REINFORCED CONCRETE COLUMN AND METHOD FOR MAKING THE SAME

Abstract

 The invention relates to a reinforced concrete column, particularly for halls with a so-called lightweight reinforced concrete framework, comprising an armature made from reinforcing steel and a column body made from concrete encompassing the armature.
The reinforced concrete column according to the invention is characterised in that the column consists of a pre-fabricated head portion (2) and a column body (6) joined to the head portion (2); and the column comprises pre-tensioned strands (17) arranged in the column body to conically converge towards a single point in a strand guide (3) disposed in the head portion (2).
The method according to the invention comprises the steps of:
- in the first step, making the head portion (2) by placing the plug (15) covering the opening of the strand guide (3) on the bottom of the formwork, inserting the armature (16) of the head portion (2) and pulling the strand guide (3) on the plug (15) and pulling injection pipe (13) on the injection stub (12) of the strand guide (3), and then, after closing the formwork, pouring concrete into the formwork in a direction opposite the direction the head portion (2) is built in (or in a horizontal position), and stripping the formwork after the concrete has set;
- in the second step, joining the pre-fabricated head portion (2) with the column body (6) of the column (1) by fixing the head portion (2) to a tensioning bed, inserting the armature of the column body (6), utilizing a strand guide (18) disposed at the bottom portion of the column body (1) for passing the strands (17) of the column (1) in a converging manner into the strand guide (3) of the head portion (2), tensioning the strands (17), closing the formwork of the tensioning bed (19), and, by pouring concrete into the formwork, joining the head portion/s and the column body/bodies (6), and, after the concrete has set, stripping the formwork.

Description

[0001] The invention relates to a reinforced concrete column, particularly for halls with a lightweight reinforced concrete framework, comprising an armature made from reinforcing steel and a column body made from concrete encompassing the armature, as well as to a method for making the column.

[0002] A hall system that has seen widespread application is the hall system with a so-called lightweight reinforced concrete framework, wherein the reinforced concrete columns are produced in a single session, i.e. the head portion and the column body are produced simultaneously.

• In these hall structures the columns are not tensioned.
• Although there exist other known building structures making use of tensioned columns, in this type of column the strands extend parallel with the axis of the column body.
• The prior art also includes systems wherein tensioning is performed after the columns have been built in. In such systems the strands or tensioning rods are arranged parallel with the axis of the column body. Applying such columns, multiple-story column systems are often formed.
• In other known systems post-tensioning is performed as the columns are secured to the foundation bodies, thereby strengthening the connection between the foundation and the columns.
• Other systems are also known wherein the columns are co-tensioned with beam elements, thus forming a framework structure and increasing the rigidity of the system.

[0003] The patent specification JP2003020754 discloses a pre-tensioned concrete structure suited for constructing multi-story buildings, wherein the structure comprises a concrete column pre-tensioned during manufacturing, with a hole, extending through the whole length of the column and adapted for receiving a post-tensioning element, being disposed in the column body. The core of the tensioning element is formed by a bundle of post-tensioning steel comprising external coating and an anchor head at its ends.

[0004] The column components, made from concrete, are assembled applying an auxiliary cable and a tensioning element, and are joined together by post-tensioning.

[0005] In the document US 3,932,975 a building structure is disclosed wherein groove-like recesses are formed in the column bodies. The grooves formed in the columns are adapted for receiving wall panels installed between columns that are erected with a predefined spacing between them. The column head portions are secured to the column bodies by clamping means protruding vertically from the columns.

[0006] The document US 1,024,852 discloses a reinforced concrete structure comprising a reinforced concrete column. The head portion of the column comprises ribs supported by corbels, the ribs protruding in four directions and being adapted for receiving beams. The columns are reinforced by metal rods extending into the corbels and the ribs.

[0007] In known systems the body portion of the columns is subjected to high torque loads but at the same time low pressure forces, especially in case of single-story halls. For the structure to be able to withstand wind loads and especially earthquakes, and also the torques caused by second-order effects arising due to great height, it is necessary to build a large amount of steel reinforcement into the structure. Due to the low pressure forces the increased torque load bearing capacity of the reinforced concrete columns cannot be fully exploited. The complicated head portion arrangements require that the formwork system is cut to size, which is costly and time consuming.

[0008] A common characteristic of column head portions having a variable-geometry configuration comprising exclusions is that the main beams are seated on the head portions vertically from above. A limit to reducing the size of concrete members is placed, in addition to structural requirements, by the difficult concrete placement caused by horizontal manufacturing.

[0009] The objective of the invention is to produce a reinforced concrete column with a head portion that can be pre-fabricated irrespective of the particular construction project, where the load bearing capacity and rigidity of the column body may be increased, and the manufacturing process can be made more economical by shortening production time.

[0010] The invention is based on the recognitions that by pre-fabricating the head portion of the reinforced concrete column so as to correspond to the beam members of the framework structure the costs of manufacturing can be reduced, and that by introducing the strands of the column body into the head portion it can be provided that the same head portion arrangement can be applied for differently sized columns.

[0011] Also, by laying concrete in a direction opposite to the direction of installation of the head portions, quality may be significantly improved.

[0012] The objective of the invention is fulfilled by providing a reinforced concrete column applicable particularly for halls with lightweight reinforced concrete framework that comprises an armature made from reinforcing steel and a column body made from concrete encompassing the armature, which is characterized in that the column consists of a pre-fabricated head portion and a column body joined to the head portion; and the column comprises pre-tensioned strands arranged in the column body to conically converge towards a single point in a strand guide disposed in the head portion.

[0013] In a preferred embodiment of the reinforced concrete column according to the invention the head portion is made integral with a strand guide disposed inside an armature known per se, by laying concrete in a direction opposite to the direction of installation, the head portion comprises reinforcing members which are arranged in a shape corresponding to the insertion location and which extend over the upper and bottom portion of the head portion, and the strand guide of the head portion is made from a pipe extending along the full length of the head portion, the pipe being fitted at its upper portion with a shaped conical element.

[0014] In another preferred embodiment of the reinforced concrete column according to the invention the conical element of the head portion's strand guide is a conical spiral or a conical pipe, the strand guide of the head portion is fitted with an injection stub adapted for receiving an injection pipe, and the pipe of the head portion's strand guide is a plastic pipe, preferably made from PVC.

[0015] The reinforced concrete column according to the invention is made in the following steps:

• in the first step, the head portion is made by placing the plug covering the opening of the strand guide on the bottom of the formwork, inserting the armature of the head portion and pulling the strand guide on the plug and pulling an injection pipe on the injection stub of the strand guide, and then, after closing the formwork, pouring concrete into the formwork in a direction opposite the direction the head portion is built in (or in a horizontal position), and stripping the formwork after the concrete has set;
• in the second step, the pre-fabricated head portion is joined with the column body of the column by fixing the head portion to a tensioning bed, inserting the armature of the column body, utilizing a strand guide disposed at the bottom portion of the column body for passing the strands of the column body in a converging manner into the strand guide of the head portion, tensioning the strands, closing the formwork of the tensioning bed, and, by pouring concrete into the formwork, joining the head portion/s and the column body/bodies, and, after the concrete has set, stripping the formwork.

[0016] A preferred embodiment of the reinforced concrete column according to the invention is explained in detail below referring to the accompanying drawings, where

Fig. 1 shows a perspective view of different reinforced concrete columns with head portions configured according to the invention,

Figs. 2a-2e illustrate, in perspective view, the head portions of the reinforced concrete columns shown in Fig. 1,

Fig. 3 is the side elevation view of the strand guide built in the head portion of the reinforced concrete column according to Fig. 1,

Fig. 4a shows a top plan view of the conical strand guide elements illustrated in Fig. 3,

Fig. 4b is the side elevation view of the conical element illustrated in Fig. 4a,

Fig. 5a shows the side elevation view of a further embodiment of the conical strand guide elements illustrated in Fig. 3,

Fig. 5b is the top plan view of the conical element according to Fig. 5a,

Fig. 6 is a flow diagram illustrating the manufacturing steps of the column head according to Fig. 2b,

Fig. 7 illustrates the strand arrangement of the reinforced concrete column according to the invention,

Fig. 8 illustrates the insertion order of the strands of the reinforced concrete column according to the invention,

Fig. 9 illustrates the manner of securing the head portion and the column body of the reinforced concrete column according to the invention to the tensioning bed,

Fig. 10 is the side elevation view of the column shown in Fig. 9, and

Fig. 11 is a section taken along the line A-A of Fig. 10.

[0017] Fig. 1 shows different embodiments A-E of the reinforced concrete column 1 according to the invention. The head portions 2 have different configurations depending on the location of the column within the structure. Embodiment A of the column 1 is a corner column, i.e. it is intended to be erected in the corners of the hall. Embodiments B and D of the column 1 are peripheral columns, i.e. they are located at the periphery of the hall between corner columns A, while embodiments C and E are inside columns intended to be erected inside the manufacturing hall, between the columns B and D. The structural arrangement of the head portions 2 is therefore dependent upon the properties and the loads taken by the roof structure supported by them.

[0018] In Figs. 2a-2c the head portions are illustrated in a magnified view - without the column body 6 - clearly showing that in each head portion 2 a respective strand guide 3 is disposed. The configuration and function of the strand guide will be explained later on. As shown in the drawing, at the top part of the head portion 2 - adjacent to the roof structure - reinforcing members 4 adapted for attaching the connecting structural elements are disposed, while at the bottom part thereof there are reinforcing members 5 adapted to be connected to the body of the column 1.

[0019] The manner of joining the head portion 2 to the column 1 will be described in detail later.

[0020] The reinforced concrete column according to the invention essentially consists of two parts: a separate pre-fabricated head portion 2, and a column body that is joined to the head portion 2 on a tensioning bed.

[0021] An important part of the head portion 2 is the strand guide 3 illustrated in Fig. 3, which is essentially made from a plastic pipe, preferably a PVC pipe, with one end of the pipe being shaped and being fitted with a conical element implemented either as a conical spiral 7 (see Figs. 4a, 4b) or as a conical pipe 8 (see Figs. 5a, 5b).

[0022] The strand guide 3 illustrated in Fig. 3 comprises a conical spiral 7.

[0023] The strand guide 3 built into the column head 2 is adapted for taking the loads arising at the direction change location of the strands of the column body that conically converge towards a single point, such that the lowest possible friction force is generated near the strands. This member is adapted for guiding the strands during the tensioning procedure to the region of the head portion 2 which does not constitute a part of the geometrical relation providing the connection of the beam structures supported by the head portion 2 and is not contacted by the structures of the supported beams.

[0024] The pipe 9 of the strand guide 3 is preferably a PVC pipe with a length of 500-2000 mm and a diameter of 80-200 mm, but it can also be a thin-walled steel pipe.

[0025] The conical strand guide 3 element is a steel member that is mounted on a strand guide 3 and is adapted for taking the forces arising from the change of direction of the strands of the column body, and provides that the strands are able to slide.

[0026] The strand guide 3 only guides the strands but is not attached to them.

[0027] The conical spiral 7 illustrated in Fig. 4 is made from round steel bar hot-wound on the pipe 9 of the strand 3.

[0028] The portions 10, 11 of the conical element of the strand guide 3 disposed in the head portion 2, extending from the bottom and upper portion of the conical element and connected to the anchors of the known-art reinforcing members of the head portion 2 are adapted for taking the forces arising in the conical spiral and therefore perform an important function for the column 1 according to the invention.

[0029] Fig. 4a and 4b, respectively, show the top plan and side elevation view of a conical spiral 7, where the portions 10 and 11 are adapted for connecting and anchoring the conical spiral 7. At the bottom of Fig. 4 a connecting member 10 adapted to be connected to the external part of a smaller (40x40 cm) column anchor is shown, while at the top of Fig. 4 a connecting member 11 arrangement is shown that is adapted to be connected to the external part of a larger (50x50 cm) column anchor.

[0030] Fig. 5a illustrates the side elevation view of another embodiment of the conical element of the strand guide 3, Fig. 5b showing the top plan view of the conical pipe 8. A respective connecting member 10, 11 is also connected to the bottom and upper periphery of the conical pipe 8, which members are in this case applied only for securing the conical element 8.

[0031] Returning now to Fig. 3, there it is shown that an injection stub 12, adapted to be connected to an injection pipe 13, is built in the pipe 9 of the strand guide 3. The injection pipe 13 may be disposed at any location of the pipe 9, its location dependent on the arrangement of the head portion 2. It can also be omitted if so desired.

[0032] Is should be noted here that the geometrical arrangement of the conical elements according to Figs. 4-5 ensures that (even for columns 1 with different length and cross sectional area) the strand does not come into contact with the outer portion or the innermost part of the conical element.

[0033] To receive the (optionally included) injection pipe 13 an injection stub 12 having a length of 30-50 mm is included. The pipe 9 of the strand guide 3 is cut to the length determined by the given head portion 2.

[0034] The manufacturing process of the head portion 2 according to Figs. 2a-2e is illustrated by way of Fig. 6.

[0035] The head portion 2 may be manufactured on its side, or in an "upside down" position, i.e. in a position rotated by 180° with respect to the installation position. Fig. 6 illustrates the "upside down" manufacturing process of the head portion 2.

[0036] The head portion 2 receives the horizontal and vertical forces transmitted from the beams of the hall structure, the head portion 2 transmitting these forces to the column body connected to the head portion 2 of the column 1. The reinforcing members 4 disposed at the upper portion of the head portion 2 perform the same function. The head portions 2 should therefore be produced such that the torque and shear loads at the root of the head are low.

[0037] As illustrated in Fig. 6, the first step (step a) of producing the head portion 2 constitutes making the formwork 14 that may be a steel or wooden formwork. The strand guide 3, and a plug 15 adapted for covering the pipe 9 end are inserted in the formwork 14, and in the next step b) the pre-fabricated armature 16 of the head portion 2, made from reinforcement steel, is placed in the formwork 14. In step c) the pipe 9 of the strand guide 3, fitted with a conical spiral 7 and an injection stub 12, is inserted, followed by pulling the injection pipe 13 on the injection stub 12.

[0038] In case injection is not required due to the dimensions of the head portion 2, the injection stub 12 is plugged instead of placing the injection pipe 13 on the stub.

[0039] It should be noted that, for the sake of clarity, the armature 16 of the head portion 2 is not shown in Fig. 6 illustrating steps c) and d).

[0040] Subsequently, after inserting the factory-made assemblies required for removing the head portion 2 from the formwork, concrete is laid in the head portion 2, and then, after the concrete has set, the formwork is stripped.

[0041] Next, the column 1 according to the invention is completed by joining the column body 6 portion to the pre-fabricated head portion 2.

[0042] Fig. 7 shows the schematic view of embodiment C of the column 1 according to the invention.

[0043] The strands 17, being terminated in the strand guide 3 of the head portion, are disposed inside the column body 6, extending from the bottom of the column 1 towards the head portion 2 in a conical fashion.

[0044] The strands 17 are encompassed by the known art armature (not shown) of the column body 6.

[0045] The head portion 2 of the column 1 is joined together in a tensioning bed 19 known per se.

[0046] In a single tensioning session, a single tensioning bed 19 can be applied for producing columns that have the same strands layout and the same height of centre of gravity as the column body 6.

[0047] The columns 1 should be distributed on the tensioning bed 19 such that the distance of a tensioning stand and the end of the first columns is 2-5 m (see Fig. 9). This distance can be increased by extending the length of the strands 17.

[0048] Expediently, an even number of columns are produced simultaneously, but the columns 1 may also be made one by one applying a so-called tensioning frame.

[0049] Strand guides 18 are disposed on the tensioning bed 19 between the tensioning stands and the column bases.

[0050] The strand guides 18 are made from steel sheet with dimensions corresponding to the dimensions of the column body 6 of the column 1.

[0051] On both sides of the strand guide 18 holes are numbered according to the tensioning order (see Fig. 8). In section a of Fig. 8 strand guides 18 of different sizes are shown.

[0052] In section b of Fig. 8 an embodiment of the strand guide 18 is illustrated, showing the tensioning order. This embodiment provides for easier assembly, while in case of the arrangement according to section c lower loads are transmitted to the securing apparatus.

[0053] In Fig. 9 the head portions 2 are arranged facing one another on the tensioning bed 19, the distance between them being 0.5-1 m.

[0054] The head portions 2 are placed on the tensioning bed 19 according to the tensioning bed layout plan, secured against displacement (i.e. against sliding, torsion, elevation).

[0055] It is to be noted here that in case of applying the tensioning order according to Fig. 8, no elevation force is produced.

[0056] The longitudinal forces causing sliding result from frictional forces arising at the location where the direction of the strands 17 changes abruptly, while the lateral forces are caused by the abrupt direction change of the strands 17. The forces resulting from the direction change should be taken into account.

[0057] The forces are taken at the pre-fabricated head portions 2 by overhead support rods arranged above the tensioning bed 19. The suggested distance between the column bases is 0.5-1 m. Distances above 1 m are explicitly not proposed (see the section on tension relief).

[0058] The strand guides 18 should be arranged between the column bases according to the tensioning bed layout plan. As with the head portions 2, the strand guides should also be secured against displacement (sliding, torsion, elevation).

[0059] The suggested strand insertion and tensioning order, which depends on the manufacturing location, is illustrated in Fig. 8.

[0060] The essential manufacturing step is wherein the pre-fabricated head portions 2 are joined to the tensioned column body 6. The strands 17 of the column body 6 are hooked in the strand guide 3 inside the head portion 2, and then concrete is laid to produce the column body 6.

[0061] It has to be noted here that it is not necessary (but possible) to secure the strands 17 to the column head portion 2 in a force-transmitting manner. Forces transmitted from the beams are taken by the pins 4 protruding from the column head portion 2, and are transferred into the column body 6 by pins 5.

[0062] After installing the conventional pre-fabricated armature of the columns 1 the strands 17 are inserted in the strand guide 3 of the head portion 2 in the order shown in Fig. 8. The proper insertion (drawing-in) of each strand 17 has to be checked.

[0063] After inserting the strands 17 the lateral pieces of the formwork of the column body 6, and, if required, further devices are installed.

[0064] Although the tensioning process is known per se, it has to be noted that in case of the solution according to the invention tensioning is performed after installing and fitting out the armature of the column body 6 of the column 1.

[0065] Additional fittings and the lateral formwork pieces can be installed and the formwork can be closed after tensioning has been completed.

[0066] After closing the formwork concreting is performed, and thus, by joining the column body 6 and the head portion 2 the completed column 1 is formed.

[0067] An important step of the manufacturing process is tension relief.

[0068] If a low number of columns 1 has been produced on the tensioning bed 19 (a case that should be avoided if possible applying production scheduling and organization), the tensions present along the high free strand lengths should be reduced.

[0069] In case the tensioning bed 19 is completely filled with columns 1, tension relief is not required.

[0070] Each strand 17 should be cut simultaneously at both of its ends (at the tensioning stands), in the order they were tensioned. The strands should be cut simultaneously using cutting torches, in compliance with the relevant technology instructions.

[0071] The strands should also be cut between the head portions 2 and the column body 6 bases, advancing towards the middle of the tensioning bed. Cutting should be performed simultaneously, in the order the strands were tensioned.

[0072] After the concrete has set and the formwork has been stripped, the completed column 1 is removed from the bed 19 and stockpiled in a manner known per se.

[0073] The reinforced concrete column and production method according to the invention have the following advantages:

• the head portion of the column can be pre-fabricated and stockpiled separately such that it corresponds to the beam elements of the structure the column is to be built into, irrespective of where it will be used,
• the strand guide built into the head portion of the column brings together the inside strands of the column body 6 into a smaller region in a conical manner, which improves the rigidity and the load bearing capacity of the completed column, and also results in a structure with high earthquake and fire resistance,
• manufacturing costs can be reduced significantly,
• the "upside down" manufacturing process of the column's head portion allows for precise shaping, lower concrete consumption and better concrete placement,
• a given head portion may be applied for columns with different cross section and length,
• formwork construction is quick, the construction time demand of the tensioning bed is reduced.

LIST OF REFERENCE NUMERALS

[0074] 

1

column

2

head portion

3

strand guide

4

reinforcing member

5

reinforcing member

6

column body

7

conical spiral

8

conical pipe

9

pipe

10

connecting member

11

connecting member

12

injection stub

13

injection pipe

14

formwork

15

plug

16

armature

17

strand

18

strand guide

19

tensioning bed

Claims

1. Reinforced concrete column, particularly for halls with lightweight reinforced concrete framework, comprising an armature made from reinforcing steel and a column body made from concrete encompassing the armature, characterized in that the column consists of a pre-fabricated head portion (2) and a column body (6) joined to the head portion (2); and the column comprises pre-tensioned strands (17) arranged in the column body to conically converge towards a single point in a strand guide (3) disposed in the head portion (2).

2. The reinforced concrete column according to Claim 1, characterized in that the head portion (2) is made integral with a strand guide (3) disposed inside an armature (16) known per se, optionally by laying concrete in a direction opposite to the direction of installation.

3. The reinforced concrete column according to Claim 1 or 2, characterized in that the head portion (2) comprises reinforcing members (4, 5) which are arranged in a shape corresponding to the insertion location and which extend over the upper and bottom portion of the head portion (2).

4. The reinforced concrete column according to any one of Claims 1-3, characterized in that the strand guide (3) of the head portion (2) is made from a pipe (9) extending along the full length of the head portion (2), the pipe (9) being fitted at its upper portion with a shaped conical element (7, 8).

5. The reinforced concrete column according to Claim 4, characterized in that the conical element of the strand guide (3) of the head portion (2) is a conical spiral (7).

6. The reinforced concrete column according to Claim 4, characterized in that the conical element of the strand guide (3) of the head portion (2) is a conical pipe (8).

7. The reinforced concrete column according to any one of Claims 1-6, characterized in that the strand guide (3) of the head portion (2) comprises an injection stub (12) adapted for receiving an injection pipe (13).

8. The reinforced concrete column according to any one of Claims 1-7, characterized in that the pipe (9) of the strand guide (3) of the head portion (2) is a plastic pipe, preferably made from PVC.

9. Method for making the reinforced concrete column according to Claim 1, characterized by comprising the steps of

- in the first step, making the head portion (2) by placing the plug (15) covering the opening of the strand guide (3) on the bottom of the formwork, inserting the armature (16) of the head portion (2) and pulling the strand guide (3) on the plug (15) and pulling injection pipe (13) on the injection stub (12) of the strand guide (3), and then, after closing the formwork, pouring concrete into the formwork in 6 direction opposite the direction the head portion (2) is built in (or in a horizontal position), and stripping the formwork after the concrete has set;

- in the second step, joining the pre-fabricated head portion (2) with the column body (6) of the column (1) by fixing the head portion (2) to a tensioning bed, inserting the armature of the column body (6), utilizing a strand guide (18) disposed at the bottom portion of the column body (6) for passing the strands (17) of the column body (6) in a converging manner into the strand guide (3) of the head portion (2), tensioning the strands (17), closing the formwork of the tensioning bed (19), and, by pouring concrete into the formwork, joining the head portion/s and the column body/bodies (6), and, after the concrete has set, stripping the formwork.

Drawing