JPH0432885B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for manufacturing prestressed concrete girders for bridges and the like.

Problems to be Solved by the Invention Generally, when a prestressed concrete girder has a large span, it is made of cast-in-place concrete and prestress is introduced by a post-tensioning method. When the span is relatively short, there are cases in which a large number of block members are lined up and glued together, and a prestressed steel rod is inserted through it to secure it under tension, but when the span is large, it is not possible to rationally introduce stress.

This invention was developed to solve the above problems.

Means for Solving the Problems In this invention, the girder is manufactured by dividing it into a central block and side blocks, and the central block has pre-tensioned PC steel material tension-fixed in the vicinity of both ends as bond control areas. . This method involves extending the prestressed steel material, inserting it into the sheath buried in the side block, and fixing it under tension using the post-tension method to produce an integrated long-span prestressed concrete girder.

Embodiment The drawing shows an embodiment of the invention, in which the girder is manufactured separately into a central block A and side blocks B.

The center block A has upper and lower PC steel materials 1 on the tension side,
1, PC steel material 2 is placed on the compression side, and the upper and lower PC steel materials 1 and 1 are connected to the bond control part W near both ends.
1, W2, and adjust the PC steel material 2 so that it does not touch the same cross section, set the middle as the bond control part W3, and use the pretension method to adjust the PC steel material 1,
1 and 2 are fixed under tension in concrete.

The production of central block A was carried out by the long line method (see Figure 8).
The steel members 1, 1 extend on both sides of the central block A to ensure a length that allows them to be inserted into the side blocks B.

Note that by embedding a steel rod in a compressed state in the bond control portion W3, it is possible to introduce tensile force on the compression side.

A sheath 3 is embedded in the side block B in a shape bent toward the end.

During assembly, the extensions of the upper and lower PC steel members 1, 1 on the tensile side of central block A are inserted into the sheath 3 of side block B, and the ends are tightened with jacks and fixed to side block B. Also, on the compression side
The PC steel material 2 is cut at both ends of the bond control section to release the prestress.

The stress state at the center of the span of each of the above members is shown in FIGS. 5 to 7. Figure 5 shows the stress state of A block before connection, where a is the prestress, b is the A block's own weight, and c is the resultant stress. Figure 6 shows the A block and B block connected by post tension, and The prestress at the lower edge of the girder is increased by releasing the tension force in the W3 section of the PC steel material 2, which is compared to the increase in bending stress due to its own weight due to the connection.

a is the prestress after adjustment b is the own weight after connection c
indicates the composite stress.

In Figure 7, a is prestress, b is design load, and c
indicates their combined stress.

The prestress is introduced in accordance with the tensile force generated in the girder depending on the magnitude of the tension introduced into the bond control part and the post tension part.

Effects of the Invention In this invention, the girder is manufactured separately into central and side blocks, each of which is prefabricated. In addition, when introducing prestress, by using both the pretension method and the posttension method, it is possible to introduce prestress in stages according to the tensile force of the girder, and it is possible to precast a girder larger than the conventional span. I can do it. Additionally, the placement of prestressing steel is simpler than with conventional cast-in-place concrete and post-tension girders, and the height of the girder can be lowered.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of the central block, Fig. 2 is an intermediate sectional view thereof, Fig. 3 is a longitudinal sectional view of the side block, Fig. 4 is a front view of the connected girders, Figs.
7 and 7 are stress diagrams, and FIG. 8 is a front view of the central block. A...Central block, B...Side block,
1...PC steel material, 2...PC steel material, 3...sheath.

Claims (1)

[Claims] 1. The girder is manufactured in two parts: a center block and a side block. The center block has prestressed steel material tensioned by a pretension method, except for the bond control areas near both ends. A method for manufacturing prestressed concrete girders, which is characterized by inserting the girder into a sheath buried in the section block and fixing it under tension using a post-tension method.