KR101577019B1 - Diaphram and reinforcement structure of the concrete filled steel tublar comumn, and the manufacturing method of it - Google Patents

Abstract

The present invention relates to a diaphragm installation structure disposed on a concrete filled steel tube (CFT) column for moment connection to a horizontal member such as a steel beam or the like; and a CFT column reinforcement structure to efficiently handle a bending moment stress caused by a horizontal weight. The diaphragm and horizontal stress reinforcement structure of a CFT column comprises: an outer steel pipe forming an outer skin of the CFT column, and restraining concrete filled therein; an inner steel pipe installed in an outer steel pipe separated from an inner surface of the outer steel pipe to reinforce hardness of the CFT column; and an upper and a lower diaphragm whose inside is attached to the inner steel pipe whose outside is exposed to the outside of the outer steel pipe to be attached to an upper and a lower flange of a steel beam. The inner steel pipe has an upper and a lower length extended from the upper and the lower diaphragm to a reinforcement range of a bending moment of the CFT column caused by a horizontal weight.

Description

Technical Field [0001] The present invention relates to a diaphragm and a horizontal stress-strengthening structure of a CFT column, and a manufacturing method of a CFT column using the same structure,

The present invention relates to an installation structure of a diaphragm provided on a CFT column for moment bonding with a horizontal member such as a steel frame, and to a reinforcing structure of a CFT column capable of effectively responding to a bending moment stress caused by a horizontal load.

CFT steel pipe (Concrete Filled Steel Tube) is a reasonable structure type that combines the advantages of steel and concrete. It is a reinforced effect of internal filled concrete by restraint effect of steel pipe forming the shell and buckling reinforcement effect of concrete by concrete. The strength of the member can be increased while the size of the cross section can be reduced. In particular, the amount of use thereof has been greatly increased in recent years due to the high strength and high ductility required in columns having a high-rise structure.

In this case, when the CFT steel pipe is used as a column, there is a structural advantage that the column itself can support a very large axial force. However, when the steel pipe is joined to a steel member such as a steel beam, the CFT steel pipe There is a problem that a thin outer shell (steel plate) is torn to cause local breakage or, in severe cases, the joint is broken prematurely.

Therefore, in order to prevent local damage of the steel pipe constituting the shell of the CFT column, it is common to use a reinforcing means such as a diaphragm to correspond to the flexural load by the beam member.

Such a diaphragm is largely provided by an inner diaphragm method for inserting into the inside of the steel pipe, an outer diaphragm method for installing the outer diaphragm on the outer surface of the steel pipe, and a through diaphragm method for inserting the steel pipe therethrough. It is not easy to manufacture and install because of the characteristics of a closed cross section and the fact that it is made of a thin steel plate and welding deformation is likely to occur.

On the other hand, local reinforcement may be required to cope with the bending moment generated by the horizontal load of the earthquake and wind load, but the reinforcement work is very difficult due to the closed sectional shape of the steel pipe.

In order to avoid such problems, it is general to apply the outer diaphragm method which does not require cutting work during the manufacture of the column and to design the member based on the axial force and the maximum bending moment value. However, this also increases the amount of steel used for the diaphragm due to the complicated joints formed by the machining and welding of the diaphragm, and designing the maximum stress value for the entire column makes it impossible to over- The problem can not be avoided.

KR 10-1328218 B1 KR 10-1187174 B1

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems of the prior art, and it is an object of the present invention to provide a CFT steel pipe for a column which can locally reinforce a region required to be reinforced with respect to a horizontal load, The present invention provides a diaphragm and a horizontal stress-strengthening structure of a CFT column in which the diaphragm is installed and the stress transmission by the diaphragm becomes clear.

According to a most preferred embodiment of the present invention for solving the above problems, there is provided an external steel pipe for restricting concrete to be filled therein while constituting an outer shell of a CFT column, and an outer steel pipe which is spaced from the inner surface of the outer steel pipe And an upper and a lower diaphragm which are attached to the inner steel pipe and the outer side is exposed to the outside of the outer steel pipe so as to be joined to the upper and lower flanges of the steel frame, respectively, Wherein the inner steel pipe has a length extending from the upper diaphragm and the lower diaphragm to the upper and lower portions of the bending moment reinforcement range of the CFT column due to the horizontal load, do.

According to another embodiment of the present invention, there is provided a method of manufacturing a CFT column, comprising the steps of: a) preparing an inner steel pipe having a length corresponding to a reinforcement range of a bending moment acting on the CFT column and having an outer diameter smaller than an inner diameter of the outer steel pipe constituting the shell of the CFT column b) installing a lower diaphragm on the inner steel pipe; c) installing an inner steel pipe for the outer steel pipe on the upper portion of the lower diaphragm, wherein the inner surface of the inner steel pipe is spaced from the outer surface of the inner steel pipe; E) installing a lower steel pipe for an outer steel pipe at a lower portion of the lower diaphragm, installing an upper steel pipe at an upper portion of the upper diaphragm, Installing an upper steel pipe; The present invention provides a method of manufacturing a CFT column to which a diaphragm and a horizontal stress-strengthening structure are applied.

According to another embodiment of the present invention, there is provided a method of manufacturing a CFT column, comprising the steps of: a) forming an inner pipe of an outer steel pipe having an outer diameter corresponding to a momentum acting on the CFT column and a reinforcement range for the parent ment, B) installing a lower diaphragm at the upper end of one of the inner steel pipes and installing an upper diaphragm at the lower end of the other inner steel pipe, installing a diaphragm in the inner steel pipe (C) installing an inner steel pipe for an outer steel pipe between the lower diaphragm and the upper diaphragm so that the two inner steel pipes are spaced apart from each other; d) installing a lower steel pipe for the outer steel pipe at a lower portion of the lower diaphragm, Installing an upper steel pipe for an outer steel pipe on the upper portion of the upper diaphragm; The present invention provides a method of manufacturing a CFT column to which a diaphragm and a horizontal stress-strengthening structure are applied.

In the present invention, a CFT column is designed on the basis of an axial force acting on a column, and when the strength of a CFT column is insufficient considering a bending moment due to a horizontal load, a separate steel pipe is installed inside the outer steel pipe for the CFT column, It is possible to design the cross section of CFT column efficiently while reducing the amount of steel used.

Also, since the diaphragm installed on the CFT column of the present invention is connected to the inner steel pipe embedded in the inner filled concrete, the stress transmission by the vertical member such as the steel frame conveyed through the diaphragm is clear, It is possible to maximize the rigidity of the CFT column because the stress transmitted to the CFT column through the inner steel pipe is widely dispersed not only in the transverse direction of the CFT column but also in the longitudinal direction.

In addition, since the diaphragm is installed by using the inner steel pipe, the installation work of the diaphragm is simple and the welding operation to the outer steel pipe constituting the shell of the CFT column can be omitted or minimized, So that the appearance is simplified and the workability is improved.

1 is a perspective view of a CFT column according to an embodiment of the present invention.
2 is a cross-sectional view and a longitudinal sectional view of a CFT column according to a first embodiment of the present invention.
3 is a view of each embodiment relating to the shape of a diaphragm applied to a CFT column according to the present invention.
FIGS. 4 and 5 are step-by-step illustrations of a method for manufacturing a CFT column according to the first embodiment, wherein (a) and (b) are explanatory views classified according to the shape of the diaphragm.
6 is a cross-sectional view and a longitudinal sectional view of a CFT column according to a second embodiment of the present invention.
Fig. 7 is an explanatory view showing a stepwise production method of the CFT column of the second embodiment.
8 is a bending moment diagram generated on a column of a building by a horizontal load.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, however, it is to be understood that the present invention is not limited to the disclosed embodiments.

FIG. 1 is a perspective view showing a state in which a steel beam 200 is installed on a CFT column 100 according to an embodiment of the present invention.

1, the CFT column 100 and the steel beam 200 are connected by diaphragms 30 and 40. The upper and lower flanges of the steel beam are connected to the upper and lower diaphragms 30 and 40 of the CFT column, 40, respectively, and the diaphragms 30, 40 are formed of an inner diaphragm or a through-hole diaphragm type as described later.

2 is a cross-sectional view and a longitudinal sectional view of the CFT column 100 according to the first embodiment of the present invention.

According to the first embodiment of the present invention, the CFT column structure of the present invention includes an outer steel pipe 10 constituting an outer shell of a CFT column while filling concrete 50 therein and restraining the concrete 50, And diaphragms 30 and 40 for attaching the steel pipe to each other are attached to the inner steel pipe 20. [

The diaphragm is divided into an upper diaphragm 30 and a lower diaphragm 40 so as to correspond to the upper and lower flanges of the steel beam joined thereto.

The inner steel pipe 20 is spaced apart from the inner surface of the outer steel pipe 10 so that the concrete 50 is inserted between the inner steel pipe 20 and the outer steel pipe 10 when the concrete 50 is placed in the outer steel pipe 10. [ So that the inner steel pipe 20 is embedded in the concrete 50.

At this time, the outer steel pipe 10 is welded at a predetermined position out of the other end portions of the diaphragms 30 and 40 having one end attached to the inner steel pipe 20, or by using separate spacing means (not shown) The gap between the steel pipe 20 and the outer steel pipe 10 can be kept constant, and this can be applied to other embodiments as will be described later.

The inner steel pipe 20 embedded in the concrete 50 functions as an anchoring function for the diaphragms 30 and 40 while compressing the stress transmitted to the CFT column 100 through the diaphragms 30 and 40 to the CFT columns As well as the cross section in the longitudinal direction.

When the building receives a horizontal load such as a wind load or an earthquake load, a bending moment as shown in FIG. 8 is generated. Since the inner steel pipe 20 functions as a reinforcing means for the CFT column 100, Reinforcing the rigidity.

In other words, considering the maximum bending moment generated in the column and designing the entire column based on this, it is necessary to over-design in some sections. Therefore, the design of the column is based on the axial force acting on the column, The internal steel pipe 20 is made to bear stress so that the CFT column is designed to be economical.

Accordingly, the inner steel pipe 20 has a length extending from the upper diaphragm 30 and the lower diaphragm 40 to the upper and lower bending moment reinforcement ranges R and R 'of the CFT column 100 by the horizontal load, And the length and size can be specified through the structural design.

The diaphragms 30 and 40 may have various shapes such that the inner side is attached to the inner steel pipe 20 and the outer side is exposed to the outside of the outer steel pipe 10, And a connecting portion (b) for connecting between the steel bar joint portions (a) and two or four steel bar joint portions (a) directly bonded to the steel bar joint portions (a). Fig. 3 shows each embodiment of such a diaphragm 30, 40. Fig. At this time, the outer side of the diaphragms 30 and 40 exposed to the outside may be protruded from the outer surface of the outer steel pipe 10 so as to have a through-type diaphragm manner and not protrude from the outer surface of the outer steel pipe 10 It is possible to have an inner diaphragm method.

3 (a), the inner surface of the steel bar joint part (a) is joined to the outer surface of the inner steel pipe 20, and the inner surface of the connecting part (b) 20) is formed between the outer surfaces of the reinforcing ribs (20, 20).

The concrete filling spaces c are formed in such a manner that the open space between the upper diaphragm 30 and the lower diaphragm 40 is also continuous with respect to the space between the outer steel pipe 10 and the inner steel pipe 20 So that the CFT column can be filled with a con- crete 50 in a tight manner.

According to another embodiment of the diaphragm, as shown in Fig. 3 (b), the inner surface of the steel bar connecting portion a and the inner surface of the connecting portion b may be configured to be jointed to the outer surface of the inner steel pipe 20 In this case, unlike the former embodiment, the sectional deflection of the diaphragm for forming the space (c) for charging concrete is not generated, which is structurally advantageous as compared with the former embodiment, The production becomes simple.

However, the diaphragms 30 and 40 of the latter embodiment form a closed space between the outer steel pipe 10 and the inner steel pipe 20. In the present invention, the upper diaphragm 30 and the lower diaphragm 40 The concrete 50 can be filled into the closed space by forming an opening through which the concrete 50 can flow in the inner steel pipe 20 between the closed space.

One embodiment of the opening formed in the inner steel pipe 20 for filling the closed space with the concrete 50 comprises a plurality of concrete flow holes 21 in the inner steel pipe 20. Therefore, it is preferable to provide the concrete flow hole 21 with respect to the entire area of the inner steel pipe 20. However, it is preferable that at least the inner steel pipe 20 is located between the upper diaphragm 30 and the lower diaphragm 40 A plurality of concrete flow holes 21 must be provided.

The concrete flow holes 21 provided in the inner steel pipe 20 can ensure a tight concrete filling property between the outer steel pipe 10 and the inner steel pipe 20 as well as the integrity of the concrete 50 between the concrete 50 and the steel pipes 20. [ Thereby enhancing the effect of the present invention.

4 and 5 illustrate a process of manufacturing the CFT column 100 of the first embodiment shown in FIG. 2. FIG. 4 is a cross-sectional view of the diaphragm 30 of the first embodiment shown in FIG. 3 (a) 40 is applied, and Fig. 5 is a view to which the diaphragms 30, 40 of the second embodiment shown in Fig. 3 (b) are applied.

4 and 5, only the shape of the diaphragm to be applied and whether or not the concrete flow hole 21 is formed in the inner steel pipe 20 are different from each other only in the following steps There is no particular difference.

The manufacturing method of the CFT column according to the first embodiment will be described step by step.

a) preparing an inner steel pipe (20) having a length corresponding to the reinforcing range of the bending moment acting on the CFT column and having an outer diameter smaller than the inner diameter of the outer steel pipe (10) constituting the sheath of the CFT column;

For reference, 'reinforcement range' refers not to the section of occurrence of bending moment but to the range of the bending moment generated in the column beyond the portion that the column designed by the axial force can bear, And the length corresponding to the reinforcement range of the bending moment acting on the CFT column means the length from the end point for reinforcement of the momentum symmetrically generated in the column to the end point for reinforcement of the momentum, It is to be noted that the term "length" is not defined uniformly.

The inner steel pipe 20 is embedded in the concrete 50 placed in the outer steel pipe 10 to perform a reinforcing function such as a vertical reinforcing steel and an anchoring function for the diaphragms 30 and 40 attached thereto The standard of the inner steel pipe 20 should be determined so that a space is formed between the inner surface of the outer steel pipe 10 and the outer surface of the inner steel pipe 20 so that the concrete 50 can be filled.

b) installing a lower diaphragm (40) on the inner steel pipe (20);

The lower diaphragm 40 should be installed at a position corresponding to the lower flange of the steel beam joined to the height of the CFT column 100 but its position can be adjusted by the length of the lower steel pipe to be described later. Therefore, it is preferable that the installation point of the lower diaphragm 40 relative to the inner steel pipe 20 in this step is set in consideration of the reinforcing length of the bending moment.

The lower diaphragm 40 is welded to the inner steel pipe 20 so that stress can be transmitted to each other.

c) an inner steel pipe (12) for an outer steel pipe is provided on the upper part of the lower diaphragm (40), and an inner surface of the inner steel pipe (12) is spaced from an outer surface of the inner steel pipe (12);

The outer steel pipe (12) serves as a space maintaining means between the upper diaphragm (30) and the lower diaphragm (40). Therefore, the length of the intermediate steel pipe 12 may vary according to the standard of the steel wire to be bonded to the CFT column 100.

On the other hand, the inter-story pipe 12 is a shell of the concrete 50 to be filled for forming the CFT column 100 while forming a part of the outer steel pipe 10, and the inner steel pipe 20 is a concrete It is necessary to provide a space between the inner surface of the inner steel pipe 12 and the outer surface of the inner steel pipe 20 so as to be filled with the concrete 50 as described above.

The steel pipe 12 is welded to the upper surface of the lower diaphragm 40 so that it can be fixed at a predetermined position while maintaining a constant gap with the inner steel pipe 20. [

d) installing an upper diaphragm (30) on the upper side of the intermediate steel pipe (12)

The upper diaphragm 30 is inserted into the upper portion of the inner steel pipe 12 and positioned on the upper portion of the inner steel pipe 12 and then the inner steel pipe 20 To be integrated with the inner steel pipe 20.

e) providing a lower steel pipe lower pipe (11) at a lower portion of the lower diaphragm (40) and installing an upper steel pipe (13) at an upper portion of the upper diaphragm (30);

The upper diaphragm 30 and the lower diaphragm 40 are installed with a predetermined interval therebetween through the intermediate pipe 12 and the upper diaphragm 40 and the lower diaphragm 40, The upper steel pipe 13 and the inner steel pipe 12 and the upper steel pipe 13 are fitted to the respective ends of the inner steel pipe 20 exposed at the upper portion of the outer steel pipe 30, So that the lower steel pipe 11 can form an entire outer steel pipe 10 as a whole.

The work of each of the above steps can be precisely performed in the factory, whereby the manufacture of a steel pipe structure for a CFT column (see FIG. 4F and FIG. 5F) in which the diaphragms 30 and 40 are installed When completed, the CFT column 100 is completed by installing the concrete 50 inside the outer steel pipe 10 after it is transferred to the site.

The CFT column according to the first embodiment of the present invention described above uses one long inner steel pipe 20. However, as described below, the CFT columns correspond to the reinforcement ranges of the longitudinal moment and the momentum acting on the CFT column Two separate inner steel pipes 20 may be used.

In this case, since the inner steel pipe is not provided between the upper diaphragm 30 and the lower diaphragm 40, the amount of steel used can be reduced as compared with the CFT column of the first embodiment.

On the other hand, as shown in Fig. 3 (b), the inner surface of the steel bar joint portion (a) and the inner surface of the connection portion (b) As described above. When the inner steel pipe is not provided between the upper diaphragm 30 and the lower diaphragm 40 as described above, the diaphragm may be attached to the outer surface of the upper diaphragm 30 and the lower diaphragm 40, There is an advantageous effect in that it does not cause any problem in the tight filling of the concrete 50 without separately providing the opening means such as the provision of the concrete flow hole 21 in the inner steel pipe.

6 is a cross-sectional view and a longitudinal sectional view of the CFT column according to the second embodiment.

The CFT column structure of the second embodiment also includes an outer steel pipe 10 which constitutes the outer surface of the CFT column while filling the concrete 50 therein and restrains the concrete 50, And the diaphragm for joining to the steel beam is not attached to the CFT column according to the first embodiment in that the diaphragm is attached to the inner steel pipes 20a and 20b.

The upper and lower diaphragms 30 and 40 are provided at the lower end or upper end of each of the divided inner steel pipes 20a and 20b, Except that the inner steel pipe 12 is provided between the diaphragm 30 and the lower diaphragm 40 so that the inner steel pipe is not located.

At this time, the diaphragms provided at the upper and lower ends of the inner steel tubes 20a and 20b may be coincided with the end surfaces of the inner steel tubes 20a and 20b. In order to facilitate installation of the diaphragm, A part of the end portions of the inner steel tubes 20a and 20b may protrude from the diaphragms 30 and 40 as shown in FIG. As in the first embodiment, a concrete flow hole 21 may be further provided in the inner steel pipe.

FIG. 7 is a step-wise view showing a manufacturing method of the CFT column 100 according to the second embodiment described above. FIG. 7 is a diagram showing a method of manufacturing a CFT column 100 according to a second embodiment of the present invention, Preparing two inner steel pipes 20a and 20b smaller than the inner diameter of the outer steel pipe 10 constituting the outer shell of the CFT column; b) preparing a lower diaphragm 40 at the upper end of one of the inner steel pipes 20b; Installing diaphragms 30 and 40 on the inner steel tubes 20a and 20b and installing the upper diaphragm 30 at the lower end of the other inner steel tube 20a; (12) between the lower diaphragm (40) and the upper diaphragm (30) so that the steel pipes (20a, 20b) are spaced apart from each other; d) The upper diaphragm 30 is provided with a lower steel pipe 11 for the outer steel pipe, Steps for installing the steel pipe section 13; .

When the diaphragms 30 and 40 are installed in the inner steel pipes 20a and 20b in the step b), a part of the end portions of the inner steel pipes 20a and 20b may protrude from the diaphragms 30 and 40 In this case, the length corresponding to the reinforcement range in step a) is a sum of the pure reinforcement length and the length protruding from the diaphragms 30 and 40.

Since the CFT column manufacturing method of the second embodiment uses two divided inner steel pipes 20a and 20b, unlike the first embodiment, the upper diaphragm 30 and the lower inner pipe 20b, There is a difference in the order of the operation steps in that the diaphragm 40 is simultaneously installed and then the outer steel pipe 12 is provided between the upper and lower diaphragms 30 and 40. [

The CFT column 100 is completed by placing the concrete 50 inside the outer steel pipe 10 after the steel pipe structure for the CFT column manufactured by each of the above steps is transported and installed in the site and is different from that of the first embodiment not.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the invention is not limited to the disclosed embodiments, but, on the contrary, It is obvious that it will be possible to carry out various modifications thereof. For example, although the outer steel pipe and the inner steel pipe are both shown in the form of a round steel pipe, the present invention is not limited thereto, and both of the outer steel pipe and the inner steel pipe may be formed of a square steel pipe. And the other is a rectangular steel pipe. It is therefore intended that such modifications are within the scope of the invention as set forth in the claims.

10: outer steel pipe 11: bottom steel pipe
12: intermediate steel pipe 13: upper steel pipe
20, 20a, 20b: internal steel pipe 21: concrete flow ball
30: upper diaphragm 40: lower diaphragm
50: Concrete

Claims (8)

An outer steel pipe 10 for restricting the concrete 50 to be filled therein while constituting the outer surface of the CFT column and an outer steel pipe 10 spaced from the inner surface of the outer steel pipe 10 inside the outer steel pipe 10, The upper and lower diaphragms 30 and 30 configured to be attached to the inner and outer steel pipes 10 and 20 so as to be respectively connected to the upper and lower flanges of the steel frame, 40,
The diaphragm (30, 40) is composed of two to four steel strip joints (a) and a connecting portion (b) connecting the steel strip joints (a) A concrete filling space c is formed between the inner surface of the connecting portion b and the outer surface of the inner steel pipe 20,
Wherein the inner steel pipe (20) has a length extending from the upper diaphragm (30) and the lower diaphragm (40) to the upper and lower portions of the bending moment reinforcing range of the CFT column due to the horizontal load, Diaphragm and horizontal stress - strengthening structure. delete The internal diaphragm according to claim 1, wherein the inner steel pipe (20) is divided into two parts, and the upper and lower diaphragms (30, 40) are attached to the upper and lower diaphragms (30, 40) Wherein a part of the section is not provided with an inner steel pipe. delete delete A) an inner steel pipe 20 having a length corresponding to a bending moment against a bending moment acting on the CFT column and whose outer diameter is smaller than the inner diameter of the outer steel pipe 10 constituting the shell of the CFT column, B) installing a lower diaphragm (40) on the inner steel pipe (20), c) installing an outer steel pipe (12) on the upper part of the lower diaphragm (40) D) installing an upper diaphragm (30) on an upper portion of the interstice pipe (12); b) inserting the inner diaphragm (12) (E) installing a lower steel pipe (11) for an outer steel pipe at a lower portion of the lower diaphragm (40) and installing an upper steel pipe (13) for an outer steel pipe at an upper portion of the upper diaphragm (30); , ≪ / RTI >
The upper and lower diaphragms 30 and 40 are made up of two to four steel beam beam joining portions a and a connecting portion b connecting the steel beam beam joining portions a, And a concrete filling space (c) is formed between the inner surface of the connecting portion (b) and the outer surface of the inner steel pipe (20) A Method of Fabrication of CFT Columns with Stress Reinforced Structures. delete In manufacturing the CFT column, it is required that: (a) the inner diameter of the outer steel pipe (10), which has the respective lengths corresponding to the reinforcement range for the moment and the momentum acting on the CFT column, B) preparing a lower diaphragm 40 at the upper end of one of the inner steel pipes 20b and a lower diaphragm 40 at the lower end of the other inner steel pipe 20a, C) installing the diaphragms (30,40) on the inner steel tubes (20a) and (20b) on which the lower diaphragm (40) D) installing a lower steel pipe (11) for an outer steel pipe at a lower portion of the lower diaphragm (40), and installing an upper diaphragm Installing an upper steel pipe (13) for an outer steel pipe on an upper portion of the outer steel pipe (30); , ≪ / RTI >
The upper and lower diaphragms 30 and 40 are made up of two to four steel beam beam joining portions a and a connecting portion b connecting the steel beam beam joining portions a, The inner surface is joined to the outer surface of the inner steel pipe 20, and the inner surface of the connecting portion (b) And a concrete filling space (c) is formed between the outer surfaces of the inner steel pipe (20), and a method of manufacturing a CFT column using the diaphragm and the horizontal stress reinforcing structure.

Images