KR19990079168A - Structural Reinforcement Method Using Welded Wire Mesh - Google Patents

Abstract

The present invention relates to a method for reinforcing concrete using a welded wire mesh. More specifically, the present invention relates to a method of increasing the structural strength of concrete by reinforcing a portion where a column meets a foundation or a slab by using a cold drawn welded wire mesh.

Structural reinforcement method using a welded wire mesh of the present invention is to cut the welded wire mesh to a dimension that is slightly smaller than the thickness of the foundation or slab, that is, the size of the base or slab subtracted the upper, lower cover thickness and the main root thickness, the welded wire mesh Rotate continuously from inside to outside in a snail, concentric or continuous diagonal fashion around the column. The gap between the inner welded wire mesh and the outer welded wire mesh is kept constant according to the result of the structural calculation, and a separator is installed between the welded wire meshes for this purpose.

The structural reinforcement method using the welded wire mesh of the present invention reinforces the joint portion between the foundation or the slab and the pillar, thereby restraining the lateral deformation occurring in the foundation or the slab by the compressive force or the shear force applied from the pillar to improve the structural strength. Can be.

Description

Method for reinforcement of concrete using welded wire fabric

The present invention relates to a method for reinforcing concrete using a welded wire mesh. More specifically, the present invention relates to a method of increasing the structural strength of concrete by reinforcing a portion where a column meets a foundation or a slab by using a cold drawn welded wire mesh.

Compression stress, tensile stress, and shear stress are applied to the structural members, and the compressive stress is burdened by the concrete, and the tensile stress is reinforced by the rebar is the basic principle of the reinforced concrete structure. On the other hand, the shear stress is mainly received by the concrete, but can be reinforced with reinforcing bars, but in the slab and foundation, instead of omitting the reinforcement to the reinforcement is designed to increase the thickness of the concrete is a generalized technique. The stress applied to the structural member is not uniform and there is a part where the stress is concentrated in a part. This is where the root and foundation of the pillar meet, and where the pillar and slab meet. Therefore, the amount of reinforcement should be increased in such a part, and the thickness of concrete should also be large.

In general, the foundation of the structure has the form of independent foundation, file foundation, mat foundation, etc. Independent foundation or file foundation can be adjusted separately, such as thickness or reinforcement of the foundation is economical advantage, but the digging work is cumbersome Often the design changes to a mat basis. However, even if the design changes to the mat foundation, in order to resist the shear force around the column, even if the tensile rebar is increased, the thickness of the concrete must be over a certain level, so it is not easy to reduce the thickness of the mat foundation, and in practice, the most stress Since the thickness of the entire mat base is determined based on the large part, the small stress part is overdesigned, which causes uneconomical problems.

This problem also occurs in the flat slab structure. In the flat slab structure, stress is concentrated at the point where the column and slab meet and this is the weakest part. Typically, to improve the shear strength of the slab is installed a fingerboard (Drop Panel) or head circumference around the column. However, although the shear stress can be reduced by installing the fingerboard or the headboard, it is difficult to manufacture the formwork for the fingerboard or the headboard, and the ceiling height is lowered in the corresponding area, which increases the height of the floor for the installation of the duct or the lighting fixture. have.

Structural reinforcement method using the welded wire mesh of the present invention in order to solve the above problems by using a welded wire mesh to reinforce the concrete structure in three dimensions to reduce the thickness of the mat foundation or to cut the plate or the head of the flat slab plate We present a way to design a plate.

An object of the present invention is to reinforce a structural member with a cold drawn welded wire mesh to improve the compressive strength and shear strength of concrete around the column and to reduce the amount of tensile reinforcement, and to improve the structural strength of the structure as well as usability, economy and construction properties. To provide.

Another object of the present invention is to provide a simpler and faster structure reinforcement method using a welded wire mesh.

Still another object of the present invention is to provide a structural reinforcement method capable of constructing a structure of better quality by using a welded wire mesh produced under strict quality control in a factory.

1 is a plan view of a state in which the welded wire mesh is snail-shaped around the inner pillar.

FIG. 2 is a plan view of the welding wire mesh snailed around the outer column.

3 is a plan view of a state in which the welded wire mesh is arranged concentrically.

4 is a plan view of the welding wire mesh in a continuous diagonal manner around the inner pillar.

5 is a plan view of the welding wire mesh in a continuous diagonal manner around the outer column.

6 is a perspective view showing a part of a welded wire mesh curved in a circle.

<Description of Symbols for Main Parts of Drawings>

1: pillar 2: welded wire mesh

3: separator

All structural members have a characteristic that the compressive force reduces the length in the load direction, while extending in the direction perpendicular to the load. This ratio is called Poisson's Ratio. The Poisson's ratio of concrete is around 0.167.

At present, it is common to measure the compressive strength of concrete to measure the uniaxial compressive strength. However, the experimental results indicate that the biaxial compressive strength is increased by about 20% more than the monoaxial compressive strength. This means that by restraining deformation in the direction orthogonal to the load, it can resist even larger loads in the load direction.

In the case of a column, the strength of compressive strength is increased by binding and restraining the circumference of the column root with a band or spiral reinforcing bar, and when the column is enclosed by a round steel pipe instead of the band or spiral bar, the greater strength is achieved.

The present invention is due to the structural characteristics as described above, and by using a welded wire mesh around the column where the pillar and the foundation or slab meets to restrain the deformation in the direction orthogonal to the load to increase the structural strength .

Structural reinforcement methods using the welded wire mesh of the present invention include a snail, concentric and continuous diagonal method.

1 is a plan view of the welding wire mesh around the inner pillar in a snail-like manner. The snail reinforcement method cuts the welded wire mesh to a dimension slightly smaller than the thickness of the foundation or slab, i.e., subtracting the upper and lower cover thickness and the main thickness from the thickness of the foundation or slab, and continuously Snail-winding from the inside out. The gap between the inner welded wire mesh and the outer welded wire mesh is kept constant according to the result of the structural calculation, and for this purpose, the separator is wound between the welded wire meshes. Separator can be made by bending other welded wire mesh in a zigzag form or by folding a thin steel sheet in a zigzag form.

FIG. 2 is a plan view of the welding wire mesh snail's shape around the outer column. In the case of the pillar facing the outside, the center of the foundation and the pillar do not coincide with each other, and the pillar is often eccentric to the outside of the foundation. Therefore, the gap of the welded wire mesh is reduced to the outside, and according to the result of the structural calculation on the inside. Use separators to keep the spacing out from the inside continuously.

3 is a plan view of a state in which the welded wire mesh is arranged concentrically. The snail reinforcement method has a structurally and materially advantageous advantage because it does not generate a joint because it is continuously reinforcement using a roll member, but there is a disadvantage in that it is somewhat inconvenient to work. Therefore, it is a method of reinforcing them in the form of concentric circles having a plurality of diameters different from each other without continuous reinforcement. In one concentric circle, the welded wire mesh overlaps a predetermined joint length, and the joint portion is not concentrated in one place. The spacing between concentric circles should be kept constant according to the result of the structural calculation. For this purpose, the separator is used to reinforce from the inside to the outside.

4 is a plan view of the welding wire mesh in a continuous diagonal manner around the inner column. First, the welded wire mesh is placed in a square around the column, and when the square is closed, the welded wire mesh is continuously arranged in a large rectangle that is inclined at 45 ° and circumscribed to the rectangle, and the size increases as the process is repeated. This method is to reinforce the welded wire mesh into a square. This is a simple reinforcement method that can be used when the magnitude of the stress is not large. It takes advantage of the fact that the square becomes larger as the magnitude of the stress decreases as it goes outwards. The stress distribution path is reasonable.

FIG. 5 is a plan view of the welding wire mesh continuously placed diagonally around the outer column. FIG. In the case of the pillar facing the outside, the center of the foundation and the pillar do not coincide with each other, and the pillar is often eccentrically toward the outside of the foundation. First, the welded wire mesh is placed in a square around the column, and when the rectangle is closed, the welded wire mesh is continuously placed in the form of a large rectangle inclined at 45 ° and circumscribed to the rectangle. It is a method to reinforce the spacing in parallel, and to reinforce the welded wire mesh into a rectangle that increases in size as the process is repeated. This reinforcement method is also a simple reinforcement method that can be used when the magnitude of stress is not large.

Welded wire mesh may be cold drawn welded wire mesh. Cold drawn is a steel rod drawn from the room temperature to the yield point near the yield point, the force is drawn, the thickness becomes thinner, the length is increased, but the strength is stronger, it is economical material. The cold drawn welded wire mesh is manufactured by automatically welding them together in a lattice shape.

Since welded wire mesh is used to weave the bars horizontally and vertically in a factory, the precision is guaranteed and the strength of the joint is greater than that of the binding line. In addition, it is possible to adjust the thickness of the welded wire mesh or the unit cell size of the wire mesh according to the results of the structural calculation.

The reinforcement of welded wire mesh can be processed by cutting the standard product produced in the factory to the required dimensions in the field, or can be installed by using the crane after processing it in the factory in advance to the predetermined dimensions to be reinforced at the site. .

Table 1 shows structural design examples for one side shear and two side shear for the bearing capacity of 80t / m ² , column dimensions 1,000mm × 1,000mm, foundation dimensions 3,600mm × 3,600mm, dead load 700t, and live load 210t. F _c was 240 kg / cm 2 and F _y was based on 4,000 kg / cm 2. Shear stress is calculated on the basis of one side of the cross-section separated by d from the column surface, and shear stress is calculated on the basis of the four-sided section around the column by d / 2 away from the column surface.

thickness Muscle mass 1 side shear 2-sided shear V _u φV _c Straight muscle diameter φV _s V _u φV _c Straight muscle diameter φV _s 1,100 HD25 ＠ 203 111.4 251.2 - 924.3 1,158 - 1,000 HD25 ＠ 182 148.5 242.4 - 964.5 511.9 W10＠403452.6 900 HD25 ＠ 161 185.7 215.5 - 1,002.7 431.1 W10＠356571.6 800 HD25 ＠ 140 222.8 188.6 W10＠78634.2 1,038.8 356.2 W10＠186682.6

V _u : Maximum shear force φV _c : Shear force on concrete

φV _s : Shear force on rebar

* Increased F _c value by 15% considering the effect of hoop tensioning during shear reinforcement

If the thickness of the foundation concrete is 1,100mm, the concrete can resist only one-side and two-side shear forces, so no additional reinforcement is needed.However, if the thickness of the foundation concrete is 1,000mm, only the two-side shear is concrete. As it cannot resist, when reinforcing and reinforcing the W10 welded wire mesh at 400mm intervals concentrically, it is also safe for two-side shearing. It is possible.

Table 2 shows structural design examples for one side shear and two side shear for the bearing capacity of 80t / m ² , column dimensions 1,000mm × 1,000mm, foundation dimensions 4,200mm × 4,200mm, dead load 950t, live load 300t. F _c was 240 kg / cm 2 and F _y was based on 4,000 kg / cm 2.

thickness Muscle mass 1 side shear 2-sided shear V _u φV _c Straight muscle diameter φV _s V _u φV _c Straight muscle diameter φV _s 1,300 HD25 ＠ 160 175.2 351.7 - 1,335.6 1,529.6 - 1,200 HD25 ＠ 146 219.1 345.7 - 1,380.3 658.6 W10＠341721.4 1,100 HD25 ＠ 132 262.9 314.3 - 1,422.7 568.8 W10＠250853.9 1,000 HD25 ＠ 118 306.7 282.9 W10 ＠ 1,60023.8 1,463.3 484.9 W10＠186978.4

V _u : Maximum shear force φV _c : Shear force on concrete

φV _s : Shear force on rebar

* Increased F _c value by 15% considering the effect of hoop tensioning during shear reinforcement

If the thickness of the foundation concrete is 1,300mm, the concrete alone can resist the one- and two-side shear forces, so no additional reinforcement is required, but if the thickness of the foundation concrete is reduced to 1,200mm, it is safe for the one-side shear. As it cannot resist two-side shear only with concrete, it is safe enough for two-side shear when reinforcing the W10 welded wire mesh at 340mm intervals concentrically, and the thickness of the foundation concrete when laying the welded wire mesh at 250mm interval is 1,100mm. It is possible to reduce up to 180mm, and it is possible to reduce up to 1,000mm when backing at intervals of 180mm.

Based on the above calculations, it is assumed that the compressive strength of the foundation concrete around the column reinforced with cold drawn wire mesh is increased by 15% as in the case of the general spiral band pillar.

By reinforcing the joint portion between the slab or the foundation and the pillar using the structural reinforcement method using the welded wire mesh of the present invention, the compressive force or the shear force applied from the pillar is in the direction orthogonal to the compressive or shear force generated in the slab or the foundation. Transverse deformation and restraint shear strength can be improved. Therefore, even concrete of the same thickness can withstand larger loads, making it possible to reduce the thickness of the mat foundation or to omit the slabs of the slab or the head of the slab, making the construction of the structure much more economical. Welded wire mesh is relatively light in weight, so it is easy to handle and can be easily cut, so the reinforcement work is quick and simple. In addition, it is possible to shorten the construction period because it can be processed in the factory in advance with the required specifications and dimensions without installing and transporting it in the field and installing it using a crane in the field.

Since the welded wire mesh is produced under thorough quality control in a factory, it is possible to reduce the variation in quality, thereby making it possible to produce a structure of higher quality by using a structural reinforcement method using the welded wire mesh of the present invention.

Claims (6)

Spirally continuously welding the welded wire mesh from the inside to the outside in a direction parallel to the direction in which the tensile, compressive or shearing force is applied, around the cross-section in which the tensile, compressive or shearing force is applied; And, Installing a separator to maintain a constant gap between the inner welded wire mesh and the outer welded wire mesh; Structural reinforcement method using a welded wire, characterized in that consisting of. The method of claim 1, wherein the outer side of the structure is closely spaced apart from the welded wire mesh. 3. The method of claim 1 or 2, wherein the welded wire mesh is a cold drawn welded wire mesh. Reinforcing the welded wire mesh into a plurality of concentric shapes in parallel with the direction in which the tensile, compressive or shearing forces are applied around the cross-section in which tensile, compressive or shearing forces are applied; And, Installing a separator to maintain a constant gap between the inner and outer welded wire meshes of the plurality of welded wire meshes; Structural reinforcement method using a welded wire, characterized in that consisting of. Reinforcing the welded wire mesh into a quadrangle parallel to a direction in which the tensile, compressive or shearing force is applied around the cross-section in which tensile, compressive or shearing force is applied; Continuously reinforcing the welded wire mesh into a shape of a large square inclined at 45 ° to the square when the quadrangles are closed; And, Continuously reinforcing the welded wire mesh into a quadrangular shape that increases in size as the process is repeated; Structural reinforcement method using a welded wire, characterized in that consisting of. The method of claim 5, wherein the outer side of the structure is a structure reinforcement method using a welded wire mesh, characterized in that the spacing of the welded wire mesh in close parallel to the outline of the structure.