JPS60242010A - Manufacture of eccentric prestress beam through centrifugal-force molding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing eccentric prestressed concrete girders by centrifugal forming.

When a prestressed concrete girder is used for bridge construction by supporting a beam or both ends thereof on an abutment or a bridge pier, a large tensile stress is generated on the girder surface due to electrical charges. Therefore, an eccentric prestress girder is desired in which a larger prestress is introduced on the lower surface side than on the upper surface side of the single digit cross section. Moreover, if this can be manufactured by centrifugal force molding method,
Within the conventional.

It is much more economical than the external formwork method.

However, until a few years ago, all centrifugal force prestressed concrete girders (hereinafter referred to as 20 girders) were manufactured by introducing uniform prestress into the girder cross section. This is because eccentric prestressing by force imparts a bending moment to the formwork as a reaction force, causing "warpage" in the formwork, which is extremely dangerous in the centrifugal force forming process.

Recently, a method of manufacturing eccentric prestressed girders by centrifugal force forming has been developed, and the inventor of this application has already proposed the method of producing the
There is a patent publication (Japanese Patent Application No. Shojj-/3; θθθ-), which states that in order to prevent bending moment from being applied to the formwork, it is necessary to The same amount of pretensioning PC steel rods or steel wires are placed close to each other on both sides, tension is applied to them, and centrifugal force forming is performed as if it were a conventional PC girder, thereby introducing uniform prestress to the girder Vfr surface. After that, additional stress was introduced on the tensile stress side using a boss tension to produce an eccentric prestressed girder.

This method requires the same amount of pre-tensioning PC @ rod or steel wire on the tensile stress side as on the compressive stress side, and also requires a separate PC steel rod for post tension.
It was extremely uneconomical.

The present invention aims to eliminate the above-mentioned drawbacks and to provide the most economical method for manufacturing eccentric prestressed girders by centrifugal force.

This method will be explained in detail below.

As shown in Figures 1 and 1, in order to rotate the centrifuge (1), the rotating
Remove the upper formwork (2a) of the rectangular hollow formwork (2) consisting of a combination of upper and lower formwork with 41 PC steel rods or steel wires (5) are placed along one side of the formwork (2) in the manual direction, adjusted to the required length, and their ends are secured to the formwork using rivets, heads, nuts, etc. It is fixed to the seat plate (8) and the ring placed on both sides.

In addition, along the other side of the formwork (2) corresponding to the tensile stress side of the manufacturing girder, an appropriate number of unbonded P for boss tension are installed.
A C steel rod or steel wire (61) is arranged, screws are machined at both ends, and one end is passed through the hole in the seat plate (8) to tighten the nut αQ'.
The nut is placed in the blind hole (9) made in the fixing plate (7) arranged on the outside of the seat plate (8), and the other end has a long threaded part (c). , the nut Q is inserted into the seat plate (Ill and the jack plate @) with its tip passed through the hole (Is) of the jack plate @, which has spacer Q'h provided outside of it to surround the left, right, and bottom sides. Screw it into the threaded part between the plates (2).

The seat plate (8) at one end is bolted to the fixed plate (7) [
The jacking plate (to) and the seat plate L are made into one piece with 10, and the seat plate α℃ at the other end is surrounded by the spacing retaining material aη on the left and right and the bottom.
Temporarily connect using the bolt (end) and nut o4 extending from.

Next, place the upper formwork (2a) on the formwork (2), and tighten the bolts (3).
to form the formwork (2), and the jack shaft (A) is connected to the seat plate A through the hole υ provided in the jack plate (to) to apply tensile force to the seat plate and press the plate. Tension PC steel rod or steel @ (51) is pulled until the specified tension is reached.

When the above-mentioned tensioning by the jack is completed, tighten the Nand I14 to anchor the seat plate to the jack plate (2), and then tighten the appropriate fasteners from the space O9 of the spacing material A surrounded on three sides. Re-tighten the NAND tto at the end of the unbonded PC steel rod or steel wire (6) for boss tension, and tighten until the "warpage" of the formwork (2) disappears. In other words, the pre-tensioning PC steel rod or steel wire (5) is used for post tension so as to give the formwork (2) a bending moment equal to and in the opposite direction to the bending moment generated in the formwork (2) by introducing tension force. Unbound PC steel rod or steel wire (6)
The "curvature" of the formwork (2) is erased by applying tension and tXS balanosing.

After completing the above process, remove the jack shaft, pour a predetermined amount of concrete into the formwork (2) through the concrete injection hole, and place the formwork (2) on the centrifuge (11). , centrifuge (11 [rotating wheel + 41 M
Centrifugal force molding is performed by rotating the formwork (2) via l.

After demolding, wait for the strength of the concrete to increase, then pull the unbonded PC steel rod or steel wire (6) for boss tension using a jatsugi, and add the necessary tension for the design to the unbonded PC steel rod or steel wire for boss tension +61. The whole process is completed by re-tightening the Nando aQ, and the inside of the 1-digit lfr surface is formed into a circular hollow, and prestress is introduced on the compressive stress side and on the tensile stress side when used in the manufacturing girder. This allows a prestressed girder to be manufactured by centrifugal force forming to introduce eccentric prestress, which is larger than the compression cutting edge side and is necessary for the design.

As described above, according to the method of manufacturing an eccentric prestressed girder by centrifugal force forming of the present invention, an unbonded PC steel rod or steel wire for post-tensioning is placed in a formwork.

It can be used both to eliminate the warpage of the formwork caused by introducing prestress using the pretension method and to add eccentric prestress, and eliminates the need for excess pretensioned steel to correct the warpage of the formwork. It is free of charge and extremely economical. Therefore, eccentric prestressed concrete girders with high strength and durability on the tensile stress side due to loads during production girder use can be manufactured safely and most economically and easily by centrifugal force forming without any movement of the formwork. is something,

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional side view taken along the line A-A in Fig. 2 showing the mold on the centrifuge according to the manufacturing method of the present invention, Fig. 1 is a sectional view taken along the line B-H in Fig. 1, and Fig. 3 is a sectional view taken along the line B-H in Fig. 1. A front view of the jack plate, FIG. q is a plan view showing a part of FIG. 1. (1)...Centrifuge, (2)...Formwork, (2a)...Upper formwork. (5)...PC steel rod or steel wire for pretension, (6)
...Unbonded PC steel rod or steel wire for boss tension. Applicant: Nichikai Giken Co., Ltd., -91 Agent: Terumi Kotani;゛1-8゛:

Claims (1)

[Claims] l When manufacturing a prestressed concrete girder using the centrifugal force forming method, a PC for pretension is installed on one side of the formwork in the longitudinal direction corresponding to the compressive stress side in the girder value. Arrange the required number of steel rods or steel wires, and place the required number of unbonded PC steel rods or steel wires for boss tension on the other side corresponding to the tensile stress side, and Introduce the necessary tension and unbond the PC steel rod or steel wire for boss tension. Introduce a temporary tension force that can give a bending moment equal to and in the opposite direction to the bending moment generated in the formwork by the tension force introduced into the JJC steel rod or steel wire for pre-tensioning, and pour concrete in this state. A centrifugal method characterized by carrying out centrifugal force forming, waiting for the concrete strength to increase after demolding, and then additionally introducing tension force into the unbonded PC steel rod or steel wire for the boss tension in order to obtain the tension force required for the design. A method for manufacturing eccentric prestressed girders by force forming.