JPH08144409A - Bearing structure for end part of precast concrete member - Google Patents

Abstract

PURPOSE: To obtain a bearing part of which the bearing structure is extremely simple and plain, by a method wherein bar-shaped metallic bearings are partially overhung from the end of precast concrete member, are placed at the upper face of the end part thereof, and are connected to reinforcements, which are positioned to the end of the precast concrete member of the bearings and are hung down in the concrete of the member from the bearings. CONSTITUTION: Bar-shaped metallic bearings 10 are partially overhung from the end of a precast concrete member, are placed at the upper face of the end part thereof, and are connected to reinforcements 11, which are positioned to the end of the member 1 of the bearings 10 and are hung down in the concrete of the member 1 from the bearings 10. In this case, these reinforcements 11 are each connected mechanically to main reinforcements 3, and are strongly fastened to the bearings 10 by mechanical connection, welding, or the like. In this way, forms for closing the clearance caused above the upper part of a supporting member, which clearance is caused between the bearing parts of precast concrete members, i.e., clearance forms, are made unnecessary, and the height of a slab is restrained at the minimum, and thus a bearing part the structure of which is extremely simple and plain can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precast concrete member end support structure, and is particularly suitable for a precast concrete slab for a synthetic slab which is preferably used for construction.

[0002]

2. Description of the Related Art In Japanese Utility Model Laid-Open No. 4-119807, as shown in FIG. 9, a support portion of a precast concrete member 40 having both ends mounted and supported on a support structure is provided with a portion to be mounted on the support structure. There is disclosed a bearing structure in which a vertical metal plate 41 having a portion embedded in a precast concrete member is provided, and a shear strength portion 42 is provided in a portion of the metal plate 41 inside the precast concrete member 40. In Japanese Utility Model Publication No. 6-28581, as shown in FIGS. 10 to 12, there are integrally formed ribs projecting in the longitudinal direction on the lower surface. In a precast concrete plate 50 for a synthetic floor, which casts a cast-in-place concrete 53 on the upper surface to form a synthetic floor, an end portion having flat plate portions without the ribs at both ends is integrally provided, and an upper edge is provided at the erection end portion. There is disclosed a precast concrete board 50 for a synthetic floor in which an end reinforcing steel frame 51 protruding to the upper surface side is embedded.

In use of the precast concrete board 50 for the synthetic floor, the erection end having a plate-like portion without a ridge on the lower surface is erected by mounting it on a large beam 52 made of reinforcing bar or steel concrete or steel frame. , Rebar 5 on it
4 is assembled and a cast-in-place concrete 53 is cast to form a composite floor. Shear stress at the erection end is mainly borne by the end-reinforcing steel frame 51. It is said that it can be combined with the reinforcing steel bars of concrete and becomes a cotter itself, strengthening its integration with cast-in-place concrete.

[0004]

SUMMARY OF THE INVENTION The present invention is different from the above-mentioned prior art in that the end portion of the precast concrete member is mounted on the upper surface of the precast concrete member or is provided so as to be shallowly buried, and the end portion is not substantially buried in the concrete. Support,
An object is to provide a new bearing structure for precast concrete members.

The present invention eliminates the need for a door-to door form (a form that closes the gap between the bearings of the members and the support member between the bearings) and minimizes plate height. An object of the present invention is to provide a bearing part that can be supported and that can sufficiently support the required load and that has a very simple bearing structure.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a steel bearing fitting is partially bulged from the end of a precast concrete member and is mounted on the upper surface of the member, or is provided by being shallowly buried. Is an end support structure for a precast concrete member, characterized in that the member is connected to a reinforcing bar hung in the concrete. In this case, the reinforcing bar is preferably a reinforcing bar that is mechanically coupled to the main reinforcing bar of the precast concrete member. Also, the precast concrete member is a precast concrete slab,
It is preferable to apply the support to a precast concrete member provided on the slab stem.

[0007]

The present invention is an end support structure for a precast concrete member, in which a steel support is placed substantially on the top surface of concrete, and a part of it is extended from the end of the concrete member. The part is suspended on a supporting member such as a beam, a girder, or a column to support a precast concrete member. The supporting hardware can be adapted to actual conditions such as dimensions and shapes of these supporting members.

The support used in the present invention has a bar shape, that is, a relatively elongated straight shape, and is, for example, a hollow or solid square steel rod, square pipe, shaped steel or a combination thereof,
It is possible to use a box shape formed by bending a flat steel plate, a frame in which flat steel plates are arranged in a vertical wall shape, or another metal object. Also,
Reinforcing bars that hang down in concrete should be firmly attached to this support by mechanical connection or welding. Further, since this support is capable of supporting a reaction force on the concrete upper surface, it is preferable to have a shape in which the supporting area is sufficiently taken.

The mechanical action of the structure of the present invention is as follows. Please refer to FIG. The support metal 10 is placed on the end of the precast concrete member 1, and the end of the support metal 10 projects from the end of the member 1. Reinforcing bars 11 hanging in the member concrete are fixed to the support metal 10. When an external force W acts as the load 20, R ₁ and R ₂ act as supporting forces 21 and 22 on the overhanging portion of the bearing metal. The supporting force R ₁ is opposed to the tensile force P of the reinforcing bar 11 and the reaction force 23 of the concrete near the tail end of the support. The distance between the supporting force R ₁ and the tensile force P of the reinforcing bar 11 is c. Although the reaction force 23 of the concrete is distributed over the length e, the average value of the distribution force is r, and the distance between the action center of the distribution force and the tensile force P of the reinforcing bar 11 is d. At this time, the mechanical relationship is as follows: P = R ₁ (c + d) / d Here, it will be examined using specific numerical values. If c = 8 cm and d = 27 cm,

[0010]

[Equation 1]

It is as follows. Tensile force P of rebar 11
Is P = 1.27 cm ² × 4 t / cm ² = 5 t / piece × 2 = 1, assuming that there are two 13 mmφ deformed bars.
Assuming that 0t bearing force R ₁ = P / 1.3 = 10 / 1.3 = 7.7t e is 9 cm, distributed reaction force r = 0.3R ₁ /e=0.3×7.7/9=
0.257 t / cm Bearing pressure stress σ generated on the concrete surface is σ = 257 / (0.9 × 2) = 143 kg / cm ² assuming that two 9 mm thick steel plates are used, and σ _max = 2σ = 286 kg / cm ² <σ _c = 333 kg
/ Cm ² where σ _c = concrete allowable compressive stress of concrete 500 kg /
It is safe at cm ² × (2/3).

Shear stress τ of steel sheet (when the thickness is 9 mm)
It becomes as follows.

[0013]

[Equation 2]

[0014]

EXAMPLE FIG. 3 shows a front view of a precast concrete member 1 according to an example of the present invention. The support 10 is placed on the stem 5 and welded to the reinforcing bar 11. FIG. 2 is a cross-sectional view including the reinforcing bar 11. Support hardware 10 is 2
The flat steel plates are arranged side by side at right angles to the concrete surface, side by side, and the left and right are connected. FIG. 1 shows a vertical cross section of an end portion of the precast concrete member 1. The support 10 is provided so as to project from the end surface 2 of the member 1, and the projecting portion 13 is suspended on a support member (not shown). The reinforcing bar 11 is welded to the support metal 10, and the lower end portion of the reinforcing bar 11 is mechanically coupled to the main reinforcing bar 3 disposed below the precast concrete member 1. These reinforcing bars are shear-reinforced by the stirrup bar 4. The welded structure for connecting the supporting member 10 and the reinforcing bar 11 is merely an example, and the present invention is not limited to this, and other known reliable and strong connecting means can be used.

A test body was prepared in which the bearing metal 10 was attached to the stem portion of a precast concrete slab having the shape shown in FIG. 3, and a load test was conducted. The vertical cross-sectional structure is shown in FIGS. The test body 30 shown in FIG.
The test body 31 shown in FIG.
And manufactured like T4 and tested.

[0016]

[Table 1]

The materials used are as follows. Compressive strength during concrete test σc = 500kg / cm
² Reinforcing bar SD295A, SR235, welded wire mesh 4
φ steel plate SS400 The test results of cracking are shown in FIGS. 7 and 8. FIG. 7 shows a test body whose members are made of reinforced concrete, and a crack 32 was generated in the concrete below the loading position 20a at 10 to 12 tons against the expected load capacity of 8 tons. FIG. 8 shows a test body in which a member is made of prestressed concrete, and a concrete crack 33 is formed below the bearing metal at the end of the member at an amount of 12 to 13 tons against the expected load capacity of 8 tons. In all cases, sufficient results were shown for the planned withstand load.

[0018]

INDUSTRIAL APPLICABILITY The precast concrete member end support structure of the present invention can effectively and safely support a load on a support having a low end length, and is particularly applied to a precast concrete slab for a composite slab. Then, the supporting structure which is its characteristic is thin, the door door form is unnecessary, and the excellent characteristics that the floor height and the plate height are suppressed to the minimum are not impaired, and the supporting load is sufficiently supported to support the supporting structure. Is a very simple structure, the bearing mechanism is simplified and labor-saving effect is great. Also, in this structure, the safety check mechanism is clear.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an end portion of a precast concrete member showing a bearing structure according to an embodiment.

FIG. 2 is a cross-sectional view of the end portion of the precast concrete member showing the support structure of the embodiment.

FIG. 3 is a front view of the precast concrete member of the embodiment.

FIG. 4 is a mechanical explanatory view of the bearing structure of the embodiment.

FIG. 5 is an explanatory diagram showing a steel material arrangement and a force application position of a test body.

FIG. 6 is an explanatory diagram showing a steel material arrangement and a force application position of a test body.

FIG. 7 is an explanatory diagram showing test results.

FIG. 8 is an explanatory diagram showing test results.

FIG. 9 is an explanatory view of a conventional bearing portion.

FIG. 10 is a front view of a conventional precast concrete member.

FIG. 11 is a side view of an end portion of a conventional precast concrete member.

FIG. 12 is an installation structure diagram of a conventional precast concrete member.

[Explanation of symbols]

1 Precast Concrete Member 2 End Surface 3 Main Reinforcing Bar 4 Stirrup Reinforcing Bar 5 Stem 6 Slab 10 Supporting Material 11 Reinforcing Bar 20 Loading Load 21, 22 Supporting Force 23 Distributed Reaction Force 30, 31 Specimen 32, 33 Crack 40 Concrete Member 41 Metal Plate 42 Shear strength section

Claims (3)

[Claims] 1. A steel bar-shaped bearing member is provided on the upper surface of the member by partially projecting from the end of the precast concrete member or provided by being shallowly buried from the upper surface, and the member of the member at a position near the member end of the bearing member is provided. An end support structure for a precast concrete member, characterized in that it is connected to a reinforcing bar suspended in concrete. 2. The precast concrete member end support structure according to claim 1, wherein the reinforcing bar is a reinforcing bar that is mechanically coupled to a main reinforcing bar of the precast concrete member. 3. A precast concrete member end support structure, wherein the precast concrete member is a precast concrete slab, and the support hardware is provided on a stem of the slab.