DESC:“MODIFIED SHEAR REINFORCEMENT METHOD FOR DOUBLE T BEAM PRODUCTION”
Field of the invention
The present invention relates to the modified shear reinforcement detailing for simplification of double T beam production, more particularly it relates to the use of single legged modified stirrup in the portion of less shear of the double T beam.
Background of the invention
There are two main types of stresses in a precast double T element. Shear stress and stress due to bending moments. Steel Reinforcement is used to counteract these stresses. For counteracting the bending moment stresses, prestressed steel reinforcement strands are used in horizontal direction, whereas, to counter-act the shear stresses, reinforcement links are provided in the vertical direction. Both the reinforcements are provided in the web of the double T beam. Shear stresses are present in the elements in two main zones – near the supports, and near the center. Shear is maximum at the two supports and reduced towards the center.
In the prior art, as mentioned above, there is double legged shear reinforcement detail throughout the length of the element. The process and the drawbacks of double legged shear reinforcement are stated as follows:
Referring to Figure 1, a flowchart of prior art method (100) for shear reinforcement of double T beam with double legged hook type stirrups is shown.
At step (1), method (100) includes cutting and bending main steel and stirrup steel, assembling the web-beam steel cage and tying the web-beam steel cage on top of the mould. Then at step (2), strands are manually pushed, usually 8 to 12 nos per double T beam and for more than 50 to 100 meters through the web-beam steel cage and the end stoppers.
In the next step (3), the strand-weaved web-beam steel cage is dropped in the web of the mould.
Step (4) includes cutting and bending main steel and distribution steel and tying slab steel mesh on mould because the bars of the slab steel mesh need to go under the loops of the web-beam steel cage.
Step (5) includes adding the cross bar and opening steel to the web steel beam, and the final step (6) includes casting the mould with concrete.
In the existing process, shape of double legged stirrup is odd to bend, hence takes more time and labor and coupled with the fact, that the diameter of these stirrups being less, the processing quantity (in terms of numbers and work to do) remains same, but the output weight is very less, thus, being uneconomical for labor contractors to execute on output (measurement) basis. Moreover, tying and assembling the web-beam steel cage takes lot of time. Tying the slab steel mesh also takes time and this has to be done on the mould, and not in parallel, at another location. In this process, automatic Strand Pushing machines are rendered useless, because the stirrups of the web beam keep obstructing in its way. Hence, requiring more labour. Automatic welding machines also are not useful because of the intersection of steel bars of web-beam steel cage and slab steel mesh. Moreover, the entire process is done serially, one after the other, hence, inducing dependency of completion of one activity on the start of the next. There is no aspect of parallelization in the process and the overall Automation scope is also reduced, because all activities are done on the mould and in series.
Accordingly, there exists a need to provide modified shear reinforcement method for double T beam production which overcomes drawbacks of the prior arts.
Objects of the invention
An object of the present invention is to provide modified shear reinforcement method for simplification of double T beam production using single legged hook-type stirrup.
Another object of the present invention is to reduce the time, labor and material cost required for double T beam production.
Summary of the invention
The present invention provides a modified shear reinforcement method for simplification of double T beam production using single legged hook type stirrup. In the existing process, a web beam steel cage is assembled on the double t beam mould and strands are pushed manually through the web beam steel cage and the end stoppers. The web beam steel cage is dropped in the web of mould. Then the slab steel mesh is assembled and tied on mould to further cast it with concrete. In the modified shear reinforcement method of the present invention for double T beam production, assembling of auto mesh, assembling of web-beam steel cage and automatically pushing the strand in the web beam is done simultaneously. The web-beam steel cage is assembled using single legged hook type stirrups. Finally, the web-beam steel cage is dropped in the web beam, auto mesh is placed on top of the double t beam mould and the mould is cased with concrete. The process is advantageous over the existing process of double T beam production as it is less labor dependent, requires less steel, more technology oriented and fast.
Brief description of the drawings
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows a flowchart of double T beam production method using double legged loop type stirrup, in accordance with the prior art;
Figure 2 shows a flowchart of the modified shear reinforcement method for double T beam production in accordance with the present invention;
Figures 3, 4, 5 and 6 are the schematic representation of the modified shear reinforcement method for double T beam production in accordance with the present invention.
Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a modified shear reinforcement method for double T beam production using single legged hook type stirrup. In double T beam, shear is maximum at the two supports and reduced towards the center. Leaving the shear reinforcement detailing near the supports untouched, the shear reinforcement detailing near the center is modified. Instead of the double legged stirrups, throughout the length of the double T beam, a single legged, modified stirrup design in the portion of less shear is provided, thereby reducing the material quantities, time required and processing as well as labor requirements.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description. The components of the invention and the reference numbers are listed in the table below:
Ref. No. Component Name
110 Stoppers
120 Double T beam mould
130 Strands
140 Web-beam steel cage
150 Auto mesh
160 Web beam notch
Referring to Figure 2, there is shown a flow chart for modified shear reinforcement method (200) for double T beam production, in accordance with the present invention.
At step (10), method (200) includes cutting and bending main steel and stirrup steel, assembling the web-beam steel cage (140) and tying the web-beam steel cage near the mould.
At step (20), method (200) includes placing the plurality of stoppers (110) very close to each other in each of the two web beam notches (160) of a double T-beam mould (120). Plurality of strands (130) is then pushed with auto pushing machine, through stoppers placed closely in each of the two web beam notches (160) of a double T-beam mould (120). Distance between stoppers (110) is then adjusted appropriately.
At step (30), method (200) includes cutting and bending main steel (150A) and distribution steel (150B) and assembling welded auto mesh (150) by welding machine at another location and adding the cross bar and opening steel to the web steel beam.
Step (10), step (20) and step (30) of the method (200) can be performed in parallel so as to reduce the time required for the process. This parallelization of activities makes the process fast and technology oriented, allowing automation.
Further at step (40), method (200) includes placing the web-beam steel cage (140) with U or T type web mesh on each of the two web beam notches (160) and the welded auto mesh (150) on the top of the double T-beam mould (120).
At step (50), method (200) includes casting the double T-beam mould (120) with concrete.
Referring to figure 3 to 6, a schematic representation of step (20A), (20B) and step (40) of the modified shear reinforcement method (200) for double T beam production using single legged hook-type stirrup is shown in accordance with the present invention. By keeping all the stoppers (110) close to each other, strands (130) are pushed by the auto pushing machine, through the end stoppers (110). The plurality stoppers (110) is then adjusted to appropriate positions in the double T-beam mould (120). Assembling of web-beam steel cage (140) and assembling of auto mesh (150) is done simultaneously near the mould (120). The web-beam steel cage (140) is assembled by cutting and bending main steel and stirrup steel and tying them together. The web-beam steel cage (140) can be of U type, T type or zigzag type, in which single leg type stirrups are used. Auto mesh (150) is assembled by cutting and bending main steel (150A) and distribution steel (150B) and welding them together and adding the cross bar and opening steel to the web steel beam. In the next step, inverted U or T-type web-beam steel cage (140) is placed from top of the mould (120) and welded auto mesh (150) is placed on the top. Finally the double T-beam mould (120) is casted with concrete.
Advantages of the present invention
1. The method (200) is fast and less labor dependent.
2. It requires less quantity of steel.
3. It includes minimum on mould activities.
4. Parallelization of activities is possible in this process.
5. It is technology oriented process and allows automation.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.
,CLAIMS:We Claim:
1. A modified shear reinforcement method (200) for production of double T-beam, the method (200) comprising:
cutting and bending main steel and stirrup steel and assembling a web-beam steel cage (140);
cutting and bending main steel (150A)and distribution steel (150B) and assembling an auto mesh (150) using welding machine;
placing a plurality of stoppers (110) close to each other in each of the two web beam notches (160) of a web mould (120), pushing a plurality of strands (130) there through, and adjusting the stoppers in each of the web beam notch (160) with appropriate gap there between;
placing the web-beam steel cage (140) on strands (130) in each of the web beam notch (160);
placing the auto-mesh (150) on top of the web mould (120);
casting the web mould (120) with concrete;
wherein the stirrups are single legged hook type stirrup and the steps of assembling of web-beam steel cage (140), assembling of auto mesh (150) and pushing the strands (130) through plurality of stoppers (110) are performed simultaneously.

2. The modified shear reinforcement method (200) as claimed in claim 1, wherein the web-beam steel cage (140) is assembled in any of the shape selected from U type, T type and zigzag type.
3. The modified shear reinforcement method (200) as claimed in claim 1, wherein pushing a plurality of strands (130) through stoppers (110) is done with auto strand pushing machine.
Dated this 10th day of November 2017,

Prafulla Wange
(Agent for Applicant)
IN-PA/2058