KR101184511B1 - Site Reinforcing Method of Thick Wall with Using Plant Welded Steel Bar Frames - Google Patents

Abstract

In order to conventionally reinforce the thick rebar on a thick reinforced concrete wall applied to an explosion-proof structure or a nuclear power plant, as shown in FIGS. 4 and 5, the radius of curvature of bending the reinforcing bar is large. It's impossible to be exact. In the case of using thick reinforcing bars, the lap joint for securing the adhesion strength is greatly increased due to the increase in the use of reinforcing bars, and accordingly, the wall thickness needs to be increased.

In nuclear power plants, the shortening of construction period is directly related to the reduction of total project cost. Therefore, in the case of nuclear power plant sites, reinforcing bars are tested by high-strength thick reinforcing bars with excellent weldability, and then mechanical joints or welding joints, such as couplers, are applied instead of lap joints. Of course, in the case of welded joints, detailed provisions for rebar welding are necessary.

Conventional wall reinforcement method uses the method of reinforcing the vertical reinforcing bar first and the horizontal reinforcing bar depending on it. However, in the method proposed in the present invention as shown in Figure 1 on the both ends of the wall frame A (6 vertical materials) in the factory fabricated by the factory, the site of the frame B is welded to the field assembly after the assembly of the remaining reinforcement in the field . Frames A and B reduce the work of formwork woodworking to secure the vertical, horizontal and wall thickness of formwork during construction, and also function as formwork.

Figure 6 is a reinforcement method when the two walls meet in the a-type or T-type, when the T-type can be used by the A, B frame in the same manner as in Figure 1. However, the C frame of type A requires 7 vertical members.

Description

Site Reinforcing Method of Thick Wall with Using Plant Welded Steel Bar Frames}

Reinforced concrete structure is the most widely used structural method in the world. The standard method is divided into the work of producing a container to hold the concrete, which is formed by the form woodworking, until it is cured as a solid with high strength, the reinforcing of the reinforcing steel and the pouring of the concrete. However, after the concrete is cured, the reinforcing bar cooperates with the tensile strength corresponding to the compressive strength of the concrete to create a new structure called "reinforced concrete." Have. In other words, the rebar and concrete formwork, a temporary material provided by woodworking, should serve as an incubator before concrete is cured. You have to hold on to it. Installations to resist the pressure of concrete are called clubbing and braces.

The pressure of the concrete on the formwork before the reinforced concrete is cured is 2.5 times the hydraulic pressure. Therefore, the formwork is a temporary material that should be removed after 4 weeks after the reinforcement of reinforced concrete is finished, but it is more important than reinforcement or concrete construction, requires more construction period, and costs more than reinforcement or concrete. However, formwork is one of the 3D sectors, so there are few domestic engineers, and the rebar works are the same. In order to overcome these difficulties, the precast concrete method, ie, the formwork, the reinforcement and the process of pouring concrete and curing, is carried out at the factory, and then assembled and put into the site. However, the members of the same standard are repeated, and it is mainly applied to special construction that does not have a large burden on transportation assembly and repair of joint defects.

In order to meet the seismic structure design standards such as the explosion-proof structure or nuclear power plant, the lap joint and anchorage length for securing the attachment strength of the thick reinforcing bar are greatly increased, resulting in the increase of rebar usage, and the vicious cycle of increasing the thickness of the wall continues. For example, if the 41 mm high strength reinforcing bar (F _y = 500 MPa) and the concrete's compressive strength f _ck = 30 MPa, the joint length is 2240 mm for the joint. In addition, such thick walls have a lot of rebars, so it is reasonable to use coarse rebars, but it is difficult to assemble on-site processing. I design it. Another reason is the heavy weight of the rebar, which is difficult to transport and assemble on site by manpower. For reference, 41mm diameter rebar has a weight of 10.5kg per unit length, so it is 84kg at 8m length and cannot be handled without the help of transport equipment. By convention, the radius of curvature to bend the rebar is three times the diameter up to 25 mm, but if it is 38 mm or more, it is five times the diameter. For example, 41 mm rebar takes up to 49.2 cm of width to bend 180 ° (see Fig. 5).

The reason for bending the end of the horizontal reinforcement in Figure 4 is to wrap the vertical reinforcement, but if the radius of curvature is large it is impossible to maintain the required position of the vertical rebar. In addition, the reduction of the construction period is directly related to the reduction of the project cost. Therefore, if the scale is large and air saving is absolutely necessary, such as in a nuclear power plant, rebar joints need to be manufactured by mechanical joints or welding, such as couplers instead of Lap Joints, to induce air savings. Of course, rebar welding, which is an absolute contraindication, must be manufactured by ordering the reinforcing bars with excellent weldability, and the necessary manufacturing regulations and specifications should be revised.

Omitting only the ridges and braces of the formwork from the reinforced concrete construction will greatly help the construction period and reduce the construction cost. When the reinforcing bars are separated by strands, they are easily bent due to their small stiffness.However, the method of reinforcing concrete, which was “form-dependent”, was reinforced using the principle that rigidity increases greatly when welding them together. It is desirable to change as much as possible. Although the reinforcing bar atomic symbol is "Fe" and is not different from other steel frame members such as H-beams, it is considered to be contraindicated to use reinforcing bars as a structural material (Standard Specification for Construction Work "3.2 Machining "Machining of rebars, rebars and welded nets is prohibited except for the special handling of the personnel in charge. This is because raw materials for rebar production are high in carbon, unlike regular steel materials such as H-beams. However, since most of the rebar processing is done at the construction site or the open air, it is considered difficult to manage, and therefore, welding and heating are prohibited as the standard specification of the Ministry of Land, Transport and Maritime Affairs. The above provisions, on the other hand, suggest that permitting the use of welded wire mesh while limiting the welding process does not forbid "welding" itself.

In the past, it was common practice to leave the reinforcing bars loaded on the site in order to easily cut the rebars, and cut the rebars in length using an oxygen welding machine. Cutting steel with oxygen can damage other steel bars below, but when partially heated steel is quenched in rainwater, local ductility and toughness are degraded. Therefore, the standard specification for building construction has added a clause that prohibits heating. In addition, the current reinforcing bar is not a circular bar, but the surface is curved and deformed, and steel structural engineers who regard precision as life do not want to recognize it as a raw material for steel structure.

Reinforcing bars are produced by melting scrap metal, and some new steel mills can produce them easily. Due to this effect, it is difficult to allow batch welding construction because bad steel is imported from China. Therefore, performance recognition and specification revision should be preceded to enable welding assembly at the factory, which has been applied as a standard construction technique for decades. In addition, in order to fabricate rebars in the factory, the performance recognition criteria of the used rebar, test and evaluation methods, and welding management must be specified. If these prerequisites are carried out, it may be sufficiently possible to weld the rebar at the factory. Gas welding is still allowed for field installation.

A system to certify the rebar welding of rebars after testing is established, and the standard for building construction is revised to allow rebar welding in the certified factory. Currently, some rebar manufacturing plants are ready to order production of welded rebars with carbon equivalents to improve weldability. In addition, in order to confirm the possibility of welding of the reinforcing bar, 13 types (26 pieces) of test specimens were manufactured and subjected to a tensile test, and the test results are attached as a reference. The test results showed that the yield strength and tensile strength were satisfactory, and the elongation was improved by heat treatment such as preheating and postheating.

Welding and reinforcing steel bars in a steel ball factory guarantees quality that is incomparable to tying them with binding lines at the construction site. In addition, thick steel can be used to increase the efficiency of the cross section, and the overall economic efficiency is secured by reducing the concrete cross section and reducing the amount of reinforcing bars due to no overlapping. Currently, the skilled workers mobilized for reinforced concrete construction in Korea are mostly foreign workers, causing social problems. However, assembling the reinforcing factories also solved the problem of supply and demand for skilled workers, and the construction period and construction cost were reduced drastically (20 ~ 30%).

The process of fabrication and installation for each part in the reinforcement of thick wall reinforcement frame after factory production is as follows.

1 and 3, the frame A (10) is assembled at both ends of the wall to be imported and installed on site after welding production in the factory. If the length of the wall is long, the frame B 20 is placed in the middle at appropriate intervals. Therefore, the frame B is arranged at intervals enough to support the horizontal rebar 40 between both ends of the frame A. The horizontal rebar is threaded at both ends, and the horizontal reinforcing bar spans the horizontal member 50 of the frame, and then the end of the horizontal rebar is fixed with the nut 62 and the washer 64 between the vertical members a and b of the frame A. The other end of the horizontal reinforcement reaches the other horizontal reinforcing bar and coupler, and then reaches the frame A to fasten the final end with the washer and nut. This method is repeated at the vertically spaced intervals, and the horizontal reinforcing bars are tied with the vertical members of the frames A and B with the binding lines. After that, the vertical reinforcing bars 45 are bundled with the horizontal reinforcing bars 40 and the binding line.

There are at least six vertical members 55 of frame A, of which a, b, c, and d are arranged outside the corners of four horizontal members arranged in well sperm shape, and the remaining two e, f are a and b, respectively. After installing the horizontal reinforcing bar to be fixed. If the height of the wall is a concern when the horizontal deformation during construction, the frame 60 is arranged diagonally on the vertical plane consisting of the upper and lower horizontal members 50 and the vertical member 55 in the frame and welded to the vertical member. Horizontal members and yarns are welded to the inside of the vertical members so that they will not be interfered with later horizontal bars. The horizontal spacing and thickness of the horizontal members and the thickness of the members are determined by the structural calculation so that they have sufficient strength until the concrete is poured into the frame after assembling the horizontal and vertical rebars on the frame. Between the vertical members of frame A, additional rebar can be added if necessary.

Frame B (20) is a welded horizontal material and yarn only on one side vertical members c, d of the frame A, and serves as a support frame for reinforcing the horizontal reinforcement when the length of the wall is long. If the height of the wall exceeds the height of one floor of a general building, frame B is made of a quadrilateral plane, such as removing verticals e and f from frame A, instead of two verticals. When reinforcing bars in this way, frame A and frame B control the transverse deformation during construction, so unlike the conventional reinforced concrete construction, the amount of work of formwork woodworking to secure the vertical, horizontal and wall thickness of the formwork Will be reduced. In other words, if the assembly in the field after manufacturing the factory while maintaining the accuracy of the millimeter in the iron ball factory, it also functions as a formwork brace. The wall has a type and a T type in addition to the straight type, the T type can be constructed in the same way as the straight wall as shown in Figure 6 (b). When two walls meet at right angles to each other, such as a-type, frame C of FIG. 6 (a) is utilized.

Frame C (30) is made of at least seven vertical members 55. Six vertical members a, b, c, d, e, and f are manufactured as frame A, and the remaining g is fixed with horizontal rebar 3 between c. Do it. After reinforcing horizontal bars 1, 2 and 3, the vertical material h is placed on site, and the horizontal bar 4 is assembled to assemble the vertical bar. The horizontal and vertical spacing and thickness of horizontal material and the thickness of the material are transferred to the construction site and placed in a predetermined position, and the structural calculations are made to have sufficient strength until the concrete and pour concrete are laid by placing the horizontal and vertical bars. Decide

The vertical members 55, the horizontal members 50, and the yarns 60 mentioned above are also made of reinforcing bars in the same way as the vertical reinforcing bars 45 or the horizontal reinforcing bars 40, but they are named differently for convenience of explanation. The vertical joints of Frame A (10), Frame B (20), and Frame C (30) are all assembled with couplers by making threads at both ends, and the joints of vertical and horizontal bars are also based on the application of couplers. However, instead of mechanical joints using couplers, welding and welding can also be applied.

1 is a conceptual view of a reinforcing frame installed in the field by combining a factory-made frame A and frame B,

Figure 2 is a perspective view of the reinforcement frame and frame A installed in the field by combining the frame A and frame B,

3 is a work flow chart for each step,

4 is a case where the reinforcing bar after bending the thick reinforcing bar according to the current building standard,

5 shows the standard hook and bend radius for rebar diameter HD41,

6 is a method of reinforcement when the two walls meet in the form of a or T,

7 shows the tensile test results of the rebar welded portion.

<Code Description of Drawings>

10; Frame A 20; Frame B

30; Frame C

40; Horizontal rebar 45; Vertical rebar

50; Horizontal members 55; vertical

60; Stock 62; nut

64; washer

Claims (4)

In constructing the wall by additionally reinforcing the rebar frame at the site after factory welding, Frame A (10) is installed at both ends of the wall, the frame A is formed in a square shape with a vertical member (55), the vertical member is welded to the vertical member with a horizontal member (50) inside the vertical member, respectively, and fixed in a well sperm form; The front and rear horizontal reinforcing bar 40 on both sides of the horizontal member on the outside of the frame to the frame A, and then add the vertical member 55 so as to be a set of two around the horizontal reinforcement; The horizontal reinforcing bar secures the end screwed between the two vertical members of the frame A with the nut 62 and the washer 64, and the other end also secures the horizontal rebar 40 between the vertical member in the same way; And When the horizontal reinforcement is fixed, the vertical reinforcement 45 is also installed on the horizontal reinforcement method by plant welding the thick wall reinforcement frame, characterized in that the reinforcement frame of the wall is formed by factory welding In the wall, Frame C (30) is installed at the corner where the two walls meet, the frame C is formed in a square shape with a vertical member 55, the horizontal member 50 inside the vertical member to be fixed with a vertical sperm by welding the vertical member; In the frame C, horizontal reinforcing bars of the front and rear of the two walls over the horizontal member on the outside of the frame, and vertical members are added to the corners at both ends, so that two sets of two horizontal bars are centered on each other; The horizontal reinforcing bar secures the end screwed between the two vertical members 55 of the frame C with a nut 62 and a washer 64; And At the opposite end of the bidirectional wall, a frame A (10) is installed, and the horizontal reinforcing bars are fixed between the vertical members of the frame A (10); And When the horizontal reinforcement is fixed, the vertical reinforcement 45 is also installed on the horizontal reinforcement method by plant welding the thick wall reinforcement frame, characterized in that the reinforcement frame of the wall is formed by factory welding delete delete

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