GB2249329A

GB2249329A - Concrete floor beams

Info

Publication number: GB2249329A
Application number: GB9122816A
Authority: GB
Inventors: Mohammad Hossein Shamsai
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-11-02
Filing date: 1991-10-28
Publication date: 1992-05-06
Anticipated expiration: 2011-10-28
Also published as: GB9122816D0; GB2249329B

Abstract

A floor beam (12) arranged to be supported by two or more building supports (10) comprises a plurality of hollow prestressed concrete cores (16) extending longitudinally of the beam. At least one portion of at least one hollow core is open to the top surface of the beam. Building reinforcement means e.g. (18) is secured within the or each open portion of the beam (12) and extends above the top surface of the beam, to be received in and bonded to a layer of curable building material (15) laid over the beam. The beams (12) may have lower side edges (60, 160) for supporting floor panels (13). <IMAGE>

Description

BEAM/FLOORING SYSTEM This invention relates to improvements in beam/flooring systems.

Until now, the use of hollow-core prestressed concrete slabs was limited to one-way systems in building construction. Concrete or steel beams, or concrete block or brick walls were used in conjunction with hollow-core slabs as flooring.

It is an object of the present invention to obviate and/or mitigate the disadvantages of the prior art.

In one aspect, the present invention resides in a prestressed concrete, hollow-core, building beam arranged to be supported by two or more building supports, in the beam comprising: a plurality of hollow-cores extending longitudinally within the beam; at least one portion of at least one of the hollow cores being open to the top surface of the beam; and building reinforcement means secured within the open portion or portions of the beam and extending above the top surface of the beam to be received in and bonded to a layer of curable building material laid over the beam.

Further according to the present invention there is provided a prestressed concrete hollow core building beam arranged to be supported by two or more building supports the beam comprising a plurality of hollow cores extending longitudinally within the beam, at least one portion of at least one of the hollow cores being open to the top surface of the beam, building reinforcement material secured within the open portion or portions of the beam and extending above the top surface of the beam, to be received in and bonded to a layer of curable building material laid over the beam and in which an upwardly directed step is provided in at least one of the lateral edges of the beam.

Preferably a step is provided along each lateral edge of the beam.

Preferably reinforcing members are cast into the beam below the or each step.

Preferably, the reinforcing members are cast into the beam during manufacture, said members having a U-shaped configuration with one limb of the U being arranged above the other limb.

Preferably the free ends of each limb of the U-shaped members has transverse extensions therefrom.

Preferably the upper limb of the U-shaped members is located above the top surface of the beam.

According to another aspect of the invention there is provided a prestressed hollow core building beam arranged to be supported by two or more building supports, the beam comprising a plurality of hollow cores extending longitudinally within the beam, at least one portion of at least one of the hollow cores being open to the top surface of the beam, and building reinforcement means secured within the open portion or portions of the beam and extending above the top surface of the beam, to be received in and bonded to a layer of curable building material laid over the beam, wherein the outer edge of at least one of the outermost cores extends upwardly for a distance less than the inner edge thereof.

Preferably, the curable building material comprises cement.

Preferably, the outer edge of each outermost core extends upwardly for a distance less than the or each inner edge.

Reinforcing members may be cast into the edges of the cores. The reinforcing members may be cast into the beam during manufacture and may have upper limbs extending into the or each outermost cores from the or each outer edge thereof.

Reinforcing members may also extend into at least one inner edgeef the cores and may extend therethrough to a position above the top surface of the beam.

According to another aspect of the invention, there is provided a building construction comprising: a plurality of supporting columns arranged in a predetermined pattern; a plurality of beams as described in any of the preceding seventeen paragraphs, supported on respective pairs of the columns in substantially parallel arrangement; and a plurality of floor panels extending transversely to, and supported by, respective beams.

Preferably floor panels are arranged between and be supported by, a pair of the beams arranged in parallel.

The ends of the floor panels may be provided with integral flange members to overlie, or be engaged in sockets along, the sides of the beams. Alternatively, the ends of the floor panels may be provided with steel support flanges to overlie or engage the sides of the beams.

Preferably reinforcing members, e.g. rods and/or mesh, which may be of steel are laid over the beams and floor panels before the concrete layer is laid.

Preferably, the reinforcing members are so laid at a column.

In a second aspect the present invention resides in a method of building construction including the steps of: casting a prestressed concrete building beam having at least one hollow-core extending longitudinally within the beam; opening at least one portion of at least one of the hollow-cores to the top surface of the beam; securing building reinforcement means within the open portion or portions of the beam the reinforcement means extending above the top surface of the beam; supporting the beam on one or more supports; and laying a layer of curable building material over the beam, the building reinforcement means being received in and bonded to the layer of building material.

Preferably the open portions of the cores are provided at or adjacent both ends of the beam. Preferably the cores are opened shortly after the casting of the beam, before the concrete has set. This can also be done by means of slipforming or extension of the beam during casting thereof.

Preferably the reinforcement means comprises one or more ligatures which are secured in the open portions of the hollow-cores by back-filling the open portions with concrete, the concrete preferably being compacted.

The curable building material may comprise concrete.

To enable the invention to be fully understood, a number of preferred embodiments will now be described with reference to the accompanying drawings, in which: Fig. 1 is a plan view of a typical bay in a building using the beams of a first embodiment of the invention; Fig. 2 is a side view of the bay; Fig. 3 is a plan view of a typical beam of the first embodiment, the hollow-cores being indicated by dashed lines, the open portions of the cores provided with rein forcing ligatures and back-filled with concrete being indicated by the hatched areas; Figs. 4, 5 and 6 are respective sectional end views taken on line 4, 5 and 6 respectively, on Fig. 3 showing the junction between a beam and two floor slabs; Fig. 7 is a side view showing two beams supported by a column with a corbel; Fig. 8 is a plan view showing the reinforcement in the corbel; ; Fig. 9 is a plan view of a second embodiment which enables a single thickness floor to be constructed; Fig. 10 is a sectional end view taken on line 10 on Fig. 9; Fig. 11 shows a detail A in Fig. 10 on a larger scale; Fig. 12 is a plan view of a third embodiment where the beams are supported on column capitols; Fig. 13 is a side view of a fourth embodiment where the beams are supported by columns cast in situ; Fig. 14 is a plan view of the reinforcing at the columns; Fig. 15 is a sectional view similar to Figs. 4 to 6, of a modified beam; Fig. 16 is a sectional view similar to Figs. 4 to 6 of another modified beam; Fig. 17 is a sectional view of only the modified beam shown in Fig. 16; Fig. 18 is a sectional view of the modified beam shown in Fig. 16 with modified reinforcements.

Referring to Figs. 1 to 8, columns 10, provided with corbels 11, are provided at predetermined modular distances over the building site.

Prestressed concrete hollow core beams 12, to be described hereinafter in more detail, are supported at each end by a respective pair of columns 10, and intermediate their length by removable props, to provide a structural member between the columns. Floor panels 13, also of prestressed concrete, are then laid transversely to the beam 12 to be supported thereby. The floor panels 13 and beams 12 constitute together a beam and floor assembly.

Suitable reinforcing rods and/or mesh 14 are provided at the junction between the beam units 12, and the beams 12 and floor panels 13, and the concrete 15 is laid over the beams and panels 13 to complete the floor.

As will be readily apparent to the skilled addressee, the beams and floor panels provide in situ formwork for the concrete, and when the concrete sets, become "locked" into the floor structure.

Referring to Fig. 3 to 6, each beam 12 is cast from prestressed concrete and has a plurality e.g. five hollow-cores 16 extending longitudinally within the length and the unit.

Before the concrete has set, openings are cut into the top surface 17 of the beams to provide access to the one or more of the hollow cores 16. As shown in Figs. 3 to 6, both of the outer cores 16a may be opened for their full length, the intermediate cores 16b for e.g.

one-quarter of their length, and the central core 16c for example one-eighth of their length.

Reinforcing ligatures 18 are positioned in the openings in the cores 16 and extend above the top surface 17 of the beam. Concrete 19 is placed in the open-cores, to back-fill them, and this concrete is compacted and when set, secures the ligatures 18 in the beams 12.

As shown in Figs. 4 to 6, the highest density of ligatures is provided at the ends of the beams 12 to provide the greatest shear resistance of the columns.

When the beams 12 and floor panels 13 have been positioned and the reinforcing steel 14 positioned, the cavity formed above the columns 10 is filled with concrete before a final topping layer is laid over the complete floor Referring now to Figs. 7 and 8, these show the arrangement of the reinforcing steel 19 in the corbel 11 of the columns 10 used to support the beams.

By varying the depth (and width) of the beams 12, the engineers can ensure that the floor, when completed, will support the designed structural loads.

As the beams 12 support the floor panels 13 before and during casting, and the combination provides in situ formwork for the concrete laid over them, few supporting props are required and the need for formwork is avoided.

Referring now to Figs. 9 to 11, a floor of uniform thickness may be required. Referring to Fig. 9, the beams 20, generally of the same construction as for beams 12, are supported on columns 21 in the manner hereinbefore described in relation to the columns 10.

The floor panels 22 are of the same thickness as the beams 20 but do not overlie them (see Fig. 11). L-shaped flanges 23 are provided across each end of the floor panels 22 and are secured thereto by suitable anchors 24.

As shown in Fig. 11, the flanges 23 bear on the top surfaces 25 along each side of respective supporting beams 20 and the gap between the floor panel end and the adjacent beam is filled with cement 26. A topping layer of cement 27 is then laid over the beams 20 and floor panels 22 to complete the floor.

Referring now to Fig. 12, the beams 12 are supported on column capitols 40 on the columns 41, and the floor panels 13 are laid and floor completed as hereinbefore described. The column capitols 40 allow the overall height of the building to be reduced as the beams 12 are on the same horizontal plane as the capitols 40.

Referring now to Figs. 13 and 14, an embodiment is shown which enables columns 50 to be cast in situ after the beams 12 and floor panels 13 have been positioned, supported on temporary supports or props.

The beams 12 are arranged in the desired layout and are supported by suitable props and then the floor panels are laid over them. The formwork for the column 50 is erected and suitable reinforcing steel rods 51 are arranged to extend through the column capitols 52 and into the hollow-cores of the adjacent beams 12.

The columns 50 are then cast in situ and the floor slab is then completed. When the concrete has set, the formwork for the columns 50 and the props are removed, leaving the completed floor.

A further modification is illustrated in Fig. 15 which shows a modified beam 12 which has been designed to support floor panels 13 in such a way that the overall thickness to beam and floor assembly is reduced. The modified beam is similar to the beam described above in that it includes a plurality of open topped hollow-cores 16 lying parallel to the longitudinal axis of the beam and it is assembled alongside and fixed to the column 10 in the manner described above. Along each lateral edge of the modified beam there is provided a step 60 which accommodates the ends of the floor panels 13, thus the height of the top of a floor panel above the top of the beam 12 is reduced by an amount equal to the depth of the step and this decreases the overall thickness of the beam 12 and floor panel assembly.

Fairly considerable end loads will be exerted on the lateral edges of the beam 12 by the ends of the floor panels and to reinforce the beam sufficiently to accommodate said loads the beam includes reinforcing members 62 extending transversely across substantially the entire width of the beam.

Fig. 15 shows reinforcing hanger bars 64 each comprising a transversely extending cross member 66. The hanger bars 64 are cast into the beam adjacent the step 60 to provide a platform and fixture for longitudinal reinforcing members 68 and mesh 70.

To facilitate to automated production of the beams, the hanger bars 64 are modified to take the form shown in Fig. 15 except that the transversely extending cross member 66 is replaced by a longitudinally extending member (not shown on the drawings) the continuation of which provides the next adjacent hanger member 64. The resultant loop formed by the upright of the two adjacent hanger members and the longitudinally extending cross member therebetween projects out of the top of the beam and can provide loops for use in handling the beam unit as well as the anchorage for the reinforcing member 68 and mesh 70 when the beam is located in place.

Referring to Figs. 16 to 18, another modified beam 112 is shown. The beam 112 shown in Figs. 16 and 17 is particularly suited for use in areas of high seismic activity. The beam 112 comprises features which are the same as those previously described, and these features have been designated with the same reference numeral. The beam 112 also comprises a support ledge 160 to support floor panels 13, and reinforcing members in the form of reinforcements 14, 51, 164 and 172.

The reinforcements 164 extend into the outermost cores 16 as shown in Figs. 16 and 17. The reinforcements 172 extend through the inner edges of the cores 16 to a position above the top surface of the beams 112.

The outer edges 114, 116 of each of the outer most cores 16 extends upwardly for a distance less than the edges 118, 120 of the inner cores to define the support ledges 160. Thus, the overall thickness of the beam and floor assembly is reduced.

The reinforcements 14, 51, 164, 172 enable the beam 112 to be disposed in position without props in the middle. Also, props are required at the ends of the beam unit only where there is no corbel on the column 10.

The beams described have the advantage that they can be made using the same core casting machines with modifications thereto as appropriate.

For areas of no seismic activity, the beam 112 shown in Fig. 18 can be used. This is generally the same as that shown in Figs. 16 and 17 except that the reinforcements 172 have been omitted, and the reinforcements 164 have been replaced by reinforcements 162.

It will be readily apparent to the skilled addressee that the present invention provides a building construction system where the beam provides a two-way system and acts as a structural entity both before and after the floor slab is completed.

Various changes and modifications may be made to the embodiments described withour departing from the scope of the present invention as defined in the appended claims.

Claims

Claims:

1. A prestressed concrete, hollow core, building beam arranged to be supported by two or more building supports, the beam comprising: a plurality of hollow cores extending longitudinally within the beam; at least one portion of at least one of the hollow cores being open to the top surface of the beam; and building reinforcement means secured within the or each open portion of the beam and extending above the top surface of the beam to be received in and bonded to a layer of curable building material laid over the beam.

2. A building beam according to Claim 1 wherein the open portions of the cores are provided at or adjacent both ends of the beam, the cores being opened shortly after the casting of the beam, before the concrete has set.

3. A building beam according to Claim 1 or 2 wherein the reinforcement means comprises one or more ligatures which are secured in the open portions of the hollow cores by back-filling the open portions with concrete.

4. A prestressed concrete hollow core building beam arranged to be supported by two or more building supports, the beam comprising: a plurality of hollow cores extending longitudinally within the beam; at least one portion of at least one of the hollow cores being open to the top surface of the beam; and building reinforcement means secured within the or each open portion of the beam and extending above the top surface of the beam, to be received in and bonded to a layer of curable building material laid over the beam in which an upwardly directed step is provided in at least one of the lateral edges of the beam.

5. A building beam according to Claim 4 wherein a step is provided along each lateral edge of the beam.

6. A building beam according to Claim 4 or 5 wherein reinforcing members are cast into the beam below the or each step.

7. A building beam according to Claim 4, 5 or 6 wherein the reinforcing members are cast into the beam during manufacture, the members having an inverted U-shaped configuration.

8. A building beam according to Claim 7 wherein the free ends of each limb of the U-shaped members has transverse extensions therefrom.

9. A building beam according to Claim 8 wherein the upper limb of the U-shaped members is located above the top surface of the beam.

10. A prestressed hollow core building beam arranged to be supported by two or more building supports, the beam comprising: a plurality of hollow cores extending longitudinally within the beam; at least one portion of at least one of the hollow cores being open to the top surface of the beam; and building reinforcement means secured within the or each open portion of the beam and extending above the top surface of the beam, to be received and bonded to a layer of curable building material laid over the beam; wherein the outer edge of at least one of the outermost cores extends upwardly for a distance less than the inner edge thereof.

11. A building beam according to Claim 10 wherein the outer edge of each outermost core extends upwardly for a distance less than the or each inner edge.

12. A building beam according to Claim 10 or 11 wherein reinforcing members are cast into the edges of the core.

13. A building beam according to Claim 12 wherein the reinforcing members have upper limbs extending into the or each outermost core from the or each outer edge thereof.

14. A building beam according to any of Claims 10 to 13 comprising reinforcing members which extend into at least one inner edge of the cores and may extend therethrough to a position above the top surface of the beam.

15. A building construction comprising: a plurality of supporting columns arranged in a predetermined pattern; a plurality of beams as claimed in any preceding claim supported on respective pairs of the columns in substantially parallel arrangement; and a plurality of floor panels extending transversely to, and supported by, respective beams.

16. A building construction according to Claim 15 wherein a layer of concrete is laid over the beam and the floor panels.

17. A building construction according to Claim 15 or 16 wherein the floor panels are provided with flange members at the ends thereof to overlie, or be engaged in sockets along the sides of the beams.

18. A building construction according to Claim 17 wherein the flanges are integral with, or are secured onto the floor panels.

19. A building construction according to Claim 18 wherein the flanges are secured onto the floor panels, the flanges are formed of steel.

20. A method of forming a building construction comprising the steps of: casting a prestressed concrete building beam having a plurality of hollow cores extending longitudinally within the beam; opening at least one portion of at least one of the hollow cores to the top surface of the beam; securing building reinforcing means within the or each open portion of the beam, the reinforcing means extending above the top surface of the beam; supporting the beam on one or more supports; and laying a layer of curable building material over the beam, the reinforcement means being recieved in and bonded to the layer of curable material.

21. A method according to Claim 20 wherein the beam comprises the features specified in any of Claims 2 to 14.

22. A beam substantially as herein described with reference to and as shown in the accompanying drawings.

23. A building construction substantially as herein described with reference to and as shown in the accompanying drawings.

24. A method of forming a building construction substantially as herein described with reference to and as shown in the accompanying drawings.

25. Any novel subject matter or combination including novel subject matter disclosed in the foregoing specification or claims and/or shown in the drawings, whether or not within the scope of or relating to the same invention as any of the preceding claims.