JP2004324322A - Aseismic reinforcing strengthening structure for steel frame and method of reinforcing construction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate welding which needs an advanced skill in assembling steel frames and to avoid using an expensive H-steel in a frame. <P>SOLUTION: A gusset plate 7 for attaching a brace 4 has a number of bolt insertion holes 10 for bolting the plate 7 to a horizontal member 1, a vertical member 2 or both. Each of the horizontal member 1 and the vertical member 2 employs two back-to-back shaped angles 9, 9 for holding the gusset plate 7 between them. The gusset plate 7 is fixed by means of a friction joint by high-strength bolts 8, 8 in a state of three tiers with the two shaped steels. Welding is not employed in the steel frame 5 including the horizontal member, the vertical member, the brace and the gusset plate to join these members to one another. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a steel frame seismic retrofitting structure and a reinforcing method, and more specifically, when attaching a steel frame incorporating a brace to an existing building for seismic retrofitting, when assembling the steel frame, a great deal of labor is required to ensure quality. The present invention relates to a structure of a steel frame which can be provided at a low cost by eliminating welding requiring skilled work and the like.
[0002]
[Prior art]
A frame formed by being surrounded by a horizontal member and a vertical member can be retrofitted to an existing building by internally or externally attaching it to columns and beams of the building. Internally, by fitting a pre-assembled framework into the opening from which the walls inside the columns and beams have been removed, and externally to the outside walls of the building along the columns and beams without removing the walls etc. By integrating the framework, the seismic resistance of existing buildings is to be enhanced.
[0003]
It is recommended that H-shaped steel be used for the horizontal and vertical members constituting the framework. The steel material is often a rolled H-section steel with standardized dimensions, but in areas where a large amount of stress is applied, a sheet thickness is large, and a welded H-section steel having an appropriate size and non-standard cross section is used. Sometimes. Thus, inexpensive channel and angle steels are almost never employed in the framework, and conversely, their use can be said to be substantially eliminated.
[0004]
Although the H-shaped steel having high rigidity or the like is used for the framework as described above, the members are usually firmly joined to each other in order to improve the shape retention of the framework. In addition, braces are incorporated into the framework to increase seismic resistance. The introduction of the brace also suppresses an increase in the size of the H-shaped steel, thereby contributing to a reduction in the weight of the steel frame.
[0005]
The braces are often arranged in the framework in a V-shape or inverted V-shape or diagonally, and gusset plates are used to attach them to the framework. The brace itself is often a steel pipe or a shaped steel having a simple sectional shape, but joints of the same structure are attached to both ends thereof, and are joined to the gusset plate via this.
[0006]
A clevis joint or a cruciform joint is used as the joint. The former is a pin connection by one thick pin, and the latter is a rigid connection by fastening with several overlapping plates and a number of high-strength bolts. In any case, no welding is performed for the joining. Even if a slight amount of welding distortion remains in this joint portion, it is not preferable in order to function as a reinforcing diagonal member.
[0007]
On the other hand, the gusset plate for fixing both ends of the brace needs to be firmly attached to a horizontal member or a vertical member. Therefore, the gusset plate is directly welded or bolted through a separately manufactured bracket. Since the brackets are again welded to the framework, the gusset plates will be fixed in any case via direct or indirect welding.
[0008]
The gusset plate is made of a thick plate because it is joined to the brace. In the case of pin joining, even though the design is such that no moment acts on the joining point, the load is concentrated at one point, so that it is necessary to further increase the thickness. The flanges or webs that attempt to attach the gusset plate to the H-beam are often thinner than the gusset plate. If a thick gusset plate is to be welded to a thin, for example, flange, the H-section steel flange must be reinforced by placing a stiffener on the underside where the gusset plate will attach.
[0009]
Incidentally, if a stiffener were to be present, a significant portion of the stresses acting on the steel frame would be transmitted through the stiffener. In this case, there is also a problem that a smooth stress transmission is not always performed to a horizontal member or a vertical member.
[0010]
Nevertheless, the horizontal and vertical members forming the framework are welded together, the gusset plate and the framework are integrated by welding, and the stiffeners as the backing material often have to be fixed by welding. . FIG. 8 is an example of a steel frame having a welded joint structure prepared for internal use.
[0011]
In this embodiment, braces 45, 45 are arranged in a V-shape via gusset plates 43, 44 in a frame composed of upper and lower horizontal members 41, 41 and left and right vertical members 42, 42. As shown in FIG. 9 (a), the steel frame 51 is formed inside the frame 56 by increasing the expression strength of the high-strength non-shrink mortar 55 by using a chemical anchor 52, a stud dowel 53, a spiral hoop 54, and the like. Attached.
[0012]
In this way, usually, a step of assembling one steel frame in advance and fitting it into the opening is performed, but the preparatory work is mostly butt welding, which is said to be the most troublesome of welding. That is, as can be seen from FIG. 10, in the case of the V-shaped brace steel frame 51, in addition to the horizontal member 41, the vertical member 42, and the brace 45, gusset plate mounting portions 46 and 47 are provided. It will be composed of a number of parts, such as a group represented by 47A.
[0013]
More specifically, since a large load is concentrated on the portion where the gusset plate is attached, a structure having higher rigidity than the horizontal member 41 or the vertical member 42 is provided. Speaking of the example of the gusset plate attaching portion 46, an H-shaped cross-section welded article having a flange portion formed by plates 48, 48 thicker than the H-section steel flange is introduced at a place where the horizontal member 41 and the vertical member 42 are connected. . Then, several stiffeners 50 which bridge between the flange portions and are integrated with the web portion 49 are arranged in consideration of the mounting positions of the gusset plates 43 and 44.
[0014]
If these components are assembled with high precision by welding, and they are to be welded to a horizontal or vertical material to form a framework, the production of a steel frame requires work at a well-equipped factory. Become. Needless to say, the assembling work requires a lot of man-hours, and also requires advanced skills to reduce welding distortion, which is not an easy task. In the butt welding, in addition to the welding time, as can be seen from FIGS. 9B and 9C, formation of the groove portions 48a and 50a and scallops 49a, 41a and 42a shown in FIG. This is because a process such as mounting the stiffener 50 is required.
[0015]
Incidentally, it has been evaluated in recent years that the joining quality by welding has been high enough to exceed the strength of the non-welded portion. However, this is achieved only by the advanced skills of skilled workers, the preparation of necessary jigs, and the working environment in which the equipment is provided. In addition, ultrasonic inspection is required for butt welds, and strict quality control is required. Therefore, it cannot be denied that costs are jumping.
[0016]
However, it is hardly considered that the steel frame is a substitute that can be easily assembled by using an H-section steel or a square pipe as a frame member and using high-strength bolts. Also, since the steel frame, which is a welded assembly, is to be transported to the construction site as it is, the construction materials are packed in bulk and the transportation is extremely time-consuming compared to the case of handling the parts alone. , Which also causes an increase in cost.
[0017]
As described above, butt welding requires a high level of knowledge and skills, but in recent years the shortage of welding technicians has become a major problem, and in view of this situation, welding can be replaced and cost can be greatly reduced. The contributing joining method is waiting.
[0018]
Incidentally, Japanese Patent Application Laid-Open No. 2002-146905 discloses an example in which a bracket for attaching a gusset plate to a framework is also fixed by bolts. Fastening and joining using high-strength bolts and the like in this manner are not performed in the field of the frame for seismic reinforcement as in other technical fields.
[0019]
The use of such brackets is due to the difficulty of bolting the gusset plate itself directly to a horizontal or vertical material, but the framework uses square pipes or H-beams, This is largely due to the fact that it must be mounted at right angles to horizontal and vertical surfaces, such as H-section flanges.
[0020]
Although not limited to this example, if a bolt fixing method is to be adopted, many brackets and angles as secondary members for fixing the gusset plate are required. Further, a large number of bolts are used for mounting, and the number of components constituting the framework is significantly increased. In addition, if a horizontal section or a vertical section is given a considerable cross-sectional defect, or if the influence thereof is suppressed, a large size must be introduced.
[0021]
Incidentally, Japanese Patent Application Laid-Open No. 2002-70329 describes a structure in which a brace is formed of two section steels, and a gusset plate is sandwiched and joined at a tip end thereof. It is made possible by pinching the channel steel by back-to-back, and has a form in which the three-ply portion is bolted. However, the gusset plate is integrated into the frame by welding to the horizontal and vertical T-section steels that make up the frame, and the idea of bolting the gusset plate to the frame with bolts is seen. Absent.
[0022]
[Patent Document 1]
JP 2002-146905 A
[Patent Document 2]
FIG. 1B of JP-A-2002-70329.
[0023]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described problems, and its object is to eliminate welding that requires advanced skills in assembling a steel frame, to select a place for assembling a steel frame, to make building or construction difficult or To enable flexible transportation and production according to the progress, not to be affected by the shortage of skilled welders, and not to limit the use of expensive H-beams to the framework, but ultimately to reduce costs Height can be suppressed, the number of component parts can be reduced as much as possible to facilitate the simplification and standardization of the construction, and the simplification of the structure simplifies stress propagation and smoothly transmits to the frame members. It is an object of the present invention to provide a steel frame seismic retrofitting structure and a reinforcing method that enable the effective utilization of input materials and suppress the consumption thereof.
[0024]
[Means for Solving the Problems]
INDUSTRIAL APPLICABILITY The present invention is applied to a steel frame seismic retrofitting structure capable of seismic retrofitting by attaching a steel frame incorporating a brace to a framework formed by being surrounded by a horizontal member and a vertical member to an existing building. The feature is that, with reference to FIG. 1, the gusset plate 7 for attaching the brace 4 is provided with a large number of bolt insertion holes 10 for bolting the horizontal member 1, the vertical member 2 or both. Can be Each of the horizontal member 1 and the vertical member 2 is formed of two section steels 9 and 9 (for example, see also (a) of FIG. 2) back to back to sandwich the gusset plate 7. The gusset plate 7 is fixed by friction joining with the high-strength bolts 8, 8 in a three-layered state with the two section steels. The steel frame 5 including the horizontal member, the vertical member, the brace, and the gusset plate is not welded for joining these members.
[0025]
In the case of the seismic retrofitting method, a horizontal member 1 and a vertical member 2 formed of two section steels that can be back-to-back are formed in three layers with a gusset plate 7 made of flat steel sheet interposed therebetween. At this point, the horizontal member 1 and the vertical member 2 each composed of two members 9 and 9 are connected to each other via the gusset plate 7 for attaching the brace 4 by friction joining with the high-strength bolt 8 so that the steel frame 5 is formed. That was done.
[0026]
Further, referring to FIG. 7, the abdominal surfaces of the channel steel 21 composed of the upper and lower flanges 21f and 21f and the web 21w connecting the flanges are opposed to the outer wall surface of the existing building, and the horizontal member with the back surface of the channel steel outward. 1 and a vertical frame 2 to form a steel frame 5A. A gusset plate 7 made of a flat steel plate is arranged on the back side of the connecting portion of the two members and at or near the center of shear against the torsion of the channel steel, and frictionally joined by high-strength bolts 8 at the overlapped portion. A horizontal frame and a vertical frame, each composed of one member, are connected to each other via a gusset plate for attaching a brace to form a steel frame, enabling external retrofitting of an existing building.
[0027]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the steel frame incorporating the brace used for the seismic reinforcement of the existing building can be easily assembled by joining the horizontal member, the vertical member, and the gusset plate for attaching the brace with high-strength bolts. Welding of the mounting portion of the gusset plate is unnecessary, and a stiffener for welding reinforcement is also eliminated, so that the cost required for assembly is significantly reduced. Therefore, it is possible to provide a uniform and high quality product without being affected by the recent shortage of welding technicians.
[0028]
The gusset plate is sandwiched between the frame members, making it possible to easily change the shape of the gusset plate by simply changing the shape of the gusset plate, regardless of whether it is clevis joint or high-strength bolt joint. it can. Since no stiffener is required, the flow of stress is simplified and can be made to function very effectively as a structural material.
[0029]
As the horizontal member and the vertical member forming the frame, an inexpensive general shaped steel (channel steel, angle steel, etc.) can be used as long as it can be back-to-back. Moreover, the processing to be performed is limited to the primary processing such as cutting, drilling, friction surface treatment, and painting, and labor-intensive work such as welding and post-processing are not required due to the frictional joining of three layers.
[0030]
In addition, the assembling location of the steel frame is not limited to the factory, it can also be used outdoors where large jigs and tools can not be prepared, making it possible to transport and manufacture flexibly according to the situation of the building site, the difficulty of construction, and the progress It also makes it easier to manage materials, including waste of time and storage. By directly attaching the gusset plate to the framework, the number of component parts is reduced as much as possible, and the number of fastening points by high-strength bolts is also significantly reduced, so that the construction can be simplified and standardized easily.
[0031]
According to the seismic retrofitting method in which the three overlapping portions formed with the gusset plate interposed therebetween are friction-bonded with high-strength bolts and the two horizontal members and the vertical members are joined via the gusset plate, the braces are made of steel. A gusset plate to be incorporated into the frame seismic reinforcement structure also functions as a frame member connector, thereby eliminating the need for a dedicated frame fastening part and forming a strong frame with a small number of parts.
[0032]
By forming a steel frame with the abdominal surface of the channel steel facing the outer wall of the existing building and arranging a gusset plate on the back side, the rigid atmosphere of the shape steel was softened and integrated with the building wall The appearance is improved. The gusset plate is located at or near the shear center of the channel steel, suppressing bending deformation of the horizontal and vertical members that make up the framework. Can be exhibited.
[0033]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a steel frame seismic retrofit structure and a reinforcing method according to the present invention will be described in detail with reference to the drawings showing the embodiments. FIG. 1 shows an entire steel frame for seismic reinforcement of an existing building. This is a frame in which braces 4, 4 are incorporated in a V-shape in a frame 3 surrounded by upper and lower horizontal members 1, 1 and left and right vertical members 2, 2, and has a structure for internal installation. I have.
[0034]
As can be seen from the drawing, a clevis joint 6 is employed in the steel frame 5 for joining the ends of the brace 4, and a gusset plate 7 for joining the clevis joint 6 is incorporated into the framework 3 by high-strength bolts 8. An H-shaped steel is not used for the horizontal member 1 and the vertical member 2 constituting the framework, and for example, an inexpensive channel steel 9 shown in FIG. 2A is used.
[0035]
The reason why the channel steel 9 is employed is that, as will be described later, it is a shape that allows the two to be combined back to back. That is, a three-layered portion is formed by the channel steels 9, 9 of the horizontal member and the gusset plate 7, and a three-layered portion of the vertical member is formed by the gusset plate, and the high-strength bolts that penetrate them are formed. 8, the gusset plate 7 is integrated into the framework 3 by frictional joining.
[0036]
Therefore, the gusset plate 7 to which the brace 4 is attached is provided with a large number of bolt insertion holes 10 for bolting the horizontal member 1 and / or the vertical member 2 as shown in FIG. Therefore, the gusset plate 7 also functions as a gusset plate and connector plate described later. The channel sections 9 to be back-to-back have the same cross-sectional shape in principle, and a punched hole 11 for passing the high-strength bolt 8 is formed in the three-layered portion, that is, inserted into the bellows of one section steel and inserted into the other. A nut is hung on the threaded portion of the bolt protruding from the abdominal surface of the shaped steel and secured (see FIG. 2A).
[0037]
As a result, the steel frame 5 including the horizontal member 1, the vertical member 2, the brace 4, and the gusset plate 7 becomes an immovable assembly without using any welding for joining these members. Therefore, a butt welding operation requiring a high skill is not required, and the joint can remain slightly softer than that by welding, which will be described later. This is because there is no need to divide the lower horizontal member into two parts as shown in FIG. 10 shown in the prior art, and it is sufficient to prepare a single-dimension horizontal member as well as the vertical member.
[0038]
Such a steel frame is intended for seismic reinforcement of an existing building, but can be applied to not only RC structures but also SRC structures and S structures, including the case of external attachment described later. Since the present invention is directed to a structure for assembling a reinforcing frame, the structure for attaching a frame to a steel frame will not be described in detail. In the case of internal attachment, for example, as shown in FIG. 2B, the stud dowel 52 may be planted and fixed in the manner shown on the outer peripheral portion (particularly on the right side) of FIG.
[0039]
In the case of this internal attachment, the work of assembling the steel frame into the frame usually involves assembling one unit in advance and fitting it into the opening. However, in the case of the steel frame according to the present invention, since there is room for assembling work anywhere because it is bolted, it can be transported to the construction site in units of members and assembled there, or extremely transported to the opening and fixed while assembling. You can do it. Therefore, even if the steel frame is often handled as one unit, considerable flexibility can be given to the construction.
[0040]
As described above, since welding can be eliminated when assembling the steel frame, the cost increase due to welding, which has been a problem in the past, can be solved. If welding is eliminated, it is not affected by the shortage of welding technicians, which has been a problem in recent years, and it is easy to exhibit high quality while maintaining the homogeneity of the steel frame.
[0041]
It is needless to say that the horizontal frame and the vertical bar are of the greatest importance on the load in the steel frame, and the conventional idea that expensive H-shaped steel must be used for them is removed. A reduction in the amount of input and aggressive use of mass-produced and off-the-shelf products will be achieved, and in this respect significant cost reductions can be expected. This is different from the case where a back-to-back material is used for the brace, and is based on a unique idea of using the main structural member as a back-to-back product, which significantly improves not only cost but also construction convenience.
[0042]
In addition, although the frame part is to be buried or formed into a shape close to that of the existing building, the brace is a member that crosses the frame, and the appearance is impaired if it is a back-to-back product. Therefore, the brace having a cylindrical body having a good appearance as shown in FIG. 1 is joined by a clevis joint for smart pin joint, or if it is a rigid joint type, a cruciform joint, which will be described later, improves the appearance.
[0043]
In any case, it can be said that it is based on the knowledge that a brace that is easy to see is given a soft impression, and that the frame part that is easy to integrate into the building often has a little lack of aesthetic sense. In the present invention, since the frame material is a back-to-back product, the gusset plate is sandwiched and attached to the frame assembly material. And, depending on the fact that welding is not employed, as shown in the lower left part of FIG. 6 described later, there is room for placing the brace 4 at any position.
[0044]
Also in this respect, a large degree of freedom can be given to the position of the gusset plate and the length of the brace, and the design can be highly flexible, which is convenient. Furthermore, bolt fastening contributes greatly in terms of simplification of work, release from high-precision processing, and simplification of assembling work, and further strengthening of seismic reinforcement work where construction work is often delayed in terms of price. Can promote the spread.
[0045]
Although the pin joint causes no moment to act, the gusset plate tends to be thick because one point is concentrated. In the example of FIG. 1, three gusset plates are required for one frame, and two gusset plates 7 are required for the diagonal arrangement in FIG. 4, but the gusset plates are not located at the corners where it is necessary to join the horizontal member and the vertical member. In this case, a joining plate (spacer / connector plate) 12 having the same thickness may be prepared. The gusset plate may be a simple single plate, and can be made of the same plate together with the joining plate.
[0046]
In other words, it means that a channel steel and a flat steel plate may be prepared as members constituting the framework, and as a result, dimensions and types of steel materials to be purchased are reduced as much as possible. For example, it is not necessary to prepare various steel materials for manufacturing brackets having various shapes as described in Japanese Patent Application Laid-Open No. 2002-146905 and to manufacture individual members from them. Therefore, the number of high-strength bolts for fixing the gusset plate to the framework is also significantly reduced, which further contributes to a reduction in the amount of bolt fastening work.
[0047]
When the form of fixing the gusset plate to the framework is simplified, the transmission of the force exchanged with the brace is also simplified as compared with the case where the stiffener is attached. The contribution as a structural material is increased, and a steel frame with reduced waste can be manufactured.
[0048]
It is preferable that the mortar is pressed into the facing gap between the horizontal member and the vertical member to be back-to-back products to improve the integrity as a member. The reason for this is that, in both the case of the internal attachment and the case of the external attachment described later (see FIG. 2 (e)), when the non-shrink mortar 55 or the like is applied to the joint with the frame 56, it should be filled naturally. If, for example, the filling operation is performed at the same time, no particularly large work load is newly caused.
[0049]
Incidentally, even in the case of the horizontal member, the vertical member, the gusset plate and the spacer / connector plate, the holes through which the high-strength bolts are inserted are fixed with nuts without engraving screws. Therefore, the bolt insertion hole has a size with some margin for the screw diameter. Joining with high-strength bolts is intended only to achieve friction joining, but the slight margin of this hole not only reduces the work of insertion work at the time of joining, but also causes unnecessary residual such as in welding. It has the effect of avoiding the generation of stress, and also facilitates the familiarity of the members with each other.
By the way, in the example shown in FIG. 2A, the disks 13 and 13 are attached to the clevis seat surface of the gusset plate 7 to stabilize the engagement state at the time of joining. . This part is handled as a single piece until it is bolted, even if distortion remains due to welding, so that it can be corrected by post-processing or the like. The present invention does not intend to eliminate the welding to this point, and it is only necessary to take measures to suppress the weight increase of the gusset plate and increase the seating surface of the base material by appropriate means.
[0051]
In the above example, an example is described in which a channel steel is used as a back-to-back product. However, the present invention is not limited to this, and the angle iron 9A shown in FIGS. 2C and 2D or a T-beam (not shown) may be used. Absent. It is only necessary to use a shaped steel that can be back-to-back, and an inexpensive rolled steel material such as a standard product is sufficient. In any case, the processing to be performed on the steel material only requires primary processing such as cutting, drilling, friction surface treatment, and painting, and labor-intensive operations such as welding and post-processing are not required. Applying a channel steel or the like to a horizontal member or a vertical member forming a framework in this way can be said to be one step against the fact that the use of an H-shaped steel is a general recommended standard.
[0052]
FIG. 4 shows an example of a steel frame including a brace 4A arranged diagonally instead of a V-shaped brace. Even in this case, theoretically, there is no difference from the case of FIG. Incidentally, this drawing shows an example in which the ends of the horizontal member 1 and the vertical member 2 are cut off at approximately 45 degrees, respectively, and the cross members of both members are obliquely butted against each other. In this case, there is an advantage that the filling mortar can be prevented from leaking out even if the small opening is not positively closed at the time of joining with the frame in the case of the internal attachment.
[0053]
FIG. 5 shows an example in which a brace 16 employing a cross joint 15 is incorporated. After the joint having a cross-section is arranged between the gusset plates 7A, 7A as shown on the left side, the backing plate 17 is overlaid on the joint surface as shown on the right side and fastened by the high-strength bolt 8. Also in this example, the intersections may be obliquely butted as shown in FIG.
[0054]
When a cruciform joint is used, a thinner gusset plate can be used than in the case of a clevis joint, and in that case, the spacer / connector plate 12A can also be thinner. As can be seen from this, the gusset plate is sandwiched between the frame members so that the shape of the gusset plate can be slightly changed or the thickness can be changed. The correspondence can be easily changed.
[0055]
FIG. 6 shows an example in the case of external work. In such a case, the members are often assembled one by one. If there is a plaza in front of the building, it can be said that a framework of several floors is integrated on the ground and leaned against it. As shown in this figure, when the horizontal member 1A passes through the left and right for a long time, the vertical member 2A becomes shorter for each section. Although not shown, if the length of the vertical member is increased, the horizontal member becomes a partition unit. In any case, the spacer / connector plate 12 is used at the intersection of the horizontal member 1 and the vertical member 2, and the gusset plate / connector plate 14 is used when the brace 4 is attached to that portion.
[0056]
Of course, the gusset plate (including the gusset plate and the connector plate) and the spacer and the connector plate do not have to be independent in one section, but have a shape in which continuity with the left, right, upper and lower sections is taken into consideration. . Regardless of whether the horizontal member or the vertical member is long, it is sufficient to prepare a limited number of gusset plates, gusset plates and connector plates, and the like.
[0057]
The attachment structure to the skeleton in the case of external attachment is substantially the same as that of the case of the internal attachment to the extent that the orientation is different, and as shown in FIG. 2 (e), between the frame 3 and the wall surface of the skeleton 56. A non-shrink mortar 55 is placed with various connecting members. As described above, the frame is not affected at all by the pin connection or the high-strength bolt connection (cross joint). Therefore, the frame can be used in common simply by changing the gusset plate, and the bolt hole is used. Except for the slight difference in the number and position of the gusset plates, the only difference is the thickness of the gusset plates.
[0058]
The present invention also provides an anti-seismic reinforcement by a steel frame in which a three-layer portion formed by sandwiching a gusset plate is friction-welded with a high-strength bolt and a two-member horizontal member and a vertical member are connected via the gusset plate. Since the construction method is used, the gusset plate for incorporating the brace into the steel frame can also function as a connector for the frame member (horizontal member / vertical member). Therefore, it is not necessary or necessary to introduce a part dedicated to frame fastening, and a strong steel frame can be formed with a small number of parts.
[0059]
By the way, when the channel steel is used for the horizontal member and the vertical member, it is also possible to adopt a form in which the steel members are not back-to-back as shown in FIG. That is, one channel steel 21 is adopted as the horizontal member 1 and the vertical member 2, and the abdominal surface faces the outer wall surface of the existing building, and the gusset plate 7 and the connecting plate 12 are fixed to the back side. .
[0060]
More specifically, by turning the back surface of the channel steel 21 composed of the upper and lower flanges 21f and 21f and the web 21w connecting the flanges outward, the flatness of the outer surface of the web is conspicuous and the existence of the steel frame is conspicuous. It is intended to be eliminated. In the example of FIG. 7, the gusset plate 7 is superimposed on the connecting portion between the horizontal member 1 and the vertical member 2 and the central portion of the horizontal member 1 from the outside and fixed by the high-strength bolts 8. In comparison with FIG. 1 and the like in which the flange protrudes, the familiarity with the skeleton side is improved in appearance.
[0061]
The gusset plate 7 will appear on the outer surface, so it will appear as if the braces are slightly protruding from the steel frame surface. The presence of braces is somewhat emphasized, but, apart from its aesthetic appeal, it forms a structure that is mechanically extremely appropriate. That is, the axial force acting on the brace is transmitted to the horizontal member and the vertical member through the gusset plate, and the gusset plate takes a very convenient form that is located at or near the shear center of the channel steel.
[0062]
When the compressive brace reaches the maximum strength at the intersection of the horizontal member and the brace due to an earthquake or the like, the strength of the tensile side brace further increases thereafter, so that a shear force is generated in the horizontal member. When a single channel is used as the horizontal member, this shearing force is accompanied by the generation of torsion in the asymmetrical channel. However, in the present invention, when an axial force acts on the brace 4 via the gusset plate 7 and a shear force acts on the horizontal member, the center of the force is located at or near the shear center of the channel steel. An extremely useful behavior in practical use that the generation of a moment is suppressed can be exhibited.
[0063]
In this manner, if the gusset plate is fixed to the back surface of the channel steel, the frame can be formed only by the channel steel and in a small number. Needless to say, the ready-made channel steel is an inexpensive steel material, so that the cost of construction is greatly reduced. Dramatic enhancement of durability of inexpensive materials, which were regarded as unusable, can also be achieved. In addition, although it depends on the degree of reinforcement, two angle members can be butted (not shown) and used in combination so as to obtain a sectional shape equivalent to a channel steel.
[Brief description of the drawings]
FIG. 1 is a front view showing a typical example of a steel frame seismic retrofit structure according to the present invention.
2 (a) to 2 (d) are explanatory views of a securing state of a member constituting a framework and a gusset plate in a three-layered manner, and FIG. 2 (e) is a sectional view of a skeleton fixed state when externally attached.
FIG. 3 is an exploded view illustrating components of the steel frame separately.
FIG. 4 is a front view when the brace is arranged diagonally.
FIG. 5 is a front view of a steel frame adopting joining by a cross joint.
FIG. 6 is a front view of a case where the layers are connected in series and externally attached.
FIG. 7 is a front view of an externally mounted steel frame to which a gusset plate is attached with the back surface of the channel steel being outside, and a view in the other direction of each part.
FIG. 8 is a front view of an internal steel frame having a welding structure according to the prior art.
9 (a) is an explanatory view of a skeleton fixing state in the case of internal attachment, and FIGS. 9 (b) and 9 (c) are cross-sectional views of a gusset plate mounting portion showing positions and shapes of a stiffener and a groove portion.
FIG. 10 is an exploded view of a steel frame having a welded structure.
[Description of Signs] 1,1A: Horizontal material, 2, 2A: Vertical material, 3: Frame, 4,4A: Brace, 5, 5A: Steel frame, 7, 7A: Gusset plate, 8: High-strength bolt, 9 ... channel steel, 9A ... angle iron, 10 ... bolt insertion hole, 14 ... gusset plate and connector plate, 16 ... brace, 21 ... channel steel, 21f ... flange, 21w ... web.

Claims (3)

In a steel frame seismic retrofit structure that is capable of seismic reinforcement by attaching a steel frame with braces incorporated into a frame formed by horizontal and vertical materials to an existing building,
The gusset plate for attaching the brace is provided with a number of bolt insertion holes for bolting to a horizontal member, a vertical member, or both,
Each of the horizontal member and the vertical member is formed of two section steels which are back to back to sandwich the gusset plate,
The gusset plate is fixed by friction joining with high-strength bolts in a three-ply state with the two section steels,
A steel frame including a horizontal member, a vertical member, a brace, and a gusset plate, wherein no welding is used for joining these members to each other. In a steel frame seismic retrofitting method that can be retrofitted by attaching a steel frame incorporating a brace to a frame formed by a horizontal material and a vertical material to an existing building,
A horizontal or vertical material made of two shaped steels that can be back-to-back, a gusset plate made of flat steel is sandwiched, and three layers are stacked. A seismic retrofitting method using a steel frame, wherein a horizontal member and a vertical member each having two members are connected to each other via a gusset plate for attachment to form a steel frame. In the steel frame seismic retrofitting method, which can be retrofitted to an existing building by attaching a steel frame with braces incorporated in a framework formed by being surrounded by horizontal members and vertical members to an existing building,
The abdominal surfaces of the upper and lower flanges and the channel steel formed by connecting the webs are opposed to the outer wall of the existing building, and the steel frame made of a horizontal member and a vertical member is formed with the back surface of the channel member facing outward. A gusset plate made of a flat steel plate is disposed on the back side of the connecting portion of the slab and at or near the center of shear against the torsion of the channel steel, and frictionally joined by high-strength bolts at the overlapping portion to attach the brace. A seismic retrofitting method using a steel frame, wherein a horizontal member and a vertical member each composed of one member are connected via a plate to form a steel frame.

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