WO2011107848A4

WO2011107848A4 - Improved reinforcing bar and method for manufacturing the same

Info

Publication number: WO2011107848A4
Application number: PCT/IB2011/000355
Authority: WO
Inventors: Anil Krishna Kar
Original assignee: Anil Krishna Kar
Priority date: 2010-03-02
Filing date: 2011-02-22
Publication date: 2011-12-22
Also published as: US20190161968A1; CN102782229A; IN2012KN02822A; US20120328896A1; WO2011107848A3; CN102782229B; WO2011107848A2

Abstract

Disclosed are an improved reinforcing bar and methods for manufacturing the same. The improved reinforcing bar is made from a high strength material, and has a circular or oval or elliptical cross section and deformation of the axis in a single plane or in multiple planes. The methods for manufacturing the improved reinforcing bar include a hot working process and a cold working process. The undulating /wavy bar with axis deformation can improve the anchorage of the bar in concrete and the bond strength without comprising any surface modifications. The amplitude and pattern of axis deformation of the bar can avoid stress concentration and its ill effects.

Claims

AMENDED CLAIMS received by the International Bureau on 10 October 201 1 (10.10.201 1 )

1. An improved reinforcing bar (REBAR) for reinforced concrete constructions and reinforced concrete structures comprising :

a) a high strength material;

b) a circular or oval or elliptical cross section of said bar;

c) deformation of the axis of the bar in specific plane(s).

2. The bar as claimed in claim 1 wherein said deformation of axis which makes the bar look undulating/wavy with the amplitude and pattern of axis deformation as well as the distance between successive peaks of the said undulations is varied such that high/increased gripping capacity and bond or resistance to pull-out forces is maintained without compromising in any significant way the overall linear characteristic of the bar and yet avoiding stress concentration and its ill effects.

3. The bar as claimed in claim 1 wherein said deformation is in single plane or in multiple planes.

4. The bar as claimed in claim 1 wherein said bar is of circular shape.

5. The bar as claimed in claim 1 wherein said amplitude of surface or axis deformation is 1 mm to 10 mm.

6. The bar as claimed in claim 1 wherein said resistance to pull out forces is at least 50% higher compared to resistance of straight bars with plain surface.

7. The bar as claimed in claim 1 to 6 wherein said bar has a plain surface and a deformed axis.

8. The bar as claimed in claim 1 wherein said high strength material comprises of glass fiber or carbon fiber or aramid or other high strength materials, made without or with the benefit of nanotechnology, preferably steel.

9. A method for manufacturing of an improved reinforcing bar (REBAR) for reinforced concrete constructions and reinforced concrete structures by hot working comprising steps of :

making of billet for high strength bar of steel;

reheating the said billet;

rolling the said billet in a rolling mill and making bars of the desired size and shape;

deforming the said bars using gear rollers or by any other device or means;

optionally providing any heating/cooling treatment;

cutting bars into desired lengths using shears

cooling of said bars in a cooling bed.

10. A method for manufacturing of an improved reinforcing bar (REBAR) for reinforced concrete constructions and reinforced concrete structures by cold working comprising steps of :

making of billet for high strength bar of steel;

reheating the billet;

rolling the said billet in a rolling mill to make bars of the desired size and shape;

cutting bars into desired lengths using shears;

cooling of said bars in a cooling bed;

deforming the said bars using gear rollers or by any other device or means;

optional annealing to relieve residual stresses.

1 1 . The method for manufacturing of an improved bar as claimed in any of claim 9 or 10 wherein said rolling mill process is followed by quenching of said billet in case of thermo mechanical treatment.

12. The method as claimed in any of claim 9 or 10 wherein said rolling mill process is further followed by quality check of splitting tendency and other quality check.

13. The method as claimed in claim 10 wherein said process of deformation is followed by annealing the said bar to remove or reduce built-in residual stresses by a process of gradually heating and cooling.

14. The method as claimed in claim 9 or 10 wherein said rollers/gears have horizontal or vertical or inclined axes.

15. The method as claimed in claim 9 or 10 wherein said hot working temperature in case of steel is around 900°C to 1200°C.

16. The improved reinforcing bar (REBAR) for reinforced concrete constructions and reinforced concrete structures and a method for manufacturing the same as substantially described herein with reference to accompanying drawings.

STATEMENT UNDER ARTICLE 19

Present invention relates to improved reinforcing bars (REBAR) which resist tensile or compressive forces, prevent shrinkage or thermal cracks in concrete, and provide resistance to flexural forces in reinforced concrete structures. The rebar has plane surface and deformed axis (wave form), for use in straight, bent or curved reinforced concrete structures as well-bonded tensile elements so as to minimize corrosion.

CN2126264 (D1) discloses waveform prestressed concrete members and prestressing steel reinforcement.

CN 1793389 (D2) discloses cost effective method for production of BS (British Standard) 460 steel from ordinary carbon steel.

CN 1067470 (D3) discloses method of constructing precast prestressed concrete components of waveform.

CN2535481 (D4) discloses essentially anchor bolts of screw or spiral pattern, used as rock anchors, slope anchors, anchors in large dams, bridges, tunnels and large industrial and civil projects.

WO9513440 (D5) discloses reinforcing steel mesh with straight longitudinal bars in one plane and cross bars (some of which are wound in wavy or helical line in their end section).

US6701688 (D6) discloses reinforcing cage comprising at least two layers of longitudinal armoring.

Presently claimed rebar differs from prestressed element of prior art as under:

Rebar Prestressed element

Rebar is passive element Prestressing element is active element

Diameter of rebars ranges 5-67 mm Diameter of prestressing elements/wires ranges 0.5 - 7 mm

Rebars have adequate bond with its Bonding between presstressing element surrounding concrete in reinforced concrete and its surrounding concrete is not structure essential In flexural element, rebar is generally Prestressing element is (pre)stressed to considered to carry load (i.e., stressed) as impart compressive force to prestressed concrete develops cracks in tensile region concrete element neutralising tensile stresses in the tensile region of flexural element preventing cracks in concrete

Generally made of mild steel or carbon Generally wire or strand of wires of steel of low, medium and high strength (250 carbon steel with yield or proof stress MPa to 700 MPa) several times higher than that of rebars

Reinforced concrete column element Concrete column element is unlikely to always has rebars have any prestressing element

Design for determination of area of rebars, Design for determination of area of with its location, on basis of preset stress prestressing element as wire or strand limits, which the rebar does not exceed of wires with its location and contour, on under service load condition the basis of preset stresses, to which prestressing element will be stretched and stressed during construction phase.

In reinforced concrete element, rebar is in In prestressed concrete element, one or multiple pieces prestressing element is in one piece.

D1 to D6 relates to prestressing elements in prestressed concrete structures or special elements like anchor bolts, casings for rebars, acting as external aid preventing slippage of rebars, bar spacer, bar locating frames which are different from reinforcing bar of present invention. There is no teaching / motivation in cited art to arrive at present invention of making and using deformed rebars.

Amended Claims 6, 11 and 14 may be regarded as amendments with Statement Under Article 19.