Reinforcing steel bar mounting structure in stair

Abstract

The utility model relates to a stair inner steel bar mounting structure. The stair inner steel bar mounting structure comprises a first full-length steel bar, a second full-length steel bar, an upper stair beam, a lower stair beam and a reinforcing piece. The first full-length reinforcing steel bar and the second full-length reinforcing steel bar are arranged between two vertically adjacent floor plates, and one end, close to the lower floor plate, of the first full-length reinforcing steel bar is anchored into the lower ladder beam and is provided with a first bending part; one end, close to the upper stair panel, of the first full-length steel bar is anchored into the upper stair beam and is provided with a second bending part, and the second bending part extends into the upper stair panel; one end, close to the lower floor plate, of the second full-length steel bar is anchored into the lower ladder beam and is provided with a third bending part; the end, close to the upper stair panel, of the second full-length steel bar is anchored into the upper stair beam and provided with a fourth bent part. The reinforcing part is anchored into the lower ladder beam, one side edge of the reinforcing part penetrates through the lower ladder beam and stretches into the lower floor plate, and the other side edge of the reinforcing part is arranged in a mode of being crossed with the first through-length steel bar and the second through-length steel bar.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of stairs, in particular to a reinforcing bar mounting structure in a stair. BACKGROUND

[0002] With the development of society and the rapid development of new buildings, stair beam design has also become very common. In order to ensure that the anchoring nodes in the stair beam are firm and reliable, we need to construct the anchoring structure of the stair beam and the through-length reinforcing bar according to the specification requirements of the current drawing set method. The traditional through-length reinforcing bar in the stair is directly anchored into the upper and lower stair beams at both ends and is fixedly connected with the upper and lower stair beams. Since the through-length reinforcing bar is designed to be inclined, under the condition of its own gravity or large stress, the lower end of the through-length reinforcing bar will give a pressure to the lower stair beam along the body length direction. With the extension of the use time of the stair, there is a hidden danger that the through-length reinforcing bar will crack the lower stair beam, and even the through-length reinforcing bar will directly fall off from the lower stair beam. SUMMARY

[0003] Therefore, the application provides a reinforcing bar mounting structure in a stair.

[0004] The first through-length reinforcing bar and the second through-length reinforcing bar are arranged between two adjacent upper and lower floor slabs, and the body length directions of the first through-length reinforcing bar and the second through-length reinforcing bar are parallel to each other.

[0005] One end of the first through-length reinforcing bar close to the lower floor slab is anchored into the lower stair beam and is provided with a first bending part; one end of the first through-length reinforcing bar close to the upper floor slab is anchored into the upper stair beam and is provided with a second bending part, and the second bending part penetrates into the inside of the upper floor slab.

[0006] One end of the second through-length reinforcing bar close to the lower floor slab is anchored into the lower stair beam and is provided with a third bending part; one end of the second through-length reinforcing bar close to the upper floor slab is anchored into the upper stair beam and is provided with a fourth bending part.

[0007] The main body of the reinforcing part is in an L-shaped structure, the opening of the reinforcing part faces the first bending part and the third bending part, the reinforcing part is anchored into the inside of the lower stair beam, and one side edge of the reinforcing part penetrates into the inside of the lower floor slab, and the other side edge of the reinforcing part is arranged to cross the first through-length reinforcing bar and the second through-length reinforcing bar.

[0008] In a possible implementation manner, the two ends of the reinforcing part are provided with bending edges,

[0009] The body length direction of the bending edge and the side edge of the reinforcing part are provided with a first preset angle.

[0010] In a possible implementation manner, the first preset angle is 30°-75°.

[0011] In a possible implementation, the reinforcing member is fixedly connected to the first and second longitudinal steel bars at the intersection thereof by the locking portion.

[0012] In a possible implementation, the first longitudinal steel bar is provided with two or more first transverse steel bars on the side thereof facing the second longitudinal steel bar.

[0013] The two or more first transverse steel bars are equidistantly arranged along the length of the first longitudinal steel bar.

[0014] In a possible implementation, the second longitudinal steel bar is provided with two or more second transverse steel bars on the side thereof facing the first longitudinal steel bar, and the two or more second transverse steel bars are equidistantly arranged along the length of the second longitudinal steel bar.

[0015] In a possible implementation, the length of the first bent portion is arranged at a second preset angle with respect to the length of the first longitudinal steel bar.

[0016] In a possible implementation, the length of the third bent portion is arranged at a third preset angle with respect to the length of the second longitudinal steel bar.

[0017] In a possible implementation, the main body of the second bent portion is in the shape of a rod with an "L" shape.

[0018] In a possible implementation, the main body of the fourth bent portion is in the shape of a rod with an "L" shape.

[0019] Advantages of the present application

[0020] Compared with the stair steel bar structure without the reinforcing member in the prior art, the reinforcing member, the first longitudinal steel bar and the second longitudinal steel bar cooperate with each other to avoid displacement of the first longitudinal steel bar and the second longitudinal steel bar along the length thereof downward, which prevents the first longitudinal steel bar and the second longitudinal steel bar from piercing the side wall of the lower stair beam, ensures firm connection between the first longitudinal steel bar, the second longitudinal steel bar and the lower stair beam, improves the shear bearing capacity of the intersection of the lower stair beam and the lower floor panel, reduces damage of the intersection of the lower stair beam and the lower floor panel due to stress concentration, and enhances the shear capacity and seismic performance of the overall structure.

[0021] The folded edge can increase the mechanical engagement force between the reinforcing member and the lower stair beam. When the reinforcing member is subjected to a pulling force, the folded edge will be embedded in the inside of the lower stair beam 320 to form a structure similar to a "barb", which prevents the reinforcing member from being pulled out of the inside of the lower stair beam. The mechanical engagement force, together with the adhesive force and the friction force, greatly improves the pullout resistance of the reinforcing member, enabling it to withstand greater tensile load and enhancing the safety of the structure.

[0022] Other features and aspects of the present application will become apparent from a detailed description of exemplary embodiments with reference to the following drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate exemplary embodiments, features, and aspects of the application and serve to explain the principles of the application.

[0024] Figure 1 Fig. 1 shows a side sectional view of a reinforcing bar installation structure in a stair of the present application;

[0025] Figure 2 Fig. 2 shows a partial enlarged view of Figure 1 Fig. 3 shows a side view of a reinforcing member;

[0026] Figure 3 Fig. 4 shows a side view of a reinforcing member. DETAILED DESCRIPTION

[0027] Various exemplary embodiments, features, and aspects of the present application will be described below in detail with reference to the accompanying drawings. Like reference numerals denote like elements throughout the drawings. Although various aspects of the embodiments are illustrated in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0028] It should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application or simplifying the description, and do not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0029] In addition, the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0030] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations.

[0031] Furthermore, to better illustrate this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented without certain specific details. In some instances, methods, means, components, and circuits well-known to those skilled in the art have not been described in detail in order to highlight the main points of this application.

[0032] This application proposes a steel reinforcement installation structure inside a staircase, such as Figures 1 to 3 As shown, it includes: a first continuous reinforcing bar 110, a second continuous reinforcing bar 120, an upper ladder beam 310, a lower ladder beam 320, and a reinforcing member 200; the first continuous reinforcing bar 110 and the second continuous reinforcing bar 120 are arranged between two adjacent floor slabs, and the length directions of the first continuous reinforcing bar 110 and the second continuous reinforcing bar 120 are parallel to each other; one end of the first continuous reinforcing bar 110 near the lower floor slab 321 is anchored into the lower ladder beam 320 and this end is provided with a first bend 111; one end of the first continuous reinforcing bar 110 near the upper floor slab 311 is anchored into the upper ladder beam 310 and this end is provided with a second bend 112, the second bend 112 extending into the upper floor slab 311. The second continuous steel bar 120 is anchored into the lower stair beam 320 at one end near the lower floor slab 321, and this end is provided with a third bend 121; the second continuous steel bar 120 is anchored into the upper stair beam 310 at one end near the upper floor slab 311, and this end is provided with a fourth bend 122; the main body of the reinforcement 200 is L-shaped, the opening of the reinforcement 200 faces the first bend 111 and the third bend 121, the reinforcement 200 is anchored into the interior of the lower stair beam 320, and one side of the reinforcement penetrates the lower stair beam 320 and extends into the interior of the lower floor slab 321, and the other side of the reinforcement intersects with the first continuous steel bar 110 and the second continuous steel bar 120.

[0033] It should be noted that the upper ladder beam 310 and the lower ladder beam 320 are both fixedly installed on one side of two adjacent floor slabs by casting. The upper ladder beam 310 and the lower ladder beam 320 are used to provide a stable support foundation for the first continuous long steel bar 110 and the second continuous long steel bar 120. The first continuous long steel bar 110 and the second continuous long steel bar 120 are both inclinedly installed between the upper ladder beam 310 and the lower ladder beam 320. The staircase is fixedly installed on the first continuous long steel bar 110 and the second continuous long steel bar 120 by casting. The first continuous long steel bar 110 is used to bear the load of the staircase structure in the vertical direction, preventing the staircase structure from deforming under stress and improving the bending resistance of the staircase. The second continuous long steel bar 120 is used to bear the load of the staircase structure in the horizontal direction, preventing the staircase structure from failing under stress and improving the shear resistance of the staircase structure. The first continuous long steel bar 110 and the second continuous long steel bar 120 are set in parallel, and can jointly bear the load of the staircase structure in the vertical and horizontal directions, so that the staircase structure reduces damage caused by stress concentration.

[0034] As shown in Figure 2 The first bending part 111 and the third bending part 121 enable the first longitudinal steel 110 and the second longitudinal steel 120 to be better anchored into the inside of the lower stair beam 320 at one end close to the lower floor panel 321, and form a close connection with the lower stair beam 320. The design of the first bending part 111 and the third bending part 121 increases the contact area of the first longitudinal steel 110, the second longitudinal steel 120 and the lower stair beam 320. The load generated by the staircase can be evenly dispersed to the lower stair beam 320 through the first bending part 111 and the third bending part 121. Compared with the existing direct anchoring method, the situation of the lower stair beam 320 being pierced due to stress concentration at one end of the first longitudinal steel 110 and the second longitudinal steel 120 is avoided, and the stability of the overall structure is ensured.

[0035] As shown in Figure 1 The design of the second bending part 112 penetrating into the inside of the upper floor panel 311 enhances the connection strength between the floor panel and the upper stair beam 310. The second bending part 112 tightly connects the first longitudinal steel 110, the upper floor panel 311 and the upper stair beam 310 together. The first through steel disperses stress to the upper stair beam 310 and the upper floor panel 311 through the second bending part 112, reduces the stress concentration at the junction of the upper stair beam 310 and the upper floor panel 311, and enhances the stability and seismic performance of the staircase structure. The fourth bending part 122 enhances the anchoring length of the second longitudinal steel 120 anchored into the upper stair beam 310, enhances the anchoring strength of the second longitudinal steel 120, and ensures the stable connection between the second longitudinal steel 120 and the upper stair beam 310.

[0036] As shown in Figures 1 to 3As shown, the reinforcing member 200 is anchored inside the lower stringer 320 and forms a close connection with the lower stringer 320. The reinforcing member 200 is suitable for extending the length of the first and second through steel bars 110 and 120 anchored in the lower stringer 320, further improving the anchoring force of the first and second through steel bars 110 and 120. The design of one side of the reinforcing member 200 crossing the first and second through steel bars 110 and 120 extends the anchoring length of the first and second through steel bars 110 and 120 inside the lower stringer 320, enhances the friction and engagement force between them, and further improves the anchoring effect of the first and second through steel bars 110 and 120, so that the first and second through steel bars 110 and 120 can better transmit loads to the lower stringer 320. The design of the other side of the reinforcing member 200 penetrating the lower stringer 320 and being anchored inside the lower floor slab 321 strengthens the connection strength between the lower stringer 320 and the lower floor slab 321 and improves the load-bearing capacity of the lower stringer 320. Under the action of shear force, this strong connection can effectively transmit and distribute shear force, so that the floor slab and the lower stringer 320 work together as a whole to resist shear force.

[0037] Compared with the stair reinforcing structure without the reinforcing member 200 in the prior art, by setting the reinforcing member 200, the reinforcing member 200, the first and second through steel bars 110 and 120 cooperate with each other to avoid the displacement of the first and second through steel bars 110 and 120 along the length direction thereof, which causes the first and second through steel bars 110 and 120 to pierce the side wall of the lower stringer 320, ensuring the firm connection between the first and second through steel bars 110 and 120 and the lower stringer 320. The reinforcing member 200 also improves the shear bearing capacity of the joint between the lower stringer 320 and the lower floor slab 321, reduces the damage of the joint between the lower stringer 320 and the lower floor slab 321 due to stress concentration, and enhances the shear resistance and seismic performance of the overall structure.

[0038] Further, the reinforcing member 200 is a bent L-shaped reinforcing steel bar, and the lengths of the two sides of the reinforcing member 200 are the same. The length of the side is in the range of 150mm-300mm, and preferably, the length of the side of the reinforcing steel bar is 220mm.

[0039] In one possible implementation manner, as shown in Figure 3 Both ends of the reinforcing member 200 are provided with a folded edge 210, and the body length direction of the folded edge 210 and the side of the reinforcing member 200 are provided with a first preset angle a.

[0040] It should be noted that the folded edge 210 is obliquely arranged at both ends of the reinforcing member 200 and extends towards the opening of the reinforcing member 200. The folded edge 210 can increase the mechanical engagement force between the reinforcing member 200 and the lower ladder beam 320. When the reinforcing member 200 is subjected to a pulling force, the folded edge 210 will be embedded in the lower ladder beam 320 to form a structure similar to a "barb", which prevents the reinforcing member 200 from being pulled out of the lower ladder beam 320. The mechanical engagement force, together with the adhesive force and the friction force, greatly improves the pull-out resistance of the reinforcing member 200, enabling it to withstand greater tensile load and enhancing the safety of the structure. The design of the first preset angle α makes the anchoring force of the reinforcing member 200 better match the main stress direction, thereby maximizing the anchoring effect of the reinforcing member 200.

[0041] Further, the first preset angle α is in the range of 30°-75°, and preferably, the first preset angle α is 45°.

[0042] Further, the length of the folded edge 210 is 500mm.

[0043] In one possible implementation, the reinforcing member 200 is fixedly connected to the intersection of the first and second through steel bars 110, 120 by a locking portion (not shown in the figure). It should be noted that the fixed connection of the locking portion forms a stable overall structure between the reinforcing member 200 and the first and second through steel bars 110, 120, increasing the anchoring length and anchoring force of the first and second through steel bars 110, 120 inside the lower ladder beam 320, and avoiding the connection failure between the first and second through steel bars 110, 120 and the lower ladder beam 320, thereby ensuring the reliability of the connection between the first and second through steel bars 110, 120 and the lower ladder beam 320.

[0044] Preferably, the locking portion is a wire or a bundle of steel bars, and the structure of the locking portion is not limited in the present application.

[0045] In one possible implementation, the first and second through steel bars 110, 120 are each provided with two or more, and the two or more first and second through steel bars 110, 120 are arranged equidistantly along the body width direction of the lower ladder beam 320. Correspondingly, the reinforcing member 200 is provided with two or more, and the two or more reinforcing members 200 are arranged equidistantly along the body width direction of the lower ladder beam 320.

[0046] Preferably, the preset distance between the adjacent two reinforcing members 200 is 500mm.

[0047] In one possible implementation, as shown in FIG. 6, the first and second through steel bars 110, 120 are arranged in the body width direction of the lower ladder beam 320, and the reinforcing member 200 is arranged between the first and second through steel bars 110, 120. Figure 2As shown, the second preset angle β is provided between the length direction of the first bending part 111 and the length direction of the first longitudinal steel 110. The design of the second preset angle β can make the first longitudinal steel 110 cooperate with the lower ladder beam 320 when resisting the shear force, enhance the resistance to shear force of the overall structure, and further enhance the anchoring effect.

[0048] Preferably, the value of the second preset angle β is 45°, and the length of the first bending part 111 is 200 mm.

[0049] Further, the first bending part 111 is formed by bending the first longitudinal steel 110, and the first bending part 111 is anchored in the lower ladder beam 320 after the first longitudinal steel 110 deeply enters the inner edge of the lower ladder beam 320.

[0050] In a possible implementation manner, as shown in Figure 2 As shown, the third preset angle γ is provided between the length direction of the third bending part 121 and the length direction of the second longitudinal steel 120. The design of the third preset angle γ can make the second longitudinal steel 120 cooperate with the lower ladder beam 320 when resisting the shear force, enhance the resistance to shear force of the overall structure, and further enhance the anchoring effect.

[0051] Preferably, the value of the third preset angle γ is 45°, and the length of the third bending part 121 is 150.

[0052] Further, the third bending part 121 is formed by bending the second longitudinal steel 120, and the third bending part 121 is anchored in the lower ladder beam 320 after the second longitudinal steel 120 deeply enters the inner edge of the lower ladder beam 320.

[0053] In a possible implementation manner, as shown in Figure 1 As shown, the main body of the second bending part 112 is in the shape of an "L"-shaped rod structure. It should be noted that the opening of the second bending part 112 is towards the side of the second longitudinal steel 120. The design of the "L" shape can increase the contact area of the second bending part 112 and the upper floor slab 311. When stressed, the L-shaped second bending part 112 can better resist the force from various directions, avoid the connection between the second bending part 112 and the upper floor slab 311 from loosening or falling off, enhance the anchoring effect, and when the first longitudinal steel 110 is subjected to a pulling force, the design of the opening towards the side of the second longitudinal steel 120 makes the second bending part 112 have better anti-pulling ability, thereby ensuring the stability of the overall structure.

[0054] Further, the second bending part 112 is formed by bending the first longitudinal steel 110.

[0055] In a possible implementation manner, as shown in Figure 1As shown, the main body of the fourth bending part 122 is in the shape of an "L"-shaped rod structure. It should be noted that the opening of the fourth bending part faces the side of the second longitudinal steel bar 120, and the "L"-shaped design can increase the cross-sectional area of the fourth bending part and the upper ladder beam 310, thereby increasing the length of the second longitudinal steel bar 120 anchored into the upper ladder beam 310 and ensuring the anchoring effect of the second longitudinal steel bar 120 anchored into the upper ladder beam 310.

[0056] Further, the fourth bending part is formed by bending the second longitudinal steel bar 120.

[0057] In one possible implementation manner, as shown in Figure 1 As shown, the first longitudinal steel bar 110 is provided with two or more first transverse steel bars 410 on the side facing the second longitudinal steel bar 120; the two or more first transverse steel bars 410 are equidistantly arranged along the length direction of the first longitudinal steel bar 110; the length directions of the two or more first transverse steel bars 410 are parallel to each other, and the two or more first transverse steel bars 410 are fixedly connected with the first longitudinal steel bar 110.

[0058] Further, as shown in Figure 1 As shown, the second longitudinal steel bar 120 is provided with two or more second transverse steel bars 420 on the side facing the first longitudinal steel bar 110; the two or more second transverse steel bars 420 are equidistantly arranged along the length direction of the second longitudinal steel bar 120; the length directions of the two or more second transverse steel bars 420 are parallel to each other, and the two or more second transverse steel bars 420 are fixedly connected with the second longitudinal steel bar 120.

[0059] It should be noted that the first transverse steel bars 410 and the second transverse steel bars 420 are symmetrically arranged between the first longitudinal steel bars 110 and the second longitudinal steel bars 120. Since the staircase is provided with two or more groups of first longitudinal steel bars 110 and second longitudinal steel bars 120 arranged adjacently, the first transverse steel bars 410 and the second transverse steel bars 420 are arranged on the first longitudinal steel bars 110 (or the second longitudinal steel bars 120) along the length directions thereof. The first longitudinal steel bars 110, the second longitudinal steel bars 120, the first transverse steel bars 410 and the second transverse steel bars 420 together form a stable grid-shaped steel frame. The staircase is fixedly arranged on the steel frame in a pouring manner, and the grid-shaped steel frame can make the load borne by the staircase more evenly distributed to the entire structure, thereby making the stress of the entire staircase structure more reasonable and improving the load-bearing capacity and durability of the staircase.

[0060] Having described various embodiments of the application, it is to be understood that the above description is meant not to limit and not to encompass all of the possible embodiments. Many modifications and variations of this application can be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. It is intended that the scope of the application be defined by the scope of the patent and by the claims as allowed by the patent office, which can include adaptations based on the description, equivalents, and / or substitutions of elements individually or collectively to the entire disclosure.

Claims

1. A steel reinforcement installation structure inside a staircase, characterized in that, The utility model relates to a reinforced structure of floor slab, which comprises: a first longitudinal steel bar, a second longitudinal steel bar, an upper ladder beam, a lower ladder beam and a reinforcing member; the first longitudinal steel bar and the second longitudinal steel bar are arranged between two adjacent floor slabs, and the lengthwise direction of the first longitudinal steel bar is parallel to the lengthwise direction of the second longitudinal steel bar; one end of the first longitudinal steel bar close to the lower floor slab is anchored into the lower ladder beam, and the end is provided with a first bent part; one end of the first longitudinal steel bar close to the upper floor slab is anchored into the upper ladder beam, and the end is provided with a second bent part, which extends into the upper floor slab; one end of the second longitudinal steel bar close to the lower floor slab is anchored into the lower ladder beam, and the end is provided with a third bent part; one end of the second longitudinal steel bar close to the upper floor slab is anchored into the upper ladder beam, and the end is provided with a fourth bent part; the main body of the reinforcing member is in the shape of L, the opening of the reinforcing member faces the first bent part and the third bent part, the reinforcing member is anchored into the lower ladder beam, and one side edge of the reinforcing member extends into the lower floor slab through the lower ladder beam, and the other side edge of the reinforcing member is arranged to cross the first longitudinal steel bar and the second longitudinal steel bar.

2. The reinforcing bar installation structure in a stair according to claim 1, wherein both ends of the reinforcing member are provided with bent edges, the lengthwise direction of the bent edge and the side edge of the reinforcing member are provided with a first preset angle.

3. The reinforcing bar installation structure in a stair according to claim 2, wherein the first preset angle ranges from 30° to 75°.

4. The reinforcing bar installation structure in a stair according to Claim 1, wherein the intersection of the reinforcing member and the first longitudinal steel bar and the second longitudinal steel bar is fixedly connected through a locking part.

5. The reinforcing bar installation structure in a stair according to Claim 1, wherein the side of the first longitudinal steel bar facing the second longitudinal steel bar is provided with two or more first transverse steel bars; the two or more first transverse steel bars are equidistantly arranged along the lengthwise direction of the first longitudinal steel bar.

6. The reinforcing bar installation structure in a stair according to Claim 1, wherein the side of the second longitudinal steel bar facing the first longitudinal steel bar is provided with two or more second transverse steel bars; the two or more second transverse steel bars are equidistantly arranged along the lengthwise direction of the second longitudinal steel bar.

7. The reinforcing bar installation structure in a stair according to Claim 1, wherein the lengthwise direction of the first bent part and the lengthwise direction of the first longitudinal steel bar are provided with a second preset angle.

8. The reinforcing bar installation structure in a stair according to Claim 1, wherein the lengthwise direction of the third bent part and the lengthwise direction of the second longitudinal steel bar are provided with a third preset angle.

9. The reinforcing bar installation structure in a stair according to Claim 1, wherein the main body of the second bent part is in the shape of L-shaped rod structure.

10. The reinforcing bar installation structure in a stair according to Claim 1, wherein the main body of the fourth bent part is in the shape of L-shaped rod structure.

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