JP2948490B2 - Precast concrete member end support structure - Google Patents

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 more particularly to a precast concrete slab for a composite slab suitably used for construction.

[0002]

2. Description of the Related Art Japanese Unexamined Utility Model Publication No. Hei 4-119807 discloses, as shown in FIG. 9, a supporting portion of a precast concrete member 40 having both ends mounted on a supporting structure, and a portion mounted on the supporting structure. 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 in the precast concrete member 40 is disclosed. As shown in FIGS. 10 to 12, Japanese Utility Model Publication No. Hei 6-28581 integrally has ribs protruding in the longitudinal direction on the lower surface. In the precast concrete plate 50 for composite floor, which forms the composite floor by casting the cast-in-place concrete 53 on the upper surface, the ends having the flat portions without the ribs at both ends are integrally provided, and the upper edge is provided at the erection end. A composite floor precast concrete plate 50 in which an end reinforcing steel frame 51 protruding toward the upper surface side is embedded is disclosed.

[0003] The precast concrete plate 50 for synthetic floors is constructed by mounting the erection end having a plate-like portion having no ridges on the lower surface thereof on a steel beam or a steel beam or a steel beam 52. , Rebar 5 on it
4, and the cast-in-place concrete 53 is cast to form a composite floor. The shear stress at the erection end is mainly borne by the end reinforcing steel frame 51, and the end reinforcing steel frame 51 is cast in place. According to the company, it can be combined with concrete reinforcing steel, and itself becomes a cotter, and its integration with cast-in-place concrete is strengthened.

[0004]

SUMMARY OF THE INVENTION The present invention differs from the prior art described above in that an end portion is provided on a precast concrete member by means of a bearing which is mounted on the upper surface of the precast concrete member or is buried shallowly and which is not substantially buried in concrete. Support,
It is an object of the present invention to provide a new bearing structure for precast concrete members.

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

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a synthetic slab.
A bearing structure for a precast concrete member, wherein a steel bearing member is mounted on the upper surface of the member by partially projecting from the end of the precast concrete member, or is provided buried shallowly, and a member near the member end of the bearing member is provided. A precast concrete member end support structure, wherein the end support structure is connected to a reinforcing bar suspended in concrete. In this case, it is preferable that the reinforcing bar is a reinforcing bar mechanically connected to the main reinforcing bar of the precast concrete member. It is preferable that the precast concrete member is a precast concrete slab, and the bearing is applied to a precast concrete member provided on a stem of the slab.

[0007]

According to the present invention, there is provided an end support structure for a precast concrete member, in which a steel support is substantially placed on the upper surface of the concrete, and a part of the support is extended from the end of the concrete member. The part is suspended on a supporting member such as a beam, a girder, a column or the like to support a precast concrete member. This support metal can be made according to the actual conditions such as the dimensions and shape of these support members.

The bearing used in the present invention has a bar shape, that is, a relatively elongated straight shape, for example, a hollow or solid square steel rod, a square pipe, a shape steel or a combination thereof,
A box shape formed by bending a flat steel plate, a framework in which flat steel plates are arranged in a vertical wall shape, and other hardware can be used. Also,
The rebar hanging in the concrete is firmly attached to this bearing by mechanical connection or welding. In addition, since the bearing metal supports the reaction force on the upper surface of the concrete, it is preferable that the supporting metal has a shape having a sufficient supporting area.

The mechanical action of the structure of the present invention is as follows. Please refer to FIG. A support 10 is placed on the end of the precast concrete member 1, and the end protrudes from the end of the member 1. A reinforcing bar 11 hanging down in the concrete of the member is fixed to the bearing hardware 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 projecting portion of the support. The supporting force R ₁ is tensile force P and the reaction force 23 concrete tail vicinity of bearing hardware rebar 11 oppose. The distance between the supporting force R ₁ and the tensile force P of the reinforcing bar 11 is defined as c. The reaction force 23 of the concrete is distributed over the length e, and the average value of the distribution force is r, and the distance between the acting 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, examination is performed using specific numerical values. If c = 8 cm and d = 27 cm,

[0010]

(Equation 1)

It is as follows. Tensile force P of reinforcing bar 11
Is two deformed reinforcing bars of 13 mmφ, P = 1.27 cm ² × 4 t / cm ² = 5 t / piece × 2 = 1
0t Supporting force R ₁ = P / 1.3 = 10 / 1.3 = 7.7 te is assumed to be 9 cm, and the distributed reaction force r = 0.3R ₁ /e=0.3×7.7/9=
0.257 t / cm The bearing stress σ generated on the concrete surface is σ = 257 / (0.9 × 2) = 143 kg / cm ² assuming that the steel plate is received by two 9 mm-thick steel plates, and σ _max = 2σ = 286 kg / cm ² <σ _c = 333 kg
/ Cm ² where σ _c = concrete allowable compressive stress 500 kg /
cm ² × (2/3), which is safe.

[0012] Shear stress τ of steel sheet (for a thickness of 9 mm)
It is as follows.

[0013]

(Equation 2)

[0014]

FIG. 3 is a front view of a precast concrete member 1 according to an embodiment of the present invention. A mounting member 10 is mounted on the stem 5 and welded to a reinforcing bar 11. FIG. 2 is a cross-sectional view including the reinforcing bar 11. Supporting hardware 10 is 2
The flat steel plates are side by side at right angles to the concrete surface and are arranged side by side. FIG. 1 shows a longitudinal section of an end of the precast concrete member 1. The support metal 10 is provided so as to protrude from the end surface 2 of the member 1, and the protruding portion 13 is suspended on a support member (not shown). The reinforcing bar 11 is welded to the bearing 10, and the lower end thereof is mechanically connected to the main reinforcing bar 3 provided at the lower part of the precast concrete member 1. These rebars are shear-reinforced by stirrup bars 4. The welded structure of the connection between the bearing member 10 and the reinforcing bar 11 is merely an example, and the present invention is not limited to this, and other known secure and strong connecting means can be used.

A test specimen was prepared by mounting a support 10 on the stem of a precast concrete slab having the shape shown in FIG. 3, and a load test was performed. The vertical sectional structure is shown in FIGS. The test piece 30 shown in FIG.
As shown in FIG. 6, the test piece 31 shown in FIG.
And T4.

[0016]

[Table 1]

The materials used are as follows. Concrete test compressive strength σc = 500 kg / cm
² rebar SD295A, SR235, welded wire mesh 4
FIG. 7 and FIG. 8 show the state of occurrence of cracks in the φ steel plate SS400 test result. FIG. 7 shows a test piece in which the member is made of reinforced concrete. Cracks 32 occurred in the concrete below the loading position 20a at 10 to 12 tons with respect to the expected withstand load of 8 tons. FIG. 8 shows a test piece in which the member was made of prestressed concrete, and a concrete crack 33 was generated below the bearing at the end of the member at a load of 12 to 13 tons with an expected load of 8 tons. In each case, sufficient results were shown for the expected load capacity.

[0018]

Industrial Applicability The precast concrete member end support structure of the present invention can effectively and safely support a loaded load at a support portion having a small end portion, and is particularly applied to a precast concrete slab for a composite slab. The supporting structure is thin enough to support the required load without impairing the excellent characteristics of the thin bearings, the need for face-door forms and the minimization of the floor height and plate height to a minimum. Is a very simple structure, the support mechanism is simplified, and the labor saving effect is great. In this structure, the safety check mechanism is clear.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an end of a precast concrete member showing a bearing structure of an embodiment.

FIG. 2 is a cross-sectional view of an end of a precast concrete member showing a bearing structure according to an 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 position of a test body.

FIG. 6 is an explanatory diagram showing a steel material arrangement and a force 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.

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

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

FIG. 12 is an installation structural view of a conventional precast concrete member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Precast concrete member 2 End surface 3 Main reinforcing bar 4 Stirrup bar 5 Stem 6 Slab 10 Bearing 11 Reinforcing bar 20 Loading 21, 22 Supporting force 23 Distribution reaction force 30, 31 Specimen 32, 33 Crack 40 Concrete member 41 Metal plate 42 Shear strength part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E04C 2/50 E04B 5/02

Claims (1)

(57) [Claims] 1. Precast concrete for synthetic slab
A support structure member, before the steel bar-shaped support hardware of
A part of the precast concrete member protrudes from the end and is mounted on the upper surface of the member or is provided shallowly buried from the upper surface, and is connected to a reinforcing bar hanging in the concrete of the member at a position near the member end of the bearing. Precast concrete member end support structure.