JP2928474B2 - Prestressed concrete girder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prestressed concrete girder in which tension is introduced by a pretension method and tension is adjusted.

[0002]

2. Description of the Related Art Bridges having relatively short diameters are often constructed using prestressed concrete bridge girders manufactured by factories. Since the prestressed concrete bridge girder of the factory is manufactured in a JIS designated factory where quality control is well controlled, high reliability can be obtained. The bridge girder as a factory product includes a bridge girder having a T-shaped cross section for a girder bridge and a hollow deck girder (hollow girder) having a hollow hole for a slab bridge.
These products are manufactured as pretensioned prestressed concrete girder using the factory's long line girder manufacturing equipment.

A long-line girder manufacturing apparatus has a plurality of girder manufacturing tables installed in series, bench abutments are constructed at both ends thereof, and a plurality of PC tendons stretched between the bench abutments are attached to the bench abutments. After tensioning with the tension jack of the installed tension introducing device, assembling the necessary reinforcing bars and formwork on multiple girder manufacturing tables between the bench abutments, casting concrete, and tightening when the strength of the concrete appears This is a device that gradually loosens the tension jack of the force introduction device and simultaneously introduces prestress to a plurality of girders. With this apparatus, a pretensioned prestressed concrete girder can be efficiently manufactured.

[0004] However, the PC tendon is stretched between the bench abutments and tension is introduced, so that it becomes a horizontal straight line.
Mechanically, it is desirable to concentrate the prestress on the cross section where the tensile stress acts below the centroid position of the girder cross section, but it is necessary to accurately resist the bending moment due to the total load including the own weight acting on the girder When a prestress is introduced, overstress occurs at the time when only the own weight acts, such as during transportation and erection, causing an increase in upslope deformation of the girder, and in the worst case, breakage.

[0005] For this reason, a bond control method has been proposed in which the maximum pre-stress amount is given to the center of the span of the girder, the adhesion of the PC tendon near the girder end to the girder concrete is reduced, and the pre-stress is reduced. Has been adopted.

[0006]

The bondless tendon which insulates the adhesion in the vicinity of the end of the girder and releases the tension does not use at all as a structural material, so that it is not only uneconomical but also uneconomical.
Water may penetrate into the sheath coated to insulate the adhesion, and corrosion may progress. In addition, since there is no adhesion, the proof stress (particularly the shearing force) decreases, and the adhesion is caused by the shearing force acting on the girders. Cracks could occur from insulated parts.

According to the specification for road bridges (edited by the Japan Road Association), the number of PC steels that can be subjected to bond control is reduced to 以下 or less of the whole, and reinforcing bars are added and reinforced when stress is insufficient. An object of the present invention is to provide a prestressed concrete girder that solves such a problem.

[0008]

SUMMARY OF THE INVENTION The present invention provides a mechanically effective structural material which is produced by a pretensioning method, in which a tension member released by a bond control of a prestressed concrete girder, which has been released by a bond control, is delayed and adhered. And Specifically, for example, a delay-setting adhesive is applied to cover the sheath, or a high-viscosity delay-setting adhesive is applied. That is, the present invention relates to a prestressed concrete girder of a pretensioning method in which a PC steel material having a bondless section provided on a part of the PC steel material is provided with a delay hardening adhesive filling layer in the bondless section of the PC steel material. This is a prestressed concrete girder characterized by adjusting the following. In this case, the delayed-curable adhesive-filled layer is P
It may be a delay hardening adhesive provided on the outer periphery of the C steel material and a sheath surrounding the same, or may be a coating layer of a high viscosity delay hardening adhesive provided on the outer circumference of the PC steel material.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A prestressed concrete hollow girder (equivalent to JIS 5313) of FIG. 1 will be described as an example. 1 is a side view, FIG. 2 is a sectional view taken along the line AA of FIG. 1, and FIG. 3 is a sectional view taken along the line BB of FIG. Normal PC
In addition to the steel material 2, there is a primary bond control steel material 3 and a secondary bond control steel material 5, and a part of the primary bondless section 4 and the secondary bondless section 6 is coated with a delayed-setting adhesive, covered with a sheath, and covered with a normal sheath. The girder was made by the method.

FIG. 4 is an explanatory view showing a covering state of the PC steel materials 3 and 5 (PC strands). The sheath 12 is filled with the delay-setting adhesive 11. As the adhesive 11, a two-part mixed type epoxy adhesive was used, and the setting time for curing was set to about 100 hours with a margin. Since the girder 1 is subjected to steam curing after casting of concrete, heat resistance is taken into consideration so that the adhesive 11 does not accelerate thermal curing, and control is performed so that the curing temperature of the girder 1 does not rise too much.

The steam-cured concrete girder 1 reaches the tensile strength introduction strength the next day, so a prestress is introduced. However, since the adhesive has viscosity but maintains fluidity, the bond control steel 3, 5 Is contracted freely without adhering to the spar and the tension is released. Thereafter, as time passes, the adhesive hardens, and the concrete of the girder 1 and the bond control steel materials 3 and 5 are integrally bonded via the adhesive 11 to generate an adhesive force with the concrete, thereby being integrated with the member concrete. Behave.

In the subsequent steps, a slab bridge is constructed by temporarily placing, transporting and erection as in the conventional method. In this example, a hollow (hollow section) girder has been described.
A girder having a character-shaped cross section or any other cross-sectional shape can be similarly applied as long as it is a concrete girder having a bondless section in a pretensioning PC steel material.

[0013]

According to the girder of the present invention, since the bond control steel material is integrally attached to the concrete of the girder after construction, there is no fear of corrosion caused by voids.
The bond control steel material effectively functions as an axial steel material and a shear strength bar, and has the effect of improving the strength of the girder.

[Brief description of the drawings]

FIG. 1 is a side view of a prestressed concrete hollow girder of an embodiment.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along the line BB of FIG. 1;

FIG. 4 is a sectional view of a PC steel material.

[Explanation of symbols]

1 Prestressed concrete hollow girder 2
PC steel 3 Primary bond control steel 4
Primary bondless section 5 Secondary bond control steel 6
Secondary bondless section 7 Reinforcing bar 8
Hollow part 11 Delayed curing adhesive 12
sheath

Claims (3)

(57) [Claims] 1. A pretensioned prestressed concrete girder having a bondless section in a part of a PC steel material, wherein a delay hardening adhesive-filled layer is provided in a bondless section of the PC steel material, and an introduction tension is adjusted. And prestressed concrete girder. 2. The prestressed concrete girder according to claim 1, wherein the delay hardening adhesive filling layer is a delay hardening adhesive provided on an outer periphery of a PC steel material and a sheath surrounding the adhesive. 3. The prestressed concrete girder according to claim 1, wherein said delay hardening adhesive filling layer is a coating layer of a high-viscosity delay hardening adhesive provided on an outer periphery of a PC steel material.