JP2009287388A - Anchor bolt aseismic construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aseismic construction method capable of moderating an earthquake action onto an anchor bolt, to reduce or delay damage and breakage of the anchor bolt caused by an earthquake. <P>SOLUTION: An energy absorption member 23 comprising a metal plastic body is interposed between a fixing plate 21 of the anchor bolt 16 embedded into concrete 17, and a lower nut 22 screwed in a lower side of the fixing plate 21 of the anchor bolt 16, and for transmitting a tension force of the anchor bolt to the fixing plate 21, earthquake energy is absorbed by a plastic deformation of the energy absorption member 23, and the earthquake action onto the anchor bolt 16 is moderated thereby. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an anchor bolt seismic method suitable for an exposed type column base for standing a steel column at a predetermined position of a foundation concrete by fastening and fixing a base plate or the like via an anchor bolt embedded in the foundation concrete. .

  In the case of an exposed-type column base that uses an anchor bolt embedded in the foundation concrete to fasten and fix the steel column base plate to the foundation concrete, the base plate is fixed using a tightening nut screwed into the upper exposed part of the anchor bolt. A method of standing a steel column at a predetermined position on the foundation concrete by directly tightening the upper surface is widely adopted.

  By the way, in the above prior art, since the method of directly tightening the upper surface of the base plate with the tightening nut screwed to the anchor bolt was adopted, the rotation acting on the column base due to the shaking of the frame during the earthquake The moment was transmitted directly to the anchor bolt as a tensile load. And if the tensile load on the anchor bolt acting on the basis of the earthquake is less than the yield strength of the anchor bolt, it will fit within the range of elastic deformation, but if it exceeds the yield strength, plastic deformation will occur, and if the maximum tensile strength is reached It will eventually break. Therefore, if the magnitude of the earthquake is small and within the range of elastic deformation, the impact of the earthquake on the column base and the frame will be small, and there will be no damage after the damage. However, as the magnitude of the earthquake increases, the anchor bolt When plastic deformation occurs, troublesome repair work, such as excavating and replacing anchor bolts after an earthquake, may occur. In addition, when damage is further increased, rebuilding may be required. In any case, a large cost was required to deal with the post-earthquake. Furthermore, when an anchor bolt breaks, damage to human life due to the collapse of the building has become a problem.

  On the other hand, when an anchor bolt made of a material having a low plastic deformation capacity is used, there is a problem that the building cannot be collapsed without being able to absorb the seismic energy and the building collapses. For this reason, for example, when high tensile steel with low plastic deformation ability is used as the material of the anchor bolt, the actual condition is that it must be designed with a strength of 50 to 60% of its yield strength. That is, the excellent ability as a high-strength steel could not be fully utilized.

  Therefore, a plasticizing member made of a cylindrical steel plate provided with a large number of apertures is interposed between the fastening nut screwed to the anchor bolt and the upper surface of the base plate, and acts on an earthquake or the like by the plasticizing member. A technique for absorbing vibration energy is also disclosed (Patent Document 1).

JP-A-3-183873

  The present invention has been developed in view of the above-described problems with respect to earthquakes in the prior art, and is an earthquake resistance for reducing or delaying the damage and breakage of anchor bolts caused by an earthquake by relaxing the seismic action on the anchor bolts. The purpose is to further improve the construction method. Another object of the present invention is to provide an anchor bolt seismic construction method that can fully utilize the excellent characteristics of the material when a material with low plastic deformation ability such as high-tensile steel is used for the anchor bolt. .

  In order to solve the above-mentioned problem, the present invention is adapted to fix the anchor bolt anchor plate embedded in the concrete and the anchor bolt below the anchor plate, and transmit the anchor bolt tensile force to the anchor plate. The technical means of interposing an energy absorbing member made of a metal plastic between the lower nut and absorbing the seismic energy by plastic deformation of the energy absorbing member to alleviate the seismic action on the anchor bolt was adopted. As the energy absorbing member, a metal plastic body having a plastic yield strength smaller than the yield strength of the anchor bolt and 60% or more of the yield strength, a plastic yield strength substantially equal to the yield strength of the anchor bolt, or the anchor bolt A metal plastic body having a plastic strength greater than the yield strength and smaller than the maximum tensile strength is used. Here, the plastic proof stress refers to the load that the metal plastic body reaches the plastic deformation region.

  According to the present invention, as described above, since the seismic energy is absorbed by the plastic deformation of the energy absorbing member made of the metal plastic body, the seismic action on the anchor bolt is mitigated, and the vibration resistance can be improved. Therefore, damage and collapse of the building are reduced by the amount of the influence of the earthquake on the column base and the like. In addition, when using a material with low plastic deformation capability such as high-tensile steel as an anchor bolt, seismic energy is absorbed by the plastic deformation of the energy absorbing member, and the low plastic deformation capability is complemented. It can be used as an anchor bolt in a form that can fully utilize its excellent characteristics. For example, the combination of the high yield strength of high-strength steel and the plastic deformation ability of the energy absorbing member makes the elongation small for small earthquakes, and the seismic energy absorption effect due to plastic deformation is good for large earthquakes. An anchor bolt seismic structure can be provided. In addition, since the energy absorbing member is installed between the fixing plate and the lower nut and embedded in the foundation concrete, the tightening space for the base plate, etc., by the tightening nut in the upper exposed part of the anchor bolt is as large as before. It is possible to fit in.

It is the state explanatory view showing the state before receiving the seismic action of the example of the present invention. It is the state explanatory view which showed the state which the energy absorption member deform | transformed by the earthquake action of the Example. It is the elements on larger scale which expanded and showed the state before receiving the earthquake action of the principal part in the Example. It is the elements on larger scale which expanded and showed the state deform | transformed by the earthquake action of the principal part in the Example. It is the front view which illustrated the installation state of the energy absorption member installed in the upper part in other examples. It is a load-displacement characteristic curve figure regarding an anchor bolt simple substance. It is a load-displacement characteristic curve figure regarding an energy absorption member single-piece | unit. It is a load-displacement characteristic curve figure at the time of using combining an anchor bolt single-piece | unit and an energy absorption member single-piece | unit. It is a load-displacement characteristic curve figure regarding the anchor bolt single-piece | unit and the energy absorption member single-piece | unit in the other Example of this invention. It is a load-displacement characteristic curve figure at the time of using combining the anchor bolt single-piece | unit and the energy absorption member single-piece | unit of the Example. It is a load-displacement characteristic curve figure regarding the anchor bolt single-piece | unit and the energy absorption member single-piece | unit in the other Example of this invention. It is a load-displacement characteristic curve figure at the time of using combining the anchor bolt single-piece | unit and the energy absorption member single-piece | unit of the Example.

  The present invention is suitable as a seismic construction method for the exposed column base of a steel column, but if it is of a form that is tightened and fixed using a tightening nut screwed to an upper exposed portion of an anchor bolt embedded in concrete Widely applicable. The metal plastic constituting the energy absorbing member is, for example, plastic deformation compared to anchor bolts such as iron, cast steel, extremely low yield point steel, copper, lead, zinc, aluminum, brass, tin, and alloys thereof. It is made of a material having a large energy absorption effect. And as for the magnitude of the plastic yield strength as the energy absorbing member, it is set to be smaller than the yield strength of the anchor bolt and within the range of 60% or more of the yield strength, or almost equal to the yield strength of the anchor bolt. It can be set so as to have a plastic strength greater than the yield strength of the anchor bolt or the anchor bolt and smaller than the maximum tensile strength. It is also possible to use a combination of energy absorbing members made of metal plastics having these characteristics. Furthermore, as a specific shape of the energy absorbing member, for example, a cylindrical shape having a hollow portion through which an anchor bolt can be inserted, a shape in which a flange portion is formed at the upper end portion or the lower end portion of the cylindrical portion, or a similar hollow shape The one having a portion and having an outer shape formed in a tapered shape is used. In addition, the specific dimensions of these are set so that the seismic function as the energy absorbing member can be satisfied in relation to the anchor bolt side strength determined by the material and dimensions of the anchor bolt and the manner of anchoring to the concrete. Will do.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show an embodiment of the present invention. FIG. 1 is an explanatory diagram showing a state before receiving an earthquake action, and FIG. 2 shows a state in which the energy absorbing member is deformed by the earthquake action. FIG. 3 and 4 are partially enlarged views showing in an enlarged manner the states of the main parts before and after receiving the seismic action. As shown in the figure, in this embodiment, the anchor bolt 16 is embedded in the foundation concrete 17 and is configured to screw and fasten the base plate 20 of the steel frame 19 by screwing a tightening nut 18 into the upper exposed portion thereof. . As shown in FIG. 5, another energy absorbing member having different plastic characteristics is interposed between the tightening nut 18 and the base plate 20, and combined with the energy absorbing member installed between the fixing plate and the lower nut. The form to be used is also possible.

  As the anchor bolt 16, an unbonded type is used, and as shown in the figure, a cylindrical energy absorbing member 23 is installed between the fixing plate 21 and the lower nut 22 embedded in the foundation concrete 17. The The energy absorbing member 23 is made of a metal plastic body having a required characteristic, and the seismic energy acting on the anchor bolt 16 is absorbed by the plastic deformation of the energy absorbing member 23 to reduce the seismic action. As shown in the figure, a sheath tube 24 is provided on the fixing plate 21 as necessary, and the energy absorbing member 23, the lower nut 22 and the lower screw portion of the anchor bolt 16 below the fixing plate 21 are surrounded. . As a result, it is possible to avoid a situation in which concrete adheres around the energy absorbing member 23, the lower nut 22 and the lower threaded portion of the anchor bolt 16 and the seismic energy absorbing action by the energy absorbing member 23 is hindered. In this case, it goes without saying that the energy absorbing member 23 is configured not to be hindered by the sheath tube 24.

  In the present embodiment, the energy absorbing member 23 is embedded in the foundation concrete 17, so that the space of the tightening portion of the base plate 20 by the tightening nut 18 can be as large as the conventional one. Become. Although depending on the magnitude of the earthquake, when the amount of plastic deformation of the energy absorbing member 23 is small, it is possible to cope with the tightening by the tightening nut 18. Further, as shown in FIG. 5, an energy absorbing member 25 made of a metal plastic material having a plastic yield strength smaller than that of the energy absorbing member 23 is installed between the tightening nut 18 and the base plate 20, and combined with the energy absorbing member 23. If the earthquake is small and the energy absorption member 25 exposed at the top is destroyed, it can be easily dealt with by replacing it, and for large earthquakes The energy absorbing member 23 embedded in the foundation concrete 17 can also be configured to exhibit a seismic function.

  Next, the seismic effect of the anchor bolt seismic construction method according to the present invention will be described. FIG. 6 is a load-displacement characteristic curve diagram schematically illustrating the relationship between the tensile load P and the displacement δ of the anchor bolt alone. FIG. 7 is a load-displacement characteristic curve diagram schematically illustrating the relationship between the compression load P and the displacement δ of the energy absorbing member alone. As shown in FIG. 6, from the load-displacement characteristics of the anchor bolt alone, elastic deformation is repeated until the tensile load acting on the anchor bolt due to the earthquake reaches the yield strength Pa. When the tensile load P reaches the yield strength Pa, after passing through a yield state in which a predetermined plastic deformation occurs while maintaining the load P substantially constant, the deformation resistance increases due to strain hardening due to the plastic deformation, and the load P increases. Start rising again. Then, after reaching the maximum tensile strength Pb, the load cannot be supported, and it falls to the breaking strength Pc and breaks. On the other hand, the energy absorbing member alone, as idealized and illustrated in FIG. 7, has a characteristic close to an elastic perfect plastic body, and elastically deforms with respect to a load P up to the plastic proof stress Pd, For loads P beyond that, it yields and plastic deformation continues. Incidentally, the area of the hatched portion below each characteristic curve represents external energy such as seismic energy absorbed by the deformation therebetween. In this example, the case of 0.6 × Pa <Pd <Pa is illustrated.

  FIG. 8 shows an example of a load-displacement characteristic curve when an anchor bolt having the above characteristics and an energy absorbing member are used in combination. That is, the characteristic curve of FIG. 6 and the characteristic curve of FIG. 7 are synthesized. Note that the load P in this composite characteristic curve diagram is a load acting between the anchor bolt 16 and a member to be tightened such as the base plate 20 via the tightening nut 18. The energy absorbing member 23 acts as a compressive load. In the following load-displacement characteristic curve diagrams, the characteristics from the point where the load P is zero are displayed, but a tensile load due to a tightening force at the time of installation acts on the anchor bolt 16 as an initial load. Therefore, the actual displacement δ generated by the earthquake is generated for the excess of the tensile load due to the earthquake exceeding the tensile load due to the tightening force as the initial load.

  Thus, as shown in the drawing, the elastic tension deformation of the anchor bolt and the elastic compression deformation of the energy absorbing member coexist until the load P reaches the plastic yield strength Pd of the energy absorbing member. The absorbed energy absorbed by deformation in this elastic region is represented by the area of the hatched (A) portion. Next, when the load P reaches the plastic yield strength Pd, it enters the plastic region of the energy absorbing member, and plastic deformation is continued while maintaining the load P substantially constant. The absorbed energy in this plastic region is represented by the area of the hatched (B) portion. Then, when the plastic deformation of the energy absorbing member reaches the limit, for example, when the load P is transmitted from the base plate 20 to the anchor bolt 16 via the tightening nut 18, the transition is made according to the remaining characteristic curve of the anchor bolt. Will do. That is, elastic deformation is performed up to the yield strength Pa after the plastic deformation, and then the plastic deformation is performed while the load P is increased to reach the maximum tensile strength Pb. It falls to the proof stress Pc and breaks. The absorbed energy during this period is represented by the area of the hatched (C) portion.

  FIG. 9 is a load-displacement characteristic curve diagram schematically illustrating the relationship between the load P and the displacement δ in another embodiment of the present invention. The tensile characteristic curve of the anchor bolt alone and the compression characteristic curve of the energy absorbing member alone. Is displayed at the same time. In the present embodiment, as shown in the figure, the case where the plastic yield strength Pe of the energy absorbing member alone is set larger than the yield strength Pa of the anchor bolt alone and smaller than the maximum tensile strength Pb is illustrated. FIG. 10 exemplifies a load-displacement characteristic curve when the anchor bolt and the energy absorbing member are used in combination, and shows both characteristic curves synthesized. As illustrated, until the load P reaches the yield strength Pa of the anchor bolt, an elastic region in which the elastic tensile deformation of the anchor bolt and the elastic compression deformation of the energy absorbing member coexist is provided. The absorbed energy absorbed by deformation in this elastic region is represented by the area of the hatched (D) portion. Next, when the load P reaches the yield strength Pa, it enters the yield region of the anchor bolt, and predetermined plastic deformation occurs while maintaining the load P substantially constant. The absorbed energy absorbed by the deformation during this period is represented by the area of the hatched (E) portion. Thereafter, the strain resistance due to plastic deformation increases the deformation resistance of the anchor bolt, and the load P begins to rise again. And until it reaches the plastic yield strength Pe of the energy absorbing member, it becomes a deformation region where the plastic deformation of the anchor bolt and the elastic deformation of the energy absorbing member coexist, and the absorbed energy absorbed by the deformation during this time is the hatching (F). It is represented by the area of the part. Further, when the load P reaches the plastic yield strength Pe of the energy absorbing member, it enters the plastic region of the energy absorbing member, and plastic deformation is continued while maintaining the load P substantially constant. The absorbed energy in this plastic region is represented by the area of the hatched (G) portion. Then, when the plastic deformation of the energy absorbing member reaches the limit, the energy absorbing member changes according to the remaining characteristic curve of the anchor bolt. That is, after the plastic deformation is performed while increasing the load P again to reach the maximum tensile strength Pb, the load cannot be supported, and the load falls to the breaking strength Pc and breaks. The absorbed energy during this period is represented by the area of the hatched (H) portion.

  As described above, in the present invention, since the energy absorbing member 23 is interposed between the fixing plate 21 and the lower nut 22 embedded in the foundation concrete 17, the load-displacement illustrated in FIG. 8 or FIG. It will have the characteristics. For example, when the plastic yield strength Pd of the energy absorbing member 23 is set so as to satisfy the condition of 0.6 × Pa <Pd <Pa, the plastic yield strength Pd of the energy absorbing member 23 is reached according to the characteristic curve of FIG. Energy absorption due to deformation of the energy absorbing member 23 itself is added in the elastic region (A) up to and the plastic region (B) after reaching the plastic yield strength Pd. Therefore, the influence of external energy such as seismic energy acting on the anchor bolt 16 is alleviated by the amount of energy absorption due to elastic deformation and plastic deformation of the energy absorbing member 23 itself. Further, when the plastic yield strength Pe of the energy absorbing member 23 is set so as to satisfy the condition Pa ≦ Pe <Pb, the energy is applied in the hatched (D) and (F) regions according to the characteristic curve of FIG. Energy absorption due to elastic deformation of the absorbing member 23 itself is added, and energy absorption due to plastic deformation of the energy absorbing member 23 itself is added in the hatched (G) region. Therefore, also in this case, the influence of external energy such as seismic energy acting on the anchor bolt 16 is alleviated by the amount of energy absorption due to elastic deformation and plastic deformation of the energy absorbing member 23 itself.

  According to the present invention, as described above, energy absorption due to elastic deformation and plastic deformation of the energy absorbing member 23 itself is added, and the influence of seismic energy acting on the anchor bolt 16 is mitigated. Thus, the arrival of the anchor bolt 16 to the yield strength Pa and the arrival of the maximum tensile strength Pb can be delayed. Therefore, the damage and collapse of the building can be delayed and the evacuation time can be increased, so that damage to human lives and the like can be reduced.

  FIG. 11 is a load-displacement characteristic curve diagram schematically illustrating the relationship between the load P and the displacement δ according to another embodiment of the present invention in which high-tensile steel is used for the anchor bolt, and the tensile characteristic curve of the anchor bolt alone. And a compression characteristic curve of the energy absorbing member alone. In the present embodiment, as shown in the figure, the case where the plastic yield strength Pi of the energy absorbing member alone is set in the vicinity of the yield strength Ph where the plastic deformation of the anchor bolt alone formed from high-tensile steel starts. FIG. 12 exemplifies a load-displacement characteristic curve diagram when the anchor bolt and the energy absorbing member are used in combination, and shows both characteristic curves synthesized. As shown in FIG. 11 and as described above, in the case of a single anchor bolt made of high-strength steel, the plastic deformation ability is low, so that it does not absorb the seismic energy and reaches the maximum tensile strength Pj at an early stage and breaks. There was a problem that. However, according to the present embodiment, as shown in FIG. 12, the low plastic deformation capability of the anchor bolt made of high-strength steel is complemented by the plastic deformation capability of the energy absorbing member. Increasing the situation leading to anchor bolt breakage is greatly reduced. Therefore, it is possible to fully utilize the excellent characteristic that the elongation as a high-tensile steel is small and the yield strength Ph is high. That is, in the range of small-scale earthquakes, the elongation indicated by hatching (P) corresponds to the elastic region, and for large earthquakes, the seismic energy absorption action by plastic deformation shown by hatching (Q). Can be dealt with in a good plastic region, and through a region indicated by hatching (R) where elasticity and plasticity coexist, it can be held until it breaks with a high maximum tensile strength Pj. A seismic structure can be provided.

  DESCRIPTION OF SYMBOLS 16 ... Anchor bolt, 17 ... Foundation concrete, 18 ... Clamping nut, 19 ... Steel frame, 20 ... Base plate, 21 ... Fixing plate, 22 ... Lower nut, 23 ... Energy absorption member, 24 ... Sheath tube, 25 ... Energy absorption member, Pa: yield strength of anchor bolt, Pb: maximum tensile strength of anchor bolt, Pc: fracture strength of anchor bolt, Pd to Pg: plastic strength of energy absorbing member, Ph: yield strength of anchor bolt, Pi ... of energy absorbing member Plastic yield strength, Pj: Maximum tensile strength of anchor bolt

Claims (3)

  It is made of a metal plastic body between a fixing plate of an anchor bolt embedded in concrete and a lower nut that is screwed below the fixing plate of the anchor bolt and transmits a tensile force of the anchor bolt to the fixing plate. An anchor bolt seismic method characterized by interposing an energy absorbing member and absorbing seismic energy by plastic deformation of the energy absorbing member to mitigate seismic action on the anchor bolt.   2. The anchor bolt seismic construction method according to claim 1, wherein a metal plastic body having a plastic yield strength that is smaller than the yield strength of the anchor bolt and 60% or more of the yield strength is used as the energy absorbing member.   A metal plastic body having a plastic yield strength substantially equal to a yield strength of the anchor bolt or a yield strength greater than the yield strength of the anchor bolt and smaller than a maximum tensile strength is used as the energy absorbing member. The anchor bolt seismic construction method according to 1.

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