JP2012246680A - Energy absorption type precast member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a precast member which holds sufficient rigidity and bearing force against stationary load and earthquake load acting on a building as a main structural member and which has a vibration control function with high attenuation effect based on a new principle.SOLUTION: When a main reinforcement is tensioned by a pretension system so that prestress is introduced to concrete and negative shear deformation is previously generated due to the compressive strain of the main reinforcement and earthquake load is applied, a viscoelastic material applied or attached to the main reinforcement at a member end part generates positive and negative shear deformation repeatedly larger than the negative shear deformation so as to absorb energy. Thus an energy absorption type precast concrete member is obtained.

Description

  The present invention relates to an energy-absorbing precast member that can reduce shaking of a building due to an earthquake load and improve earthquake resistance.

  Since the Great Hanshin Earthquake, the introduction of vibration control devices has been widespread mainly in high-rise buildings with the aim of reducing the shaking of buildings due to seismic loads and improving earthquake resistance. In recent years, the development and popularization of vibration control technology has been remarkable, and various and diverse methods have been proposed.

  In general, the vibration control method is often incorporated into buildings as a device separately from the main structure of pillars and beams, but the functionality of the building may be impaired by the installation of the device. In some cases, it may be limited in a plane or elevation.

As a method for solving these problems, there are a method for imparting a damping effect to the column or beam member itself, and a method for incorporating a device in the column or beam member itself.
As a relatively simple construction method, viscoelastic material is pre-applied to the main reinforcement at the end of the reinforced concrete member, and when the member is deformed during an earthquake, the viscoelastic material applied to the main end of the member is subjected to shear deformation. There is a construction method that gives a damping effect, that is, a damping effect (for example, Patent Document 1 and Patent Document 2).

As shown in the shear stress-shear strain characteristics of the viscoelastic material of FIG. 1, the viscoelastic material used in these construction methods has a large hysteresis area and can be expected to have a damping effect when subjected to repeated positive and negative shear deformation. High damping rubber and resin-based materials having similar mechanical characteristics, such as acrylic resin, asphalt resin, silicon resin, and the like are used.
The viscoelastic material has a greater damping effect when it undergoes shear deformation as shown in Fig. 1 than when it undergoes repeated compression and tension deformation. Are expected.
When subjected to only positive shear deformation, the history area remains extremely small as shown by the broken line in the upper right of the figure.

FIG. 2 shows a deformed state of the member in the construction method in which a viscoelastic material is applied to the main muscle of the member end.
When a tensile force is generated in the main bar located on the member pulling side, the main bar comes out of the beam end surface and the column side surface. The total amount of withdrawal of the main bars is the sum of the amount of extension (Sa) of the main bars in the viscoelastic material application area, the amount of withdrawal of the main bars from the beam (Sb), and the amount of withdrawal of the main bars from the column side surface (Sc) (Sa + Sb + Sc).

As described above, in a state in which a tensile force is generated in the main muscle located on the member tension side, shear deformation occurs in the viscoelastic material, and the deformation of the viscoelastic material increases according to the size of the member deformation.
However, when the main bar is on the compression side, the concrete bears a compressive stress at the end of the member, and only the compressive stress is generated in the viscoelastic material as in the concrete, and no shear stress is generated.
In other words, the damping effect of the construction method shown in FIG. 2 is that shear deformation occurs in the viscoelastic material only when the main bar is on the tension side, so one-way shearing (positive or negative only) of the same material. It is limited to the damping effect by.
For this reason, a high damping effect with a large hysteresis area when subjected to positive and negative repeated shear deformation unique to the viscoelastic material as shown in FIG. 1 cannot be expected.

Therefore, for example, in the invention described in the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 11-350593), a semi-rigid joint structure is provided so that the end of the member can be easily rotated for the purpose of increasing the shear deformation occurring only in one direction. Is adopted.
That is, as shown in FIG. 3, this conventional invention is provided with a slit at the end of the member, and a buffer material made of a viscoelastic material or a soft resin material is applied to the slit, thereby facilitating the rotation of the member. The invention has been devised to increase the shear deformation in one direction of the viscoelastic material. In other inventions of the same type, there are many examples in which a cushioning material is applied to the end face of the member to make it easier to rotate the end of the member.

However, a major problem of this kind of invention is that the member having a vibration damping effect has a semi-rigid joint at the end of the member in order to impart a large shear deformation to the viscoelastic material and acts on the building. The rigidity as a member against a constant load or an earthquake load is reduced, and the bending strength is also reduced. In other words, the member itself will mainly function as a vibration control device, and the original function and role as a main structural member in which the member resists seismic loads and building constant loads can be fully fulfilled. Disappear.
It is no exaggeration to say that this functional reduction is fatal for pillars and beams.

JP 11-350593 A JP 09-317054 A

  The present invention has been made in order to solve the above-described various problems, and maintains sufficient rigidity and proof strength as a main structural member against a constant load or seismic load acting on a building. An object of the present invention is to provide a precast member having a damping function having a high damping effect based on the principle.

  The basis of the new principle is that when a seismic load is applied to the building, the viscoelastic material applied to or attached to the main bar at the end of the member is rationally and efficiently subjected to repeated positive and negative shear deformation.

  In the invention according to claim 1, the viscoelastic material applied or attached to the main bar at the end of the member has been subjected to a negative shear deformation in advance due to the penetration of the main bar and is subjected to an earthquake load. An energy-absorbing precast concrete member that absorbs energy by generating larger positive and negative shear deformation than the above.

  The invention according to claim 2 is characterized in that negative shear deformation is caused in advance by tensioning the main reinforcement by the pre-tension method and introducing pre-stress into the concrete.

  The invention according to claim 3 is a viscoelastic material, a high-damping rubber that has a large hysteresis area and can be expected to have a damping effect when subjected to positive and negative shear deformation, and a resin-based material having similar mechanical characteristics. It is characterized by that.

  The invention according to claim 4 is characterized in that a buffer region made of a material having a smaller viscoelasticity than that of the viscoelastic material is formed inside the member of the viscoelastic material.

  According to the fifth aspect of the present invention, a crack control reinforcing bar having a diameter smaller than that of the main reinforcing bar is arranged between the lower main reinforcing bar and the upper main reinforcing bar separately from the main reinforcing bar, so that cracks in the vicinity of the viscoelastic material mounting position are prevented. It is characterized by controlling and increasing the amount of the main bar coming out from the end of the member.

  In the invention according to claim 6, prestressing prestress is applied in a state where a viscoelastic material is applied to or attached to the main muscle, a reinforcing bar other than the main muscle is assembled in a state where the tension of the main muscle is maintained, and the form is installed. Then, the concrete was placed, and when the concrete was cured and reached a predetermined compressive strength, the tension of the main reinforcement was gradually reduced and gradually loaded to produce an energy absorbing precast concrete member.

  According to the invention according to claim 1, in addition to the main structural members such as columns and beams, the main structure having sufficient rigidity and proof stress without additionally installing a vibration damping device that impedes the functionality of the building. Although it is a member, it is possible to construct a building frame with excellent seismic resistance that is constructed of only columns and beams by having a high energy absorption performance, that is, a high damping performance, which is contradictory to this.

According to the second aspect of the present invention, negative shear deformation can be caused in advance by a commonly used technical means of tensioning the main bars and introducing prestress into the concrete by the pretension method.
In order to cause negative shear deformation in advance, it is only necessary to squeeze the main bar from the end face of the member, so a spiral sheath is placed in the concrete as in the post-tension method. It is also effective to insert a reinforcing bar inside and attach a viscoelastic material to the beam end region, and then apply a tensile force to the reinforcing bar.

  According to the invention of claim 3, the seismic load can be obtained by a simple means of applying or attaching a commercially available high-damping rubber or a resin-based material having similar mechanical properties to the main bar of the member end as a viscoelastic material. A large damping effect can be expected.

  According to the invention according to claim 4, since the buffer region made of a material having a smaller viscoelasticity than the viscoelastic material is formed on the inside of the member of the viscoelastic material, when negative shear deformation occurs in the viscoelastic material, As with the main reinforcement, the shear deformation has a uniform distribution, and a high damping effect can be imparted more efficiently.

  According to the fifth aspect of the invention, by arranging a crack control reinforcing bar having a small diameter separately from the main reinforcing bar and controlling the crack in the vicinity of the viscoelastic material mounting position, the amount of the main reinforcing bar protruding from the end of the member can be reduced. By increasing the length, the positive and negative cyclic deformation of the viscoelastic material can be increased, and a high damping effect can be maintained.

  According to the invention of claim 6, negative shear deformation is caused in advance by performing a simple process of applying pre-stressing prestress in a state in which a viscoelastic material is applied to or attached to the main muscles. In addition to main structural members such as beams and beams, it is possible to omit the process of additionally installing a vibration damping device that impedes the functionality of the building, and to provide high damping performance without impairing the rigidity and proof strength of the main structural members It is possible to build a building frame with excellent earthquake resistance that is constructed with only columns and beams.

FIG. 1 is a diagram showing shear stress-shear strain characteristics of a viscoelastic material applied to the main reinforcement of the energy absorbing precast concrete of the present invention. FIG. 2 is a diagram showing a deformed state of the vibration damping member in which a viscoelastic material is applied to the main muscles of the member end portion of the present invention. FIG. 3 is a view showing an example of semi-rigid joining at the end of a member according to the conventional invention. FIG. 4 is a diagram showing a manufacturing procedure of the precast concrete beam of the present invention. FIG. 5 is a diagram showing the deformation state of the beam and the viscoelastic material during the earthquake of the precast concrete beam of the present invention. FIG. 6 is a diagram showing an increase in negative shear deformation of a viscoelastic material due to a decrease in tensile force of the main muscle. FIG. 7 is a view showing an example in which a buffer material is provided on the beam inner side in the viscoelastic material attachment region. FIG. 8 is a diagram illustrating an example in which crack control reinforcing bars are provided. FIG. 9 is a diagram illustrating an example in which split reinforcement is applied.

Embodiment 1
First, the manufacturing method of the precast concrete member of this invention is demonstrated with reference to FIG.
A major feature of the method for producing a precast beam, which is a representative example of the precast concrete member of the present invention, is that a tensile force is applied in advance to a main bar used for the precast beam in a state where a viscoelastic material is applied or attached.
This method is a pre-tension type pre-stress introduction method that is already widely used in pre-stressed concrete structures. The tendon is in this case the main bar of the precast beam.

<Procedure 1>
A viscoelastic material is previously attached to a main bar used for the precast beam at a position corresponding to the beam end. The installation method includes a method of winding a ready-made product such as high damping rubber around a predetermined position of the main bar, and a spiral sheath with ribs to effectively transmit shear stress to the viscoelastic material as shown in the upper part of FIG. A method may be considered in which a liquid viscoelastic material is filled between the main muscles and then integrated by heat curing.
In the above state, prestress is introduced into the main muscle, and the subsequent work is performed in the same manner as the general pre-tension system work process, with the tension of the main muscle held, rebar assembly other than the main muscle, formwork installation, Work in the concrete placing procedure.

<Procedure 2>
After confirming that the compressive strength of the concrete has reached a predetermined strength, the tension force introduction by the pre-tension method is completed by gradually reducing and unloading the tension force of the main muscle.
When the introduction of the tension force by the pre-tension method is completed, the viscoelastic material is in a state of shear deformation as shown in the middle stage of FIG. The pre-tension method is based on the principle that pre-stress is introduced into the pre-cast member due to the adhesion between the main reinforcement and concrete near both ends of the beam.
The lower part of the figure shows the distribution of the tensile force of the main bar when tension is introduced. Although the viscoelastic material is softer than concrete, the tensile force A remains slightly in the region where the material is attached. Become.

  In the precast beam manufactured in the precast factory according to procedures 1 and 2, the main bars protruding from both ends of the beam are integrated with the column on the site. At this time, for example, it is easy to attach a general plate / nut type fixing tool in order to fix the main reinforcement in the column.

FIG. 5 shows the state of the column / beam joint constructed by the procedure as described above, and the deformation state of the beam member when subjected to an earthquake load.
In this figure, (a) shows the deformation state when the work is completed, (b) and (c) show the deformed state subjected to the seismic load, (b) shows when the beam bottom main bar is tensioned, and (c) shows that the beam bottom main bar is compressed. Indicates the state of the hour.
In the state of FIG. 5 (a), as described in the procedure 2 of FIG. 4, shear deformation (negative deformation) has already occurred in the viscoelastic material due to the indentation based on the prestress of the main muscle.

  Next, when a tensile force is generated in the corresponding main reinforcement, the state shown in FIG. 5B is obtained, and a reverse shear deformation (positive deformation) occurs in the viscoelastic material. When the tensile force of the main muscle is unloaded from that state, it returns to the initial state, i.e., the state in which negative shear deformation has occurred in the viscoelastic material, but the shear deformation at that time is more negative than the initial state. Deformation occurs.

  The reason for this is that, as shown in FIG. 6, when the main bar is subjected to a tensile force, adhesion deterioration between the main bar and the concrete occurs in the pre-tension anchoring area, as shown in FIG. This is because if the tensile force is unloaded under the influence, the remaining main bar tensile force in the anchoring area is reduced, and the anchoring area also spreads into the beam. In other words, it means that the tensile force originally applied at the time of beam manufacture is reduced, so that the main bar is further indented from the initial state, and as a result, the negative shear deformation of the viscoelastic material becomes larger.

  Repeated positive and negative shear deformation of the viscoelastic material in the process of changing the tensile force generated in the main bar at the beam end due to the seismic load from 0 to the state corresponding to the bending stress of the beam (unloading state). Even if the same member deformation occurs, a considerably high attenuation effect can be obtained more efficiently than the conventional invention described in Patent Documents 1 and 2 that receive shear deformation in only one direction (FIG. 1). reference). This phenomenon is a new principle proposed in the present invention, which is a point greatly different from the conventional invention.

In the state of FIG. 5 (c), the lower main bar is on the compression side and is in the same state as the above-described conventional invention. However, the viscoelastic material of the upper main bar is sheared with positive and negative cycles on the same principle as when the lower main bar is pulled. Deformation will occur, and the entire member will always be given a high damping effect by the viscoelastic material.
Therefore, in the present invention, when the deformation of the beam increases due to the seismic load, the viscoelastic material always undergoes positive and negative repeated shear deformation, and a damping effect can be obtained reasonably and efficiently. In addition, since a damping effect can be obtained simply by attaching a viscoelastic material to the main bar at the end of the beam and applying a tensile force (tension) to the main bar in advance, the beam member is sufficient for both constant loads and seismic loads. It also fulfills the role of a main structural member having a high rigidity and bending strength.

<< Embodiment 2 >>
As shown in FIG. 2 and FIG. 5, the viscoelastic material undergoes almost uniform positive shear deformation in the attachment region of the same material when the main bar is pulled, as shown in FIGS.
On the other hand, in the initial state (when construction is completed) and the state in which the main bar's tensile force is unloaded, the column face surface (beam end surface) to which the beam is attached is in a negative shear deformation state due to the main bar indentation. As shown in Fig. 5, the compressive stress is applied to the same material at the position inside the beam, and uniform shear deformation does not occur as in the case of pulling the main bar.

  Therefore, a buffer region as shown in FIG. 7B is provided on the beam inner side of the region where the viscoelastic material is attached (opposite the beam end). For the buffer region, grease or asphalt that is softer than the viscoelastic material is suitable. By adopting this configuration, when negative shear deformation occurs in the viscoelastic material, the shear deformation becomes a uniform distribution in the same manner as when the main muscle is pulled, and a high damping effect can be more efficiently imparted. .

<< Embodiment 3 >>
The present invention has a reinforced concrete structure at the end of the member and a prestressed concrete structure at the center of the member. Therefore, compared to the reinforced concrete structure as a whole, prestress is introduced in the center of the member, so almost no cracks occur, and the cracks concentrate on the edges, so that positive and negative cyclic deformation of the viscoelastic material is also possible. Has the advantage of becoming larger.
In order to further enhance the effect, as shown in FIG. 8, a relatively thin crack control reinforcing bar is arranged between the lower main bar and the upper main bar at the end of the member separately from the main bar, thereby attaching a viscoelastic material. By controlling the cracks near the position, it is possible to lengthen the length of the main bars coming out from the end of the member.

<< Embodiment 4 >>
In the present invention, by using high-strength reinforcing bars (SD490 to SD685) and high-strength concrete of 60 N / mm ² or more as the main bars, if the main bars are designed not to yield even in a large earthquake, the energy absorption during a large earthquake Regardless of the hysteretic damping that accompanies plasticization, the main reinforcement is not yielded after the earthquake, and residual cracks can be reduced after the earthquake. You can design a skeleton.

<< Other Embodiments >>
<Pillar>
So far, the beam member has been described, but the same effect can be expected for the column member.
If the present invention is applied to a piloty-type lower pillar with severe use restrictions, a building with high design and functionality can be constructed without providing a separate vibration control device or the like.

<Long span beam>
As a conventional technique, there is a pre-tensioned pre-stressed concrete beam using a high-strength reinforcing bar as a tension material. In this beam, if the strength of the high-strength reinforcing bar used as a tension material is high (SD590 or higher), or if the cover thickness of the main bar is small, when the pretension type tension is introduced, the concrete along the main bar at the end of the beam Split fracture may occur.
As a countermeasure, an invention as shown in FIG. 9 (Japanese Patent No. 4326518) has been proposed. As shown in the figure, the present invention is a construction method in which an unbonded region is provided in the main reinforcement at the beam end portion that is the starting point of split fracture, and the spiral reinforcement is reinforced around the main reinforcement in the vicinity thereof.
However, this invention has a problem that energy absorption ability cannot be expected when used as a girder, but in this unbonded area, negative shear deformation has occurred in advance due to penetration of the main reinforcement in the present invention, and when subjected to an earthquake load, it is negative. A high damping effect can be imparted to the beam by attaching a viscoelastic material that generates a shear deformation with a greater positive and negative cycle than the shear deformation.

Claims (6)

  When the viscoelastic material applied to or attached to the main bar at the end of the member is subjected to a negative shear deformation in advance due to the penetration of the main bar and is subjected to an earthquake load, the shear deformation is greater than the negative shear deformation. Energy absorbing precast concrete member that produces   The viscoelastic material applied or attached to the main bar at the end of the member is prestressed in the pretension system and prestress is introduced into the concrete, and negative shear deformation has occurred in advance due to the penetration of the main bar. An energy-absorbing precast concrete member that absorbs energy by generating a positive and negative cyclic shear deformation larger than the negative shear deformation when receiving.   The viscoelastic material is a high-damping rubber or a resin-based material having a similar mechanical characteristic that has a large hysteresis area and can be expected to have a damping effect when subjected to repeated positive and negative shear deformations. The energy absorption type precast concrete member according to any one of claims 1 to 2.   The buffer region made of a material having a smaller viscoelasticity than the viscoelastic material is formed on the inside of the member of the viscoelastic material applied or attached to the main muscle. The energy absorption type precast concrete member described in any one.   By placing a crack control reinforcing bar with a smaller diameter than the main reinforcing bar between the lower and upper main reinforcing bars at the end of the member, the cracks near the attachment position of the viscoelastic material can be controlled. The energy absorption type precast concrete member according to any one of claims 1 to 4, wherein an amount of the main reinforcement is increased.   Prestressing prestress is applied with viscoelastic material applied to or attached to the main reinforcement, and reinforcing bars other than the main reinforcement are assembled, a formwork is installed, and concrete is placed, while maintaining the tension of the main reinforcement. A method for producing an energy-absorbing precast concrete member in which the tension of the main muscle is gradually reduced and the load is gradually reduced when a predetermined compressive strength is reached.