JP2001011938A - Shear preventive for coupling steel with concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shear preventive for coupling steel with concrete to prevent cracks by minimizing the effect of the deformation restriction of a concrete by a steel against the deformation caused by the time-dependent creep and drying/shrinkage which is a phenomenon specific to the concrete and the deformation of the concrete caused by the temperature difference from that of the steel accompanied by the curing heat of the concrete at the timing of the young life of the concrete immediately after the placement of the concrete to until the specified time is elapsed. SOLUTION: In a shear preventive to couple a concrete provided on a surface of a steel 3 in a structure formed of the steel 3 and the concrete, a resin 7 long in curing time is covered around the shear stopper to control the delay of the timing of demonstrating the synthesis effect of the steel 3 and the concrete when the concrete is placed on the surface of the steel 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for preventing slippage of steel and concrete in a structure made of steel and concrete such as a building or a bridge.

[0002]

2. Description of the Related Art Steel and concrete constituting a structure are
As the material properties, steel has a high material strength and excellent plastic deformation, and concrete has a property that it is strong against compression, but has extremely low tensile strength as compared with compressive strength.

[0003] Among structures made of steel and concrete,
The composite girder known from old times is a structure that is formed by rationally combining such characteristics of steel and concrete, and that the steel and concrete integrally resist the cross-sectional force.

Conventionally, as a structure for integrating these different materials, steel and concrete, it has been generally used to provide a mechanical coupling means such as a slip stopper on the surface of the steel material. What is known is FIG.
And studs with heads, horseshoe-shaped dowels and the like as shown in FIG.

[0005] The composite girder structure is a structure combining the material properties of steel and concrete as described above. However, concrete phenomena such as remarkably low tensile strength and shrinkage due to creep and drying. is there. For example, in continuous composite girder, due to creep and drying shrinkage of concrete and temperature difference between concrete slab and steel girder,
Tensile stress is generated in the floor slab, and particularly on the intermediate fulcrum, large tensile stress is generated in the concrete slab and cracks may occur in the concrete.

Conventionally, as a method for solving such a problem, a method in which prestress is introduced into a tension region of concrete as necessary is disclosed in Japanese Patent Laid-Open No. 63-1935.
No. 3 and Japanese Patent Application Laid-Open No. 10-317324, there is a method in which the force transmitted to concrete is reduced by using a soft stop which is expected to be elastically combined to prevent or limit cracks in the concrete structure. Are known.

[0007]

Among the above prior art methods, the method of introducing prestress into the tension region of concrete involves a method in which concrete and steel girders are completely combined with headed studs or horseshoe dowels. If prestress is introduced by steel, the compressive force of PC steel will be introduced not only into concrete but also into steel girders, and stress transfer between steel girders and concrete due to the plastic deformation of concrete due to creep. Occurs,
A problem arises in that the compression force introduced into the concrete slab causes stress relaxation.

[0008] The influence of creep increases as the binding force of the steel girder increases. Therefore, the prestress introduced into the concrete slab using the PC steel material needs to be introduced in a larger amount by adding this stress relaxation amount. There is a problem that steel materials cannot be arranged.

On the other hand, in the method of reducing the tensile stress acting on the concrete floor slab as an elastic composite girder structure in which the rigidity of the slip stopper itself is softened as disclosed in JP-A-63-19353 and JP-A-10-317324, concrete is On the other hand, it is possible to reduce the force acting on the steel girder, but it is pointed out that the required ratio of the steel girder to the force is increased, so that the required cross section of the steel girder becomes larger than that of the complete composite girder.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems in the conventional method for preventing a steel material and a concrete from being connected with each other and has been described above. When the concrete age is young, the deformation caused by time-dependent creep and drying shrinkage, which is a phenomenon peculiar to concrete, and the deformation of concrete caused by the temperature difference from steel due to the heat of hardening of concrete. It is another object of the present invention to provide a joining slip stopper that minimizes the influence of concrete deformation constraint by steel and prevents the occurrence of cracks.

According to a first aspect of the present invention, there is provided a slip stopper for connecting concrete to a steel surface in a structure made of steel and concrete, wherein the slip stopper is provided around the slip stopper. The present invention is characterized in that a resin having a long hardening time is coated so that when concrete is cast on the surface of steel, the time when the effect of synthesizing steel and concrete is exerted can be delayed and controlled.

According to a second aspect of the present invention, in the first aspect of the invention, the resin coated around the slip stopper is in a gel state when not cured, but when cured, the compressive strength changes to be higher than the compressive strength of concrete. It is characterized by that.

According to a third aspect of the present invention, in the first aspect of the present invention, the resin coated around the slip stopper is a room temperature curing type epoxy resin, and the curing time is from one week to one week depending on the amount of the curing agent added. The feature is that it can be adjusted to the range of the year.

According to a fourth aspect of the present invention, in the first aspect of the present invention, a cylinder is provided coaxially around the lower half of the slip stopper fixed to the steel, and a resin having a long curing time is provided inside the cylinder. The resin is coated around the slip stopper by filling.

[0015]

With the slip stopper of the present invention, a gel-like resin, which cures gradually over a long period of time, is provided on the outer periphery of the slip stopper. When deformation due to creep / drying shrinkage due to hardening over time, or deformation due to the temperature difference from steel due to the heat of hardening of the concrete occurs, the gel-like resin appropriately follows these deformations of the concrete, Is appropriately deformed into a shape corresponding to the deformation of.

As a result, in the joint between the steel material and the concrete, the joint between the concrete and the periphery of the slip stopper provided with the gel resin is seen. The effect of the deformation constraint can be greatly reduced, and the tensile stress on concrete can be reduced to suppress the occurrence of cracks.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a steel-concrete coupling stopper according to an embodiment of the present invention. FIG. 1 shows a structure in which a stud with a head is used as a stopper. After welding the lower end of the part 1 to the steel material 3, a cylindrical body 6 made of plastic, metal, cardboard, or the like is fitted around the lower part of the shaft part 1 except for the head part 2, and the room temperature is set in the cylindrical body 6. A gel-like delayed-setting synthetic resin 7 having a consistency of about 300, in which the lower curing gradually progresses with the passage of a relatively long time, is filled and sealed so as to maintain a predetermined thickness t.

The cylindrical body 6 for filling the inside with the resin 7 is
In a state fitted to the outer periphery of the stud shaft portion 1, the cylindrical body 6 is held coaxially with the shaft portion 1, and the lower end of the cylindrical body 6 is separated from the steel material 3, and the resin 7 filled therein is filled with the external material. It is preferable that the lower end of the cylindrical body 6 is fixed to the steel material 3 with an adhesive 8 or the like so as not to leak to the steel material 3, and concrete 12 is cast on the steel material 3 later on the upper end of the cylindrical body 6. In order to prevent the concrete 12 from being mixed into the cylindrical body 6 when it is done, it is preferable to provide a thin lid plate 9 which can move freely with respect to the cylindrical body 6 at the upper end of the cylindrical body 6.

As shown in FIG. 3, the stud shaft 1
In order that the cylindrical body 6 fitted to the outer periphery of the cylindrical body 6 is held coaxially with the shaft part 1, a stud shaft part
Alternatively, a bottom plate 11 having a hole 10 through which is relatively flexible and which does not restrain the cylindrical body 6 may be provided.

However, the cylindrical body 6 is for holding the gel-like resin 7 to be filled therein only to a predetermined thickness t on the outer periphery of the shaft portion 1, and the concrete 12 is later struck by the concrete 12. When installed, or when the concrete 12 shrinks and deforms due to hardening or the like, the internal resin 7 must be able to freely deform and follow the movement and deformation of the concrete. Hardness and steel 3
Should not restrict the movement of the resin 7 inside.

FIG. 4 shows a structure in which a horseshoe-shaped dowel is used as a slip stopper. After welding a block 5 having both ends of a loop bar 4 fixed to a steel material 3, the outer periphery of the block 5 is made of the same material as described above. A cylindrical body 6 made of the following is fitted into the cylindrical body 6, and the same gel-like setting delay type synthetic resin 7 as described above is filled and sealed. Is provided with a thin lid plate 9 which can freely move.

The above-mentioned gel-like setting delay type synthetic resin 7 is
Cold-setting epoxy resin is preferred
Adjust the amount of amine-based curing agent in advance in consideration of
The curing time can be set freely according to the target structure.
It can be set, and in the case of this embodiment, from one month to
Uses one that gradually cures over a long period of about one year
Is done. The gel resin 7 has a compressive strength after curing.
Is 700kg / cm² And the compressive strength of concrete (3
00kg / cm²) Is more than twice the value of
Outside, tensile strength 200kg / cm², Modulus of elasticity 800
00kg / cm²130kg shear bond strength with steel
/ Cm²With characteristic values such as curing shrinkage of 1.0% or less
ing.

As a guide for freely setting the hardening time according to the purpose, for example, the concrete tensile force generated due to the temperature difference from the steel material due to the heat of hardening of the concrete at the time of placing the slab concrete is reduced. For the purpose, since the heat generation of the concrete lasts for about one week, it is suitable that the amount of the amine-based hardener is slightly increased and the hardening is not performed for about one week after the concrete is poured.

Further, in the case of a composite structure in which prestress is introduced into concrete by using a PC steel material, if the purpose is to reduce the restraint of the steel material so that the prestress can be directly applied to the concrete, the prestress is introduced when the prestress is introduced. It is preferable to adjust so that the state where the resin is not cured is maintained.

Further, for the purpose of reducing the tensile force of the concrete generated by the drying shrinkage of the concrete, most of the drying shrinkage ends relatively early after the concrete is cast. The curing time is set so that the resin does not cure for about three months after casting concrete.

Similarly, when it is desired to reduce the effect of concrete creep, the longer the period until the continuous load acts on the concrete, the smaller the creep coefficient becomes. Therefore, the resin hardens for at least three months after the concrete is cast. The curing time is set so that it does not.

This slip-preventing structure is a structure in which a gel-like resin 7 is coated on the outer periphery of a stud or a dowel to allow a shear force generated when the steel material 3 and the concrete 12 are joined to be shifted. The lift acting on the studs and dowels is a structure that bears the force, so in the case of the stud with head shown in FIG.
In the case of the horseshoe-shaped dowel shown in FIG. 4, the loop 4 is fixed to the concrete 12.

Accordingly, in the case of a stud with a head, the range in which the resin 7 is coated on the stud or the dowel is from 1/2 to 2 from the lower end of the shaft portion 1 except for the head 2.
It is preferable that the cylindrical body 6 is provided on the outer periphery of a height portion of about / 3, and in the case of a horseshoe-shaped dowel, the outer periphery of the block portion 5 is covered with the cylindrical body 6.

FIG. 6 is a graph showing the ratio of the shear force to the displacement between the steel material 3 and the concrete 12 before and after the resin 7 is cured. After hardening of the resin, the slip property between the steel material and the concrete is similar to that of a general slip stopper.
Therefore, as shown in FIG. 6, the thickness t of the resin 7 to be provided on the outer periphery of the headed stud or the horseshoe-shaped dovetail is a thickness that is equal to or more than the amount that can absorb the deviation between the steel material and the concrete assumed in the design. Required.

For example, in a composite structure in which a prestress is introduced into concrete by using a PC steel material, a concrete part of a synthetic girder having a length of 20 m is used as an example when it is desired to directly apply prestress to the concrete by reducing the restraint of the steel material. In a structure in which a compression amount of 50 kgf / cm ² is introduced into the concrete, the concrete is shrunk by about 3 mm by elastic deformation and 1.5 mm at both ends of the girder by the introduction of prestress. 5 mm is sufficient for the thickness t including the construction error. But,
This is an example of the case where the concrete shrinks and deforms due to the introduction of prestress, and it is necessary to absorb other deformation such as drying shrinkage and creep,
Therefore, the thickness t of the resin 7 provided on the outer periphery of the stud or the dowel is preferably set to about 10 mm.

[0031]

As described above, in the slip stopper for connection of the present invention, since the gel resin which gradually proceeds over a longer time is coated around the slip stopper, concrete During the period when the concrete age is short from the time immediately after the casting is completed until the predetermined time has elapsed, the concrete is affected by time-dependent deformation due to creep and drying shrinkage, which is a phenomenon peculiar to concrete, and the concrete is caused by the heat of hardening. Even if deformation due to the temperature difference from the steel girder occurs, the uncured resin appropriately follows the deformation, minimizing the effect of the concrete deformation constraint by the steel material, reducing the tensile stress, and Occurrence can be suppressed.

Further, in the coupling slip stopper of the present invention, before the resin around the slip stopper is hardened, it exhibits the same behavior as that of the conventional elastic composite structure in which rigidity is softened. After the resin hardens over time, its compressive strength changes more than the compressive strength of concrete,
Since a completely composite structure different from the conventional elastic composite structure is provided, the share of the force borne by the steel material is smaller than that of the elastic composite structure, and the required steel material cross section can be reduced.

Further, in the composite structure in which a prestress of a PC steel material is introduced into concrete cast on steel using the slip stopper for connection according to the present invention, the uncured resin of the slip stopper at the time of introducing the prestress is replaced with concrete. The effect of the steel material that restrains the compressive deformation can be reduced, so that the prestress loss due to the restraint of the steel material can be reduced, and the amount of prestress introduced can be reduced, and the required amount of PC steel material can be reduced. It can be an economic structure.

[Brief description of the drawings]

FIG. 1 is a side cross-sectional view in a case where a coupling stopper according to the present invention is applied to a stud with a head.

FIG. 2 is a horizontal sectional view of the same.

FIG. 3 is a side sectional view using a cylinder having a shape different from that of FIG. 1;

FIG. 4 is a side cross-sectional view when the coupling slip stopper is applied to a horseshoe dowel.

FIG. 5 is a horizontal sectional view of the coupling stopper in FIG. 4;

FIG. 6 is a graph showing a ratio between a shear force and a shift between a steel material and concrete in a state before and after hardening of a hardening-delay resin provided on an outer periphery of a slip stopper.

[Explanation of symbols]

 1: Shaft part 2: Head part 3: Steel material 4: Loop streaks 5: Block 6: Cylindrical body 7: Hardening delay type synthetic resin 8: Adhesive 9: Cover plate 10: Hole 11: Bottom plate 12: Concrete

Continued on the front page F term (reference) 2D059 AA11 GG02 GG55 2E125 AA76 AB11 AC04 AC28 AF01 BA03 BA25 BA33 BA52 BB08 BB28 BB37 BD03 BE03 BF08 CA82

Claims (4)

[Claims] 1. A slip stopper for joining concrete provided on a surface of steel in a structure composed of steel and concrete, wherein a resin having a long hardening time is coated around the slip stopper. A non-slip joint for steel and concrete that enables delay control of the time when the effect of combining steel and concrete is exhibited when concrete is poured on the surface of the concrete. 2. The steel and concrete according to claim 1, wherein the resin coated around the slip stopper is in a gel state when uncured, but when cured, the compressive strength changes to be equal to or greater than the compressive strength of concrete. Non-slip for coupling. 3. The resin coated around the slip stopper is a cold-setting epoxy resin, and the curing time can be adjusted within a range of one week to one year by adding an amount of a curing agent. For connecting steel and concrete. 4. A cylinder is coaxially provided on the outer periphery of the lower half of the slip stopper fixed to the steel, and a resin having a long hardening time is filled in the inside of the cylinder, whereby the resin is surrounded around the slip stopper. A slip stopper for bonding the steel and concrete of claim 1 with the coating.