Pre-pressing disc spring self-resetting reinforced concrete nuclear cylinder suspension structure

Abstract

The invention discloses a pre-pressing disc spring self-resetting reinforced concrete nuclear cylinder suspension structure. Comprising a foundation, a self-resetting shear wall and a swinging column which are connected with the foundation, a column-wall connecting piece for connecting the self-resetting shear wall and the swinging column, self-resetting connecting beams which are distributed in the vertical direction and are connected with the self-resetting shear wall, a gravity resetting support arranged on the top surface of the self-resetting shear wall, and a roof truss arranged on the top surface of the gravity resetting support, the upper end of the cable anchor is connected with the bottom face of the roof truss, the upper end of the sling is anchored by the lower end of the cable anchor, the cable plate connecting pieces are distributed in the vertical direction and fixed to the sling, and the floor slab is arranged on the cable plate connecting pieces. One end of the viscous damper is hinged to the floor, and the other end of the viscous damper is hinged to the swing column or the self-resetting shear wall arranged in the direction perpendicular to the plane. According to the invention, the post-earthquake self-resetting of the concrete nuclear cylinder suspension structure can be realized, and the economical efficiency and practicability of the self-resetting structure system applied to high-rise buildings can be improved.

Description

Technical Field

[0001] The invention relates to a pre-stressed disc spring self-resetting reinforced concrete core tube suspension structure technology, belonging to the field of civil engineering earthquake resistance. Background Art

[0002] Traditional structures are designed based on the concept of ductility and earthquake resistance. They dissipate earthquake energy through plastic deformation of the main structure. After a strong earthquake, they often suffer serious damage or even collapse. Post-earthquake recovery is difficult and costly. With the development of society, the number of buildings and municipal infrastructure has gradually increased, and the time and cost of post-earthquake recovery have become increasingly huge. In view of this, the concept of resilient cities, which advocates that cities have the ability to recover quickly after disasters, has emerged and has gradually become the research frontier in the field of international earthquake engineering.

[0003] In order to improve the seismic toughness of structures, scholars have developed many self-resetting structural systems with recoverable post-earthquake functions. The self-resetting structural system can achieve the main structure being basically intact after an earthquake by relaxing the constraints between the structural components and between the components and the foundation. However, the existing self-resetting structural systems are all derived from the self-resetting transformation of traditional structures such as frames and frame-shear structures, and inherit the disadvantages of a large number of traditional structural nodes and compression components (especially when applied to high-rise buildings). The connection interface between the load-bearing components at the self-resetting structural node generally needs to be strengthened and a reset energy-absorbing device is added. In addition, compared with traditional structures, self-resetting structures have a greater floor acceleration response due to insufficient energy-absorbing capacity. The harm of excessive floor acceleration will be particularly serious in high-rise buildings with large top floor acceleration. In summary, the existing self-resetting structures have problems such as many connection interfaces and reset energy-absorbing devices, complex structures, and large floor accelerations, which limits their development and application in high-rise buildings.

[0004] The suspension structure is significantly different from traditional structures such as frames and frame-shear structures. It is a novel structural system that is particularly suitable for high-rise buildings. It is composed of cables or hangers that suspend the floor system on the main structure (core tube or giant frame), so its floor system does not have the problem of compression instability. Compared with traditional structures, the suspension structure can significantly save building materials and increase the building's usable area. It can also reduce the building's footprint and obstruction to ground traffic by suspending the floor system off the ground. In addition, the natural frequency of the suspension structure is small, and its floor system can be used as a tuned mass damper to control the vibration of the main structure, with excellent seismic performance. The suspension structure with the above unique advantages has been generally considered to be of great promotion value, and has been applied to hundreds of important buildings so far. Therefore, the development and application of suspension structures is not only theoretically superior and technically feasible, but also can reduce carbon emissions in the construction industry and alleviate the shortage of land for urban construction and transportation. However, previous research on suspension structures has mostly focused on earthquake resistance and seismic isolation, which still cannot prevent damage or destruction of the structure under strong earthquakes. So far, there has been no research on concrete suspension structure systems with recoverable post-earthquake functions, making it difficult to meet the new generation of earthquake resistance requirements. Summary of the invention

[0005] Purpose of the invention: The present invention provides a prestressed disc spring self-resetting reinforced concrete core-tube suspension structure with few structural load-bearing component connection interfaces and reset energy-absorbing devices, simple structure, controlled floor vibration, stable reset energy-absorbing capacity, and economical and practical.

[0006] The technical solution adopted by the present invention is: a pre-stressed disc spring self-resetting reinforced concrete core-tube suspension structure, including a self-resetting shear wall, a swing column, a column-wall connector, a self-resetting connecting beam, a gravity reset support, a roof truss, a cable anchor, a suspension cable, a cable-plate connector, a floor slab, a viscous damper and a foundation;

[0007] The bottoms of the self-resetting shear wall and the rocking column are connected to the foundation, a column-wall connector is provided between the self-resetting shear wall and the rocking column, a self-resetting connecting beam distributed vertically is provided between the two self-resetting shear walls, a gravity reset support is provided on the top surface of the self-resetting shear wall, a roof truss is installed on the gravity reset support, the upper end of the cable anchor is connected to the bottom surface of the roof truss, the upper end of the suspension cable is anchored by the lower end of the cable anchor, the cable-plate connector is distributed vertically and fixed on the suspension cable, the floor slab is placed on the cable-plate connector, the viscous damper is distributed vertically, one end of the viscous damper is hinged to the floor slab, and the other end of the viscous damper is hinged to the rocking column or to the self-resetting shear wall arranged in a direction perpendicular to the plane;

[0008] An inverted triangle support is provided at the bottom of the self-resetting shear wall, and the bottom of the inverted triangle support is hinged to the foundation through a hinged support. The upper crossbeam of the inverted triangle support is connected to the reinforced concrete wall part of the self-resetting shear wall. One end of the upper crossbeam of the inverted triangle support is connected to the upper end of the axial tube through a hinged support. The axial tube passes through the center of the preloaded butterfly spring group 1 and its lower end is connected to the square steel. The side plate of the square steel with a circular hole is connected to the outer groove with a slotted hole of the side plate through a high-strength bolt. The friction plate is clamped between the side plate of the outer groove and the side plate of the square steel. The bottom end of the outer groove is connected to the foundation through a hinged support.

[0009] The bottom of the swing column is provided with a column bottom support connected to the foundation through a screw rod, a conical connector is embedded in the column bottom support, and the top of the conical connector is embedded in the reinforced concrete part of the swing column;

[0010] The column-wall connector comprises a slotted steel plate, a round-hole steel plate and bolts, wherein the slotted steel plate is embedded in the self-resetting shear wall, the round-hole steel plate is embedded in the swing column, and the bolts pass through the round holes of the round-hole steel plate and the slotted holes of the slotted steel plate to connect the two;

[0011] The self-resetting connecting beam comprises two reinforced concrete parts, an axial tube, a preloaded disc spring group, a steel beam with a circular hole and a steel beam with a slotted hole, one of the reinforced concrete parts is embedded in a steel beam with a circular hole, and the other reinforced concrete part is embedded in a steel beam with a slotted hole, the circular hole of the steel beam with a circular hole and the slotted hole of the steel beam with a slotted hole are connected by high-strength bolts, and a friction plate is clamped between the steel plate with a circular hole and the steel plate with a slotted hole, and the axial tube passes through the center of the second preloaded disc spring group and the center of two steel plates with circular holes respectively arranged on the top and bottom surfaces of the steel beam with a circular hole and the steel beam with a slotted hole, and then the two ends are fixed by nuts;

[0012] The gravity reset support includes a bottom steel plate, a concave support, a ball-cone connector and a top steel plate. The bottom steel plate is fixed to the top surface of the self-resetting shear wall by screws. A concave support is welded on the bottom steel plate, and a ball-cone connector is placed on the concave support. The bottom of the ball-cone connector is a large half of an iron ball and the top steel plate is welded on the top, and the roof truss is fixed on the top steel plate.

[0013] Furthermore, the present invention adjusts the reset capacity of the overall structure by adjusting the preload of preloaded disc spring group 1 in the self-resetting shear wall and preloaded disc spring group 2 in the self-resetting connecting beam, and their energy-consuming post-start stiffness can be adjusted by adjusting the size and number of the disc springs in the disc spring group 1 and the preloaded disc spring group 2.

[0014] Furthermore, the present invention can adjust the energy dissipation capacity of the overall structure by adjusting the pre-tightening force of the bolts connecting the square steel and the outer groove in the self-resetting shear wall and the bolts connecting the slotted hole steel plate of the slotted hole steel beam and the round hole steel plate of the round hole steel beam in the self-resetting connecting beam. The overall structure dissipates seismic energy through sliding friction.

[0015] Furthermore, in the present invention, the hinged support at the bottom of the inverted triangle support of the self-resetting shear wall is located on the central axis of the self-resetting shear wall, and the gravity reset support on the top surface of the self-resetting shear wall can be arranged in multiple numbers according to needs.

[0016] Furthermore, in the present invention, the bottom of the conical connecting piece of the rocking column is a majority iron ball embedded in the column bottom support, and this majority iron ball is in close contact with the depression of the column bottom support but not fixed; the rocking column can rock in any direction, but the horizontal and vertical degrees of freedom of the column bottom are constrained.

[0017] Furthermore, in the present invention, the slotted steel plate and the circular steel plate of the column-wall connector can slide relative to each other in the vertical direction, but cannot move relative to each other in the horizontal direction.

[0018] Furthermore, in the present invention, the reinforced concrete part of the self-resetting connecting beam is cast in situ as one with the reinforced concrete wall part of the self-resetting shear wall; the slotted hole steel beam and the circular hole steel beam of the self-resetting connecting beam can slide relative to each other in the vertical direction, but cannot move relative to each other in the horizontal direction.

[0019] Furthermore, in the present invention, the roof truss is a steel grid or a giant hollow prestressed reinforced concrete roof, and the sling is a steel strand sling or a sling made of a fiber-reinforced composite material.

[0020] Beneficial effects: Compared with the existing self-resetting structure, the present invention has the characteristics of less connection interfaces of structural force-bearing components and reset energy-absorbing devices, controlled floor vibration, simple structure, stable reset energy-absorbing capacity, economical and reliable, and also gives the novel suspension structure the recoverability of post-earthquake functions. The pre-stressed disc spring self-resetting reinforced concrete core-tube suspension structure uses a friction device to dissipate the earthquake input energy, and uses a disc spring group with pre-applied compression force as a reset element. By changing the deformation mechanism and energy consumption mode of the ordinary concrete core-tube suspension structure, the post-earthquake self-recovery of the ordinary reinforced concrete core-tube suspension structure is achieved, and the economy and practicality of applying the self-resetting structural system to high-rise building structures are greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the self-resetting shear wall of the present invention;

[0022] Figure 2 It is a schematic diagram of the swing column of the present invention;

[0023] Figure 3This is a schematic diagram of a column-wall connector of the present invention;

[0024] Figure 4 This is a schematic diagram of the self-resetting connecting beam of the present invention;

[0025] Figure 5 It is a cross-sectional schematic diagram of the gravity reset support of the present invention;

[0026] Figure 6 It is a schematic plan view of the self-resetting reinforced concrete core-tube suspension structure of the present invention;

[0027] Figure 7 A three-dimensional schematic diagram of the self-resetting reinforced concrete core-tube suspension structure of the present invention;

[0028] Figure 8 It is a three-dimensional schematic diagram of the self-resetting cylinder of the present invention;

[0029] Fig. 9 It is a three-dimensional schematic diagram of the suspension system of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0031] like Figures 1 to 9 As shown, a prestressed disc spring self-resetting reinforced concrete core-tube suspension structure includes a self-resetting shear wall 1, a swing column 2, a column-wall connector 3, a self-resetting connecting beam 4, a gravity reset support 5, a roof truss 6, a cable anchor 7, a suspension cable 8, a cable-plate connector 9, a floor slab 10, a viscous damper 11 and a foundation 12;

[0032] The bottoms of the self-resetting shear wall 1 and the rocking column 2 are connected to the foundation 12, a column-wall connector 3 is provided between the self-resetting shear wall 1 and the rocking column 2, a self-resetting connecting beam 4 distributed vertically is provided between the two self-resetting shear walls 1, a gravity reset support 5 is provided on the top surface of the self-resetting shear wall 1, a roof truss 6 is installed on the gravity reset support 5, the upper end of the cable anchor 7 is connected to the bottom surface of the roof truss 6, the upper end of the suspension cable 8 is anchored by the lower end of the cable anchor 7, the cable-plate connector 9 is distributed vertically and fixed on the suspension cable 8, the floor slab 10 is placed on the cable-plate connector 9, the viscous damper 11 is distributed vertically, one end of the viscous damper 11 is hinged to the floor slab 10, and the other end of the viscous damper 11 is hinged to the rocking column 2 or to the self-resetting shear wall 1 arranged in a direction perpendicular to the plane;

[0033] The bottom of the self-resetting shear wall 1 is provided with an inverted triangle support 1001, and the bottom of the inverted triangle support 1001 is hinged to the foundation 12 through a hinged support 1002. The upper crossbeam of the inverted triangle support 1001 is connected to the reinforced concrete wall part 1003 of the self-resetting shear wall 1. One end of the upper crossbeam of the inverted triangle support 1001 is connected to the upper end of the axial tube 1004 through a hinged support. The axial tube 1004 passes through the center of the pre-stressed butterfly spring group 1005, and its lower end is connected to the square steel 1006. The side plate of the square steel 1006 with a circular hole is connected to the outer groove 1007 with a slotted hole in the side plate through high-strength bolts. The friction plate is clamped between the side plate of the outer groove 1007 and the side plate of the square steel 1006. The bottom end of the outer groove 1007 is connected to the foundation 12 through a hinged support.

[0034] The bottom of the swing column 2 is provided with a column bottom support 2002 connected to the foundation 12 through a screw rod, and a conical connector 2003 is embedded on the column bottom support 2002, and the top of the conical connector 2003 is embedded in the reinforced concrete part 2001 of the swing column 2;

[0035] The column-wall connector 3 includes a slotted steel plate 3001, a round-hole steel plate 3002 and bolts 3003. The slotted steel plate 3001 is embedded in the self-resetting shear wall 1, and the round-hole steel plate 3002 is embedded in the swing column 2. The bolts 3003 pass through the round holes of the round-hole steel plate 3002 and the slot holes of the slotted steel plate 3001 to connect the two.

[0036] The self-resetting connecting beam 4 includes two reinforced concrete parts 4001, an axial tube 4002, a preloaded disc spring group 4003, a circular hole steel beam 4004 and a slotted hole steel beam 4005, one of the reinforced concrete parts 4001 is embedded in a circular hole steel beam 4004, and the other reinforced concrete part 4001 is embedded in a slotted hole steel beam 4005, the circular hole of the circular hole steel beam 4004 and the slotted hole of the slotted hole steel beam 4005 are connected by high-strength bolts, and a friction plate is clamped between the steel plate with a circular hole and the steel plate with a slotted hole, and the axial tube 4002 passes through the center of the preloaded disc spring group 2 4003 and the center of two circular hole steel plates respectively arranged on the top and bottom surfaces of the circular hole steel beam 4004 and the slotted hole steel beam 4005, and then the two ends are fixed by nuts;

[0037] The gravity reset support 5 includes a bottom steel plate 5001, a concave support 5002, a spherical-conical connector 5003 and a top steel plate 5004. The bottom steel plate 5001 is fixed to the top surface of the self-resetting shear wall 1 by screws. The concave support 5002 is welded to the bottom steel plate 5001, and the spherical-conical connector 5003 is placed on the concave support 5002. The bottom of the spherical-conical connector 5003 is half an iron ball and the top steel plate 5004 is welded to the top. The roof truss 6 is fixed to the top steel plate 5004.

[0038] The preloaded disc spring self-resetting reinforced concrete core-tube suspension structure of the present invention is installed and used in the following manner:

[0039] 1. Assemble the reset energy absorbing device in the self-resetting shear wall and the self-resetting connecting beam according to the designed preload of the preloaded disc spring group and the designed friction force of the friction energy absorbing device, then connect the inverted triangle support of the self-resetting shear wall to the foundation by using hinged supports and screws, hinge the upper end of the reset energy absorbing device of the self-resetting shear wall to the cross beam on the upper part of the inverted triangle support by using hinged supports and the lower end to the foundation, and connect the column bottom support of the rocking column to the foundation by using screws.

[0040] 2. Tie up the steel cages of the self-resetting shear walls, self-resetting connecting beams and rocking columns, and embed the corresponding parts of the column-wall connectors, the reset energy-absorbing devices in the self-resetting connecting beams and the gravity reset supports into the corresponding positions of the steel cages, then support the formwork and pour concrete.

[0041] 3. Place the roof truss on the gravity reset support and secure it to the top plate of the gravity reset support.

[0042] 4. Fix the upper end of the cable anchor to the bottom surface of the roof truss and anchor the lower end to the upper end of the sling. Then use the cable-plate connector to connect the top floor slab and the sling. Continue working downwards until all the floor slabs are installed.

[0043] 5. Use hinged supports and screws to hinge one end of the viscous damper to the floor slab and the other end to the rocking column or the self-resetting shear wall arranged in a direction perpendicular to the plane.

[0044] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A preloaded disc spring self-resetting reinforced concrete core-tube suspension structure, characterized in that: It comprises a self-resetting shear wall (1), a rocking column (2), a column-wall connector (3), a self-resetting connecting beam (4), a gravity reset support (5), a roof truss (6), a cable anchor (7), a suspension cable (8), a cable-plate connector (9), a floor slab (10), a viscous damper (11) and a foundation (12); The bottoms of the self-resetting shear wall (1) and the rocking column (2) are connected to the foundation (12); a column-wall connector (3) is provided between the self-resetting shear wall (1) and the rocking column (2); a self-resetting connecting beam (4) distributed vertically is provided between the two self-resetting shear walls (1); a gravity reset support (5) is provided on the top surface of the self-resetting shear wall (1); a roof truss (6) is installed on the gravity reset support (5); the upper end of the cable anchor (7) is connected to the bottom surface of the roof truss (6); The upper end of the suspension cable (8) is anchored by the lower end of the cable anchor (7), the cable-plate connecting member (9) is vertically distributed and fixed on the suspension cable (8), the floor slab (10) is placed on the cable-plate connecting member (9), the viscous damper (11) is vertically distributed, one end of the viscous damper (11) is hinged to the floor slab (10), and the other end of the viscous damper (11) is hinged to the rocking column (2) or to a self-resetting shear wall (1) arranged in a direction perpendicular to the plane; The bottom of the self-resetting shear wall (1) is provided with an inverted triangular support (1001), the bottom of the inverted triangular support (1001) is hinged to the foundation (12) via a hinged support (1002), the upper crossbeam of the inverted triangular support (1001) is connected to the reinforced concrete wall part (1003) of the self-resetting shear wall (1), and one end of the upper crossbeam of the inverted triangular support (1001) is connected to the upper end of the axial tube (1004) via a hinged support. The ends are connected, the axial tube (1004) passes through the center of the preloaded butterfly spring group (1005) and its lower end is connected to the square steel (1006), the side plate with a circular hole in the square steel (1006) is connected to the outer groove (1007) with a slotted hole in the side plate through high-strength bolts, the friction plate is clamped between the side plate of the outer groove (1007) and the side plate of the square steel (1006), and the bottom end of the outer groove (1007) is connected to the foundation (12) through a hinged support; The bottom of the swing column (2) is provided with a column bottom support (2002) connected to the foundation (12) through a screw rod, and a conical connecting piece (2003) is embedded on the column bottom support (2002), and the top of the conical connecting piece (2003) is embedded in the reinforced concrete part (2001) of the swing column (2); The column-wall connector (3) comprises a slotted steel plate (3001), a round-hole steel plate (3002) and a bolt (3003); the slotted steel plate (3001) is embedded in the self-resetting shear wall (1); the round-hole steel plate (3002) is embedded in the swing column (2); and the bolt (3003) passes through the round hole of the round-hole steel plate (3002) and the slot hole of the slotted steel plate (3001) to connect the two. The self-resetting connecting beam (4) comprises two reinforced concrete parts (4001), an axial tube (4002), a preloaded disc spring group (4003), a steel beam with a circular hole (4004) and a steel beam with a slotted hole (4005), one of the reinforced concrete parts (4001) is embedded in a steel beam with a circular hole (4004), and the other reinforced concrete part (4001) is embedded in a steel beam with a slotted hole (4005), the circular hole of the steel beam with a circular hole (4004) and the slotted hole of the steel beam with a slotted hole (4005) are connected by high-strength bolts, and a friction plate is clamped between the steel plate with a circular hole and the steel plate with a slotted hole, and the axial tube (4002) passes through the center of the second preloaded disc spring group (4003) and the centers of two steel plates with circular holes respectively arranged on the top and bottom surfaces of the steel beam with a circular hole (4004) and the slotted hole (4005), and then the two ends are fixed by nuts; The gravity reset support (5) comprises a bottom steel plate (5001), a concave support (5002), a ball-cone connector (5003) and a top steel plate (5004); the bottom steel plate (5001) is fixed to the top surface of the self-resetting shear wall (1) by screws; the concave support (5002) is welded to the bottom steel plate (5001); the ball-cone connector (5003) is placed on the concave support (5002); the bottom of the ball-cone connector (5003) is a large half of an iron ball and the top is welded to the top of the top steel plate (5004); the roof truss (6) is fixed to the top steel plate (5004).

2. The preloaded disc spring self-resetting reinforced concrete core-tube suspension structure according to claim 1 is characterized in that: The reset capability of the overall structure is adjusted by adjusting the preload of the preloaded disc spring group 1 (1005) in the self-resetting shear wall (1) and the preloaded disc spring group 2 (4003) in the self-resetting connecting beam (4), and the energy-dissipating post-start stiffness of the self-resetting shear wall (1) and the self-resetting connecting beam (4) is adjusted by adjusting the size and number of the disc springs in the disc spring group 1 (1005) and the preloaded disc spring group 2 (4003).

3. The preloaded disc spring self-resetting reinforced concrete core-tube suspension structure according to claim 2 is characterized in that: The energy dissipation capacity of the overall structure is adjusted by adjusting the pre-tightening force of the bolts connecting the square steel (1006) and the outer groove (1007) in the self-resetting shear wall (1) and the bolts connecting the slotted hole steel plate of the slotted hole steel beam (4005) and the round hole steel plate of the round hole steel beam (4004) in the self-resetting connecting beam (4), and the overall structure dissipates seismic energy through sliding friction.

4. The preloaded disc spring self-resetting reinforced concrete core-tube suspension structure according to claim 3 is characterized in that: The hinged support at the bottom of the inverted triangle support (1001) of the self-resetting shear wall (1) is located on the central axis of the self-resetting shear wall (1), and a plurality of gravity reset supports (5) are provided on the top surface of the self-resetting shear wall (1).

5. The preloaded disc spring self-resetting reinforced concrete core-tube suspension structure according to claim 4 is characterized in that: The bottom of the conical connecting piece (2003) of the swing column (2) is a majority iron ball embedded in the column base support (2002), and the majority iron ball is in close contact with the depression of the column base support (2002) but is not fixed; the swing column (2) swings in any direction, but the horizontal and vertical degrees of freedom of the column base are constrained.

6. The preloaded disc spring self-resetting reinforced concrete core-tube suspension structure according to claim 5 is characterized in that: The slotted hole steel plate (3001) and the circular hole steel plate (3002) of the column-wall connector (3) slide relative to each other in the vertical direction, but cannot move relative to each other in the horizontal direction.

7. The preloaded disc spring self-resetting reinforced concrete core-tube suspension structure according to claim 6 is characterized in that: The reinforced concrete part (4001) of the self-resetting connecting beam (4) and the reinforced concrete wall part (1003) of the self-resetting shear wall (1) are cast in situ as one; the slotted hole steel beam (4005) and the circular hole steel beam (4004) of the self-resetting connecting beam (4) slide relative to each other in the vertical direction, but cannot move relative to each other in the horizontal direction.

8. The preloaded disc spring self-resetting reinforced concrete core-tube suspension structure according to claim 7 is characterized in that: The roof truss (6) is a steel grid or a giant hollow prestressed reinforced concrete roof, and the sling (8) is a steel strand sling or a sling made of fiber-reinforced composite material.

Images