JP3429222B2 - Non-slip for joining steel and concrete - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slip-prevention structure for joining steel and concrete in a structure made of steel and concrete such as a building and a bridge.

[0002]

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

Among structures made of steel and concrete,
A composite girder that has been known for a long time is a structure that is configured by reasonably combining the characteristics of such steel and concrete, and that the steel and concrete integrally resist the cross-sectional force.

As a structure for integrating steel and concrete, which are different materials, it has been customary in the past to provide a mechanical coupling means such as a slip stopper on the surface of the steel material. As is known, Figure 1
And headed studs, horseshoe dowels, etc., as shown in FIG.

The composite girder structure is a structure in which the above-mentioned material properties of steel and concrete are combined, but concrete has a peculiar phenomenon such as low tensile strength and shrinkage due to creep and drying. is there. For example, in a continuous composite girder, due to creep / dry shrinkage of concrete, temperature difference between concrete floor slab and steel girder, etc.
Tensile stress is generated in the slab, and particularly on the intermediate fulcrum, a large tensile stress is generated in the concrete slab, which may cause cracking in the concrete.

[0006] Conventionally, as a method of coping with such a problem, there is a method of introducing a prestress into a tensile region of concrete, if necessary, as disclosed in JP-A-63-1935.
No. 3 and Japanese Patent Laid-Open No. 10-317324, there is a method for preventing or limiting cracking of a concrete structure part by reducing the force transmitted to concrete by using a soft or some stopper which is expected to be elastically synthesized. Are known.

[0007]

Among the above-mentioned conventional techniques, in the method of introducing prestress in the tensile region of concrete, PC is used in the state where concrete and steel girders are completely combined by headed studs or horseshoe-shaped dowels. If the prestress is introduced by the steel material, the compressive force by the PC steel material will be introduced not only by the concrete but also by the steel girder, and the stress of the steel girder and the concrete will be transferred due to the phenomenon that the concrete is plastically deformed by creep. Occurs,
There is a problem that the compressive force introduced into the concrete floor slab causes stress relaxation.

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

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 shift stopper itself is softened, as in Japanese Patent Laid-Open No. 63-19353 and Japanese Patent Laid-Open No. 10-317324, concrete is used. Although the force acting on the steel can be reduced, the proportion of steel girder that bears the force is large, so defects such as the required steel girder cross section being larger than that of a completely composite girder are pointed out.

[0010]

SUMMARY OF THE INVENTION The present invention takes into consideration the problems in the conventional slip stopper for joining steel material and concrete as described above, until a predetermined time elapses immediately after the concrete is placed. During the period when the concrete material age is young, deformation caused by time-dependent creep / drying shrinkage, which is a phenomenon peculiar to concrete, and deformation of concrete caused by the temperature difference between steel and the heat of hardening of concrete The purpose of the present invention is to provide a slip stopper for coupling in which the influence of the deformation restraint of concrete by the steel material is minimized to prevent the occurrence of cracks.

As a specific means therefor, the invention is a slip stopper for joining concrete to the surface of steel in a structure composed of steel and concrete, and is provided around the slip stopper. It is characterized in that a resin having a long curing time is coated so that when the concrete is cast on the surface of the steel, the timing at which the combined effect of the steel and the concrete is exerted can be delayed and controlled.

According to a second aspect of the present invention, in the first aspect of the present invention, the resin coated around the slip stopper is in a gel state when uncured, but when it is cured, the compressive strength is changed to a value higher than that of concrete. It is characterized by being

According to a third aspect of the invention, in the first aspect of the invention, the resin coated around the stopper is a room temperature curing type epoxy resin, and the curing time is 1 week to 1 depending on the amount of the curing agent added. It is characterized in 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 coaxially provided on the outer periphery of the lower half portion of the slip stopper fixed to steel, and a resin having a long curing time is provided inside the cylinder. The filling is characterized in that the resin is coated around the shift stopper.

[0015]

In the binding stopper of the present invention, a gel resin is provided on the outer periphery of the stopper so that the hardening gradually progresses over a long time. When the deformation due to creep / drying shrinkage due to hardening over time or the deformation due to the temperature difference with the steel due to the hardening heat of concrete occurs, the gel resin appropriately follows these deformations of concrete, The shape is appropriately changed to correspond to the deformation of.

As a result, of the joints between the steel material and the concrete, regarding the joints between the concrete and the slip stopper provided with the gel-like resin, at this portion, the deformation of the gel-like resin causes It is possible to significantly reduce the influence of deformation constraint, reduce the tensile stress on concrete, and suppress the occurrence of cracks.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The construction of a slip stopper for joining steel and concrete according to the present invention will be described with reference to an embodiment shown in the drawings. FIG. 1 shows a structure in which a headed stud is used as the slip stopper. After the lower end of the portion 1 is welded to the steel material 3, a tubular body 6 made of plastic, metal, cardboard or the like is fitted to the outer periphery of the lower portion of the shaft portion 1 excluding the head portion 2, and the tubular body 6 is kept at room temperature. A gel-like retardation-type synthetic resin 7 having a consistency of about 300, in which the curing under the gradual progress of a relatively long time, is filled and sealed so as to maintain a predetermined thickness t.

The tubular body 6 for filling the inside with the resin 7 is
In the state of being fitted to the outer periphery of the stud shaft portion 1, the tubular body 6 is held coaxially with the shaft portion 1, and the lower end of the tubular body 6 is separated from the steel material 3 and the resin 7 filled inside is external. In order to prevent leakage to the steel material 3, it is preferable to fix the lower end of the cylindrical material 6 to the steel material 3 with an adhesive 8 or the like, and at the upper end of the cylindrical material 6, concrete 12 is placed on the steel material 3 later. In order to prevent the concrete 12 from mixing into the tubular body 6 when it is crushed, it is preferable to provide a thin lid plate 9 that can freely move with the tubular body 6 on the upper end of the tubular body 6.

As shown in FIG. 3, the stud shaft portion 1
In order to hold the cylindrical body 6 fitted to the outer periphery of the stud shaft portion 1 coaxially with the shaft portion 1, the stud shaft portion 1 is previously attached to the lower end of the cylindrical body 6.
It is also possible to provide a bottom plate 11 having a hole 10 formed therethrough and which is relatively flexible and does not restrain the tubular body 6.

However, the cylindrical body 6 is only for holding the gel-like resin 7 to be filled inside on the outer periphery of the shaft portion 1 with a predetermined thickness t, and the concrete 12 will be poured later. When installed, or when the concrete 12 contracts and deforms due to hardening or the like, the resin 6 inside must be allowed to freely follow the movement and deformation of the concrete, so that the tubular body 6 can be deformed by itself. Hardness and steel 3
The movement of the resin 7 inside should not be restricted by the fixing with.

FIG. 4 shows a structure in which a horseshoe-shaped dowel is used as a slip stopper. After the block 5 having both ends of the loop muscle 4 fixed thereto is welded to the steel material 3, the outer periphery of the block 5 is made of the same material as described above. The cylindrical body 6 made of the above is fitted, and the gel-like hardening retardation synthetic resin 7 similar to the above is filled and sealed in the cylindrical body 6, and the cylindrical body 6 is provided on the upper end of the cylindrical body 6 including the upper surface of the block 5. A thin cover plate 9 that can move freely is provided.

As the gel-type delayed curing synthetic resin 7,
For room temperature curing type epoxy resin is preferable,
In consideration of the above, adjust the amount of amine curing agent added in advance.
Allows you to set the curing time freely according to the target structure.
In the case of this embodiment, one month to
Used that gradually cures over a long period of about one year
To be done. Also, this gel-like resin 7 has a compressive strength after curing.
Is 700 kg / cm^Two And the compressive strength of concrete (3
00 kg / cm^Two) Is more than twice the value of
Outside, tensile strength 200 kg / cm^Two, Modulus of elasticity 800
00 kg / cm^Two, Shear bond strength with steel materials 130kg
/ Cm^TwoWith a characteristic value such as curing shrinkage of 1.0% or less
ing.

As a guideline for freely setting the hardening timing according to the purpose, for example, the concrete pulling force generated by the temperature difference between the concrete and the steel material due to the hardening heat of the concrete at the time of placing the slab concrete is reduced. For this purpose, the heat of the concrete continues for about one week, so it is suitable to add a slightly larger amount of the amine-based curing agent so that it does not cure for about one week after placing the floor slab concrete.

Further, in the case of a composite structure in which prestress is introduced into the concrete by PC steel material, when the purpose is to reduce the restraint of the steel material so that the prestress is directly applied to the concrete, when the prestress is introduced, It is preferable to adjust so that the uncured state of the resin is maintained.

Further, for the purpose of reducing the tensile force of the concrete caused by the drying shrinkage of the concrete, most of the drying shrinkage ends relatively early after the concrete is placed, so that the addition amount of the curing agent is reduced. Set the curing time so that the resin does not cure for about 3 months after the concrete is placed.

Similarly, when it is desired to reduce the effect of concrete creep, the creep coefficient becomes smaller as the period until the continuous load acts on the concrete becomes smaller. Therefore, the resin hardens for 3 months or more after the concrete is placed. The curing time is set so as not to.

This slip-preventing structure is a structure in which the outer periphery of a stud or a dowel is covered with a gel-like resin 7 to allow the shearing force generated when the steel material 3 and the concrete 12 are joined to be offset. As for the lift force acting on the studs and gibber, the structure is responsible for the force, so in the case of the headed stud of Fig. 1, the head 2,
In the case of the horseshoe-shaped dowel shown in FIG. 4, the loop bar 4 is fixed to the concrete 12.

Therefore, in the case of a headed stud, the range in which the resin 7 is coated on the stud or the dowel is 1/2 to 2 from the lower end of the shaft 1 with the head 2 left.
It is preferable that the cylindrical body 6 is provided on the outer periphery of the 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 deviation between the steel material 3 and the concrete 12 before and after the resin 7 is hardened. Before the resin 7 is hardened, a large deviation is caused by a low load. After the hardening of the resin, the slip property between the steel material and the concrete is the same as the general slip prevention.
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 dowel is not less than the amount that can absorb the deviation between the steel material and the concrete assumed in the design. Will be needed.

For example, in the case of a composite structure in which prestress is introduced into concrete by PC steel material and it is desired to directly prestress the concrete by reducing the restraint of the steel material, the concrete part of the composite girder with a length of 20 m is used. In the structure in which a compression amount of 50 kgf / cm ² is introduced, the concrete contracts by elastic deformation by about 3 mm due to the introduction of prestress and deforms 1.5 mm at both ends of the girder. The thickness t of 5 mm is sufficient including the construction error. But,
This is an example of the case where concrete is contracted and deformed by the introduction of prestress, and it is necessary to be able to absorb other deformations such as drying contraction and creep.
Therefore, it is preferable that the thickness t of the resin 7 provided on the outer periphery of the stud or the dowel be about 10 mm.

[0031]

As described above, in the binding stopper according to the present invention, since the gel-like resin which gradually advances over a long curing time is coated around the stopper, concrete is prevented. During the period when the age of the concrete is young from immediately after placing the concrete until the predetermined time elapses, the phenomenon due to the time-dependent creep / drying shrinkage, which is a phenomenon peculiar to concrete, and the heat of hardening of the concrete Even if deformation occurs due to the temperature difference between the steel girder and the steel girder, the uncured resin appropriately follows the deformation and the effect of the deformation constraint of the concrete by the steel material is reduced as much as possible to reduce the tensile stress and cracks. Occurrence can be suppressed.

Further, in the coupling stopper of the present invention, before the resin around the stopper is hardened, the same behavior as that of the conventional stopper having an elastic synthetic structure with softened rigidity is exhibited. After the resin hardens with the passage of time, its compressive strength changes beyond the compressive strength of concrete.
Since the completely synthetic structure is different from the conventional slip-prevention of the elastic composite structure, the force sharing by the steel material is less than that of the slip-prevention of the elastic composite structure, and the required steel material cross section can be reduced.

Further, in the synthetic structure in which the prestress of the PC steel material is introduced into the concrete cast into the steel material using the slip stopper for coupling of the present invention, the uncured resin which is the slip stopper at the time of introducing the prestress is made of the concrete. It is possible to reduce the influence of the steel material that restrains the compressive deformation, and therefore it is possible to reduce the prestress loss due to the restraint of the steel material and the amount of prestress to be introduced, and to reduce the required amount of PC steel material. It can have an economical structure.

[Brief description of drawings]

FIG. 1 is a side cross-sectional view of a headed stud to which a coupling stopper according to the present invention is applied.

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

FIG. 3 is a side sectional view using a cylindrical body having a shape different from that of FIG.

FIG. 4 is a side sectional view of the horseshoe-shaped dowel provided with the coupling stopper.

5 is a horizontal cross-sectional view of the coupling stopper in FIG.

FIG. 6 is a graph showing the ratio of the shear force to the shear between the steel material and the concrete before and after the curing of the delayed curing resin provided on the outer periphery of the shift stopper.

[Explanation of symbols]

1: Shaft 2: Head 3: Steel 4: Loop muscle 5: Block 6: cylinder 7: Delayed curing type synthetic resin 8: Adhesive 9: lid plate 10: hole 11: Bottom plate 12: Concrete

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-317324 (JP, A) JP-A-11-166208 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) E04B 1/16 E04B 1/30 E04B 1/38 E01D 1/00

Claims (3)

(57) [Claims] 1. A displacement preventing for joining concrete provided on the surface of the steel in the constructed structure of steel and concrete, around the displacement-preventing, Not
When cured, it is gel-like, but when cured it has a compressive strength
By coating a resin with a long curing time that changes beyond the compressive strength of the reit, when concrete is placed on the surface of the steel, the uncured resin follows the deformation of the concrete,
With the passage of time, after the resin has hardened, it becomes a composite structure with concrete so that the timing at which the composite effect of steel and concrete is exerted can be delayed and controlled. Stop. 2. The resin coated around the anti-slip member is an ordinary temperature curing type epoxy resin, and the curing time can be adjusted within the range of 1 week to 1 year depending on the addition amount of the curing agent. A slip stopper for joining steel and concrete. 3. A cylindrical body is coaxially provided on the outer periphery of the lower half of the shift stopper fixed to steel, and a resin having a long curing time is filled inside the cylindrical body to prevent the resin from surrounding the shift stopper. A slip stopper for joining the coated steel and concrete according to claim 1.