JPH0485435A - Manufacturing method of precast concrete beams - Google Patents

Abstract

PURPOSE:To reduce cost by installing threaded reinforcing bars at the bottom of beam, inserting the threaded portion of each end of reinforcing bar into the reinforcing member disposed between the side pieces of PC beam to tighten it, and releasing the tightening force after concrete is placed between the side pieces and set. CONSTITUTION:A pair of side pieces 2 of precast concrete beam opposing to each other on a steel bed 1 are fabricated in advance. Next, threaded reinforcing bars 5 are installed at the bottom between the opposing side pieces 2. The threaded portion of each end of reinforcing bar 5 is inserted into a reinforcing member 6 disposed between the side pieces 2 and a nut 7 is installed and tightened. Then, concrete 8 is placed at the beam bottom between the side pieces 2. After the concrete 8 has been set, the tightening force is released to introduce a prestress in the concrete.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a method for manufacturing a precast concrete beam.

(Prior Art) Precast concrete beams are usually designed with reinforced concrete construction without introducing prestress.

When special prestressing is introduced, the desired purpose is achieved by using prestressing steel, tensioning of the steel, and anchorage devices.

(Problem N that the invention seeks to solve) In the case of precast concrete beams made of reinforced concrete that do not introduce prestress, the span length is restricted and the bending strength of the beam is insufficient during erection and floor concrete pouring. , requires shoring.

In addition, when introducing prestress using PC steel, tensioning of the PC steel, and anchoring equipment, a large amount of cost is required, and there is a problem in terms of economic efficiency.

The present invention has been proposed in view of the problems of the prior art described above, and its purpose is to manufacture precast concrete beams with a simple structure that can introduce prestress and are economical and workable. The point is to provide a method.

(Means for Solving the Problem) In order to achieve the above object, according to the method for manufacturing a precast concrete beam according to the present invention, a pair of side pieces of a precast concrete beam facing each other on a base are manufactured,
Next, a threaded reinforcing bar is placed at the bottom of the beam, and the threaded portions of the reinforcing bar are inserted and tightened into the reinforcing material spanned between the two side pieces, and beam concrete is poured between the two side pieces. After the poured concrete has hardened, the tightening force on the reinforcing bars is released.

(Function) According to the present invention, side pieces of a pair of precast concrete beams facing each other are prepared in advance on a foundation, and threaded reinforcing bars are arranged at the bottom of the beams sandwiched between the side pieces. The threaded portions at both ends of the concrete are inserted into and tightened through the reinforcing material spanned between the two side pieces, the reinforcing material supports the reaction force, and in this state, the beam concrete is poured between the two side pieces. It is.

Next, after the poured concrete has hardened, prestress is introduced into the concrete part by releasing the tension on the reinforcing bars.

(Example) The present invention will be described below with reference to the illustrated embodiments.

1 to 6 show an embodiment in which the present invention is applied to the manufacture of a precast concrete beam having two hollow sections in the center of its cross section.

A pair of side pieces (2) of precast concrete beams facing each other are prepared in advance on the base of the preparation head' (11 etc.) (see Figures 1 and 40). (2) is the beam main reinforcement, and (4) is a rib which is embedded in the same side piece (2) and has both ends protruding from the top and inner side of the side piece (2).

Next, a threaded reinforcing bar (5) is arranged at the bottom between the opposing side pieces (2), and the threaded portions at both ends of the reinforcing bar (5) are connected to the reinforcing material spanned between the both side pieces (2). (6) and tighten the nut (7), and with the reinforcing bar (5) tightened, the beam bottom concrete (
8). (See Figures 2 and 5) (9) in the figure
is an end plate installed between the front three and both side parts (2).

Then, after hardening of the bottom concrete (8), the reinforcing bars (
5) to release the tightening force and introduce prestress into the concrete part. (See Figure 3 and Section 6) The ends of the reinforcing bars (5) may be bent if necessary.

Note that FIGS. 7 and 8 show an embodiment in which the present invention is applied to a solid precast concrete beam. In the figure (8') is the post-cast concrete between the side pieces (2).

In the figure, parts equivalent to those of the above embodiment are given the same reference numerals.

(Effects of the Invention) As described above, the present invention provides a structure in which a threaded reinforcing bar is provided at the bottom of the beam between the side pieces of a pair of precast concrete beams prefabricated on a base, and a bridge is constructed between the side pieces of the same pair of precast concrete beams. The screws at both ends of the reinforcing bars are inserted into the reinforcing material and tightened to allow the reinforcing material to support the reaction force. In this state, beam concrete is poured between the pieces on both sides, and the poured concrete is allowed to harden. By releasing the tightening force on the reinforcing bars after introducing large-scale prestressing, your company can introduce prestressing without using any equipment.

According to the present invention, the above-mentioned twin side pieces serve as a formwork when concrete is poured into the intermediate beam, and as attachment members for reinforcing materials for supporting reaction force when tensioning threaded reinforcing bars for introducing prestress. This greatly simplifies the configuration.

As described above, according to the present invention, it is possible to easily introduce prestress into precast concrete beams, thereby reducing the need for supporting during erection and floor construction. The length can be increased.

[Brief explanation of the drawings] Figures 1 to 3 show the actual and male steps of the method for manufacturing a precast concrete beam according to the present invention, and Figures 1 and 3 are the front stage, and Figure 2 is the front stage, and Figure 2 is the front stage. are longitudinal sectional views, Figures 4 and 5.
6 and 6 are longitudinal sectional side views of FIGS. 1, 2, and 3, respectively, and FIGS. 7 and 8 are other examples of precast concrete beams manufactured by the method of the present invention. FIG. (1)...Steel head, (2)...Side piece, (
5) Threaded reinforcing bar, (6) Reinforcement material, (7) Nut, (8) Beam bottom concrete.

Claims (1)

[Claims] Fabricate side pieces of a pair of precast concrete beams facing each other on the foundation, then install threaded reinforcing bars at the bottom of the beams,
Threaded portions at both ends of the reinforcing bar are inserted and tightened into the reinforcing material spanned between the two side pieces, and beam concrete is poured between the two side pieces, and after the poured concrete hardens, a tightening force is applied to the reinforcing bar. A method for manufacturing a precast concrete beam characterized by releasing.