KR100402546B1 - A method to remove steel post inducing local buckling after completion of bridge erection to use it - Google Patents

Abstract

The present invention relates to a method for dismantling a steel column using buckling, in which the lower part of the steel column is cut off to form a cross-sectional cutout when the steel column is removed after completion of the construction in the prop support supporting method for supporting the structure to be constructed using the steel column and the screw jack. Therefore, buckling phenomenon occurs in the steel column, the load on the structure is applied to the steel column is reduced, the screw of the screw jack is easily rotated, and relates to the method of demolition of the steel column using the buckling that can be removed quickly and easily.

Description

A method to remove steel post inducing local buckling after completion of bridge erection to use it}

The present invention relates to a method for dismantling a steel column using buckling, and more particularly, a section cutout is formed by cutting a lower portion of the steel column, so that a buckling phenomenon occurs and the load applied to the steel column can be reduced to easily remove the steel column. The present invention relates to a method for demolishing steel column using buckling.

There are many types of construction methods for laying heavy structures such as bridges, but post construction is the bridge construction method that has been used for the longest time, and even heavy structures can be installed without special expensive equipment. It is used a lot.

That is, as shown in FIG. 1, which is a schematic diagram of bridge construction according to a support method of a steel column as an example of a general bridge construction work, a large weight structure 13 such as a bridge installed on an upper portion of a bridge 11 is pier 11. In the hypothesis, the steel column 12 is temporarily installed between the pier 11 and the pier 11 to support the structure 13 until the construction of the structure 13 is completed. To support it.

In addition, the steel column 12 has a problem that the base 12a of the steel column 12 is settled by increasing the load applied as the structure 13 is additionally hypothesized. Therefore, in order to keep the height of the support 12 supporting the structure 13, the screw jack 14 is installed between the support 12 and the structure 13 so that the height at which the structure 13 is supported is fixed. Control (leveling or rise control)

That is, the management of the rise during such bridge construction is a very important part in the overall construction of the bridge construction, and it is not only an important management item because it can greatly affect the road runability, structural stability and quality when the bridge is completed. During the progress, the holder 12 may experience variations in the initial adjustment level due to unexpected settlement of the foundation 12a and other causes, as shown in FIG. The screw jack 14 is installed in the upper end of the steel column 12, and level adjustment is possible with the screw jack 14 also during temporary construction work.

In this way, in order to complete the construction of the structure 13 in the steel column 12 in which the screw jack 14 is installed and to remove the steel column 12, the screw 14a of the screw jack 14 installed on the top of the steel column 12 is provided. By adjusting the level so that the height of the screw jack 14 is lowered by rotating, the steel column 12 is detached and dismantled so that it no longer supports the structure 13.

By the way, in the early and the middle of the temporary work, only a part of the weight of the entire structure 13 of the self-acting acts on the screw jack 14 does not cause a large operational problem. However, since it usually takes more than 6 months to complete the construction work, the screws 14a of the screw jack 14, which rotated smoothly at the beginning of construction work, may be rusted by long-term standing or other foreign substances such as dust may be adsorbed. Since the screw 14a of the jack 14 does not rotate smoothly, and the weight of the completed structure is loaded, the screw 14a of the screw jack 14 does not rotate more smoothly due to the large weight.

Therefore, the operator hits the screw 14a using a hammering tool such as a hammer or rotates the pipe by attaching the pipe to the handle 14b formed to protrude conically in the side of the screw 14a in order to rotate the screw 14a. The method of rotating the screw 14a by increasing the moment is used. In some cases, the above two methods may be used together to insert a pipe into the handle 14b of the screw 14a and strike the pipe with a hammer or the like. All of the above methods impact the screw 14a and cause the wear of the screw 14a to degrade the performance of the screw jack 14 and become a major cause of reducing the life of the screw jack 14. In addition, since the worker has to hit by using a hammer directly, the work is inconvenient and noise, as well as a lot of work time and manpower.

The present invention has been made in order to solve the above problems, by reducing the working load acting on the steel column and screw jack installed for the support of the structure to install the steel column using the buckling to safely and easily dismantle the steel column It is to provide a demolition method.

1 is a schematic diagram of bridge construction by a general support method;

2 is a screw jack layout view,

3 is a schematic diagram of bridge construction for explaining the present invention,

4 is an enlarged bottom view of the circular brace according to the first embodiment of the present invention,

5 is an enlarged bottom view of a rectangular steel column according to a second embodiment of the present invention;

6 is a schematic view showing that buckling occurs in the stronghold through the method of the present invention,

7A is an enlarged view illustrating a state where buckling occurs in a circular brace according to a first embodiment of the present invention;

FIG. 7B is a side view of the circular brace shown in FIG. 7A.

Explanation of symbols on the main parts of the drawings

1: Pier 2, 2 ': Kang Ji-joo

2a, 2a ': stronghold foundation 3: structure

4: Screw Jack 4a: Screw

AA, BB: Cross Section Cutout

In order to achieve the above object, the gangju demolition method using the buckling of the present invention by installing a screw jack on the upper end of the support and the support structure to support the structure, and then to support the structure after the construction construction work In dismantling, cutting a portion of the steel column supporting the structure to form a cross-sectional cutout, and when the local buckling occurs to reduce the load on the steel column, rotating the screw of the screw jack to remove the steel column Characterized in that consists of.

In addition, the cross-sectional cut portion is formed at the bottom of the steel column, the cross-sectional cut portion is formed to be symmetrical in the width and height corresponding to 1/2 of the cross section of the steel column is characterized in that the local buckling is induced.

Hereinafter, a preferred embodiment of the present invention that can specifically realize the above object will be described.

As shown in FIG. 3, which is a schematic diagram of bridge construction for explaining the present invention, for the construction of a structure 3 such as a bridge, a steel column 2 is installed between the bridge 1 and the bridge 1, and the level adjustment is performed. It is the same as the conventional to install the screw jack 4 between the structure 3 to the upper end of the steel column 2 so as to support the bridge during bridge construction work.

In order to demolish the steel column 2 after the bridge construction work is completed, a portion of the steel column 2 is cut to form a cross-sectional cut portion so as to cause a local buckling in the steel column 2, and a local buckling occurs at the cross-sectional cut portion. When the load applied to the steel column 2 is reduced, the steel column 2 is dismantled by rotating the screw 4a of the screw jack 4.

That is, as shown in the lower enlarged view of the circular brace according to the first embodiment of the present invention in Fig. 4, while holding the lower part of the brace 2 in contact with the base 2a of the brace In the case of the circular brace (2) at the position corresponding to 1/2 of the cross section width of the brace (2), that is, the half of the diameter (D) for the circular brace (2), the diameter of the brace (D) ( A cross section cutout AA having a height corresponding to the cross section width of the steel column and a quarter circumference πD is cut and formed at two positions symmetrically at the same height. At this time, to cut the steel column 2 is used a general oxygen cutting machine, the shape of the cross-sectional cut portion (AA) is preferably cut into a rectangular in consideration of the calculation and workability.

Further, the section cutout AA is formed at a position corresponding to 1/2 of the steel column diameter D from the base 2a of the steel column 2 in order to recycle the steel column 2. Therefore, the cut-out section AA that is to be cut should be formed at the end side as much as possible, so that it is formed at the lower side of the steel column 2, but formed at a height of 1/2 or more of the cross section width of the steel column at the end of the steel column 2 so that stable buckling occurs. desirable.

That is, by first calculating the maximum load that the steel column 2 can support the load without causing buckling using the critical load of the circular steel column 2, the maximum load can be calculated by the following formula.

From here Is the maximum load critical load that can be supported without causing buckling, where E is the elastic modulus and I is the cross-sectional secondary moment. ki is a theoretical value multiplied for the theoretical effective length of the column, and depends on the rotation and displacement of the top and bottom, and there are theoretical values and recommended design values, and the recommended design value will be applied in the calculation formula of the present invention. . Li represents the length of the holder.

In the example of P508 × 10t circular ledge, the critical load before buckling

If k ₁ = 0.8 (upper hinge, lower fixed), E = 2100, I ₁ = 485 × 10 ²

Becomes

However, after cutting the section cut-out AA to induce buckling (section area 40 cm × 1.0 cm, where 40 cm = π × 50.8 ÷ 4), the total load acting on the holding column is 1/2 each of the two sections. Assuming that the two cross sections are assumed to be the maximum load that can be supported,

k ₂ = 0.65 (top locked, bottom locked),

ego,

Become.

Thus, the circular gangjiju the maximum load that can be supported without causing buckling _(cr2 P) is the _{P cr2 = 2 EA × 63.23 =} 126.46 Tons.

Consider the allowable stress of 1.5 to 1.7 times a safety factor in the calculation of gangjiju if P so _cr1 and P _cr2 ratio is approximately 5.5 times that of the make enough buckling spilling applied to gangjiju so that the screw jack screw can easily be rotated The load is reduced.

In the formula, I value was calculated as a simple value because there is no big difference between the precise value and the simple value.

5 is a schematic bottom view of the rectangular steel column according to the second embodiment of the present invention, in which a portion of the lower side of the steel column 2 'is cut out from the rectangular cross-sectional steel column 2', and at this time, each surface of the steel column 2 ' In order to make buckling symmetrical with the width and height corresponding to 1/2 of the cross-sectional area, the local buckling is induced.

That is, the lower end of the steel column 2 'is cut off, and the height corresponding to the steel column section width B at a position corresponding to 1/2 of the long section width B among the sections of the steel column section from the base of the steel column section 2a'. , 4 sections cut portions BB having a width of B / 2 are cut to form symmetrically on each surface. At this time, the cutting of the steel column 2 'uses a general oxygen cutting machine, the shape of the cross-sectional cut portion (BB) is preferably cut into a rectangle in consideration of the calculation and workability.

In addition, in order to recycle the steel column 2 ', the section cutout BB to be cut must be formed at the end side as much as possible, so that at least a position corresponding to 1/2 of the cross section width of the steel column from the base 2a' of the steel column 2 '. Form a cross-sectional cutout (BB).

Further, forming the cross-sectional cutout BB at a position corresponding to the long cross-sectional width B 1/2 of the steel column cross section, that is, the rectangular steel column, from the base 2a 'of the steel column 2' is recycled. In order to cut the cross-section cutout BB to be formed at the end side as much as possible, it is formed at the lower end side of the steel column 2 ', but in order to generate stable buckling, 1 / of the steel column section width B at the end of the steel column 2'. It is preferable to form at 2 or more heights.

In addition, in the case of a large bending rigidity structure such as a bridge firmly supported by a bridge, if a partial cross section of the lower end of the steel column installed between the bridges is cut to cause local buckling in the steel column, the bridge does not generate a sudden impact or large deflection. No damage will occur. 6 is a schematic view showing that buckling occurs in the steel column through the method of the present invention, and an enlarged view showing the state in which the buckling occurs in the circular steel column according to the first embodiment of the present invention. As shown in FIG. 7B, the buckling phenomenon occurs at the cross-sectional cutout, and the load applied to the steel column and the screw jack is reduced. That is, since the load applied to the screw jack is reduced, the rotation of the screw is facilitated, and thus, it is easy to dismantle the strut.

In the present invention, the section cutouts AA and BB are cut out by accurate calculation so that a predetermined buckling is induced. However, in the actual site, a predetermined section of the lower end of the rigid column is cut with an oxygen cutting machine to form a small cross-sectional cutout, and when the buckling occurs too little while determining the degree of buckling, it is formed if there is no effect of sufficient load reduction. Larger cuts may be made to expand or additionally multiple cuts may be induced to cause greater buckling to reduce the load on the screw jack.

According to the present invention as described above, in removing the steel column after the completion of the construction of the structure, by cutting a portion of the lower end of the steel column to induce a local buckling safely, it is easy to screw the screw jack by reducing the load of the structure applied to the steel column Since the impact is applied to the screw jack is minimized to maintain the life, it is possible to minimize the operator has the advantage that can be safely and quickly dismantle the stronghold of the heavy structure hypothesized by the support method.

Claims (6)

In installing the structure by the support method of supporting the structure by installing the screw jack on the top of the stronghold and the stronghold, and in dismantling the support after the construction work is completed, Cutting a portion of the steel column (2, 2 ') supporting the structure (3) to form cross-sectional cutouts (AA, BB), When local buckling occurs and the load applied to the steel column 2, 2 'is reduced, rotating the screw 4a of the screw jack 4 to remove the steel column 2, 2' Method of demolition of steel column using buckling. The method according to claim 1, wherein the sectional cutting parts (AA, BB) are formed in plural. The method according to claim 1, wherein the section cutouts AA and BB are formed at a height of 1/2 or more of the width of the cross section of the steel column at the lower end of the steel column 2, 2 '. The method according to claim 1, wherein when the steel column is a circular cross-section steel column (2), the cut section AA is formed by cutting to have a width corresponding to πD / 4 of the cross-sectional diameter and the same height as the cross-sectional diameter. Gangju demolition method using a buckling, characterized in that formed in two to form a symmetry in height. The method according to claim 1, wherein when the steel column is a rectangular cross-sectional steel column (2 '), the section cutout BB is cut out to have a width corresponding to 1/2 of the long cross-sectional width and a height corresponding to the long cross-sectional width of the steel column cross-section width. Forming, demolition method using buckling, characterized in that formed on each side at the same height to form a symmetry. The method according to claim 1, wherein the end sections AA, BB are cut in a rectangular shape.