Prefabricated stair mounting and connecting structure

Abstract

The utility model discloses a prefabricated stair installing and connecting structure which comprises a prefabricated stair, an upper stair beam and a lower stair beam, and the upper stair beam and the lower stair beam are provided with an upper lifting lug and a lower lifting lug respectively. Inverted-U-shaped steel embedded parts are embedded in the upper and lower ends of the prefabricated staircase, the outer side faces of the inverted-U-shaped steel embedded parts extend out of the prefabricated staircase, and first reinforcing ribs are arranged at the upper and lower ends of the inner side faces of the inverted-U-shaped steel embedded parts; u-shaped steel embedded parts are embedded in the junction of the upper surface of the upper lifting lug and the upper stair beam and the junction of the upper surface of the lower lifting lug and the lower stair beam respectively, the inner side faces of the U-shaped steel embedded parts extend out of the upper lifting lug and the lower lifting lug respectively, second reinforcing ribs are arranged at the upper end and the lower end of the outer side face respectively, and the first reinforcing ribs and the second reinforcing ribs are embedded in the prefabricated stair. The outer side faces of the upper inverted-U-shaped steel embedded parts and the lower inverted-U-shaped steel embedded parts are inserted into the U-shaped steel embedded parts correspondingly, so that the prefabricated stair is connected with the upper stair beam and the lower stair beam. Installation is simpler and more flexible, construction is convenient, the construction period is shortened, cost is saved, construction quality and efficiency are improved, and the connecting mode is economical, convenient, fast and reliable.

Description

Technical Field

[0001] The utility model belongs to the technical field of construction, and particularly relates to a precast staircase installation and connection structure. Background Art

[0002] At present, the method for installing precast staircases is to embed bolts in the ear projections and reserve bolt holes at both ends of the precast staircase. In theory, the embedded bolts and bolt holes can be aligned, but the on-site installation situation often deviates from the theory. This deviation may be due to the deviation of the on-site embedded bolts or the deviation of the embedded bolt holes during factory processing; when multiple factors are superimposed, the situation where the embedded bolts and bolt holes cannot be aligned may occur. If it is found that they cannot be aligned during installation, on-site workers may directly saw off the embedded bolts, which will seriously affect the structural safety; or the component factory may rework and adjust the position of the bolt holes, or the on-site rework may be carried out to re-reserve the position of the embedded bolts on the ear projections; all of these will cause great losses to the construction period, labor, and cost. When hoisting the staircase, the bolt holes need to be aligned with the bolts and then lowered. Since the precast staircase is relatively heavy and has a large swinging inertia, and the sizes of the bolt holes and bolts are relatively small and relatively concealed, it is difficult to carry out on-site operations and will consume more adjustment time. Summary of the Invention

[0003] In view of the above problems existing in the prior art, the utility model provides a precast staircase installation and connection structure to improve the construction quality and efficiency.

[0004] To achieve the above object, the technical solution of the utility model is as follows:

[0005] The utility model provides a precast staircase installation and connection structure, including a precast staircase, an upper staircase beam, and a lower staircase beam. The upper staircase beam is provided with an upper ear projection, and the lower staircase beam is provided with a lower ear projection; inverted U-shaped steel embedded parts are respectively embedded inside the upper and lower ends of the precast staircase. The outer side surfaces of the inverted U-shaped steel embedded parts respectively extend out of the upper and lower ends of the precast staircase, and the upper and lower ends of the inner side surfaces are respectively provided with first reinforcing bars embedded in the precast staircase; U-shaped steel embedded parts are respectively embedded at the junctions of the upper surfaces of the upper ear projections and the upper staircase beam and the junctions of the upper surfaces of the lower ear projections and the lower staircase beam. The inner side surfaces of the U-shaped steel embedded parts respectively extend out of the inner ends of the upper ear projections and the lower ear projections, and the upper and lower ends of the outer side surfaces are respectively provided with second reinforcing bars embedded in the upper ear projections and the lower ear projections; the outer side surfaces of the upper and lower inverted U-shaped steel embedded parts are respectively inserted into the U-shaped steel embedded parts to realize the connection of the precast staircase with the upper staircase beam and the lower staircase beam respectively.

[0006] The utility model discloses a prefabricated stair installation connection structure, the upper and lower ends of the prefabricated staircase are respectively embedded with the inverted U-shaped steel embedded parts, the upper cantilever ear and the lower cantilever ear are respectively embedded with the U-shaped steel embedded parts, and the upper and lower inverted U-shaped steel embedded parts are buckled and connected with the upper and lower U-shaped steel embedded parts, so that the upper and lower ends of the prefabricated staircase are respectively connected with the upper ladder beam and the lower ladder beam, thereby overcoming the defect in the prior art that bolts and bolt holes are easily misaligned, thereby shortening the construction period and avoiding wasting manpower and expenses.

[0007] Preferably, an upper vertical gap is provided between the inner side surface of the upper stair beam and the outer side surface of the upper end of the prefabricated staircase, and a grouting material layer is provided in the upper vertical gap.

[0008] Preferably, a mortar sealing layer is provided in the top of the upper vertical gap, and the mortar sealing layer is provided on the top of the grouting material.

[0009] Preferably, an upper cement mortar leveling layer is provided between the inner top surface of the upper cantilever and the outer bottom surface of the upper end of the prefabricated staircase.

[0010] Preferably, a lower vertical gap is provided between the inner side surface of the lower stair beam and the outer side surface of the upper end of the prefabricated staircase, and a polystyrene filling layer is provided in the lower vertical gap.

[0011] Preferably, PE rods are arranged in the polystyrene filling layer.

[0012] Preferably, a glue injection layer is provided in the top of the lower vertical gap, and the glue injection layer is provided on the polystyrene filling layer.

[0013] Preferably, a lower cement mortar leveling layer is provided between the inner top surface of the lower cantilever and the outer bottom surface of the lower end of the prefabricated staircase.

[0014] Preferably, a felt layer is provided in the top of the lower transverse gap, and the felt layer is provided on top of the lower cement mortar leveling layer.

[0015] Preferably, the inverted U-shaped steel embedded parts embedded inside the upper and lower ends of the prefabricated staircase are respectively set to two and symmetrically distributed; the U-shaped steel embedded parts embedded inside the inner ends of the upper cantilever and the lower cantilever are respectively set to two and symmetrically distributed.

[0016] The utility model provides a prefabricated staircase installation connection structure, which has the following beneficial effects:

[0017] 1. The precast staircase installation and connection structure of the present utility model can overcome the defect that when the lug is installed and connected to the ladder beam in the prior art, it is easy for the bolts and bolt holes not to align; compared with the traditional hidden connection method, it realizes the connection between the lug and the precast staircase by the snap connection of the U-shaped steel embedded part and the inverted U-shaped steel embedded part. Its installation is simpler, more flexible, the construction is convenient, the construction period is shortened, the cost is saved, and the construction quality and efficiency are improved. It is an economical, convenient and reliable connection method.

[0018] 2. The precast staircase installation and connection structure of the present utility model can form a sliding support at the bottom end through a felt isolation layer, a flexible joint, etc., so that the staircase can slide when facing external forces such as earthquakes, thereby reducing the damage to the staircase structure; the shear moment and bending moment released by the sliding support can significantly improve the seismic performance of the staircase; through the sliding support, the stress concentration at the connection between the staircase slab and the ladder beam can be reduced, the risk of structural damage can be reduced, the stress concentration can be reduced, and the structural safety can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the upper structure diagram of the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0020] Figure 2 It is the lower structure diagram of the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0021] Figure 3 It is the structural schematic diagram of the inverted U-shaped steel embedded part of the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0022] Figure 4 It is the structural schematic diagram of the U-shaped steel embedded part of the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0023] Figure 5 It is the snap connection schematic diagram of the inverted U-shaped steel embedded part and the U-shaped steel embedded part of the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0024] Figure 6 It is the structural schematic diagram of the upper lug and its U-shaped steel embedded part of the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0025] Figure 7 It is the structural diagram of the upper lug and its U-shaped steel embedded part of the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0026] Figure 8 It is the structural schematic diagram of the upper part of the staircase and its inverted U-shaped steel embedded part of the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0027] Figure 9 It is a structural diagram of the upper part of the precast staircase and its inverted U-shaped steel embedded parts in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0028] Figure 10 It is a structural diagram of the upper lug and its upper cement mortar leveling layer in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0029] Figure 11 It is a buckling connection structural diagram of the U-shaped steel embedded part of the upper lug and the inverted U-shaped steel embedded part of the upper part of the staircase in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0030] Figure 12 It is a schematic structural diagram of the lower lug and its U-shaped steel embedded part in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0031] Figure 13 It is a structural diagram of the lower lug and its U-shaped steel embedded part in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0032] Figure 14 It is a schematic structural diagram of the lower part of the staircase and its inverted U-shaped steel embedded part in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0033] Figure 15 It is a structural diagram of the lower part of the staircase and its inverted U-shaped steel embedded part in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0034] Figure 16 It is a structural diagram of the lower lug and its lower cement mortar leveling layer in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0035] Figure 17 It is a buckling connection structural diagram of the U-shaped steel embedded part of the lower lug and the inverted U-shaped steel embedded part of the lower part of the staircase in the precast staircase installation and connection structure provided by an embodiment of the present utility model.

[0036] Reference numerals in the figure:

[0037] 1 is the precast staircase, 2 is the upper ladder beam, 210 is the upper lug, 220 is the upper rest platform, 3 is the lower ladder beam, 310 is the lower lug, 320 is the lower rest platform, 4 is the inverted U-shaped steel embedded part, 5 is the first reinforcing bar, 6 is the U-shaped steel embedded part, 7 is the second reinforcing bar, 8 is the grouting layer, 9 is the mortar plugging layer, 10 is the upper cement mortar leveling layer, 11 is the polystyrene filling layer, 12 is the PE rod, 13 is the glue injection layer, 14 is the lower cement mortar leveling layer, 15 is the asphalt felt layer. Detailed implementation manners

[0038] The present utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments. Embodiment

[0039] Please refer to Figures 1 to 5 , a precast staircase installation and connection structure, including a precast staircase 1, an upper beam 2 and a lower beam 3. The upper beam 2 is provided with an upper lug 210, and the lower beam 3 is provided with a lower lug 310; inverted U-shaped steel embedded parts 4 are respectively embedded in the upper and lower ends of the precast staircase 1. The outer side surfaces of the inverted U-shaped steel embedded parts 4 respectively extend to the outside of the upper and lower ends of the precast staircase 1, and the upper and lower ends of the inner side surfaces are respectively provided with first reinforcing bars 5 embedded in the precast staircase 1; U-shaped steel embedded parts 6 are respectively embedded at the junction of the upper surface of the upper lug 210 and the upper beam 2 and at the junction of the upper surface of the lower lug 310 and the lower beam 3. The inner side surfaces of the U-shaped steel embedded parts 6 respectively extend to the outside of the inner ends of the upper lug 210 and the lower lug 310, and the upper and lower ends of the outer side surfaces are respectively provided with second reinforcing bars 7 embedded in the upper lug 210 and the lower lug 310; the outer side surfaces of the upper and lower inverted U-shaped steel embedded parts 4 are respectively inserted into the U-shaped steel embedded parts 6 to realize the connection between the precast staircase 1 and the upper beam 2 and the lower beam 3 respectively.

[0040] Please refer to Figures 1 to 2 , Figure 8 and Figure 9 , Figure 11 , Figure 14 Figure 15 and Figure 17 , the inner side and the outer side respectively refer to the side close to and far from the center position of the precast staircase 1. The upper lug 210 is provided on the inner side of the upper beam 2, and the lower lug 310 is provided on the inner side of the lower beam 3. The upper rest platform 220 is provided on the outer side of the upper beam 2, and the lower rest platform 320 is provided on the outer side of the lower beam 3. The upper rest platform 220, the upper beam 2 and the upper lug 210 are set as an integral structure, and the lower rest platform 320, the lower beam 3 and the lower lug 310 are set as an integral structure.

[0041] Please refer to Figures 1 to 2 , Figure 5 , Figure 11 and Figure 17 , for the precast staircase installation and connection structure of this embodiment, the upper and lower ends of the precast staircase 1 are respectively buckled and connected with the U-shaped steel embedded parts 6 of the upper beam 2 and the lower beam 3 through the inverted U-shaped steel embedded parts 4 to realize the installation and connection of the precast staircase, which can shorten the construction period and avoid wasting manpower and costs.

[0042] Please refer to Figure 1 and Figure 11 , specifically, there is an upper vertical gap between the inner side surface of the upper beam 2 and the outer side surface of the upper end of the precast staircase 1, and a grout layer 8 is provided in the upper vertical gap.

[0043] Please refer to Figure 1 , specifically, a mortar sealing layer 9 is provided inside the top of the upper vertical gap, and the mortar sealing layer 9 is arranged above the grouting material 8.

[0044] Please refer to Figure 1 、 Figure 10 and Figure 11 , specifically, an upper cement mortar leveling layer 10 is provided between the inner top surface of the upper lug 210 and the outer bottom surface of the upper end of the precast staircase 1.

[0045] Please refer to Figure 2 and Figure 17 , specifically, a lower vertical gap is provided between the inner side surface of the lower beam 3 and the outer side surface of the upper end of the precast staircase 1, and a polystyrene filling layer 11 is provided inside the lower vertical gap.

[0046] Please refer to Figure 2 , specifically, a PE rod 12 is provided inside the polystyrene filling layer 11.

[0047] Specifically, a glue injection layer 13 is provided inside the top of the lower vertical gap, and the glue injection layer 13 is arranged above the polystyrene filling layer 11.

[0048] Please refer to Figure 2 、 Figure 16 and Figure 17 , specifically, a lower cement mortar leveling layer 14 is provided between the inner top surface of the lower lug 310 and the outer bottom surface of the lower end of the precast staircase 1.

[0049] Specifically, a felt layer 15 is provided inside the top of the lower horizontal gap, and the felt layer 15 is arranged above the lower cement mortar leveling layer 14.

[0050] Please refer to Figure 6 and Figure 8 、 Figure 12 and Figure 14 , specifically, two inverted U-shaped steel embedded parts 4 embedded inside the upper and lower ends of the precast staircase 1 are respectively provided and symmetrically distributed; two U-shaped steel embedded parts 6 embedded inside the inner ends of the upper lug 210 and the lower lug 310 are respectively provided and symmetrically distributed.

[0051] Please refer to Figures 1 to 17 , specifically, both the inverted U-shaped steel embedded part 4 and the U-shaped steel embedded part 6 are provided as U-shaped structures with right-angle bends, and their shape structures and dimensions are the same.

[0052] Please refer to Figure 1 and Figure 2 、 Figures 7 to 17, the inner and outer side surfaces of the inverted U-shaped steel embedded part 4 and the U-shaped steel embedded part 6 are parallel to the outer side surfaces of the upper and lower ends of the ladder beam 1.

[0053] Please refer to Figure 1 and Figure 2 、 Figure 7 、 Figures 9 to 11 、 Figure 13 、 Figures 15 to 17 , the first reinforcing bar 5 is parallel to and in contact with the inner side surface of the inverted U-shaped steel embedded part 4. The second reinforcing bar 7 is parallel to and in contact with the outer side surface of the U-shaped steel embedded part 6.

[0054] Please refer to Figures 1 to 5 、 Figure 7 、 Figures 9 to 11 、 Figure 13 、 Figures 15 to 17 , the length of the outer side surface of the inverted U-shaped steel embedded part 4 is greater than the length of the inner side form. The length of the inner side surface of the U-shaped steel embedded part 6 is greater than the length of the outer side surface.

[0055] Please refer to Figure 6 and Figure 7 , when installing the upper part of the staircase, when casting the precast staircase 1 and the upper cantilever ear 2 on-site, embed the U-shaped steel embedded part 6 in the upper cantilever ear 210, and it is located at the junction of the upper cantilever ear 210 and the precast staircase 1, and place the second reinforcing bar 7; the second reinforcing bar 7 is placed throughout the length, that is, the length of the second reinforcing bar 7 is equal to the width of the U-shaped steel embedded part 6;

[0056] Please refer to Figure 8 and Figure 9 , when processing the precast staircase, embed the inverted U-shaped steel embedded part 4 at the upper end of the staircase. The distance between the inverted U-shaped steel embedded part 4 buried in the staircase and the bottom surface of the staircase can be 20 mm as a protective layer; and place the first reinforcing bar 5; the first reinforcing bar 5 is placed throughout the length, that is, the length of the first reinforcing bar 5 is equal to the width of the inverted U-shaped steel embedded part 4;

[0057] Please refer to Figure 10 , before installing the precast staircase, set an upper cement mortar leveling layer 10 with a cement-to-mortar mass ratio of 1:1 at the upper cantilever ear 210, and the strength grade of the upper cement mortar leveling layer 10 ≥ M15;

[0058] Please refer to Figure 11 , when installing the precast staircase, place the inverted U-shaped steel embedded part 4 at the upper end of the ladder beam 1 at the position corresponding to the U-shaped steel embedded part 5 of the upper cantilever ear 2, and clamp the inverted U-shaped steel embedded part 4 on the U-shaped steel embedded part 6;

[0059] Please refer to Figure 1, after the precast stairs are installed, the upper vertical gaps between the cast-in-place platform and the two ends of the precast stairs are filled with C40 CGM grout, and the end is sealed with mortar until it is flat, dense and smooth.

[0060] Please refer to Figure 12 and Figure 13 , when installing the lower part of the stairs, when casting the precast stairs 1 and the lower cantilever 310 on site, embed the U-shaped steel embedded part 6 in the lower cantilever 310, and it is located at the junction of the lower cantilever 310 and the precast stairs 1, and place the second reinforcement bar 7; the second reinforcement bar 7 is placed longitudinally;

[0061] Please refer to Figure 14 and Figure 15 , when processing the precast stairs, embed the inverted U-shaped steel embedded part 4 at the lower end of the stairs. The distance between the inverted U-shaped steel embedded part 4 embedded in the stairs and the bottom surface of the stairs can be 20 mm as a protective layer; and place the first reinforcement bar 5; the first reinforcement bar 5 is placed longitudinally;

[0062] Please refer to Figure 16 , before installing the precast stairs, set a 1:1 cement mortar leveling layer 14 (strength grade ≥ M15) at the lower cantilever 310; and lay a layer of oil felt on it to form an oil felt layer 15 to isolate the bonding strength and reduce the friction force.

[0063] Please refer to Figure 17 , when installing the precast stairs, place the inverted U-shaped steel embedded part 4 at the lower end of the precast stairs 1 at the position corresponding to the U-shaped steel embedded part 5 of the lower cantilever 310, and clamp the inverted U-shaped steel embedded part 4 on the U-shaped steel embedded part 6;

[0064] Please refer to Figure 2 , after the precast stairs are installed, the lower vertical gaps between the cast-in-place platform and the two ends of the precast stairs are filled with polystyrene and compacted with a PE rod, and the glue injection is full.

[0065] Since the oil felt layer 15 is a smooth material, after the stairs are installed, the end of the stairs located on the oil felt layer 15 can slide, so as to reduce the damage to the stair structure when subjected to external forces such as earthquakes.

[0066] The above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

[0067] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0068] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to has a specific orientation, is constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present utility model. In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present utility model, unless otherwise stated, the meaning of "a plurality" is two or more.

[0069] In the description of the present utility model, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood through specific circumstances.

Claims

1. A precast staircase installation and connection structure, characterized in that It includes a precast staircase, an upper ladder beam and a lower ladder beam. The upper ladder beam is provided with upper lugs, and the lower ladder beam is provided with lower lugs; At the upper and lower ends of the precast staircase, inverted U-shaped steel embedded parts are respectively embedded. The outer sides of the inverted U-shaped steel embedded parts extend out of the upper and lower ends of the precast staircase respectively, and the upper and lower ends of the inner sides are respectively provided with first reinforcing bars embedded in the precast staircase; At the junction of the upper surface of the upper lug and the upper ladder beam, and at the junction of the upper surface of the lower lug and the lower ladder beam, U-shaped steel embedded parts are respectively embedded. The inner sides of the U-shaped steel embedded parts extend out of the inner ends of the upper lug and the lower lug respectively, and the upper and lower ends of the outer sides are respectively provided with second reinforcing bars embedded in the upper lug and the lower lug; The outer sides of the upper and lower inverted U-shaped steel embedded parts are respectively inserted into the U-shaped steel embedded parts to realize the connection of the precast staircase with the upper ladder beam and the lower ladder beam respectively.

2. The precast staircase installation and connection structure according to claim 1, characterized in that, There is an upper vertical gap between the inner side of the upper ladder beam and the outer side of the upper end of the precast staircase, and a grouting material layer is arranged in the upper vertical gap.

3. The precast staircase installation and connection structure according to claim 2, characterized in that, A mortar plugging layer is arranged inside the top of the upper vertical gap, and the mortar plugging layer is arranged above the grouting material.

4. The precast staircase installation and connection structure according to claim 1, wherein, An upper cement mortar leveling layer is arranged between the inner top surface of the upper lug and the outer bottom surface of the upper end of the precast staircase.

5. The precast staircase installation and connection structure according to claim 1, characterized in that, There is a lower vertical gap between the inner side of the lower ladder beam and the outer side of the upper end of the precast staircase, and a polystyrene filling layer is arranged in the lower vertical gap.

6. The precast staircase installation and connection structure according to claim 5, characterized in that, A PE rod is arranged in the polystyrene filling layer.

7. The precast stair installation and connection structure according to claim 5, characterized in that, An injection layer is arranged inside the top of the lower vertical gap, and the injection layer is arranged above the polystyrene filling layer.

8. The precast stair installation and connection structure according to claim 1, characterized in that, A lower cement mortar leveling layer is arranged between the inner top surface of the lower lug and the outer bottom surface of the lower end of the precast staircase.

9. The precast staircase installation and connection structure according to claim 8, characterized in that, A felt layer is arranged inside the top of the lower horizontal gap, and the felt layer is arranged above the lower cement mortar leveling layer.

10. The precast staircase installation and connection structure according to any one of claims 1-9, characterized in that, The inverted U-shaped steel embedded parts embedded in the upper and lower ends of the precast staircase are respectively arranged in two and are symmetrically distributed; the U-shaped steel embedded parts embedded in the inner ends of the upper lug and the lower lug are respectively arranged in two and are symmetrically distributed.

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