KR102000261B1 - A quadrilateral lattice girder having high strength Spider - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lattice girder which is used in the construction of an arch type girder in tunnel construction, and more particularly to a lattice girder which is used for constructing a pair of upper steels And a pair of lower steel bars arranged in a quadrangular shape such as a square or a rectangular or trapezoidal shape such that the spider forms at least two or more spotted portions corresponding to the upper steel bar and the lower steel bar,
The upper steel bar and the lower steel bar can be strongly interlocked with each other through a large number of interfacing parts formed on the top and bottom surfaces of the spider, and the grid support can be varied in a quadrangular shape such as square or rectangular or trapezoid And the stronger bearing capacity between the upper steel bar and the lower steel bar as well as the greater holding force between the upper steel bar and the lower steel bar can be greatly increased from the structure of the improved spider, Is increased greatly to increase the rigidity of the lattice girder as a whole to improve the supporting force against earth pressure and to increase the penetration and mutual adhesion of shotcrete, thereby forming a more stable tunnel structure.

Description

{A quadrilateral lattice girder having a high strength spider}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a lattice girder which is used when constructing an arcuate girder in tunnel construction, and more particularly to a lattice girder which is constructed by connecting a pair of upper steel bars and a pair of lower steel bars arranged in parallel to each other via an improved spider The stiffness of the lattice girder and the holding capacity of the steel bar are greatly increased, and the penetration of the shotcrete and the mutual adhesion force of the shotcrete are improved. In addition, since the upper steel bar and the lower steel bar can be maintained mutually spaced through the spider, And the like.

In general, the tunnel construction is to drill the tunnel and to install the grid support to prevent the sinking of the ground and the falling of the rock.

The lattice girder is installed in the New Austrian Turning Method (NATM) method together with the installation of an arch type guardrail during tunnel construction together with a rock bolt wire mesh, a shock, and the like.

Here, the NATM method can prevent the strength of the ground from being lowered by keeping the ground sheet in a triaxial compression state by installing shotcrete and rock bolts having good adhesion to the ground and flexibility before the initial ground is deformed after the tunnel excavation, ) Is used to make maximum use of the supporting force of the ground itself, and it is possible to secure the stability of the tunnel by measuring and controlling the stress and displacement behavior of the surrounding ground and the ground guard during construction.

Since the lattice girder is one kind of steel support material, it is possible to effectively support the earth pressure generated around the tunnel and to bundle the steel rods into a triangular shape. Therefore, the shotcrete can be easily poured and the cavities generated on the back surface of the support material can be minimized, It is a steel supporting material to make the tunnel structure.

To explain this in more detail, a plurality of connections (referred to as a tentative spider) are formed between a pair of lower reinforcing bars having a circular cross section extending in the longitudinal direction and a relatively smaller diameter than the upper reinforcing bars, And the members are welded to each other while maintaining constant spacing in the longitudinal direction.

Here, the spider is formed by bending a lattice wire or a steel wire in the form of a triangular truss in the longitudinal direction, that is, in the form of a three-dimensional closed polygon, and then welding both ends.

In addition, as disclosed in Japanese Patent Laid-Open No. 10-0534456, a conventional steel plate has a lower steel bar extending in parallel and forming a bottom curve, a lower steel bar at an upper portion of the lower steel bar, A lower steel bar and a lower steel bar; a top steel bar forming a curve; and a connecting member connecting the lower steel bar and the upper steel bar, the second steel bar having a pair of first areas adjacent to the ground and a second area connecting the pair of first areas Wherein the lower steel bar and the upper steel bar gradually change their spacing distance toward the upper end of the arcuate curve, and the reinforcing grid support for tunnel support has been registered and registered .

Also, as in the case of Japanese Patent No. 10-1033228 and Japanese Patent No. 10-1033229, the shape of the reinforcing bar supporting the upper reinforcing bars and the pair of lower reinforcing bars can be simply formed to reduce costs as well as mass production In addition, the upper reinforcing bars and the lower reinforcing bars are combined with the reinforcing bars so as to form a joining structure, thereby resolving the problems caused by the existing welding joins.

However, in the case of the above-mentioned reinforcing grid support, the upper and lower reinforcing bars are assembled together through the reinforcing bars, and the upper and lower reinforcing bars are assembled through the tightening grooves of the reinforcing bars, In the course of moving or installing the lattice girders in the assembled state, the assembling part is often separated or slipped off, and in the course of construction, due to the separation and removal of the reinforcing bars, inevitably, It is necessary to perform supplementary fixing work through welding of the relevant part.

In addition, as disclosed in Japanese Patent No. 10-1257106, there is provided an upper steel bar extending along a tunnel, a lower steel bar extending along the upper steel bar at a predetermined distance from the upper steel bar, Wherein the upper steel bar and the lower steel bar have a polygonal cross-sectional shape, and the fixing member has an upper contact portion in surface contact with one side surface of the upper steel bar having a polygonal cross section, And a lower contact portion which is in surface contact with a side surface of the lower steel bar bent at an end of each of the connecting portions and has a polygonal cross section, A reinforced so that the strength and rigidity of the upper steel bar and the lower steel bar can be improved Penis is been made, and registration bar beams.

However, in the case of the grid support, the fixing member is manufactured by bending the plate material, so that the amount of the steel material is very large, which is not economical, and the welding portion between the upper and lower steel bars is excessively wide and long, It has a problem that the mutual gap retention force is relatively weak.

Korean Registered Patent No. 10-0534456 (registered on December 1, 2005) Korean Registered Patent No. 10-1033228 (registered on April 28, 2011) Korean Registered Patent No. 10-1033229 (registered on April 28, 2011) Korean Registered Patent No. 10-1257106 (Registered April 16, 2013)

SUMMARY OF THE INVENTION The present invention has been made to solve the problems as described above, and it is an object of the present invention to provide a spider which is formed by bending a steel material having upper and lower surfaces formed thereon and a pair of upper steel bars and a pair of lower steel bars, And the spider forms at least two or more spot welded portions corresponding to the upper steel bar and the lower steel bar,

The upper and lower steel bar and the spider can be strongly interfaced with each other through the interviews. The spider can maintain strong spacing and support between the upper steel bar and the lower steel bar, The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a quadrangular lattice girder having such a feature that the rigidity of the entire lattice autonomous system is greatly increased.

According to the present invention, a pair of upper steel bars and a pair of lower steel bars are arranged and fixed with a quadrilateral cross-section of each steel bar through a plurality of spiders, Respectively,

The spider includes a pair of first lower horizontal portions which are in close contact with the upper surface of the lower steel bar; A pair of first inclined portions bent from one end of the first lower horizontal portion; A pair of first upper horizontal portions bent from the first inclined support portion; A pair of second inclined portions bent from the first upper horizontal portion; A pair of second lower horizontal portions bent from the second inclined portions; A pair of upper and lower support portions bent from the second lower horizontal portion; A lower spacing portion connecting the other ends of the first lower horizontal portion to each other; And an upper space holding portion for connecting ends of the upper and lower holding portions to each other.

In the present invention, the upper steel bar and the lower steel bar are strongly interlocked with each other through a plurality of interfacing portions formed on the upper and lower surfaces of the spider, and a quadrangle such as a square or a rectangle or a trapezoid It is believed that the lattice girders can be modified in various ways, and that the improved spider structure can greatly enhance the holding force between the upper steel bar and the lower steel bar as well as the mutual gap retention, The gap holding force is also greatly increased to increase the rigidity of the lattice girder as a whole to improve the bearing capacity against the earth pressure and to increase the penetration of the shotcrete and the mutual adhesion force so that a more stable tunnel structure can be constructed .

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial perspective view of a quadrilateral lattice girder according to the present invention.
FIG. 2 is a partially exploded perspective view of a quadrangular lattice girder according to the present invention.
3 is a partial side view of the quadrilateral grid support according to the present invention
Fig. 4 is an overall sectional front view of a quadrilateral lattice girder according to the present invention
FIG. 5 is a perspective view of a spider applied to a quadrilateral grid support according to the present invention.
FIG. 6 shows another embodiment of the spider and steel bar applied to the quadrilateral grid support according to the present invention
FIG. 7 is a view showing another embodiment of the spider applied to the quadrilateral grid according to the present invention
Fig. 8 is a partial side view of the lattice girder according to the spider of Fig. 7
9 is a view showing another embodiment of the spider applied to the quadrangular lattice girder according to the present invention
Fig. 10 is an overall partial side view of the lattice girder according to the spider of Fig. 9
11 is a view showing another embodiment of the spider applied to the quadrilateral grid support according to the present invention
Fig. 12 is a partial side view of the lattice girder according to the spider of Fig. 10
13 is a view showing another embodiment of the spider applied to the quadrilateral grid support according to the present invention
Fig. 14 is an overall front view of the lattice girder according to the spider of Fig. 13
15 is a view showing another embodiment of the spider applied to the quadrilateral grid support according to the present invention
16 is a view showing another embodiment of the spider applied to the quadrilateral grid support according to the present invention
17 is a view showing another embodiment of the spider applied to the quadrilateral grid support according to the present invention

The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary meanings and the inventor may properly define the concept of the term to describe its invention in the best possible way And should be construed in accordance with the principles and meanings and concepts consistent with the technical idea of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a partial side view of a quadrangular lattice girder according to the present invention. FIG. 4 is a partial side view of a quadrilateral lattice girder according to the present invention. FIG. 5 is a perspective view of a spider applied to a quadrilateral grid according to an embodiment of the present invention. FIG.

As shown, the quadrilateral grid according to the present invention includes a pair of upper steel bars 10 and 10 ', a pair of lower steel bars 20 and 20' And a plurality of spiders 30 and 30 'for connecting and fixing the lower steel bars 20 and 20' to each other.

At this time, the spiders 30 and 30 'are formed by bending a member having a circular section or a rectangular section, or preferably a member having a circular section, The left and right spacing and the upper and lower spacings of the upper steel bars 10 and 10 'and the lower steel bars 20 and 20' can be adjusted according to the shape of the spiders 30 and 30 ' It is possible to complete a lattice girder of a quadrilateral structure in which the cross section of each steel bar is arranged in a square shape or a rectangular shape in an upward or downward direction, a rectangular shape in a leftward or rightward direction, or a trapezoidal shape.

Particularly, the spiders 30 and 30 'are formed by continuously bending the steel material and then welding the ends of the spider 30' against each other. The spiders 30 and 30 'are composed of a pair of the steel bars 20 and 20' First lower side horizontal portions 30a and 30a '; A pair of first inclined support portions 30b and 30b 'bent from one end of the first lower horizontal portions 30a and 30a'; A pair of first upper side horizontal portions 30c and 30c 'bent from the first inclined support portions 30b and 30b'; A pair of second inclined support portions 30d and 30d 'bent from the first upper side horizontal portions 30c and 30c'; A pair of second lower horizontal portions 30e and 30e 'bent from the second inclined support portions 30d and 30d'; A pair of upper and lower support portions 30f and 30f 'bent from the second lower side horizontal portions 30e and 30e'; A lower gap holding portion 30g connecting the other ends of the first lower horizontal portions 30a and 30a 'to each other; And upper spacing portions 30h for connecting the ends of the upper and lower support portions 30f and 30f 'to each other.

Therefore, the first lower side horizontal portion 30a 'and the second lower side horizontal portion 30e' of the respective spiders 30 and 30 'and the second lower side horizontal portions 30e' are formed on the upper side of the lower steel bars 20 and 20 ' The lower steel bars 20 and 20 'are horizontally spaced apart from each other and welded to the lower ends of the upper steel bars 20 and 20' while welding the spiders 30 and 30 ' The upper steel bars 10 and 10 'are also laterally spaced apart while being welded and fixed in a state of being in close contact with the first upper side horizontal portions 30c and 30c' of the upper steel bars 10 and 10 '.

The horizontal spacing between the upper steel bars 10 and 10 'and the lower steel bars 20 and 20' is greater than that between the first lower horizontal portions 30a and 30a 'and the second lower horizontal portions 30e Is determined by the spacing between the upper steel bars 10 and 10 'and the first upper horizontal portions 30c and 30c' The directional interval is determined by the lengths of the first inclined support portions 30b and 30b ', the second inclined support portions 30d and 30d' and the upper and lower support portions 30f and 30f ' Square shape or rectangular shape can be completed.

In particular, the horizontal spacing of the lower steel bars 20 and 20 'is determined by the lower gap holding portion 30g connecting the other ends of the first lower horizontal portions 30a and 30a' The gap between the bars 20 and 20 'can be kept constant and the upper space bar 30h connecting the ends of the upper and lower support parts 30f and 30f' ) 10 'of the upper steel bars 10 and 10' is determined and the gap between the upper steel bars 10 and 10 'can be kept constant.

The first inclined support portion 30b and the second inclined support portions 30d and 30d 'and the upper and lower support portions 30f and 30f' are connected to the upper steel bar 10 and 10 ' The lower spacing portion 30g and the upper spacing portion 30h are formed in the upper portion of the upper steel bar 10 so as to increase the rigidity of the lattice girder, The lower steel bars 20 and 20 'are provided with a strong supporting force between the upper steel bars 10' and the lower steel bars 20 ', thereby greatly enhancing the rigidity of the lattice girder.

As shown in FIG. 6, the upper steel bars 10 and 10 'and the lower steel bars 20 and 20' are formed with upper and lower flat contact surfaces 11 and 11 ' The contact surface portions 11 and 11 'increase the contact area with the spiders 30 and 30' so that a firmer fixing force between the spiders 30 and 30 'can be obtained will be.

Particularly, when the upper steel bar 10 'and the lower steel bar 20' are constituted by the screw rods formed with the contact surface portions 11 ', 21', 21 'and 21' When the upper steel bar 10 'and the lower steel bar 20' are connected to each other using the threaded coupler or the like, it is possible to quickly and easily connect the upper steel bar 10 'and the lower steel bar 20' will be.

Since the steel material 31 for manufacturing the spiders 30 and 30 'also has the upper and lower flat surfaces 32 and 32' formed thereon along the longitudinal direction thereof, Facing surfaces 32 and 32 'can be in close contact with the contact surface portions 11, 11', 21 and 21 'of the steel bar in a face-to-face manner, And the ends can be closed or connected with each other through the screw couplers or the like with respect to the steel joints of the spiders 30 and 30 'made by bending the steel material 31, which is more efficient.

Accordingly, the lattice girders having various quadrangle structures can be mass-produced according to the shape of the spider 30 (30 ') to see the quadrilateral grid of the present invention, and the upper steel bar 10 10 ', the lower steel bars 20, 20', and the spiders 30, 30 'are strongly fixed in mutual surface contact, and the spider is disposed between the steel bars at least at two or more positions It has a strong supporting force, a supporting force and a fixing force, thereby greatly enhancing the rigidity of the grid support as a whole.

7 and 8, a pair of second lower horizontal portions 30e and 30e 'and a pair of upper and lower support portions 30f' and 30f 'are formed on the spider 30' A pair of third inclined support portions 30i and 30i 'which are continuously formed between the pair of third inclined support portions 30a and 30f' and a pair of second upper horizontal portions 30j and 30j ' 30k 'and the pair of third lower horizontal portions 30l, 30l' are further bent.

Therefore, the spiders 30 and 30 'generate at least three or more spot intervals with respect to the upper steel bars 10 and 10', and at least three spots are formed with respect to the lower steel bars 20 and 20 ' The number of application spiders 30 and 30 'is decreased compared to the total length of the steel bars. [0050] As described above, according to the present invention, You can.

9 and 10, a pair of second lower horizontal portions 30e and 30e 'and a pair of upper and lower support portions 30e' and 30e ' A pair of third inclined support portions 30i and 30i 'and a pair of second upper side horizontal portions 30j and 30j' which are continuously bent and formed between the pair of third inclined support portions 30i and 30f ' A pair of third lower horizontal portions 30l and 30l 'and a pair of fifth inclined supporting portions 30m and 30m' and a pair of third upper horizontal portions 30k 'and 30k' A pair of sixth inclined support portions 30o and 30o 'and a pair of fourth lower horizontal portions 30p and 30p' are further formed by bending the first and second inclined portions 30n and 30n '.

Accordingly, the spiders 30 and 30 'are formed such that at least four intervals are provided for the upper steel bars 10 and 10', and at least four intervals for the lower steel bars 20 and 20 ' It is possible to improve the gap holding force and the supporting force between the steel bars as well as the strong and good bonding strength between the steel bars and the application amount of the spiders 30 and 30 ' You can.

As another example of the spiders 30 and 30 ', as shown in FIGS. 11 and 12, the first lower horizontal portions 30a and 30a' of the spiders 30 and 30 ' The first inclined support portions 30b and the first upper horizontal portions 30c and 30c 'and the second inclined support portions 30d and 30d' are repeatedly bent to form a plurality of nth lower horizontal portions The n-th slanted support 30v and the n-th slanted support 30x and the n-th slanted support 30x and 30x '

On both of the first to n-th lower horizontal parts, both ends are bent downward, and section supporting rods 30z and 30z 'welded to the first to n-th lower horizontal parts are further formed at predetermined intervals.

Therefore, it is possible to complete the spider 30 (30 ') having the repeated lower side horizontal portion, the upper side horizontal portion and the inclined support portion, and the continuous spider 30 (30' The upper steel bar 10 (10 (10 ')) can be manufactured efficiently because of the section support 30z (30z') formed upright at a predetermined interval on the lower horizontal portion of the continuous spiders 30 ', As well as a strong supporting and clamping force between the upper steel bars 10 and 10' and the lower steel bars 20 and 20 '.

Further, the interval support rods 30z and 30z 'can freely adjust the installation intervals as necessary. If the earth pressure is relatively weak, the spacing between the interval support rods 30z and 30z' When the earth pressure is high, the distance between the zone supports 30z and 30z 'can be narrowed and the zones 30z and 30z' can be manufactured compactly. If the earth pressure is strong at the corner zone or locally, It is more effective because it can actively respond to earth pressure by fixed installation.

As another embodiment of the spiders 30 and 30 ', as shown in FIG. 13, a pair of first inclined support portions 30b and 30b' and a pair of second inclined support portions 30b ' The pair of upper and lower support portions 30f and 30f 'are bent in an inwardly inclined state such that the pair of first upper side horizontal portions 30c and 30c' The length of the upper spacing portion 30h is shortened by being bent in an inwardly inclined state like the first slant portion 30b 'and the second slant portion 30d' 30d '

The side surfaces of the upper steel bars 10 and 10 'are in contact with each other along the longitudinal direction on the first upper side horizontal portions 30c and 30c' close to each other and the upper gap holding portion 30h whose length is shortened The cross sections of the steel bars may be arranged and fixed with a trapezoidal structure as shown in Fig.

Such a trapezoidal lattice girder can be used as a substitute for the existing triangular lattice girder, and is capable of exhibiting stronger rigidity than the existing triangular lattice girder, and the pair of first upper horizontal portions 30c and 30c 'of the upper steel bars 10 and 10' can freely adjust the width of the upper side of the trapezoidal shape according to the mutual spacing width, thereby making it possible to freely and variably apply the thickness or diameter of the upper steel bars 10 and 10 '.

15, the upper spacing portions 30h may be spaced apart from the upper ends of the upper and lower spindles 30f and 30f ' The upper and lower holding portions 30f and 30f 'are bent so that they are bent toward the lower ends of the upper and lower holding portions 30f and 30f' It is possible to obtain a holding force and a mutual interval holding force.

That is, the upper gap holding part 30h inclined in mutually opposite directions transmits the earth pressure acting on the upper steel bars 10 and 10 'to the lower steel bars 20 and 20' The upper steel bars 10 and 10 'as well as the lower steel bars 20 (the upper steel bar 10 and the lower steel bar 20) are formed by mutual welding points on the overlapped portions of the upper gap holding portions 30h. 20 ').

16, the upper spacing portion 30h is formed by a pair of upper and lower support portions 30f and 30f ', and a pair of upper and lower support portions 30f and 30f' The upper and lower ends of the second upper and lower support portions 30f and 30f 'are bent from the upper ends of the first and second upper and lower support portions 30f and 30f' toward the lower ends of the second upper and lower support portions 30f and 30f ' And the upper spacing portion 30h is connected to the upper end of the upper spacer 30f or 30f '.

Thus, the upper and lower steel bars 10 and 10 'and the lower steel bars 20 and 20' can be maintained at the upper and lower intervals due to the inclined upper gap retaining portion 30h, And another upper space retaining portion 30h connected to and fixed to the other upper and lower support portions 30f and 30f 'by horizontally extending the upper and lower support portions 30f and 30f' A pair of upper and lower support portions 30f and 30f 'bent in the vertical direction are formed in the upper and lower steel bars 10 and 10' and the lower steel bar 20, respectively, A strong holding force and a gap maintaining force for the first and second connecting members 20 '.

17, the upper ends of the upper steel bars 10 and 10 'are provided at upper ends of the upper and lower support portions 30f and 30f', as shown in FIG. 17, as another embodiment of the spiders 30 and 30 ' The upper extended horizontal portion 30q and the upper extended horizontal portion 30q may be formed so as to extend from the end of the upper extended horizontal portion 30q to the upper horizontal holding portion 30h. There,

The upper extended horizontal portions 30q and 30q 'are brought into contact with the bottom surfaces of the upper steel bars 10 and 10' so that a fixed section is formed by mutual surface contact. The upper extended horizontal portions 30q ' The upper spacing portion 30h connecting the upper steel bar 10 and the upper spindle 30 to the upper steel bar 10 and 10 ' ', As well as a strong supporting force for the upper steel bars 10, 10' and the lower steel bars 20, 20 '.

As described above, the quadrilateral grid according to the present invention can be selectively used in various quadrilateral structures in consideration of the field conditions and earth pressure in the tunnel construction, and it is also possible to selectively use the quadrilateral grid grid in the existing triangular structure or the square grid It is possible to produce more excellent efficiency by using the same or reduced steel material amount, and it is suitable for mass production and is very economical.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the present invention as defined by the appended claims. Examples should be understood.

10, 10 ': upper steel bar 11, 11'
20, 20 ': lower steel bar 21, 21'
30,30 ': Spider 31: Steel
32, 32 ': corresponding surface

Claims (10)

A pair of upper steel bars 10 and 10 'formed of upper and lower threaded portions 11', 11 ', 21 and 21' formed on upper and lower sides along the longitudinal direction and a pair of lower steel bars 10 ' The bars 20 and 20 'are arranged and fixed so that the cross section of each steel bar has a quadrangular structure through a plurality of spiders 30 and 30', and the spiders 30 and 30 ' And a lower end of the upper steel bar 10 and a lower end of the lower steel bar 20 are formed by bending a steel material 31 composed of a threaded bar having corresponding surface portions 32 and 32 ' 21 and 21 'of the spider 30 and 30' are welded and fixed to each other in the surface contact state with the contact surface portions 11 ', 21', 21 'and 21' However,
The spiders 30 and 30 'include a pair of first lower horizontal portions 30a' and 30a 'that are in close contact with the upper surfaces of the lower steel bars 20 and 20'; A pair of first inclined support portions 30b and 30b 'bent from one end of the first lower horizontal portions 30a and 30a'; A pair of first upper side horizontal portions 30c and 30c 'bent from the first inclined support portions 30b and 30b'; A pair of second inclined support portions 30d and 30d 'bent from the first upper side horizontal portions 30c and 30c'; A pair of second lower horizontal portions 30e and 30e 'bent from the second inclined support portions 30d and 30d'; A pair of upper and lower support portions 30f and 30f 'bent from the second lower side horizontal portions 30e and 30e'; A lower gap holding portion 30g connecting the other ends of the first lower horizontal portions 30a and 30a 'to each other; And an upper space-maintaining portion (30h) connecting ends of the upper and lower support portions (30f) and (30f '). The quadrilateral lattice girder according to claim 1,
delete delete The method according to claim 1,
A pair of third inclined support portions 30i and 30i 'that are continuously formed between the pair of second lower horizontal portions 30e and 30e' and the pair of upper and lower support portions 30f and 30f ' , A pair of second upper horizontal portions 30j and 30j ', a pair of fourth inclined support portions 30k and 30k', and a pair of third lower horizontal portions 30l and 30l ' Wherein the spider is provided with a gap maintaining and stiffness increasing structure.
The method according to claim 1,
A pair of third inclined support portions 30i and 30i 'that are continuously formed between the pair of second lower horizontal portions 30e and 30e' and the pair of upper and lower support portions 30f and 30f ' A pair of second upper horizontal portions 30j and 30j ', a pair of fourth inclined support portions 30k and 30k', a pair of third lower horizontal portions 30l and 30l ' A pair of fifth inclined support portions 30m and 30m ', a pair of third upper side horizontal portions 30n and 30n', a pair of sixth inclined support portions 30o and 30o ' And a lower horizontal portion (30p) (30p ') is further formed on the lower horizontal portion (30p).
The method according to claim 1,
The first lower side horizontal portions 30a and 30a 'and the first inclined upper side portions 30b and 30b' and the first upper side horizontal portions 30c and 30c 'of the spiders 30 and 30' The n-th lower horizontal portion 30u ', the n-th inclined support portion 30v, and the n-th upper horizontal portion 30w' are formed by repeatedly bending the first and second upper and lower horizontal portions 30d and 30d ' 30w 'and the n' -th inclined support portion 30x, 30x '
The first to the n-th lower horizontal parts are further bent downward at both ends to form interval support rods 30z and 30z 'welded to the first to nth lower horizontal parts at a predetermined interval. A quadratic lattice girder with spider applied to maintain and increase the stiffness.
The method according to claim 1,
The pair of first inclined support portions 30b and 30b 'and the pair of second inclined support portions 30d and 30d', which are opposed to each other, have a pair of first upper side horizontal portions 30c and 30c ' And the pair of upper and lower support portions 30f and 30f 'are bent inwardly to be close to the first inclined support portion 30b and the second inclined support portions 30d and 30d' And the length of the upper space-holding portion 30h is shortened by being bent in an inclined state,
The side surfaces of the upper steel bars 10 and 10 'are in contact with each other along the longitudinal direction on the first upper side horizontal portions 30c and 30c' close to each other and the upper gap holding portion 30h whose length is shortened Wherein a cross section of each of the steel bars is arranged and fixed with a trapezoidal structure according to a mutual welding fixation.
The method according to claim 1,
The upper gap holding portion 30h is formed to be bent toward the lower end of the upper and lower holding portions 30f and 30f 'opposite to each other from the upper end of the upper and lower holding portions 30f and 30f' A quadrilateral lattice girder with a spider with a stiffness increase structure.
The method according to claim 1,
The upper gap retaining portion 30h is provided at the lower end of the second upper and lower support portions 30f and 30f 'from the upper ends of the first upper and lower support portions 30f and 30f' of the pair of upper and lower support portions 30f and 30f ' And the upper ends of the second upper and lower support portions 30f and 30f 'are connected to the upper ends of the first and second upper support portions 30f and 30f' A quadrilateral lattice girder with a spider with a stiffness increase structure.
The method according to claim 1,
An upper extending horizontal portion 30q (30q ') extending in the longitudinal direction of the upper steel bar 10 (10') is further formed at the upper end of the upper and lower holding portions 30f and 30f ' And the upper spacing part (30h) is connected from the end of the upper span part (30q) (30q ').

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