JP2011032664A - Structure for supporting glass plate, glass panel unit, and glass curtain wall - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the slimming down of a frame material by surely bearing a horizontal inertia force, applied to a glass plate during earthquakes, by the frame material, even when the glass plate increases in weight by upsizing. <P>SOLUTION: In this structure for supporting the glass plate, the glass plate G constituting a wall surface of a glass curtain wall 10 is supported by the frame material 14 which is provided on the periphery of the glass plate G. An inertia force transfer member 16 as a rigid member, which transfers the horizontal inertia force F, applied to the glass plate G during the earthquakes, to a horizontal member 14A of vertical and horizontal members 14B and 14A constituting the frame material 14, is provided so that the glass plate G can be supported by the horizontal member 14A via the inertia force transfer member 16. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glass plate support structure, a glass unit, and a glass curtain wall, and more particularly, to a countermeasure technique for a horizontal inertia force applied to the glass plate during an earthquake.

  As one type of building outer wall construction method, there is a curtain wall structure in which pillars and beams are mainly structured, and the wall is regarded as an exterior material or a partition material with the outside. As a method for constructing this curtain wall, a unit type and a knockdown type are known. In the former, frame materials such as vertical (longitudinal) and plain (horizontal) are assembled in advance into a panel material at the factory to form a unit, and the unit produced in this way is used as the construction site at the construction site. Bring them together and build a curtain wall. On the other hand, the latter brings a structural member such as a vertical or invisible to the construction site as it is, and constructs a curtain wall by assembling the vertical and invisible at the construction site and assembling the panel material. Examples of the former include Patent Documents 1 to 3, and examples of the latter include Patent Document 4.

  And what uses a glass plate as a panel material is a glass curtain wall, and the wall surface of a building is comprised by arrange | positioning the glass panel unit which assembled | attached the glass plate to the frame material adjacent to the vertical direction and / or horizontal direction. .

  In the glass panel unit, as a method of holding the glass plate on the frame material, as shown in Non-Patent Document 1, a sealing material method in which a sealing material is provided between the glass plate and the frame material, and no sealing material is provided. There is a gasket method using rubber or the like. In the latter case, a rubber block material is provided between the vertical plate of the frame material and the small edge surface of the glass plate, mainly for buffering at the time of contact between the frame material and the glass.

  As a trend of today's glass curtain walls, both the sealing method and the gasket method tend to make the frame material of the glass panel unit thinner and slim from the viewpoint of openness and design.

By the way, when designing a glass curtain wall, a seismic design that can sufficiently secure the horizontal inertial force that the glass plate receives during an earthquake is required. Specifically, as shown in Non-Patent Document 2, it is required that the design horizontal seismic intensity K _H = 1.0 with respect to the horizontal inertia force, which is the horizontal inertia force corresponding to the weight of the glass plate. Can be supported by a frame material.

  However, the slimness of the frame material improves the feeling of opening and the design, but the rigidity of the frame material is lowered, so that there is a problem that the rigidity resistance when a horizontal inertia force is applied cannot be secured.

For example, FIG. 9 shows the horizontal direction of the glass panel unit 3 in which the frame material 1 is made of a thick material that is not slimmed, and the peripheral edge portion of the glass plate 2 and the frame material 1 are joined by a sealing material (not shown). This is a case where inertial force F is applied. In this case, the horizontal inertia force F is transmitted to the vertical member 1A of the frame member 1 through the sealing material, and the horizontal inertia force F is supported by the reaction force f of the vertical member 1A. However, since the vertical member 1 is thick and has high rigidity, it does not deform. Therefore, even if the horizontal inertia force F is supported by the longitudinal member 1, the design horizontal seismic intensity K _H = 1.0 can be secured. Reference numeral 1 </ b> B is a cross member of the frame member 1.

FIG. 10 shows a horizontal inertial force applied to a glass panel unit 3 in which the frame material 1 is slimmed and a thin material is used, and the peripheral edge portion of the glass plate 2 and the frame material 1 are joined by a seal material (not shown). This is the case when F is added. Also in this case, the horizontal inertia force F is transmitted to the vertical member 1A of the frame member 1 through the sealing material, and the horizontal inertia force is supported by the reaction force f of the vertical member 1A. However, since the frame member 1 is thin and has low rigidity, the vertical member 1A is deformed without being able to support the horizontal inertial force F by the vertical member 1A. Therefore, the design horizontal seismic intensity K _H = 1.0 cannot be secured.

As shown in FIG. 11, when the frame material 1 is made thin when there is no sealing material at the peripheral edge of the glass 2 and only the rubber block 4 that absorbs the contact force of the glass plate 2 is present at the upper and lower portions of the vertical material 1A. Is more serious and the horizontal inertia force F cannot be supported by the longitudinal member 1A. That is, the design horizontal seismic intensity K _H = 1.0 cannot be secured.

Japanese Patent Laid-Open No. 7-180246 JP 2006-152560 A JP 2005-155178 A Japanese Patent Laid-Open No. 2001-140390 "Glass curtain wall option joint", page 8, published by Shokokusha Co., Ltd., published on November 10, 1987, first edition "Architectural Standard Use Document / Comment, JASS14, Curtain Wall Construction", pages 48-49, published by the Architectural Institute of Japan, April 20, 2006 (2nd edition, 5th print)

  Therefore, when the frame member, particularly the vertical member, is slimmed, there is a problem that the size and weight of the glass plate constituting the glass curtain wall must be limited.

  However, glass plates tend to be larger and heavier from the viewpoints of openness and design, and it is required that the inertial force in the horizontal direction can be reliably supported by a frame material even when the glass plate is larger and heavier. For example, some large glass plates have a width of 1800 × length 3600 and a weight of 400 kg, and a structural design capable of supporting a horizontal inertial force corresponding to 400 kg is required.

  The present invention has been made in view of such circumstances, and even if the glass plate becomes larger and heavier, it can reliably support the horizontal inertial force applied to the glass plate in the event of an earthquake with the frame material. An object of the present invention is to provide a glass plate support structure, a glass unit, and a glass curtain wall which can be slimmed.

  In order to achieve the above object, the present invention provides a glass plate that constitutes a wall surface of a building, a frame member that is provided around the glass plate and includes vertical and cross members, and the glass plate receives during an earthquake. An inertial force transmitting member made of a rigid member that transmits a horizontal inertial force to the transverse member of the frame member, and the glass plate is supported by the transverse member via the inertial force transmitting member. A glass plate support structure is provided.

  According to the glass plate support structure of the present invention, when a horizontal inertial force is applied to the glass plate constituting the wall surface of the building due to an earthquake or the like, the horizontal inertial force is an inertial force transmission member made of a rigid member. It is transmitted to the cross member through.

  Thereby, the horizontal direction inertial force added to a glass plate can be received in the axial center direction of the cross member which can ensure high rigidity. Therefore, even if the glass plate becomes larger and heavier, the horizontal inertia force can be reliably supported by the cross member, and it is not necessary to excessively increase the rigidity of the vertical member, so that the vertical member can be thinned. Thereby, since a frame material can be slimmed, the open feeling and design property of the support structure of a glass plate can be aimed at.

  Here, the rigid member refers to a material having a strength that can withstand the generated stress without causing harmful deformation (deformation incapable of function expression) when a horizontal inertia force is applied.

  In the glass plate support structure of the present invention, the inertial force transmission member includes a first member joined to the glass plate, a second member supported by the cross member, the first and the first members. It is preferable that each of the two members is provided with a fitting portion that detachably fits the first and second members.

  As described above, as the inertial force transmission member, the first support member joined to the glass plate and the second member supported by the cross member of the frame member can be detachably attached to each other via the fitting portions. Since it was set as the structure fitted, a glass plate can be easily assembled | attached to a frame material. Therefore, the construction for constructing the glass curtain wall is facilitated.

  In the glass plate support structure of the present invention, the glass plate is a multi-layer glass, and the first member is an L-shape connecting a vertical spacer material and a horizontal spacer material which are spacers of the multi-layer glass. It is preferable that the fitting portion is formed on a corner key.

  This specifies a preferable glass form to which the support structure of the present invention is applied, and it is preferably applied to a multilayer glass. The multi-layer glass has a structure in which a spacer is interposed along the peripheral edge of the two glass plates in order to secure a space between the two glass plates, and the spacer is hollow to be filled with the desiccant. It is formed. Therefore, the first member has a configuration in which a fitting portion is formed on an L-shaped corner key, and the frame is simply inserted into the hollow of the vertical spacer and the hollow of the horizontal spacer that are the spacers of the double-glazed glass. The material and the first member can be easily formed at a time. In addition, since most of the corner keys are inserted and hidden in the hollow of the spacer, the design is improved and the support structure can be made compact. Furthermore, since the first member can be formed as a part of the corner key, no special member is required as the first member, and an increase in the number of parts can be prevented.

  In the glass plate support structure of the present invention, in the case of the multi-layer glass, the first member is preferably provided with an abutment plate that abuts against the edge surface of the glass plate.

  In the case of double-glazed glass, the spacer and the peripheral edge of the glass plate are bonded with an adhesive, so that the horizontal inertia force is transmitted to the horizontal spacer via the adhesive. However, since the adhesive is easily elastically deformed, it is difficult to reliably transmit the horizontal inertia force to the cross member.

  In the present invention, since the first member is provided with a contact plate with which the small edge surface of the glass plate contacts, the horizontal inertia force is transmitted to the inertia force transmission member via the contact plate without using the adhesive. The inertial force transmission member is transmitted to the cross member. Thereby, a horizontal inertia force can be reliably transmitted to a cross member.

  In the glass plate support structure of the present invention, the glass plate is laminated glass, and the supported portion of the first member joined to the glass plate is composed of two glass plates constituting the laminated glass. It is preferable to be sandwiched.

  This specifies another preferred glass form to which the support structure of the present invention is applied, and is preferably applied to laminated glass. Since the laminated glass has a structure in which a resin intermediate film is sandwiched between two glass plates, the first member can be supported on the glass plate using this sandwiching structure. Thereby, a special support jig for supporting the first member on the glass plate is not required, and the supported portion of the first member does not protrude to the outside of the glass plate, so that the design is improved.

  In order to achieve the above object, the present invention provides a glass panel unit comprising a glass plate support structure according to any one of claims 1 to 5, wherein a glass plate and a frame member are assembled together in advance. To do.

  According to the glass panel unit of the present invention, since it is constituted by the glass plate support structure according to any one of claims 1 to 5, even if the glass plate becomes large and heavy, the horizontal direction during an earthquake The inertia force can be reliably supported by the cross member.

  In order to achieve the above object, the present invention provides a glass curtain wall in which the glass panel unit according to claim 6 is arranged adjacent to each other in the vertical direction and / or the horizontal direction to form a wall surface.

  According to the glass curtain wall of the present invention, the glass panel unit according to claim 6 is arranged adjacent to each other in the vertical direction and / or the horizontal direction so that the wall surface is configured. The horizontal inertia force can be reliably supported by the frame material.

  Therefore, since the glass panel unit and the glass curtain wall provided with the glass plate support structure of the present invention can slim the frame material, it is possible to further improve the open feeling and the design.

  As described above, according to the glass plate support structure of the present invention, even if the glass plate becomes large and heavy, the horizontal inertia force applied to the glass plate during an earthquake can be reliably supported by the frame material, The material can be slimmed down.

  Therefore, the glass panel unit and the glass curtain wall made of the glass plate support structure of the present invention can make the frame material slim, thereby further improving the open feeling and the design.

  In addition, although this invention was made | formed with respect to the in-plane horizontal direction inertia force at the time of an earthquake, the following effect can be anticipated simultaneously by the function brought about by this invention. That is, it is possible to support a glass in-plane direction force generated during transportation, construction, and the like, and it is possible to prevent excessive frame deformation during absorption of interlayer deformation angles.

External perspective view of glass curtain wall The perspective view of the glass panel unit of embodiment Exploded view of main components of glass plate support structure of the present invention Main part assembly drawing of glass plate support structure of the present invention (A) is front sectional drawing of the inertial force transmission member which is the principal part of the support structure of the glass plate of this invention, (B) is in the inertial force transmission member which is the principal part of the support structure of the glass plate of this invention. Longitudinal sectional view along line AA in FIG. The conceptual diagram explaining the effect | action of the support structure of the glass plate of this invention This is a case where a contact plate is provided on the glass plate support structure of the present invention, and is a horizontal cross-sectional view of the main part along the line BB in FIG. The principal part longitudinal cross-sectional view which shows the shape of the inertial force transmission member at the time of using a laminated glass as an aspect of a glass plate Conceptual diagram explaining the relationship between the horizontal inertia force and the frame material when the frame material is not slimmed in the prior art Conceptual diagram explaining the relationship between the horizontal inertia force and the frame material when the frame material is slimmed down in the prior art The conceptual diagram explaining the relationship between the horizontal direction inertia force and frame material in another aspect at the time of slimming a frame material in a prior art

  Hereinafter, preferred embodiments of a glass plate support structure, a glass panel unit, and a glass curtain wall according to the present invention will be described with reference to the accompanying drawings. In addition, in this Embodiment, it demonstrates below with the example of the optimal multi-layer glass for utilizing the support structure body of the glass plate of this invention as a form of a glass plate.

  FIG. 1 shows a glass curtain wall 10 in which the outer wall of a building is formed of a glass plate, and FIG. 2 is an enlarged view of glass panel units 12, 12... Is.

  As shown in FIGS. 1 and 2, the glass curtain wall 10 includes glass panel units 12, 12... In which a frame member 14 is integrally assembled on the peripheral ends of glass plates 20 and 22 constituting the multilayer glass G. It is constructed by arranging adjacently in the horizontal and vertical directions.

  And the glass panel unit 12 is comprised by the support structure of the glass plate of this invention, and the inertial force transmission member 16 which is the characterizing part of this invention is provided in the glass panel unit 12. FIG.

  3 and 4 are diagrams in which an inertial force transmission member 16 is provided in the upper left corner portion of the glass panel unit 12, and the lower left, upper right, and lower right corner portions of the glass panel unit 12 as shown in FIG. Are preferably provided in the same manner.

  As shown in FIGS. 3 and 4, the rectangular glass G (see FIGS. 1 and 2) has a glass plate 20 between two glass plates 20, 22 in order to secure the hollow layer 18. A rectangular ring-shaped spacer 24 having substantially the same size as 22 is arranged so as to be sandwiched. The spacer 24 ensures the space between the hollow layers 18. The spacer 24 is usually formed of a metal member formed of aluminum, and a low moisture-permeable sealing material (primary seal) 26 such as a butyl seal is provided between the side surface of the spacer 24 and the glass plates 20 and 22 (see FIG. 5 (B), see FIG. 7). In addition, the space defined by the peripheral edges of the glass plates 20 and 22 that are spaced apart and the spacer 24 is sealed with an adhesive (secondary seal) 28 (see FIGS. 5B and 7). The spacers 24 and the glass plates 20 and 22 are bonded and integrated to restrain and hold the glass plates 20 and 22.

  The spacer 24 is formed in a hollow shape so as to fill the inside with a desiccant, and an L-shaped corner key 30 (first member) which is one component constituting the inertial force transmission member 16 using the hollow space. ) Is integrated into the multilayer glass G. That is, as shown in FIG. 3, the spacer 24 is separated into two vertical spacers 24A (one is not shown) and two horizontal spacers 24B (one is not shown). The corner key 30 is formed in an L shape by a horizontal plate 30A and a vertical plate 30B. As a result, the horizontal plate 30A of the corner key 30 is inserted into the hollow of the horizontal spacer 24B, and the vertical plate 30B is inserted into the hollow of the vertical spacer 24A. Similarly, by inserting the corner key 30 in the lower left, upper right, and lower right corner portions of the glass panel unit 12, the two vertical spacers 24A and the two horizontal spacers 24B are connected to form a rectangular ring shape. A spacer 24 is formed. Thereby, the corner key 30 is supported by the multilayer glass G through the spacer 24. In this case, most of the corner keys 30 are inserted into the spacers 24 and hidden, so that the design is improved and the support structure can be made compact.

  The corner keys 30 that connect the four corners of the spacer 24 are each formed with a concave fitting portion 30C. 3 and 4 show the upper left corner portion of the glass panel unit 12, the concave fitting portion 30C is formed on the upper surface of the corner key 30, but in the lower left corner portion, the concave fitting portion 30C is It is formed on the lower surface of the corner key 30.

  On the other hand, the frame member 14 is composed of a cross member 14A and a vertical member 14B (see FIG. 4). The cross member 14A is supported by the vertical member 14B, and the vertical member 14B is supported by a fastener (not shown) or the like. It is fixed to a housing (not shown). A T-shaped key 34 (second member), which is one part constituting the inertial force transmission member 16, is supported on the cross member 14 </ b> A of the frame member 14. The T-shaped key 34 is formed in a T shape by a horizontal plate 34A and a convex fitting portion 34B hanging from the horizontal plate 34A. The corner key 30 and the T key 34 are formed of a rigid member, and are preferably formed of a metal such as aluminum or steel.

  Then, the convex fitting portion 34B of the T-key 34 is fitted into the concave fitting portion 30C of the corner key 30. Accordingly, as shown in FIGS. 5A and 5B, the multilayer glass G is supported by the cross member 14 </ b> A via the inertial force transmission member 16.

  By configuring the glass panel unit 12 as described above, when a horizontal inertia force is applied to the glass plates 20 and 22 of the multilayer glass G due to an earthquake or the like, the horizontal inertia force is an inertial force transmission that is a rigid member. It is transmitted to the cross member 14 </ b> A through the member 16. As a result, as shown in FIG. 6, a reaction force f is generated in the axial direction of the cross member 14A with respect to the horizontal inertia force F applied to the glass plate 20 (22). Therefore, since the horizontal inertia force F can be received in the axial direction of the cross member 14A that can ensure high rigidity, the horizontal inertia force F is increased even if the glass plate 20 (22) becomes large and heavy. Can be reliably supported by the cross member 14A. Thereby, since the vertical member 14B can be slimmed, the entire frame member 14 can be slimmed as a result.

  In this case, the concave fitting part 30C of the corner key 30 and the convex fitting part 34B of the T-shaped key 34 do not need to be closely fitted without a gap, and the multilayer glass G is attached to or detached from the frame member 14. In doing so, a gap may be provided so that the corner key 30 and the T-shaped key 34 can be easily attached and detached. Moreover, although the concave fitting part 30C was formed in the corner key 30, and the convex fitting part 34B was formed in the T-shaped key 34, the convex fitting part (equivalent to 34B) is formed in the corner key 30. In addition, a concave fitting portion (corresponding to 30C) may be formed in the T-shaped key 34.

  Further, as shown in FIGS. 3 and 4, the corner key 30 has a small edge surface of the two glass plates 20 and 22 constituting the multilayer glass G (FIG. 3 and FIG. 4 are the left edge surface of the glass plate). It is preferable to provide an abutment plate 36 that abuts on the surface. The contact plate 36 has a length corresponding to the thickness of the multi-layer glass G and has a hole 36A formed at the center, and is screwed and fixed to a female screw 30D formed on the corner key 30 by a screw 38. The contact plate 36 is formed of a rigid member, like the corner key 30 and the T-type key 34, and is preferably formed of a metal such as aluminum or steel. Further, it is more preferable to attach a mat 36B formed of an elastic material such as rubber as a cushion material to the surface of the contact plate 36 on the side of the glass plates 20 and 22.

  In the case of the multi-layer glass G, a space defined by the spacer 24 and the peripheral edges of the glass plates 20 and 22 is sealed with an adhesive 28 to bond and integrate the spacer 24 and the glass plates 20 and 22. Thus, the horizontal inertia force F applied to the multi-layer glass G is transmitted to the lateral spacer 24B via the adhesive 28, and is transmitted from the lateral spacer 24B to the lateral member 14A via the inertial force transmitting member 16. . Therefore, in the transmission path of the horizontal inertia force F, there is an adhesive 28 that requires a large cross section and a bonding area in order to sufficiently transmit stress without harmful deformation, and the horizontal inertia force F is reduced. It is difficult to reliably transmit to the cross member 14A.

  However, because the corner key 30 is provided with the contact plate 36 with which the small edge surfaces of the glass plates 20 and 22 come into contact, the horizontal inertia force F can be transmitted to the cross member 14A without using the adhesive 28. That is, as shown by the arrow A in FIG. 7, the path through which the horizontal inertia force F is transmitted is transmitted to the abutment plate 36 by the horizontal inertia force F applied to the glass plates 20 and 22. 30 and the T-shaped key 34 to be transmitted to the cross member 14A. Therefore, since the transmission path for transmitting the horizontal inertia force F is entirely composed of a rigid member, the horizontal inertia force F can be reliably transmitted to the cross member 14A.

  In the embodiment described above, the glass panel unit 12 is configured to detachably fit the inertial force transmission member 16 with the concave fitting portion 30C of the corner key 30 and the convex fitting portion 34B of the T-key 34. did. However, the original purpose of the inertial force transmitting member 16 may be a structure that transmits the horizontal inertial force F applied to the glass plates 20 and 22 to the cross member 14A. Therefore, the corner key 30 and the T-shaped key 34 may be integrally configured if the convenience when attaching or removing the multilayer glass G to or from the frame member 14 is ignored. In addition, since the corner key 30 that does not have a fitting portion and the T-key that does not have a fitting portion are connected by a bolt or the like, since they can be attached and detached, the convenience during construction can be considered.

  Moreover, in embodiment mentioned above, although the glass panel unit 12 which assembled | attached the frame material 14 to the sheet glass G of 1 sheet was illustrated, the support structure of the glass plate of this invention is single layer glass or a laminated glass. Can also be applied. In particular, as shown in FIG. 8, in the case of a laminated glass 40, since an intermediate film 46 made of resin is sandwiched between two glass plates 42, 44, an inertial force transmission member is utilized using this sandwiching structure. Can be supported on the laminated glass plate 40. In this case, as shown in FIG. 8, the first member 48 is formed in a plate shape, the upper part is a convex fitting part, and the lower part is an intermediate film on two glass plates 42 and 44 of laminated glass 40. Adhere and clamp using 46 etc. On the other hand, the second member 50 is formed in a concave shape and is fitted to the upper portion of the first member. Thereby, the inertial force transmission member 16 for laminated glass can be comprised.

  In addition, the glass plate support structure of the present invention is a gasket in which the horizontal inertia force F tends to concentrate on the vertical members of the frame material among the sealing material method and the gasket method described as the glass plate holding method in the prior art. The effect can be particularly exerted by applying the method.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the present invention is not limited to the above-described embodiments, and various design changes and the like can be made without departing from the scope of the present invention. Is possible.

  DESCRIPTION OF SYMBOLS 10 ... Glass curtain wall, 12 ... Glass panel unit, 14 ... Frame material, 14A ... Cross member, 14B ... Vertical member, 16 ... Inertial force transmission member, 18 ... Hollow layer of multilayer glass, 20, 22 ... Glass plate, 24 ... Spacer, 24A ... Vertical spacer, 24B ... Horizontal spacer, 26 ... Sealing material, 28 ... Adhesive, 30 ... Corner key, 30C ... Concave fitting part of the corner key, 34 ... T key, 34A ... T key Horizontal plate, 34B ... convex fitting part of T-type key, 36 ... contact plate, G ... double glazing, F ... horizontal inertia force

Claims (7)

A glass plate constituting the wall of the building;
A frame member provided around the glass plate and made of a longitudinal member and a transverse member;
An inertial force transmission member made of a rigid member that transmits a horizontal inertial force that the glass plate receives during an earthquake to a transverse member of the frame member, and the glass plate is configured to pass through the inertial force transmission member. A support structure for a glass plate, which is supported by a cross member. The inertial force transmission member is
A first member joined to the glass plate;
A second member supported by the cross member;
The glass plate according to claim 1, further comprising: a fitting portion that is provided on each of the first and second members and detachably fits the first and second members. Support structure.   The glass plate is a multi-layer glass, and the first member forms the fitting portion in an L-shaped corner key that connects a vertical spacer material and a horizontal spacer material which are spacers of the multi-layer glass. The glass plate support structure according to claim 2, wherein   4. The glass plate support structure according to claim 2, wherein the first member is provided with an abutment plate that abuts against a facet of the glass plate. 5.   The glass plate is laminated glass, and a supported portion of the first member joined to the glass plate is sandwiched between two glass plates constituting the laminated glass. 3. A glass plate support structure according to 2.   A glass panel unit comprising the glass plate support structure according to any one of claims 1 to 5, wherein the glass plate and the frame member are assembled together in advance.   A glass curtain wall in which the glass panel unit according to claim 6 is disposed adjacent to each other in a vertical direction and / or a horizontal direction to constitute a wall surface of a building.

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