables which are securely attached to the foundation at one end and the outer annular ring at the other. Thus, uniform tension is imposed upon the roof framework. After the appropriate tension is placed on the roof tendons, a form is built on the underside of the framework and a concrete aggregate is applied to both the top and the bottom sides of a reinforcing wire mesh so as to thoroughly encase the tensioned high tensile roof strands. The wire rope strands remain in tension until the roof covering concrete aggregate has reached its initial set and can withstand the compressive forces exerted by the release of the tensioned force. The external tensioning is then released thereby causing the roof tendons to apply a vertical lift force to the outer annular compression ring. The inverted cone-shaped aggregate roof shell is then under compressive forces which more than compensate for the dead weight tensile load of the roof structure.

SUMMARY OF THE INVENTION In this invention, a new and useful advance over the prior art methods and structure for roof and floor construction is obtained by providing an annular compression beam of any desired diameter within which is encapsulated annular reinforcing rods. Concentric with and co-planar to an annular girder is located a steel tensioning ring. Connecting the annular girder and the steel tensioning ring are a plurality of high tensile steel tendons which are arranged such that they may be tensioned prior to pouring a concrete aggregate into the area defined by the annular girder and the tension ring, and known as the web slab.

In a second embodiment an annular slab of reinforced concrete may be cantilevered on the annular girder, to form an outer annulus slab such that the internal web slab has the approximate moment of inertia as the outer annulus slab.

In another embodiment, other high tensile tendons are stressed between the annular girder and the peripheral edge of the annulus slab such that after the pouring of the annulus slab, the tension can be relieved whereby the annular slab will be prestressed as is the web slab.

In yet another embodiment one continuous high tensile strength tendon may extend from the steel tension ring to the periphery of the annulus slab where it is placed under tension until after the concrete aggregate has set in both the annulus slab and the web slab portions.

In yet another embodiment, post stressing can be utilized to set a compressive force up within both the web slab and the annulus slab sections. In these embodiments, after the annular compression beam is formed the concrete aggregate is placed about the high tensile strength tendons but there is not tension within these tendons nor is the concrete aggregate allowed to bond thereto. Subsequently, after the concrete has set, a tension force is applied to the high tensile strength tendon and is maintained thereafter in order to hold the web slab and the annulus slab in compression.

The invention accordingly comprises the features of construction, combination of elements and arrange ment of parts which will be exemplified in the construction hereinafter set forth and the scope of the invention will be indicated by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial top view of one embodiment of the annular beam of the instant invention.

FIG. 2 is a partial cross sectional view through line 22 of FIG. 5.

FIG. 3 is a broken cross-sectional view through line 33 of FIG. 11.

FIG. 4 is a broken, partial view through line 44 of FIG. 11.

FIG. 5 is a partial top of one embodiment of the annular beam of the instant invention.

FIG. 6 is a broken cross-sectional view through line 66 of FIG. 1.

FIG. 7 is a broken, cross-sectional view through line 7--7 ofFIG. 10.

FIG. 8 is a broken, cross-sectional view through line 88 of FIG. 10.

FIG. 9 is a top view of the compression beam of the instant invention without the cantilevered annulus slab.

FIG. 10 is a partial top view of one embodiment of the annular compression beam of the instant invention.

FIG. 11 is a partial top view of one embodiment of the annular compression beam of the instant invention.

Similar reference characters refer to similar parts of the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, FIGS. 1, 5, l0 and l 1 each represent one quadrant of a solid compression beam 10. This beam 10 is generally circular and is designed to be utilized as ceilings and floors, especially for high rise circular buildings. It should be noted that as each of the above mentioned

quadrants

12, 14, 16 and 18 have a particular type of internal structure and when a particular quadrant is discussed the particular internal structure extends throughout beam 10.

Referring now to FIGS. 2 and 5, a first embodiment of the present invention is shown. Here, annular girder 20 is provided with a plurality of annular reinforcing bars or rods 22. Annular girder 20 is surrounded with suitable standard forms (not shown) and is cast with a suitable concrete aggregate 26 to form an annular ring with a generally rectangular cross section. Before concrete aggregate 26 is poured into the form surrounding the annular girder 20, a plurality of radially extending web-annulus tendons 24 are placed transverse to girder 20. Web-annulus tendons 24 are in a substantially non-stressed condition at the time girder 20 is cast. After concrete 26 has set, the interior ends 28 of web-annulus tendon 24 are attached to stress ring means, such as steel tension ring 30. Tension ring 30 as well as annular girder 20 are held in a fixed, spaced concentric co-planar relationship by suitable means (not shown). Additionally, the outer ends 32 are provided with holding and tensioning means such as flange 34, nut 36 and standard support frame (not shown) which hold web-annulus tendon 24 fixedly with respect to annular girder 20. 1

The tensioning means then place a stress on web-annulus tendons 24 and while web-annulus tendons 24 are in a tensioned state, concrete 26 is poured. After concrete 26 has set, the release of the tension at inner end 28 and outer end 32 places concrete 26 in compression. The compression beam is now ready to be utilized as floor or roof in a building.

The diameter of compression beam 10 is a matter of choice. Additionally, the dimensions of beam 10 may be calculated such that the moment of inertia of the interior slab, designated as web slab 38, about annular girder .20 will be substantially equal and opposite the moment of inertia of the exterior slab, designated as annulus slab 40, such that the balancing effect allows for better load bearing characteristics for a given amount of concrete and tendon reinforcing.

The compression beams are supported by standard support columns 42, here, three equidistant supports are shown to be placed under annular girder 20, however, the number and spacing of these column supports is a matter of choice depending upon the structural needs of the construction.

Referring now to FIGS. 3, 4 and 11, a second embodiment of compression beam is shown. In this embodiment a plurality of web tendons 44 are radially cast, inwardly within annular girder 20 and threadedly attached to tension ring 30 by bolt 36. An integral flange 46 is provided on the outer end of tendon 44 and it is arranged to abut the outer side of girder 20. As in the first embodiment, tendon 44 is placed in a tensioned state which is released after concrete 26 in web slab 38 has set. Thus prestressing web 38.

Additionally, a set of outwardly extending annulus tendons 48 may be embedded within girder 20. Annulus tendons 48 have an integral flange 46 which abut the inner wall of compression ring 20 in a manner similar to web tendon 44. Annulus tendons 48 may be tensioned prior to the pouring and setting of concrete 26 as with web tendons 44 whereby annulus slab 40 is termed prestressed. However, annulus slab 40 may also be formed with annulus tendons 48 in a non-stress condition wherein annulus slab 40 is termed reinforced as opposed to prestressed.

The remaining two embodiments, illustrated in FIGS. 1, 6, 7, 8 and 10 deal with the same generalized structure of compression beam 10 as discussed supra. However, here, the various tendons are stressed by post tensioning. In post tensioning the concrete 26 is poured about the tendons but it is not bonded thereto. Subsequently, after concrete 26 has set, a tension force is applied to the tendons and is maintained to hold concrete 26 in compression.

FIGS. 1 and 6 illustrate the web-annulus tendon 24 in the post tensioned state. It will be noted that in FIG. 6 tendon 24 is not bonded to concrete 26 at the tendon cement interface 50.

The same basic post tensioning procedure follows for the fourth embodiment illustrated by FIGS. 7, 8 and 10. Here both annulus tendons and web tendons are stressed and maintained in that condition only after the concrete has set in web slab 38 and annulus slab 40.

In FIG. 9 another embodiment is illustrated in which compression beam 52 consists only of girder 20, web slab 38, web tendons 44 and tension ring 30. Additionally it is contemplated that either the prestressing or post stressing methods may be used to place web slab 38 under compression.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description as shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Now that the invention has been described,

What is claimed is: 1. A prestressed concrete beam for use in ceiling and floor construction comprising; an annular girder comprising a concrete aggregate, a plurality of prestressed rods fixedly attached to said annular girder and extending radially inward to engage an inner annular tension ring, an inner annulus slab of concrete in a surrounding relationship to said rods whereby when the stress on said prestressed rods is released said rods will place said surrounding inner annulus slab in compression, said annular girder cooperatively engaging a plurality of support beams to support said concrete beam above the supporting surface.

2. The concrete beam of claim 1 wherein said prestressed rods extend radially outward from said annular girder to engage an outer annular tension ring and further wherein said outwardly extending portions are surrounded by an outer annulus slab of concrete whereby when the stress of said prestressed rods is released said prestressed rods place said outer annulus slab in compression, said inner and outer annulus slabs being substantially balanced about said annular girder.

3. The concrete beam of claim 1 wherein said annu' lar girder includes at least one supportingannular rod embedded in said concrete aggregate.

4. The concrete beam of claim 1 wherein the interior ends of said plurality of rods are releasably attached to said inner annular tension ring whereby said plurality of radially extending rods are held in a stressed condition prior to the time said inner annulus slab of concrete sets.

5. The concrete beam of claim 4 wherein said inner annular tension ring is held in a fixed, spaced concentric, coplanar relationship with said annular girder.

6. The concrete beam of claim 1 wherein a second set of prestressed rods are attached at one end to said annular girder and extend radially outward from said annular girder and further wherein said outwardly extending portions are surrounded by an annular slab of concrete whereby when the stress on said prestressed rods is released said prestressed rods place said surrounding concrete annular slab in compression.

7. A post stress concrete beam for use in ceiling and floor construction comprising an annular girder com prising a concrete aggregate, a plurality of stressable rods fixedly attached to said annular girder and extending radially inward, an inner annulus slab of concrete poured in a surrounding relationship to said rods but wherein said rods are not bonded to said concrete, stressing means attached to the interior ends of said rods whereby after said inner annular slab has set, said rod may be stressed thereby placing said concrete of said inner annulus slab in compression.

8. The concrete beam of claim 7 wherein said post stressed rod extend radially outward from said annular girder and further wherein said outwardly extending portions are surrounded by an outer annulus slab of concrete, stressing means provided on the periphery of said outer annulus slab whereby after said concrete in said outer annulus slab has set said rods are placed in tension thereby placing said concrete of said surrounding outer annulus in compression.

Claims

1. A prestressed concrete beam for use in ceiling and floor construction comprising; an annular girder comprising a concrete aggregate, a plurality of prestressed rods fixedly attached to said annular girder and extending radially inward to engage an inner annular tension ring, an inner annulus slab of concrete in a surrounding relationship to said rods whereby when the stress on said prestressed rods is released said rods will place said surrounding inner annulus slab in compression, said annular girder cooperatively engaging a plurality of support beams to support said concrete beam above the supporting surface.

3. The concrete beam of claim 1 wherein said annular girder includes at least one supporting annular rod embedded in said concrete aggregate.

7. A post stress concrete beam for use in ceiling and floor construction comprising an annular girder comprising a concrete aggregate, a plurality of stressable rods fixedly attached to said annular girder and extending radially inward, an inner annulus slab of concrete poured in a surrounding relationship to said rods but wherein said rods are not bonded to said concrete, stressing means attached to the interior ends of said rods whereby after said inner annular slab has set, said rod may be stressed thereby placing saId concrete of said inner annulus slab in compression.