JPS6160940B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for arranging unbonded PC strands in a flat slab structure using unbonded PC strands.

Since flat slab structures do not have beams, they are advantageous in terms of space utilization and construction. However, as the distance between columns becomes larger, the floor must be thicker to prevent the floor slab from bending, which makes it difficult to use normal beam structures. There was a tendency for costs to increase even further.

Therefore, the applicant has already developed a flat slab structure that uses unbonded PC strands to reduce slab thickness, reduce dead weight, and reduce long-term deflection. These flat slab structures using unbonded PC stranded wires use unbonded PC stranded wires in addition to regular reinforcing bars, and introduce prestress using the post-tension method. Regarding the location of the unbonded PC strands, we have adopted methods such as arranging them in a catenary line shape so that they are convex on the tension side of the slab, corresponding to the bending moment gradient of the flat slab. Note that convex on the tensile side here means that the tangent gradient of the curve formed by the line from the unbonded PC monotonically decreases (convexes upward) or monotonically increases (convexes downwardly) in plane coordinates. In addition, the distribution of bending moment forms a quadratic curve when a uniformly distributed load is assumed, but when considering a catenary line within the thickness of a flat slab, the catenary line approximately becomes a quadratic curve (parabola), The catenary line shape also includes such a quadratic curve.

In addition, especially for unbonded PC stranded wires installed in the column row zone of flat slabs, it is important to keep the unbonded PC stranded wires in the range where no shear force is generated in the slab at the joint with the columns, that is, from the intersection line of the bottom surface of the slab and the outer peripheral surface of the column upwards. By arranging the line so that it is convex upward from the unbonded PC within the range that extends at an angle of 45° toward the slab 2 side (the range surrounded by the dashed-dotted lines a and a' in Figure 1), In many cases, the top of the upwardly convex part must be horizontal due to the thickness of the slab; it is sufficient if it is convex at least at both ends of the above range), which transmits the suspension force of the unbonded PC strand directly to the column. (Unexamined Japanese Patent Publication No. 1987-
(See Publication No. 96162).

However, depending on the design, unbonded PC
It may not be possible to fit the stranded wire within this range.

In such cases, this invention provides an unbond method that does not impair stress transmission to the column as much as possible.
This provides a method for arranging PC stranded wires. In other words, the unbonded PC of the flat slab column band
When arranging the stranded wires in vertical, horizontal, and catenary shapes so that they are convex on the slab tension side in response to the bending moment gradient, first, it is necessary to ensure that no shear force is generated in the slab at the joints with the columns mentioned above. Arrange the unbonded PC strands in one direction and in the direction perpendicular to this through the section, and then arrange the unbonded PC strands in one direction and in the direction perpendicular to this to be located outside the part where no shear force occurs. This paper proposes a method for arranging unbonded PC stranded wires in flat slabs, which is characterized by the installation of unbonded PC strands.

In addition, in this case, by transmitting the suspension force of the unbonded PC strands to the column, it is possible to reduce the shear force on the lower surface side of the slab at the joint with the column (below the dashed-dotted lines a and a'). Therefore, the flat slab can also have a flat plate structure without a supporting plate on the lower surface of the joint with the column.

The illustrated embodiment will be described below.

In the figure, 5 indicates a column, 6 indicates a slab, 1, 2, 3,
4 shows the unbonded PC strand of the columnar band.

Unbonded PC of mutually orthogonal columns X ₁ and Y ₁
Stranded wires 1, 2, 3, and 4 are made to correspond to the bending moment gradient of the slab 6, and the catenary lines are made so that they convex upward at the column 5 position where the upper side is in tension, and convex downward at the intermediate position where the lower side is in tension. It is arranged in a shape. this house,
1 and 2 are unbonded PC stranded lines placed so as to pass through the area where the above-mentioned shearing force does not occur at the joint between the slab 6 and the column 5, and 3 and 4 are unbonded PC stranded lines placed outside of these.

The arrangement procedure is to first place wire 1 from the unbonded PC of column band X ₁ , and then place wire 1 from the unbonded PC of column band Y ₁ on top of it.
Lay out strand 2. After that, line 3 is placed from the unbonded PC of column band X ₁ , and line 4 is placed above it from the unbonded PC of column band Y ₁ .

By adopting this arrangement method, the upward suspension force due to the tension of the unbonded PC strands 1 and 2, which are arranged so as to pass through the range where no shearing force occurs, is reduced by the unbonded PC strands arranged in a catenary shape. This reaction force acts in the range where this shear force does not occur, and the upward suspension force is directly applied to the column 5.
I can tell you.

Note that at the column 5 position, the top of the unbonded PC wire is horizontal due to the thickness of the slab 6 and construction considerations, but due to the tension acting on the wire from the unbonded PC, a downward reaction force to the suspension force is generated. There is no problem because the power is transmitted. Also the outer unbond
This does not interfere with the arrangement of the PC stranded wires 3 and 4, and forms a structure with a small bending moment and shear force on the lower surface side of the joint of the slab 6 with the column 5 as a whole.

In addition, wire 7 is connected to the unbonded PC in the inter-column zone X ₂ and Y ₂ ,
8, the section intersecting the column bands X ₁ and Y ₁ should be above the slab 6, and the middle section should be below it.

In addition, unbonded PC stranded wire is a wire that has been cut off from the concrete, for example, if multiple wires are inside the sheath.
A PC steel stranded wire is inserted through it, and the gap between the sheath and the PC steel stranded wire is filled with grease, etc.

This invention has the above-mentioned configuration, and as described above, the unbonded PC strands extend upward from the intersection line of the lower surface of the slab and the outer circumferential surface of the column at an angle of 45 degrees toward the slab side and pass within a range where no shear force is generated. The unbonded PC strands and the outer unbonded PC strands are arranged so that they do not interfere with each other, and by transmitting the suspension force to the column, the stress on the lower side of the connection with the concrete column is reduced, resulting in a safe and economical structure. It will be done.

[Brief explanation of the drawing]

The drawings show an embodiment of the invention, and the first
The figure is a longitudinal sectional view, FIG. 2 is a horizontal sectional view, FIG. 3 is a horizontal sectional view showing an outline of the arrangement position of the unbonded PC strands, and FIG. 4 is a longitudinal sectional view. 1, 2, 3, 4... Unbonded PC stranded wire, 5
...Column, 6...Slab, 7,8...Unbond
PC stranded wire.

Claims (1)

[Claims] 1. When arranging the unbonded PC strands of the flat slab column row in vertical, horizontal, and catenary lines so that they are convex on the slab tension side in accordance with the bending moment gradient, the lower surface of the slab Unbonded PC strands are laid out in one direction and in a direction perpendicular to this, passing through an area extending upward at an angle of 45° toward the slab side from the intersection line of the outer peripheral surface of the column. Unbonding in a flat slab characterized by arranging unbonded PC strands in one direction and in a direction perpendicular to this.
How to arrange PC stranded wire. 2. A method for arranging unbonded PC stranded wires in a flat slab according to claim 1, wherein the flat slab has a flat plate structure without a supporting plate.