A temporary structure suitable for the end of an assembled station

Abstract

The utility model discloses a kind of suitable for assembly type station end temporary type structure, including the temporary support structure of the setting of field-shaped, temporary support structure is divided into the base support frame of outer ring setting and the cross-shaped inner support frame body between the base support frame, further including the underpinning system of setting in temporary support structure;Through first erecting temporary type steel beam column, the construction method and structure of first support after underpinning, it is suitable for this working condition at the assembly starting point and terminal position of full prefabricated rectangular flat roof assembly type station, this method can solve the problem of conflict in space and time between assembly trolley and temporary steel column, ensure the normal use of assembly trolley, reduce the installation and dismantling workload of temporary steel beam column, speed up construction efficiency under the premise of ensuring assembly quality, and reduce the risk of high-altitude operation, and can also ensure that post-cast beam column system can be normally applied, reduce the installation and dismantling amount of large steel components.

Description

Technical Field

[0001] This utility model belongs to the field of building construction technology. Specifically, this utility model relates to a temporary structure suitable for the finishing end of prefabricated stations. Background Technology

[0002] During the assembly of a fully prefabricated subway station, the end sections cannot form an integral prefabricated beam-column system. Temporary steel beams and columns are needed to replace this system and bear the loads of the middle and top slabs. However, to avoid the beam-column system of the post-cast strip, these temporary steel beams and columns are typically divided in two and placed on both sides of the structural columns. They are used to support the superstructure during the assembly phase, and then removed after the post-cast beams and columns are completed. However, this approach has the following risks and drawbacks: 1. Placing temporary steel beams and columns on both sides of the post-cast beam-column system occupies a significant amount of limited internal space, rendering the core equipment, the assembly trolley, unusable. 2. The inability to use the assembly trolley leads to a decrease in overall assembly accuracy, causing component misalignment, and in severe cases, preventing the next component from being assembled correctly. 3. Dividing the temporary steel beams and columns in two increases the workload of later dismantling. Dismantling large steel components within a limited space is difficult and carries high safety risks.

[0003] A patent application with patent number 201910355831.3 and publication date of January 16, 2024, discloses a prefabricated rail-top ventilation duct for a subway station. The prefabricated rail-top ventilation duct includes a left side wall, a right side wall, a bottom plate, inverted U-shaped reinforcing bars, longitudinal perforations, and longitudinal locking reinforcing bars. The left side wall, right side wall, and bottom plate form a trough-shaped structure. Several inverted U-shaped reinforcing bars are pre-embedded longitudinally in the upper part of the left and right side walls, with the upper part extending beyond the top of the side wall to form a closed loop. These loops are used to insert pins to lift the inverted U-shaped reinforcing bars and embed them integrally into the prefabricated slots of the prefabricated middle plate of the subway station. Longitudinal perforations are longitudinally drilled below the inverted U-shaped reinforcing bars in the left and right side walls of the rail-top ventilation duct for inserting longitudinal locking reinforcing bars, thereby fixing two adjacent prefabricated rail-top ventilation duct sections. This invention solves the problem of difficult construction of ventilation ducts on the top of subway stations, and is simple, convenient, and fast to construct.

[0004] Of the aforementioned issues, issue 1 directly impacts construction feasibility. The trolley requires a large operating space, and the installation of temporary steel beams and columns cannot be carried out simultaneously with the assembly trolley. Furthermore, the timing of their use is sequential, making it impossible to perform trolley assembly operations without removing the temporary steel beams. Issue 2 directly impacts construction quality. The assembly accuracy of components at the beginning and end of the prefabricated station is extremely critical, especially the first ring component, which serves as the reference ring. Inaccurate positioning of this component will lead to significant initial errors that are difficult to eliminate. Issue 3 directly impacts construction efficiency and safety. The removal of temporary steel beams and columns cannot be assisted by cranes and must be done manually, resulting in slow construction efficiency and posing significant safety risks due to the high-altitude nature of the work. Utility Model Content

[0005] The present invention aims to provide a solution that fully utilizes the internal space of the structure, solves the problem of complementary interference between the trolley and the steel beams and columns, and allows for the normal implementation of the post-cast beam and column system in the later stages.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a temporary structure suitable for the end of a prefabricated station, including a temporary support structure arranged in a grid pattern, the temporary support structure being divided into a basic support frame with an outer ring and a cross-shaped inner support frame arranged between the basic support frames, and also including a support system arranged within the temporary support structure.

[0007] The basic support frame consists of a precast base slab, a left precast side wall, a right precast side wall, and a precast top slab that are connected together. The precast top slab is equipped with a top longitudinal beam for supporting the internal support frame. The left and right precast side walls are respectively located between the two ends of the precast base slab and the precast top slab. The internal support frame consists of a precast middle slab that runs through the left and right precast side walls. Temporary support columns are provided on the upper and lower sides of the precast middle slab.

[0008] The temporary support columns are lower temporary steel columns and upper temporary steel columns set on the upper and lower sides of the precast intermediate slab. The precast intermediate slab is provided with lower temporary steel beams and intermediate slab temporary steel beams for connecting the lower temporary steel columns and upper temporary steel columns.

[0009] The temporary support columns are lower temporary steel pipe columns and upper temporary steel pipe columns set on the upper and lower sides of the precast slab. A temporary steel beam for the slab is provided between the upper temporary steel pipe columns and the precast slab.

[0010] The underpinning system includes an upper support system installed within a temporary support structure. The upper support system is divided into a lower disc-lock support frame and transverse and longitudinal distribution beams installed on the lower disc-lock support frame. The longitudinal distribution beams are installed on top of the transverse distribution beams. The transverse and longitudinal distribution beams intersect each other perpendicularly on the horizontal plane and are arranged in an array.

[0011] The lower disc-lock support frame is equipped with inclined bracing and edge protection on both sides. The inclined bracing is set on the temporary support structure, and the edge protection is connected to the temporary support structure.

[0012] The lower disc-lock support frame is equipped with a double-groove support beam at the top, and a lifting cylinder assembly for supporting the transverse distribution beam is provided at the top of the double-groove support beam. A double-groove support beam is provided between the lower disc-lock support frame and the double-groove support beam.

[0013] The precast intermediate plate is equipped with a lifting device for lifting. The lifting device consists of intermediate plate lifting lugs installed on the precast intermediate plate, embedded steel plates for installing the intermediate plate lifting lugs on the precast intermediate plate, wire ropes on the precast intermediate plate, and steel section lifting lugs connected to the ends of the wire ropes. Temporary steel section beams are installed on the steel section lifting lugs.

[0014] The temporary support structure is equipped with a post-cast bottom longitudinal beam and a post-cast top longitudinal beam. The post-cast bottom longitudinal beam is equipped with a post-cast lower column, the post-cast top longitudinal beam is equipped with a post-cast upper column, and the end of the post-cast lower column is equipped with a post-cast middle longitudinal beam.

[0015] A construction method for the finishing stage of a prefabricated railway station, used to build a temporary structure suitable for the finishing stage of a prefabricated railway station, includes the following steps: S1: During the precast bottom slab, precast middle slab, and precast top slab stages, steel plates for fixing steel beams and columns are pre-embedded on the upper and lower surfaces of the structure. The numerical simulation calculation results are used as the accurate position for the steel pre-embedded steel plates. S2: Hoist the steel longitudinal beam to the position of the steel plate embedded in the bottom longitudinal beam, and weld it to the steel plate embedded in the upper surface of the precast base plate. Then install the steel column. S3: Install the underpinning system. The underpinning system erection includes the erection of underpinning supports and the installation of longitudinal and transverse distribution beams. First, the underpinning supports are erected. S4: With the center line of the left and right tensioning holes of the precast top slab as the center, a full-span disc buckle scaffold is erected on both sides. Six rows of five frames are erected horizontally and the scaffold is erected vertically to the center line of the fifth ring of the precast top slab. Steel pipes are used to evenly set up diagonal bracing. S5: Next, install the horizontal and vertical distribution beams. First, lift the I-22 steel into the top support, then lift the I-10 steel onto the top of the I-22 steel. Leave a 10cm gap between the I-10 steel and the lower surface of the precast top slab or precast middle slab. Erect the double-slot support beam of the I-10 steel. Weld hydraulic jacks onto the support beams. The jacks use the double-slot support beams as reaction force support. A total of 2 sets of steel supports are set up. Simultaneously extend the I-22 steel beams every three spans to make the I-10 steel bead tightly against the bottom surface of the slab. Rotate the top support screw to make the top support tightly against the bottom surface of the I-22 steel bead. The two middle rows of I-22 steel beads are then extended to tighten against the bottom surface of the I-10 steel bead. The longitudinal cycle is repeated until all distribution beam systems are tightened. S6: The final dismantling stage is divided into the steel section dismantling stage and the underpinning system dismantling stage. The steel section is dismantled first. After the underpinning system is erected from top to bottom at each end of the second basement level and the first basement level, and there are no monitoring warnings for the structure, the temporary steel beams and columns in the middle can be dismantled. The dismantling is carried out in the order of upper longitudinal beam → steel pipe column → steel section beam and column → steel section support → lower longitudinal beam using a hand chain hoist. During the dismantling process, the hand chain hoist can be used with the help of the pre-embedded sleeves in the precast top slab or the reserved holes in the post-cast beam. S7: After the post-cast beams and columns are completed, remove the support system on both sides in the following order: top support removal → 10# I-beam → 22# I-beam → disc buckle bracket.

[0016] The technical advantages of this invention are as follows: it is applicable to the assembly starting and ending points of a fully rectangular flat-roof prefabricated station. This method can solve the problem of spatial and temporal conflicts between the assembly trolley and the temporary steel columns, ensuring the normal use of the assembly trolley. At the same time, it reduces the workload of installing and dismantling temporary steel beams and columns, speeds up construction efficiency while ensuring assembly quality, and reduces the risks of working at heights. Attached Figure Description

[0017] This manual includes the following figures, which illustrate the following: Figure 1 This is a structural schematic diagram of a temporary structure suitable for the finishing end of a prefabricated station according to the present invention; Figure 2 for Figure 1 A schematic diagram of a temporary steel support system suitable for temporary structures at the end of prefabricated stations; Figure 3 for Figure 1 A schematic diagram of a support system suitable for temporary structures at the end of prefabricated stations; Figure 4 for Figure 1 A schematic diagram of a lifting structure suitable for a temporary structure at the end of a prefabricated station; Figure 5 for Figure 1 A schematic diagram of an upper support system suitable for temporary structures at the end of prefabricated stations.

[0018] The following are marked in the diagram: 1. Precast base slab; 2. Steel pier; 3. Lower temporary steel column; 4. Left precast side wall; 5. Right precast side wall; 6. Lower temporary steel beam of the middle slab; 7. Precast middle slab; 8. Upper temporary steel beam of the middle slab; 9. Upper temporary steel column; 10. Precast top longitudinal beam; 11. Precast top slab; 12. Lower temporary steel pipe column; 13. Upper temporary steel pipe column; 14. Temporary steel beam of the top slab; 15. Lower disc-lock support frame. 16. Diagonal bracing; 17. Edge protection; 18. Horizontal distribution beam; 19. Longitudinal distribution beam; 20. Upper support system; 21. Post-cast bottom longitudinal beam; 22. Post-cast lower column; 23. Post-cast middle longitudinal beam; 24. Post-cast upper column; 25. Post-cast top longitudinal beam; 26. Steel wire rope; 27. Middle plate lifting lug; 28. Temporary steel beam; 29. ​​Steel lifting lug; 30. Embedded steel plate; 31. Double-slot support beam; 32. Disc-lock top support; 33. Lifting cylinder assembly. Detailed Implementation

[0019] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings, in order to help those skilled in the art to have a more complete, accurate and in-depth understanding of the utility model concept and technical solution, and to facilitate its implementation.

[0020] Please see Figure 1-5 A temporary structure suitable for the finishing stage of prefabricated stations includes a temporary support structure arranged in a grid pattern. The temporary support structure is divided into a base support frame with an outer ring and a cross-shaped inner support frame set between the base support frames. It also includes a support system set within the temporary support structure. By first building temporary steel beams and columns, and then supporting and supporting them, the construction method and structure can solve the problem of spatial and temporal conflicts between the assembly trolley and the temporary steel columns, ensuring the normal use of the assembly trolley. At the same time, it reduces the workload of installing and dismantling temporary steel beams and columns, speeds up construction efficiency while ensuring assembly quality, and reduces the risks of working at heights.

[0021] The basic support frame consists of a precast base slab 1, a left precast side wall 4, a right precast side wall 5, and a precast top slab 11, all connected together. The precast top slab 11 is equipped with a top longitudinal beam 10 for supporting the inner support frame. The left precast side wall 4 and the right precast side wall 5 are respectively located between the two ends of the precast base slab 1 and the precast top slab 11. The inner support frame consists of a precast middle slab 7 that runs horizontally between the left precast side wall 4 and the right precast side wall 5. Temporary support columns are provided on the upper and lower sides of the precast middle slab 7. The precast base slab 1 and the precast top slab 11 are located at the upper and lower ends of the left precast side wall 4 and the right precast side wall 5, respectively. The precast base slab 1, the left precast side wall 4, the right precast side wall 5, and the precast top slab 11 form a U-shaped outer frame structure. The precast middle slab 7 is horizontal and serves as a support in the middle of the overall structure.

[0022] The temporary support columns are lower temporary steel columns 3 and upper temporary steel columns 9 set on the upper and lower sides of the precast middle plate 7. The precast middle plate 7 is provided with lower temporary steel beams 6 and middle plate temporary steel beams 8 for connecting the lower temporary steel columns 3 and upper temporary steel columns 9. The temporary support columns are lower temporary steel pipe columns 12 and upper temporary steel pipe columns 13 set on the upper and lower sides of the precast middle plate 7. A top plate temporary steel beam 14 is provided between the upper temporary steel pipe column 13 and the precast top plate 11.

[0023] The underpinning system includes an upper support system 20 installed within a temporary support structure. The upper support system 20 is divided into a lower disc-lock support frame 15 and transverse distribution beams 18 and longitudinal distribution beams 19 installed on the lower disc-lock support frame 15. The longitudinal distribution beams 19 are installed on top of the transverse distribution beams 18. The transverse distribution beams 18 and the longitudinal distribution beams 19 intersect each other perpendicularly on the horizontal plane and are arranged in an array. The underpinning system is used to support the foundation support frame for subsequent pouring and is dismantled after the pouring is completed.

[0024] The lower disc buckle support frame 15 is provided with inclined bracing 16 and edge protection 17 on both sides. The inclined bracing 16 is set on the temporary support structure, and the edge protection 17 is connected to the temporary support structure. The inclined bracing 16 and edge protection 17 are respectively connected to the upper and lower beams and columns of the support system to support the upper support system 20, improve stability, and reduce swaying.

[0025] The lower disc-lock support frame 15 is provided with a double-groove support beam 31 at the top. The top of the double-groove support beam 31 is provided with a lifting cylinder assembly 33 for supporting the transverse distribution beam 18. The double-groove support beam 31 is provided between the lower disc-lock support frame 15 and the double-groove support beam 31 to raise and lower the height of the transverse distribution beam 18 and the longitudinal distribution beam 19 to adapt to the height of the overall structure. The upper support system 20 is provided with a disc-lock top support 32 for fixing the double-groove support beam 31.

[0026] The precast intermediate slab 7 is equipped with a lifting device for lifting. The lifting device consists of an intermediate slab lifting lug 27 installed on the precast intermediate slab 7, an embedded steel plate 30 for installing the intermediate slab lifting lug 27, a wire rope 26 installed on the precast intermediate slab 7, and a steel section lifting lug 29 connected to the end of the wire rope 26. A temporary steel section beam 28 is installed on the steel section lifting lug 29 to lift the temporary steel section beam 28.

[0027] The temporary support structure includes a post-cast bottom longitudinal beam 21 and a post-cast top longitudinal beam 25. The post-cast bottom longitudinal beam 21 is equipped with a post-cast lower column 22, and the post-cast top longitudinal beam 25 is equipped with a post-cast upper column 24. The end of the post-cast lower column 22 is equipped with a post-cast middle longitudinal beam 23; this is the overall structure after casting.

[0028] A construction method for the finishing stage of a prefabricated railway station, used to construct a temporary structure suitable for the finishing stage of a prefabricated railway station, characterized by the following steps: S1: In the stages of precast bottom slab 1, precast middle slab 7, and precast top slab 11, steel plates for fixing steel beams and columns are pre-embedded on the upper and lower surfaces of the structure. The numerical simulation calculation results are used as the accurate position for the steel pre-embedding. The size of the steel plate is related to the size of the steel and steel pipe columns. It can be formed into a uniform size of 900×900×10mm through the longitudinal distribution beam 19. S2: A truck crane is used to lift the double-jointed I-beam 45mm steel longitudinal beam to the position of the steel plate embedded in the bottom longitudinal beam, and weld it to the embedded steel plate on the upper surface of the bottom plate. Then, φ609mm steel pipe columns are installed. φ609mm steel pipe supports and I-beam 45mm steel are used as temporary columns. The double-jointed I-beam 45mm steel serves as the upper and lower longitudinal distribution beams to ensure that the upper components are evenly stressed. When the span is ≥4m, φ609 steel pipe columns are used. When the span is <4m, I-beam 45mm steel is used. When the first bottom longitudinal beam steel is interfered with, a portal pier structure is used to avoid it. The portal pier is made of double-jointed I-beam 45mm steel, and double-jointed I-beam 45mm steel columns are installed on top of the pier. S3: Install the underpinning system. The underpinning system erection includes the erection of the underpinning support and the installation of the longitudinal and transverse distribution beams 18. First, the underpinning support is erected. S4: With the center line of the tensioning holes on the left and right sides of the precast top slab 11 as the center, a full-span disc buckle scaffold is erected on both sides with a spacing of 600mm×600mm×1500mm (horizontal×vertical×step). Six rows of five frames are erected horizontally, and the scaffold is erected vertically to the center line of the fifth ring of the precast top slab 11. Steel pipes are used to evenly set the diagonal bracing 16. The scaffold top support is erected to a position 42cm away from the lower surface of the precast top slab 11 or the precast middle slab 7. S5: Next, install the horizontal and vertical distribution beams. First, lift the I-22 steel into the top support, then lift the I-10 steel onto the top of the I-22 steel. Leave a 10cm gap between the I-10 steel and the lower surface of the precast top slab 11 or precast middle slab 7. Erect the I-10# channel steel double-slot support beam 31. Weld hydraulic jacks onto the support beams. The jacks use the double-slot support beam 31 as reaction force support. Set up 2 sets of steel piers. Simultaneously extend the I-22# steel crossbeams every three spans to make the I-10# steel bead tightly against the bottom surface of the slab. Rotate the top support screw to make the top support tightly against the bottom surface of the I-22# steel bead. Then extend the middle two rows of I-22# steel beads to make them tightly against the bottom surface of the I-10# steel bead. Repeat the longitudinal cycle until all distribution beam systems are tightly supported. S6: The final dismantling stage is divided into the steel section dismantling stage and the underpinning system dismantling stage. The steel section is dismantled first. After the underpinning system is erected from top to bottom at each end of the second basement level and the first basement level, and there are no monitoring warnings for the structure, the temporary steel beams and columns in the middle can be dismantled. The dismantling is carried out in the following order using hand-operated hoists: upper longitudinal beam → steel pipe column → steel section beam and column → steel section support 2 → lower longitudinal beam. During the dismantling process, the hand-operated hoists can be used with the help of the pre-embedded sleeves in the precast top slab 11. For pre-reserved holes in post-cast beams, when dismantling steel beams, use two hand-operated hoists to lift them longitudinally, and use gas welding to directly cut off the column head steel at the beam-column joint. Use an inclined hand-operated hoist to remove the steel and lower it to the ground. Before cutting off the steel column or steel pipe column, use the hand-operated hoist of the precast middle plate 7 or precast top plate 11 to select two lifting points to secure it. After cutting, slowly lower the steel pipe and transport it from the precast bottom plate 1 or precast middle plate 7 to the post-cast strip position for lifting. S7: After the post-cast beams and columns are completed, remove the support system on both sides in the following order: top support removal → 10# I-beam → 22# I-beam → disc buckle bracket.

[0029] The technical advantages of this invention are as follows: it is applicable to the assembly starting and ending points of a fully rectangular flat-roof prefabricated station. This method can solve the problem of spatial and temporal conflicts between the assembly trolley and the temporary steel columns, ensuring the normal use of the assembly trolley. At the same time, it reduces the workload of installing and dismantling temporary steel beams and columns, speeds up construction efficiency while ensuring assembly quality, and reduces the risks of working at heights.

[0030] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution of the present invention; or the direct application of the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A temporary structure suitable for the finishing stage of prefabricated railway stations, characterized in that: It includes a temporary support structure arranged in a grid pattern, which is divided into a basic support frame with an outer ring and a cross-shaped inner support frame arranged between the basic support frames, and also includes a support system arranged within the temporary support structure.

2. A temporary structure suitable for the finishing stage of a prefabricated station according to claim 1, characterized in that: The basic support frame is divided into a precast base plate (1), a left precast side wall (4), a right precast side wall (5) and a precast top plate (11) that are connected together. The precast top plate (11) is provided with a top longitudinal beam (10) for supporting the inner support frame. The left precast side wall (4) and the right precast side wall (5) are respectively set between the two ends of the precast base plate (1) and the precast top plate (11). The inner support frame is divided into a precast middle plate (7) that runs through the left precast side wall (4) and the right precast side wall (5). Temporary support columns are provided on the upper and lower sides of the precast middle plate (7).

3. A temporary structure suitable for the finishing stage of a prefabricated station according to claim 2, characterized in that: The temporary support columns are lower temporary steel columns (3) and upper temporary steel columns (9) set on the upper and lower sides of the precast middle plate (7). The precast middle plate (7) is provided with a lower temporary steel beam (6) and a middle plate temporary steel beam (8) for connecting the lower temporary steel columns (3) and the upper temporary steel columns (9).

4. A temporary structure suitable for the finishing stage of a prefabricated station according to claim 2, characterized in that: The temporary support columns are lower temporary steel pipe columns (12) and upper temporary steel pipe columns (13) set on the upper and lower sides of the precast middle plate (7). A temporary steel beam (14) is provided between the upper temporary steel pipe column (13) and the precast top plate (11).

5. A temporary structure suitable for the finishing stage of a prefabricated station according to claim 1, characterized in that: The support system includes an upper support system (20) set in a temporary support structure. The upper support system (20) is divided into a lower disc buckle support frame (15) and a transverse distribution beam (18) and a longitudinal distribution beam (19) set on the lower disc buckle support frame (15). The longitudinal distribution beam (19) is set on top of the transverse distribution beam (18). The transverse distribution beam (18) and the longitudinal distribution beam (19) intersect each other perpendicularly on the horizontal plane and are arranged in an array.

6. A temporary structure suitable for the finishing stage of a prefabricated station according to claim 5, characterized in that: The lower disc buckle support frame (15) is provided with inclined bracing (16) and edge protection (17) on both sides. The inclined bracing (16) is set on the temporary support structure, and the edge protection (17) is connected to the temporary support structure.

7. A temporary structure suitable for the finishing stage of a prefabricated station according to claim 5, characterized in that: The lower disc buckle support frame (15) is provided with a double groove support beam (31) at the top, and the double groove support beam (31) is provided with a lifting cylinder group (33) for supporting the transverse distribution beam (18) at the top. The lower disc buckle support frame (15) and the double groove support beam (31) are provided with a double groove support beam (31).

8. A temporary structure suitable for the finishing stage of a prefabricated station according to claim 2, characterized in that: The precast middle plate (7) is provided with a lifting device for lifting. The lifting device is divided into a middle plate lifting lug (27) set on the precast middle plate (7). The precast middle plate (7) is provided with a pre-embedded steel plate (30) for installing the middle plate lifting lug (27). The precast middle plate (7) is provided with a wire rope (26). The end of the wire rope (26) is connected to a steel section lifting lug (29). The steel section lifting lug (29) is provided with a temporary steel section beam (28).

9. A temporary structure suitable for the finishing stage of a prefabricated station according to claim 1, characterized in that: The temporary support structure is provided with a post-cast bottom longitudinal beam (21) and a post-cast top longitudinal beam (25). The post-cast bottom longitudinal beam (21) is provided with a post-cast lower column (22), the post-cast top longitudinal beam (25) is provided with a post-cast upper column (24), and the end of the post-cast lower column (22) is provided with a post-cast middle longitudinal beam (23).

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