A precast prestressed double-T slab with air duct function

Abstract

This utility model discloses a precast prestressed double-T slab with air duct function, including a double-T slab top plate and double-T slab ribs. Flat steel embedded parts are embedded in the inner surface of the double-T slab ribs, with two flat steel embedded parts corresponding in height. An L-shaped metal connector is fixed to each flat steel embedded part, including a connecting edge and a bearing edge. The connecting edge is fitted to the double-T slab rib and fixed to the flat steel embedded part. The bearing edge is located at the top of the connecting edge and is horizontally positioned. A fireproof bottom plate for the air duct is laid on the bearing edge of the two L-shaped metal connectors, and the fireproof bottom plate for the air duct is fixedly connected to the bearing edge by bolts. The double-T slab itself serves as the three sides of the air duct. During the fabrication of the double-T slab, flat steel embedded parts are pre-embedded, and then the fireproof bottom plate for the air duct is fixedly installed, forming an integrally assembled precast prestressed double-T slab with air duct function. This saves space and net height, reduces costs, and improves construction efficiency.

Description

Technical Field

[0001] This utility model belongs to the field of precast components, and specifically relates to a precast prestressed double-T slab with air duct function. Background Technology

[0002] Double-T slabs are precast reinforced concrete load-bearing components that combine slab and beam structures. They consist of a wide panel and two narrow, tall ribs and are widely used in various industrial and logistics warehousing buildings that require large spans, high load-bearing capacity, and rapid construction.

[0003] The current technical problems are: double-T slabs typically have high ribs, resulting in significant headroom losses; meanwhile, ventilation and smoke extraction system ducts (such as supply and exhaust ducts, smoke exhaust ducts, and make-up air ducts) with large height requirements are conventionally installed using metal or composite ducts suspended from beams. In practical project applications, this leads to problems such as large headroom losses, high material costs, long construction periods, and numerous overlapping operations, which are not conducive to prefabricated construction and space intensification. Utility Model Content

[0004] This invention provides a precast prestressed double-T slab with ventilation duct functionality, aiming to solve the aforementioned problems caused by the traditional beam-suspended installation of ventilation and smoke extraction ducts in industrial plants, logistics warehouses, and other buildings using double-T slab systems. By integrating the ventilation duct function with the load-bearing structure in the factory prefabrication process, structural-mechanical integration is achieved, saving headroom, reducing costs, and improving assembly efficiency.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a precast prestressed double-T slab with a ventilation duct function, comprising an integral double-T slab top plate and two double-T slab ribs, with horizontally embedded flat steel embedded parts inlaid on the inner side of the double-T slab ribs, the two flat steel embedded parts corresponding in height, and an L-shaped metal connector fixed on the flat steel embedded parts, the L-shaped metal connector including a connecting edge and a bearing edge, the connecting edge fitting against the double-T slab rib and fixed to the flat steel embedded parts, the bearing edge being located at the top of the connecting edge and horizontally arranged, and a ventilation duct bottom fireproof board being erected on the bearing edge of the two L-shaped metal connectors, the ventilation duct bottom fireproof board being fixedly connected to the bearing edge by a bolt.

[0006] By adopting the above technical solution, the structure of the double-T plate itself serves as the three sides of the air duct. Flat steel embedded parts are pre-embedded during the production of the double-T plate, and then the fireproof board at the bottom of the air duct is fixedly installed to form an integrated prefabricated prestressed double-T plate with air duct function, which saves space and net height, reduces costs, and improves construction efficiency.

[0007] Preferably, the top dimension of the double T-plate rib is larger than the bottom dimension, the double T-plate rib is a trapezoidal shape with inclined sides and the inner side is rounded near the top of the double T-plate, the side shape of the bottom fireproof plate of the air duct matches the double T-plate rib, and fireproof sealant is filled between the bottom fireproof plate of the air duct and the double T-plate rib, and fireproof sealant is filled between the bottom fireproof plate of the air duct and the L-shaped metal connector.

[0008] By adopting the above technical solution, it can be applied to the previously common double-T panel, and the fireproof board at the bottom of the air duct has good sealing performance.

[0009] Preferably, the bottom fireproof plate of the air duct is composed of multiple sections spliced ​​together, and the bottom fireproof plates of adjacent air ducts are connected by H-shaped metal clips. The bottom fireproof plates of adjacent air ducts are respectively embedded in the grooves at both ends of the H-shaped metal clips, and the H-shaped metal clips are connected to the bottom fireproof plates of the air ducts by bolts. The junction between the H-shaped metal clips and the bottom fireproof plates of the air ducts is filled with fireproof sealant.

[0010] By adopting the above technical solution, multiple segments can be spliced ​​together, reducing the size of each construction operation, facilitating construction, and ensuring good sealing at the connection.

[0011] Preferably, near the end of the double-T plate rib beam, a flat steel embedded part 1 is vertically provided. An L-shaped metal connector 2 is connected to the flat steel embedded part 1. The receiving edge of the L-shaped metal connector 2 is connected to the fireproof plate at the end of the air duct by bolt 3. The fireproof plate at the end of the air duct seals between the fireproof plate at the bottom of the air duct, the top plate of the double-T plate, and the double-T plate rib beam. The bottom end of the fireproof plate at the bottom of the air duct has a connecting port, and an air duct is connected to the connecting port by a flange. A flat steel embedded part 2 is provided on the top plate of the double-T plate. An L-shaped metal connector 3 is connected to the flat steel embedded part 2. The receiving edge of the L-shaped metal connector 3 is connected to the fireproof plate at the end of the air duct by bolt 4. An L-shaped metal connector 3 is provided between the bottom end of the fireproof plate at the end of the air duct and the fireproof plate at the bottom of the air duct. The L-shaped metal connector 3 is fixedly connected to the bottom end of the fireproof plate at the end of the air duct and the fireproof plate at the bottom of the air duct by bolt 5.

[0012] By adopting the above technical solution, when there are main beams between the air ducts, the air duct functions of the two double T plates can be connected through the air ducts for continuous transmission, thereby forming a complete ventilation system.

[0013] Preferably, fire-resistant sealant is filled between the fireproof plate at the end of the duct and the second L-shaped metal connector, and between the fireproof plate at the end of the duct and the third L-shaped metal connector. The shapes of the two sides of the fireproof plate at the end of the duct match the arc transition of the double-T plate ribs. The second L-shaped metal connector matches the arc transition of the double-T plate ribs. Fire-resistant sealant is filled between the fireproof plate at the end of the duct and the fourth L-shaped metal connector. Fire-resistant sealant is filled between the fireproof plate at the end of the duct and the double-T plate ribs. Fire-resistant sealant is filled between the fireproof plate at the end of the duct and the top plate of the double-T plate. Fire-resistant sealant is filled between the second L-shaped metal connector and the double-T plate ribs. Fire-resistant sealant is filled between the third L-shaped metal connector and the second end plate flat steel embedded part. Fire-resistant sealant is filled between the fourth L-shaped metal connector and the bottom fireproof plate of the duct. The second L-shaped metal connector is welded to the third L-shaped metal connector and the fourth L-shaped metal connector.

[0014] By adopting the above technical solution, fire-resistant sealant is applied around the perimeter of each fireproof board. Fire-resistant sealant is also used to fill the spaces between each L-shaped metal connector and the double-T board, as well as between the fireproof boards, forming a sealed space with good sealing performance. The L-shaped metal connectors are connected to form a whole, exhibiting good stability.

[0015] Preferably, the fireproof board at the bottom of the air duct and the fireproof board at the end of the air duct are both non-combustible inorganic composite boards.

[0016] By adopting the above technical solutions, good fire resistance can be achieved, and suitable materials can be selected according to the fire resistance limit requirements of the air duct application.

[0017] Preferably, the L-shaped metal connector one is welded to the double T-plate rib beam or connected by fastener one, the L-shaped metal connector two is welded to the end plate flat steel embedded part one or connected by fastener two, and the L-shaped metal connector three is welded to the end plate flat steel embedded part two or connected by fastener three.

[0018] By adopting the above technical solutions, welding connections or component connections can be used.

[0019] Preferably, fastener one, fastener two, and fastener three are respectively rear-expanded machine bolts or self-tapping screws.

[0020] By adopting the above technical solution, the L-shaped metal connector and the flat steel embedded part can be fixed by using rear-expanded mechanical bolts or self-tapping screws.

[0021] Preferably, the bolt holes of bolts one, two, and three are filled with fire-retardant sealant, the exposed parts of bolts one, two, and three are sealed with fire-retardant sealant, and fire-retardant gaskets are provided on the inner side of the nuts on bolts one, two, and three.

[0022] By adopting the above technical solution, the bolted connection can achieve good sealing performance and has good fire resistance stability.

[0023] The beneficial effects of this utility model are reflected in the following: the structure of the double T plate itself serves as the three sides of the air duct. When making the double T plate, flat steel embedded parts are pre-embedded in advance, and then the fireproof board at the bottom of the air duct is fixedly installed to form an integrated prefabricated prestressed double T plate with air duct function, which saves space and net height, saves costs, and improves construction efficiency.

[0024] Other features and advantages of this invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention; the main objectives and other advantages of this invention may be realized and obtained by means of the methods particularly pointed out in the description. Attached Figure Description

[0025] Figure 1 This is a front view schematic diagram of an embodiment of the present utility model; Figure 2 This is the connection node between the fireproof board at the bottom of the air duct and the double T-plate rib beam in this embodiment of the utility model; Figure 3 This is an overall schematic diagram of the splicing and connection of the fireproof board at the bottom of the air duct in an embodiment of this utility model; Figure 4 This is a schematic diagram of the connection node of the fireproof board splicing at the bottom of the air duct in an embodiment of this utility model; Figure 5 This is a schematic diagram of the connection of the double-T plate separated by the main beam through the air duct in an embodiment of this utility model; Figure 6 This is a schematic diagram of the installation of the fireproof plate at the end of the air duct according to an embodiment of this utility model; Figure 7 This is a schematic diagram of the installation embedded part of the fireproof plate at the end of the air duct in an embodiment of this utility model; Figure 8 This is a schematic diagram of the installation of the fireproof plate and duct at the end of the air duct according to an embodiment of this utility model; Figure 9 This is an installation node diagram of the fireproof plate at the end of the air duct according to an embodiment of this utility model.

[0026] Attached reference numerals: 1. Double T-plate top plate; 2. Double T-plate rib beam; 3. Flat steel embedded part; 4. L-shaped metal connector one; 5. Connecting edge; 6. Bearing edge; 7. Fastener one; 8. Fireproof board at the bottom of the air duct; 9. Bolt one; 10. Fireproof sealant; 11. H-shaped metal clip; 12. Bolt two; 13. Flat steel embedded part one of the end plate; 14. Fastener two; 15. L-shaped metal connector two; 16. Bolt three; 17. Fireproof board at the end of the air duct; 18. Connecting opening; 19. Air duct; 20. Flat steel embedded part two of the end plate; 21. Fastener three; 22. L-shaped metal connector three; 23. Bolt four; 24. L-shaped metal connector four; 25. Bolt five. Detailed Implementation

[0027] The technical solution of this utility model will be described in detail below through embodiments. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solution of this utility model, and should not be construed as limiting the technical solution of this utility model.

[0028] Combination Figure 1-9 A precast prestressed double-T slab with ventilation duct function includes an integral double-T slab top plate 1 and two double-T slab ribs 2. Flat steel embedded parts 3 are embedded on the inner side of the double-T slab ribs 2 along the horizontal direction. The two flat steel embedded parts 3 are at corresponding heights. An L-shaped metal connector 4 is fixed on the flat steel embedded part 3. The L-shaped metal connector 4 includes a connecting edge 5 and a bearing edge 6. The connecting edge 5 is fitted to the double-T slab rib 2 and fixed to the flat steel embedded part 3. The bearing edge 6 is located at the top of the connecting edge 5 and is set horizontally. A ventilation duct bottom fireproof plate 8 is laid on the bearing edge 6 of the two L-shaped metal connectors 4. The ventilation duct bottom fireproof plate 8 is fixedly connected to the bearing edge 6 by bolts 9.

[0029] The double-T slab itself serves as the three sides of the air duct. When making the double-T slab, flat steel embedded parts 3 are pre-embedded in advance, and then the fireproof board 8 at the bottom of the air duct is fixedly installed to form an integrated prefabricated prestressed double-T slab with air duct function, which saves space and net height, saves costs, and improves construction efficiency.

[0030] The top dimension of the double T-plate rib beam 2 is larger than the bottom dimension. The double T-plate rib beam 2 is a trapezoidal shape with inclined sides and the inner side is rounded near the top plate 1 of the double T-plate. The side shape of the bottom fireproof plate 8 of the air duct matches the double T-plate rib beam 2. Fireproof sealant 10 is filled between the bottom fireproof plate 8 of the air duct and the double T-plate rib beam 2. Fireproof sealant 10 is also filled between the bottom fireproof plate 8 of the air duct and the L-shaped metal connector 4. This design is suitable for double T-plates with common shapes and has good sealing performance.

[0031] The fireproof panel 8 at the bottom of the air duct is composed of multiple segments. Adjacent fireproof panels 8 are connected by H-shaped metal clips 11. Each adjacent fireproof panel 8 is embedded in the grooves at both ends of the H-shaped metal clip 11, and the H-shaped metal clip 11 is connected to the fireproof panel 8 by bolts 12. The junction between the H-shaped metal clip 11 and the fireproof panel 8 is filled with fire-retardant sealant 10. This multi-segment design reduces the size required for each construction step, simplifies construction, and provides good sealing.

[0032] Near the end of the double-T plate rib beam 2, a vertical end plate flat steel embedded part 13 is installed. An L-shaped metal connector 15 is connected to the end plate flat steel embedded part 13. The receiving edge of the L-shaped metal connector 15 is connected to the duct end fireproof plate 17 via bolt 3 16. The duct end fireproof plate 17 is located outside the L-shaped metal connector 15 and seals the space between the bottom fireproof plate 8 of the duct, the top plate 1 of the double-T plate, and the double-T plate rib beam 2. The bottom end of the bottom fireproof plate 8 of the duct has a connecting opening 18. A duct 19 is connected to the top plate 1 via a flange. A flat steel embedded part 20 is installed on the top plate 1. An L-shaped metal connector 22 is connected to the flat steel embedded part 20. The receiving edge of the L-shaped metal connector 22 is connected to the fireproof plate 17 at the end of the duct via bolt 23. An L-shaped metal connector 24 is installed between the bottom end of the fireproof plate 17 at the end of the duct and the fireproof plate 8 at the bottom of the duct. The L-shaped metal connector 24 is fixedly connected to the bottom end of the fireproof plate 17 at the end of the duct and the fireproof plate 8 at the bottom of the duct via bolt 25.

[0033] When there is a main beam between the air ducts, the air duct functions of the two double T plates can be connected through the air ducts, and the air can be continuously transmitted, thus forming a complete ventilation system.

[0034] Fire-resistant sealant 10 is filled between the fireproof plate 17 at the end of the duct and the L-shaped metal connector 25. Fire-resistant sealant 10 is also filled between the fireproof plate 17 at the end of the duct and the L-shaped metal connector 32. The shapes of the two sides of the fireproof plate 17 at the end of the duct match the arc transition of the double T-plate rib beam 2. The L-shaped metal connector 25... Matching the arc transition of the double T-plate rib beam 2, fireproof sealant 10 is filled between the fireproof plate 17 at the end of the air duct and the L-shaped metal connector 24, fireproof sealant 10 is filled between the fireproof plate 17 at the end of the air duct and the double T-plate rib beam 2, fireproof sealant 10 is filled between the fireproof plate 17 at the end of the air duct and the top plate 1 of the double T-plate, fireproof sealant 10 is filled between the L-shaped metal connector 25 and the double T-plate rib beam 2, fireproof sealant 10 is filled between the L-shaped metal connector 322 and the end plate flat steel embedded part 20, fireproof sealant 10 is filled between the L-shaped metal connector 424 and the fireproof plate 8 at the bottom of the air duct, and L-shaped metal connector 215 is welded to L-shaped metal connector 322 and L-shaped metal connector 424 respectively.

[0035] Fire-resistant sealant is applied around the perimeter of each fireproof panel. Fire-resistant sealant is also used to fill the spaces between each L-shaped metal connector and the double-T panel, as well as between the fireproof panels, creating a sealed space with good sealing performance. The L-shaped metal connectors are connected to form a unified whole, providing good stability.

[0036] Both the bottom fireproof board 8 and the end fireproof board 17 of the air duct are non-combustible inorganic composite boards with good fire resistance. Alternatively, a suitable material can be selected based on the fire resistance limit required for the air duct application.

[0037] L-shaped metal connector 14 is welded to double T-plate rib beam 2 or connected by fastener 17; L-shaped metal connector 25 is welded to end plate flat steel embedded part 13 or connected by fastener 24; L-shaped metal connector 32 is welded to end plate flat steel embedded part 20 or connected by fastener 321.

[0038] By adopting the above technical solutions, welding connections or component connections can be used. Fastener 1 (7), Fastener 2 (14), and Fastener 3 (21) are respectively rear-expanded machine bolts or self-tapping screws. The L-shaped metal connector and the flat steel embedded part can be fixed by using rear-expanded machine bolts or self-tapping screws.

[0039] The bolt holes at bolts 1-9, 2-12, and 3-16 are filled with fire-retardant sealant. The exposed portions of bolts 1-9, 2-12, and 3-16 are sealed with fire-retardant sealant. Fire-retardant gaskets are installed on the inner side of the nuts on bolts 1-9, 2-12, and 3-16. The bolt connections can achieve good sealing and have good fire resistance stability.

[0040] Flat steel embedded part 3, end plate flat steel embedded part 13 and end plate flat steel embedded part 20 are fixed by welding the connecting steel bars to the built-in steel bars of the double T plate.

[0041] The L-shaped metal connectors 1 and 4 on both sides and the L-shaped metal connectors 3 and 24 at both ends form a horizontal ring, while the L-shaped metal connectors 3 and 24, L-shaped metal connectors 2 and 15 and L-shaped metal connectors 4 form a vertical ring.

[0042] The preparation process is as follows: two end plate flat steel embedded parts 20 are pre-embedded at both ends of the top plate 1 of the double T plate; two flat steel embedded parts 3 are pre-embedded at the bottom of the two inner sides of the double T plate rib beam 2; four end plate flat steel embedded parts 13 are pre-embedded at both ends of the double T plate rib beam 2; then L-shaped metal connectors are installed by welding or fasteners; and then the bottom fireproof plate 8 and the end fireproof plate 17 of the air duct are installed to form a complete channel.

[0043] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any changes or substitutions that can be conceived by those skilled in the art within the technical scope disclosed in the present utility model should be included within the protection scope of the present utility model.

Claims

1. A prefabricated prestressed double T plate with air duct function, characterized in that: It includes an integral double-T plate top plate (1) and two double-T plate ribs (2). Flat steel embedded parts (3) are embedded on the inner side of the double-T plate ribs (2) along the horizontal direction. The two flat steel embedded parts (3) are at the same height. An L-shaped metal connector (4) is fixed on the flat steel embedded part (3). The L-shaped metal connector (4) includes a connecting edge (5) and a bearing edge (6). The connecting edge (5) is attached to the double-T plate ribs (2) and fixed to the flat steel embedded part (3). The bearing edge (6) is located at the top of the connecting edge (5) and is set horizontally. A fireproof board (8) at the bottom of the air duct is erected on the bearing edge (6) of the two L-shaped metal connectors (4). The fireproof board (8) at the bottom of the air duct is fixedly connected to the bearing edge (6) by bolts (9).

2. A precast prestressed double-T slab with air duct function according to claim 1, characterized in that: The top dimension of the double T-plate rib (2) is larger than the bottom dimension. The double T-plate rib (2) is a trapezoidal shape with both sides inclined and the inner side is a rounded transition near the top plate (1) of the double T-plate. The side shape of the fireproof board (8) at the bottom of the air duct matches the shape of the double T-plate rib (2). Fireproof sealant (10) is filled between the fireproof board (8) at the bottom of the air duct and the double T-plate rib (2). Fireproof sealant (10) is filled between the fireproof board (8) at the bottom of the air duct and the L-shaped metal connector (4).

3. A precast prestressed double-T slab with air duct function according to claim 2, characterized in that: The bottom fireproof board (8) of the air duct is made up of multiple sections spliced ​​together. The adjacent bottom fireproof boards (8) of the air duct are connected by H-shaped metal clips (11). The adjacent bottom fireproof boards (8) of the air duct are respectively embedded in the grooves at both ends of the H-shaped metal clips (11). The H-shaped metal clips (11) and the bottom fireproof boards (8) of the air duct are connected by bolts (12). The junction of the H-shaped metal clips (11) and the bottom fireproof boards (8) of the air duct is filled with fireproof sealant (10).

4. A precast prestressed double-T slab with air duct function according to claim 3, characterized in that: Near the end of the double T-plate rib (2), a flat steel embedded part (13) is vertically installed. An L-shaped metal connector (15) is connected to the flat steel embedded part (13). The receiving edge of the L-shaped metal connector (15) is connected to the fireproof plate (17) at the end of the air duct by bolt (16). The fireproof plate (17) at the end of the air duct seals between the fireproof plate (8) at the bottom of the air duct, the top plate (1) of the double T-plate, and the double T-plate rib (2). The bottom end of the fireproof plate (8) at the bottom of the air duct has a connecting port (18). A duct (19) is connected to the connecting port (18) by a flange. The top plate (1) of the double T plate is provided with a flat steel embedded part 2 (20) for the end plate. The flat steel embedded part 2 (20) for the end plate is connected with an L-shaped metal connector 3 (22). The receiving edge of the L-shaped metal connector 3 (22) is connected to the fireproof plate (17) at the end of the air duct by bolt 4 (23). The bottom end of the fireproof plate (17) at the end of the air duct and the fireproof plate (8) at the bottom of the air duct are provided with an L-shaped metal connector 4 (24). The L-shaped metal connector 4 (24) is fixedly connected to the bottom end of the fireproof plate (17) at the end of the air duct and the fireproof plate (8) at the bottom of the air duct by bolt 5 (25).

5. A precast prestressed double-T slab with air duct function according to claim 4, characterized in that: Fireproof sealant (10) is filled between the fireproof plate (17) at the end of the duct and the L-shaped metal connector two (15), and fireproof sealant (10) is filled between the fireproof plate (17) at the end of the duct and the L-shaped metal connector three (22). The shape of both sides of the fireproof plate (17) at the end of the duct matches the arc transition of the double T-plate rib beam (2). L-shaped metal connector two (15) Matching the arc transition of the double T-plate rib (2), fireproof sealant (10) is filled between the fireproof plate (17) at the end of the air duct and the L-shaped metal connector four (24), fireproof sealant (10) is filled between the fireproof plate (17) at the end of the air duct and the double T-plate rib (2), fireproof sealant (10) is filled between the fireproof plate (17) at the end of the air duct and the double T-plate top plate (1), fireproof sealant (10) is filled between the L-shaped metal connector two (15) and the double T-plate rib (2), fireproof sealant (10) is filled between the L-shaped metal connector three (22) and the end plate flat steel embedded part two (20), fireproof sealant (10) is filled between the L-shaped metal connector four (24) and the fireproof plate (8) at the bottom of the air duct, and the L-shaped metal connector two (15) is welded to the L-shaped metal connector three (22) and the L-shaped metal connector four (24) respectively.

6. A precast prestressed double-T slab with air duct function according to claim 5, characterized in that: The fireproof board (8) at the bottom of the air duct and the fireproof board (17) at the end of the air duct are both non-combustible inorganic composite boards.

7. A precast prestressed double-T slab with air duct function according to claim 6, characterized in that: The L-shaped metal connector one (4) is welded to the double T-plate rib beam (2) or connected by fastener one (7), the L-shaped metal connector two (15) is welded to the end plate flat steel embedded part one (13) or connected by fastener two (14), and the L-shaped metal connector three (22) is welded to the end plate flat steel embedded part two (20) or connected by fastener three (21).

8. A precast prestressed double-T slab with air duct function according to claim 7, characterized in that: The fasteners 1 (7), 2 (14) and 3 (21) are respectively rear-expanded mechanical bolts or self-tapping screws.

9. A precast prestressed double-T slab with air duct function according to claim 8, characterized in that: The bolt holes of bolt 1 (9), bolt 2 (12) and bolt 3 (16) are filled with fireproof sealant. The exposed parts of bolt 1 (9), bolt 2 (12) and bolt 3 (16) are sealed with fireproof sealant. Fireproof sealing gaskets are provided on the inner side of the nuts on bolt 1 (9), bolt 2 (12) and bolt 3 (16).

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