WO2019186600A1

WO2019186600A1 - Precast structural element and method for connecting the precast structural element to each other

Info

Publication number: WO2019186600A1
Application number: PCT/IN2019/050265
Authority: WO
Inventors: Ajit BHATE
Original assignee: Precast India Infrastructures Pvt. Ltd.
Priority date: 2018-03-31
Filing date: 2019-03-30
Publication date: 2019-10-03
Also published as: EP3775420A4; EP3775420A1; US20210025157A1

Abstract

Disclosed is a precast structural element capable of connecting with each. The precast structural element made by a method which comprises preparing one or more layers of plurality of horizontal and vertical reinforcement bars. The method further comprises fixing plurality of hollow tubes to the layers at predefined locations by holding means. Specifically, the hollow tubes further provided with openings at predefined locations. The hollow tubes are characterized by having any one of plurality of protrusions, plurality of corrugation, plurality of ribs, plurality of serrations and combination thereof, on internal and external surfaces. The method further comprises providing a means to fill or discharge adhesive in the hollow tubes and pouring concrete to create a precast structural element.

Description

PRECAST STRUCTURAL ELEMENT AND METHOD FOR CONNECTING THE PRECAST STRUCTURAL ELEMENT TO EACH

OTHER

Field of the invention:

The present invention generally relates to building construction technology, and more particularly, relates to a precast structural element and method for connecting the precast structural element to each other.

Background of the invention: Today, the most common practice to construct a precast structural element, for example, a precast wall is to cast it entirely on site, by using reinforcement steel and vertical shuttering (formwork) on two sides and pouring concrete in between. This formwork needs to be supported from outsides (one or both), and needs to be poured only in maximum of 2 to 3m heights, in order to concrete it without any quality issues like segregation due to down-pour from larger heights, etc. First, the reinforcement of the wall is tied, then the above mentioned shuttering is erected and then concrete is poured. This is repeated till the wall reached from one floor to another. For all of these operations, there is need to erect scaffolding, from one or both sides of the walls, for allowing labour and material to reach the top height of 3 m for tying steel, pouring concrete.

The above process is highly labor oriented and time consuming. Most of the material shifting is either done with a crane, or in most cases, with labour. Lot of supervisory staff must also be planned in order to drive the operations in the right direction, with lot of coordination with the different agencies (usually, a site has many different specialty contractors for different abovementioned activities) Specifically, transportation of all the above mentioned material to site must be made especially, concrete, by ready mix method, frequently. Another prior art methodology includes precast shear walls with CIS joint in between wall to wall. In this method, most of the on-site labour oriented and time consuming works are eliminated by producing the walls horizontally (which is simpler and longer walls than 2-3 m) and can be casted in one shot. The walls are prepared on shop floor level all the time, so no need to shift material from one height to another. This also reduces loss in time and labour in material shifting, increases accuracy and quality of the concrete, etc. Since the walls are made in factory, we can introduce lot of mechanization in production of elements, as compared to site. The utility of mechanization can be continually used, for good effects, in the following stages i) Production ii) Transportation iii) Installation.

However, after installation of walls next to each other, the mechanized process stops, because, the most reliable methodology to connect the 2 walls to each other, remains a cast-in-situ joint. This is defeating the purpose of mechanizing till about say 90% of the process and ending up with doing the remaining 10% in the same primitive methodology. For a technocrat, it is all the more frustrating, as this particular 10% ends up being the critical and delaying activity whereby he has leveraged the effectiveness of Precast for the rest of the 90% of the processes.

Accordingly, there exists a need to provide a precast structural element and method for connecting the precast structural element to each other that overcome the abovementioned drawbacks of the prior art.

Object of invention:

An object of the present invention is to automate a process of interconnecting any precast structural elements such as precast walls.

Another object of the present invention is to provide a fast, automatic, qualitative method of the precast structural element connection as per design strength requirements with zero error guarantee and freedom from dependency on labor for multiple activities. Summary of the invention:

Accordingly, the present invention provides a precast structural element capable of connecting with each. The precast structural element made by a method which comprises preparing one or more layers of plurality of horizontal and vertical reinforcement bars. The method further comprises fixing plurality of hollow tubes to the layers at predefined locations by holding means. Specifically, the hollow tubes further provided with openings at predefined locations. The hollow tubes are characterized by having any one of plurality of protrusions, plurality of corrugation, plurality of ribs, plurality of serrations and combination thereof, on internal and external surfaces. The method further comprises providing a means to fill or discharge adhesive in the hollow tubes and pouring concrete to create a precast structural element. In another aspect, the present invention a method for connecting precast structural elements. The method comprises bringing together two precast structural elements close to each other, and placing load transferring element in the hollow tubes of the first precast structural element. The load transferring element is characterized in that the load transferring element is configured with markings thereon at predetermined locations. The method further comprises erecting the second precast structural element next to the first precast structural element and aligning the center fines of the openings of the hollow tubes in the second precast structural element with the openings of the hollow tubes in the first precast structural element. The method furthermore comprises sliding the load transferring element into the second precast structural element till the desired marking, and filling an adhesive in the openings and gap between the two precast structural elements.

Brief description of drawings: Figure 1 shows a schematic drawing showing one precast structural element configured next to other precast structural element;

Figure 2 shows another schematic drawing of the precast structural elements of figure 1 ;

Figure 3 shows a top view showing one precast structural element connected to other precast structural element;

Figure 4 shows another schematic drawing of the precast structural elements of figure 3;

Figure 5 A shows a schematic drawing of the precast structural element for central wall of T type connection 1 ;

Figure 5B shows a schematic drawing of the precast structural element for central wall of T type connection 2;

Figure 6A shows a schematic drawing of the precast structural element for central wall of plus type connection 1 ; Figure 6B shows a schematic drawing of the precast structural element for central wall of plus type connection 2;

Figure 7 shows a schematic drawing of the precast structural element for corner wall of L type connection in accordance with the present invention; and

Figure 8a and 8b shows the precast structural element for interconnecting precast structural elements and method therefor.

Detail description of the invention:

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 embodiments. The present invention provides a precast structural element and method for connecting the precast structural element to each other. The precast structural element and method provides a fast and qualitative method for connecting the precast structural elements with zero error guarantee and freedom from dependency on labor for multiple activities.

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 and in the table below. Referring to the figure from 1 to 8b, a precast structural element and a method for connecting the precast structural element (100) to each other (hereinafter referred as,“the method (200)”), in accordance with the present invention is shown. The method (200) is used for connecting at least two precast structural elements including a first precast structural element (17) and a second precast structural element (18) as shown in figure 1 and 2.

In an embodiment, the precast structural elements includes but not limited to precast shear walls, precast columns, precast spandrel, precast retaining walls, precast non-load-bearing walls, precast load bearing walls, precast slabs, precast foundation, precast ducts, precast chambers, precast culverts, precast channels, precast pipes, precast trenches, precast linings, precast medians, 3-d precast modules, precast beams like rafters, girders, stringers, and the like and also includes segmentally constructed precast elements, or a cast in situ element to any of the above listed precast elements.

In first aspect, the present invention provides a method (200) for interconnecting precast structural elements or cast in situ elements for effective transferring tension, compression, in plane shear forces, out of plane shear forces, bending moments and any combination thereof. The method (200) comprises preparing one or more layers of plurality of horizontal and vertical reinforcement bars.

The method (100) further comprises fixing plurality of hollow tubes to the layers at predefined locations by holding means. The hollow tubes further provided with openings at predefined locations. The openings at the predefined location are for the purpose of filling adhesive or for connecting tubes thereto for filling adhesive.

For the purpose of explanation, the hollow tubes are shown as a first hollow tube (11 A) and a second hollow tube (11B).

In preferred embodiment, the hollow tubes i.e. first hollow tube (11 A) and a second hollow tube (11B) are characterized by having any one of plurality of protrusions, plurality of corrugation, plurality of ribs, plurality of serrations and combination thereof, on internal and external surfaces as shown in figure 8 a ad 8b. The optimal shape of the hollow tubes is provided to transfer the tensile force by bond. The hollow tubes for example, the first hollow tube (11 A) and second hollow tube (11B) are placed inside the first structural element (17) and second structural element (18) at pre-defined locations within suitable tolerances so that the second hollow tube (11B) comes coaxial to the first hollow tube (11 A) after erection. Through the present invention and drawings are showing one hollow tube in one structural element, it is evident to those skilled in the art that multiple hollows tubes can be configured within the structural element.

The first hollow tube (11 A) and the second hollow tube (11B) are provided with holdfasts (not shown) mounted on rails (not shown). Use of mounting rails/ holdfasts minimize tolerance errors and increase the speed of assembly, saving labor cost and time

In the embodiment, the first hollow tube (11 A) and second hollow tube (11B) are of corrugated carbon steel, stainless steel pipes, or cold rolled cold annealed strips of bright metal/galvanized finish. The first hollow tube (11 A) and the second hollow tube (11B) may be made of polymeric sleeve with suitable adhesive bond acting as an interface bonding agent which is pro-polymer as well as pro-fresh concrete.

In another embodiment, the hollow tubes (11 A and 11B) can also be made from any one or combination of the materials selected from, mild steel, high strength steel, tin, aluminum, galvanized iron, galvanized steel, cast iron, plastic (all variants of polymers like HDPE, LDPE), fiber reinforced plastic (FRP), or any other alloy or CPVC (Chlorinated polyvinyl chloride), UPVC (plasticized polyvinyl chloride), PVC (polyvinyl chloride). The hollow tubes (11 A, 11B) further comprises means for preventing a load transferring element (12) to rest at bottom of the hollow tube. In an embodiment, the means for preventing the load transferring element (12) to rest at the bottom of the hollow tubes are blocks or protruding rings configured within the internal diameter of the hollow tubes (11 A, 11B) at a predefined distance. The means maintain the load transferring element (12) coaxial to the tubes in order to maintain a fixed layer of adhesive/injection mortar, with allowable tolerance between the bar and the inner surface of the tube, for required structural action.

The method (100) furthermore comprises providing a means to fill or discharge adhesive in the hollow tubes (11 A, 11B). In an embodiment, the means for filling or discharging the adhesive is an adhesive/injection mortar inlet/outlet (19 and 23) formed by bending the hollow tubes (11 A, 11B). at production stage and configured inside the precast structural elements (17, 18) to receive the adhesive/injection mortar. The adhesive/injection mortar flows through the hollow tubes (11 A, 11B). by any of the process pressure, non-pressure or self flowabifity. In an alternate embodiment, the adhesive/injection mortar inlet (19, 23) is made by connecting a flexible hose pipe (not shown) of polymer or rubber material to the predefined openings of the hollow tubes (11 A, 11B).. In an embodiment, the adhesive/injection mortar inlet (19, 23) may act as the adhesive/injection mortar inlet and vice a versa. In an alternate embodiment, the adhesive/injection mortar inlet/outlet (19 and 23) is a separate part similar to an elbow or bend part made of any one or combination of the materials selected from stainless steel, mild steel, high strength steel, tin, aluminum, galvanized iron, galvanized steel, cast iron, plastic, fibre reinforced plastic (FRP), or any other alloy or CPVC (Chlorinated polyvinyl chloride), UPVC (unplasticized polyvinyl chloride), PVC (polyvinyl chloride)

Finally, the method (200) comprises pouring concrete into the one or more layers of plurality of horizontal and vertical reinforcement bars to create a precast structural element (100).

In an embodiment, the load transferring element (12) is also alternatively referred as reinforcement bar (12) throughout the description.

The precast structural element (100) also comprises supplementary reinforcement bars (27) configured in the region of the hollow tubes which transfer forces to horizontal and vertical bars.

The at least one in the pair of opposing hollow tubes (11 A, 11B) of the precast structural elements (17,18) optionally comprises a joint assembly connected thereto. The joint assembly comprises a T shaped connecting member (13) for accessing the load transferring element (12), a reducing shaped member (14) with one end having greater diameter than the other end, the reducing shaped member (14) connected to T shaped connecter (13) at larger diameter; and a connecting means for connecting to any one of the T shaped connecting member, the reducing shaped member and the hollow tube. In an embodiment, the connecting means is housing pipe (15). The joint assembly can be optionally used for the precast structural element in order to save the cost of adhesive as the joint assembly requires less volume of adhesive/injection mortar.

The housing pipe (15) configured for example, inside precast structural element (17, 18) and brought to the face thereof which forms the adhesive/injection mortar inlet/outlet (19, 23). The housing pipe (15) is made of any one or combination of the materials selected from, stainless steel, mild steel, high strength steel, tin, aluminum, galvanized iron, galvanized steel, cast iron, plastic (all variants of polymers like HDPE, LDPE and like), fibre reinforced plastic (FRP), or any other alloy or CPVC(Chlorinated polyvinyl chloride), UPVC (unplasticized polyvinyl chloride), PVC(polyvinyl chloride). In a specific embodiment, the diameter of the housing pipe (15) is reduced to lower the adhesive/injection mortar cost.

The two arms of the T connector (13) that are in straight line and 180 degrees opposite to each other are used to interconnect the tube (11 A or 11B) and the reducing shaped member (14). The third arm (perpendicular arm) of the T connector (13) is used to gain access to the load transferring element (12) from the face of the second precast structural element (18), and to slide the load transferring element (12) from the second precast structural element (18) to the first precast structural element (17). The T connector is (13) made of any one or combination of the materials selected from stainless steel, mild steel, high strength steel, tin, aluminum, galvanized iron, galvanized steel, cast iron, plastic (all variants of polymers like HDPE, LDPE, etc), fibre reinforced plastic (FRP), or any other alloy or CPVC (Chlorinated polyvinyl chloride), UPVC (unplasticized polyvinyl chloride), PVC (polyvinyl chloride)

The load transferring element (12) is sent from one precast structural element to the other through the reducing shaped member (14), T Connector (13) and second hollow tube (11B) either by any one of the method selected from an electrical machine with drive mechanism, by attaching a wire to the end of the load transferring element (12) that opens into the gap of the joint with suitable means (not shown) such as simply tying, inserting a hooked end of the wire into a hole bored in the bar/end cap attached to the load transferring element (12) and pulling it from, for example from second precast structural element (17) to the first precast structural element (17) by gaining access to the wire through the adhesive/injection mortar inlet/outlet (19, 23) of the first element. In an alternative embodiment, the load transferring element (12) is sent from the one precast structural element to another precast structural element by magnetic means, manual operation with or without a suitable tool.

In the embodiment, the reducing shaped member (14) is made of any one or combination of the materials selected from relatively economical range of material, however, ranging from stainless steel, mild steel, high strength steel, tin, aluminum, galvanized iron, galvanized steel, cast iron, plastic (all variants of polymers like High-density polyethylene (HDPE), Low-density polyethylene(LDPE)and like), fibre reinforced plastic (FRP), or any other alloy or CPVC (Chlorinated polyvinyl chloride), UPVC (unplasticized polyvinyl chloride), PVC (polyvinyl chloride).

In another aspect, the present invention provides a method (300) for connecting precast structural elements. The method (300) comprises bringing two precast structural elements (17, 18) close to each other.

The method (300) further comprises placing the load transferring element (12) in the hollow tubes of the first precast structural element (17). The load transferring element (12) is configured with markings (26) thereon at predetermined locations.

The load transferring element (12) is the structural load transferring members that gives shear strength to the connection. The load transferring element (12) also contribute to bending strength called as tension force of the precast structural element connection depending on the intended structural action expected to be taken. The diameter, spacing and tolerance with the hollow tube (11 A and 11B) depend on the forces that need to be transferred. In a specific embodiment, the orientation of the load transferring element (12) varies from orthogonal in horizontal or vertical to inclined or angular in any plane, within the elements as well.

In an embodiment, the load transferring element (12) is configured with a marking (26) made by a suitable paint or sticker thereon. The marking can be seen at the gap (16) between the two precast structural elements (17 and 18). The marking is used as an indicator to indicate when the load transferring element (12) is fully translated from the one precast structural element (18) to the other element (17). This is the zero error guarantee indication.

In the embodiment, the load transferring element (12) is made of any one of the materials selected from Fe 250, 415, 450, 500, 500D, 600, 600D , higher grade thermo mechanical treatment (TMT), normal steel bars and treated rods that are structural in nature. Ina specific embodiment, the reinforcement bars (12) are made of a specially designed and manufactured material such that they can yield under transmission of an expected force, in order to dissipate energy. The method (300) furthermore comprises erecting the second precast structural element (18) next to the first precast structural element (17).

The method (300) furthermore moreover comprises aligning the center lines of the openings of the hollow tubes in the second precast structural element (18) with the openings of the hollow tubes in the first precast structural element (17). The method (300) thereafter comprises sliding the load transferring element (12) into the second precast structural element (18) till the desired marking. Though it has been described that the load transferring element (12) is kept in the hollow tubes of the first precast structural element (17) and moved to the hollow tube of the second structural element (18), it is evident to those skilled in the art that the load transferring element (12) may be kept in the hollow tubes of the second precast structural element (18) and moved to the hollow tube of the first structural element (17).

The method (300) finally comprises filling an adhesive in the openings and gap (16) between the two precast structural elements (17, 18). In an embodiment, the sliding the load transferring element is by any one of the electrical machine with drive mechanism, pulling the bar via a wire from first element, magnetic means and manual.

Advantages of the invention: 1. The method is simpler to achieve.

2. Minimum on-site activities are needed.

3 The method is very safe as the method eliminates multiple labor oriented activities and material handling activities.

5. No modifications in mold to prepare shear keys, at time of casting. 6. The corrugations in the hollow tubes and the high strength adhesive provide a strong connection to the precast concrete between precast structural elements via bond transfer.

7. Indicator/marking on steel bar, to indicate whether the desired result (development length) considered in design stage is achieved on site or not, which is unprecedented

8. Due to the less number of components and lesser dimensions, wastage of raw materials is reduced, thereby, making the system‘greener’ than other systems.

9. The method (200, 300) with supplementary reinforcement device (27), corrugated and specifically designed tubes (11 A, l lb), adhesive/injection mortar(23) filled in the tubes as well as in the gap (16) effectively transfers higher amounts of forces such as shear in plane, shear out of plane as well as transfer of tension via bond.

10. The method (200,300) provides strong and effective connection, achieved after installation of ah the neighboring precast structural elements which is unique, whereby the reinforcement bar is transferred from one element to another from the outside of the element in a much simpler manner than prior arts.

11. The method (200,300) provides ability to transfer normal forces (tension, compression), shear forces (in plane, out of plane), bending moments and any combination of these forces, wherein the prior art systems either transfer shear forces only or shear forces and (small)tension forces only, and tubes must be connected to a reinforcing bar in the precast structural elements to be connected which is rather complicated and requires that the tensile strength of the tube must be at least as large as that of the connector bar.

12. In the method (200, 300) in case of failure of the connection, the gap acts as valuable back up provision to access the bar, which is not disclosed anywhere in the prior art. The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the scope of the claims of the present invention.

Claims

We Claim:

1. A precast structural element capable of connecting with each, the precast structural element made by a method comprising:

preparing one or more layers of plurality of horizontal and vertical reinforcement bars;

fixing plurality of hollow tubes to the layers at predefined locations by holding means, the hollow tubes further provided with openings at predefined locations, the hollow tubes characterized by having any one of plurality of protrusions, plurality of corrugation, plurality of ribs, plurality of serrations and combination thereof, on internal and external surfaces,

providing a means to fill or discharge adhesive in the hollow tubes; and pouring concrete to create a precast structural element.

2. The precast structural element as claimed in claim 1, wherein the hollow tubes further comprises means for preventing a load transferring element to rest at bottom of the hollow tube. (OK)

3. The precast structural element as claimed in claim 1 , wherein supplementary reinforcement bars are configured in the region of horizontal and vertical reinforcement bars.

4. The precast structural element as claimed in claim 1, wherein at least one in the pair of opposing hollow tubes further comprises a joint assembly connected thereto, wherein the joint assembly comprises:

a T shaped connecting member (13) for accessing the load transferring element (12);

a reducing shaped member (14) with one end having greater diameter than the other end, the reducing shaped member (14) connected to T shaped connecter (13) at larger diameter; and a connecting means for connecting to any one of the T shaped connecting member, the reducing shaped member and the hollow tube.

5. A method for connecting precast structural elements, the method comprising:

bringing together two precast structural elements close to each other; placing load transferring element in the hollow tubes of the first precast structural element, characterized in that the load transferring element is configured with markings thereon at predetermined locations;

erecting the second precast structural element next to the first precast structural element;

aligning the center lines of the openings of the hollow tubes in the second precast structural element with the openings of the hollow tubes in the first precast structural element;

sliding the load transferring element into the second precast structural element till the desired marking; and

filling an adhesive in the openings and gap between the two precast structural elements.

6. The method as claimed in claim 5, wherein the sliding the load transferring element is by any one of the electrical machine with drive mechanism, pulling the bar via a wire from first element, magnetic means and manual.