JPS6140906A - Formation of synthetic structural member following stress adjustment - 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] Technical Field The present invention is directed to, for example, when constructing a continuous composite girder bridge, when a reinforced concrete deck slab and a steel girder are combined to form a composite girder, the reinforced concrete deck slab is compressed in advance. stress, then integrate the reinforced concrete deck and steel girder, and release a predetermined amount of compressive stress in the intervening concrete deck in each span or in selectively set span hairs. This invention relates to a construction method that can generate desired amounts of negative bending moments and positive bending moments at intermediate supports and corners.

Background Art Continuous composite girder bridges have a problem in that a large negative bending moment occurs near the fulcrums, and as a result, tensile force acts on the concrete slabs near the fulcrums, making them susceptible to cracking. Therefore, in the past, a predetermined amount of reinforcing bars were buried in the concrete F deck along the axial direction of the bridge. In such prior art, the concrete cross section cannot be considered effective, and therefore the steel girder cross section designed with emphasis on load bearing capacity becomes relatively large, and the steel girder itself becomes large. Therefore, the cost is high (.

Purpose The purpose of the present invention is to solve the above-mentioned technical problem, and to reduce the negative bending moment at the intermediate fulcrum as much as possible, and also to reduce the positive bending moment at the span. An object of the present invention is to provide a method for forming a composite structural member that involves stress adjustment.

Embodiment FIG. 1 is a side view of an embodiment of a bridge in which the present invention is used, FIG. 2 is a plan view thereof, and FIG. 3 is a cross section taken from the section line ■-■ in FIG. It is a diagram. Both ends of the bridge 1 are supported by abutments 2.3, and the middle part of the bridge 1 is supported by piers 5.
It is supported by 0.51. The bridge 1 has a frame including a plurality of main girders 4 made of steel girders with an I-shaped cross section extending in the axial direction, and steel members 5 called transverse girders or anti-tilt structures supported by these main girders. do.

A passage plate 6 is installed on the upper surface of the steel girder 4 as a foundation member. The right half of this passage plate 6 is omitted in Figure 2 for ease of illustration. This passage board 6 is constructed by connecting a plurality of concrete floor slabs 7 as auxiliary members. As will be described later, this concrete floor slab 7 has 'pc steel (commercial tension steel) wires 8 (sixth
7) are buried in parallel to each other. The concrete slab 7 is installed so that the PC steel m8 buried therein is parallel to the steel girder 4.

Note that PE steel bars may be used in place of the P and C steel wires 8. FIG. The figure is a side view seen from the arrow H side, Fig. 6 is a plan view seen from the arrow F side, and Fig. 7 is a sectional view taken from the section line ■-■ in Fig. 6. be. The horizontally extending steel girder 4 includes a vertically extending web 9 and an upper 7 flange 10 and a lower 7 flange 11 extending perpendicularly to the web 9 at both ends of the web 9.

A slip prevention member 12 for preventing the concrete floor slab 7 from sliding is provided on the upper surface of the upper runch 10. This anti-slip member 12 is, for example, a novel, and is made up of a plurality of rod-shaped protrusions 13, which are welded and fixed on the upper surface of the upper 7 flange 10. A plurality of these anti-slip members 12 are arranged at intervals on the upper surface of the upper seven langes 10.

The concrete slab 7 has a long hole 14 into which the anti-slip member 12 can fit when installed between the steel girders 4.
A plurality of protrusions 13 are formed along the member axis direction of the steel girder 4 corresponding to the positions of the protrusions 13. Further, a plurality of sheath pipes 15 are inserted into the concrete slab 7 in advance so as to pass through the steel girder 4 in parallel with the member axis direction. The diameter of this sheath tube 15 is pe
The value is selected to allow the steel wire 8 to be inserted gently.

The process of laying the concrete slab 7 on the steel girder 4 to form the passage board 6 will be described below.

First, the concrete slab 7 is temporarily joined between the steel girders 4 without any gaps. After that, the joint part of each concrete slab 7 401:1
Each concrete slab 7 is integrated by applying adhesive or injecting or pouring cement mortar. Next, prestress along the member transport direction of the steel girder 4 is introduced into the concrete slab 7, and compressive stress is applied to the concrete slab 7.

Specifically, the PE steel wire 8 is inserted into the sheath pipe 15. After that, pL! Tension is applied to the steel wire 8 and it is fixed by a support plate 16 and a fixing member 17. At this time, compressive force acts on the concrete via the support plate 16, and compressive stress is generated inside. Fixing member 1
7 is a means for fixing the compressive stress to the concrete floor slab 7, and as will be described later, the compressive stress in the concrete F floor slab 7 can be arbitrarily adjusted to l! It also has a luxurious function.

The concrete deck slab 7 into which prestress has been introduced in this way is integrated with the steel girder 4. Specifically, the long holes 14 of the concrete slab 7 are filled with concrete, cement mortar, or the like. As a result, the concrete deck slab 7 and the steel girder 4 are fixed to each other and integrated. In this way, the steel girder 4 and the concrete slab 7 become a composite girder. After the concrete slab 7 is combined with the steel girder 4 in this way, the span 1 and the pier 5 supported by the abutment 2 and the pier 50 are
Span J supported by 0 and pier 51! 2. Span J supported by pier 51 and abutment 3! +i to 3 (see Figure 1)
The span of the steel girder 4, i? 1. J?
2. ! 3, a negative bending moment can be generated and a positive bending moment can be generated in the steel girder 4 near the bridge 4111150.51 as an intermediate fulcrum. To explain the prestress release procedure in detail, the tension on the PCA wire is released by loosening the fixing member 17. As a result, the concrete slab 7, which had been contracted by prestress (compressive stress generated in advance), attempts to extend in the axial direction of the bridge. However, since the concrete slab 7 and the steel girder 4 are integrated, their extension is restricted, and therefore a negative bending moment and tensile force act on the section of the steel girder 4 where the prestress is released. Due to this, a positive bending moment is generated in the steel girder 4 near the bridge pier 50°51 serving as the intermediate support 7α. Therefore, consecutive composite digits
It is possible to reduce the negative bending moment near the intermediate fulcrum part, which is a particular problem of No. 11, and also to reduce the positive bending moment in the span part. Therefore, it is also possible to reduce the cross section of the steel girder.

Note that after the prestress is unloaded, the sheath pipe 15 is grouted with cement paste or the like.

Note that when releasing the prestress, by releasing only a desired amount using the fixing member 17, it becomes possible to reduce the stress acting on the composite structural member as a whole by *q.

In this embodiment, the concrete slab 7 was manufactured in advance at a factory, but it may also be formed by pouring concrete into a form using a form, as in conventional cast-in-place concrete.

FIG. 8 is a plan view of another embodiment of the concrete slab, and FIG. 9 is an enlarged perspective view of the - section. This concrete floor slab 7a has an uneven surface 21 formed at both ends along its longitudinal direction.

This uneven surface 21 has a plurality of recesses 22 formed along its width direction. For example, if the width and length of this concrete floor slab 7a is 1.5 m, the depth of this recess 22 is d.
1 is 2 m, and the pitch d2 is 20 cm. Note that the shape of the uneven surface 21 is not limited to the shape shown in FIG. 9, and the values of the depth d1 and the pitch d2 are, of course, not limited to this. Concrete deck slabs 7a having such a shape are placed on the upper rungs 10 of the steel girders 4 so as to face each other at a constant interval. Thereafter, prestress is introduced in the same manner as in the previous embodiment, and after compressive stress is generated, the fixing member 17 is used to fix the structure. After that, when integrating the concrete slab 7a with the steel girder 4, the uneven surface 21 of the concrete slab 7a
The concrete slab 7a and the steel girder 4 are integrated by filling the space 23 between the concrete slab 7a and the opposing uneven surface 21 with a fixing agent such as concrete or cement mortar. The subsequent method of unloading the prestress is similar to the previous embodiment. In this embodiment, since the uneven surface 21 is formed on the concrete slab 7a, the concrete slab 7a is reliably integrated with the steel girder 4, and therefore even when the prestress is released, the concrete This prevents the floor slab 7a from slipping on the steel girder 4.

FIG. 10 is a bending moment diagram of the continuous composite girder v41, and FIG. 11 is a diagram showing its stress distribution.

The principle of the present invention will be explained in more detail with reference to FIG. 10 and FIG. 11. In FIG. 10 (1), it is assumed that the continuous composite girder I11 is supported by fulcrums A, B, C, and D, and the prestress is released in the prestress release sections Pi, P2, and P3. In addition, span no 1 and span! It shall be equal to 3. The bending moment caused by the dead load and live load after combining the concrete slab 7 and the steel girder 4 is shown in FIG. 10 (2). Note that here, the reference numeral 1 indicates the predetermined minimum value of the bending moment, and the reference numeral m2 indicates the maximum value of the bending moment. At this time, the stress distribution in the medium heat section x1 of the span 1 is shown in FIG. 11 (5), and the stress state at the intermediate supports B and C is shown in FIG. 11 (6).

When prestress is introduced into the continuous composite girder bridge 1, the stress distribution of the central part x 1 and the intermediate supports B and C is 11th
This is shown in Figure (1) and Figure 11 (2).

Section Pi, P2. When the prestress is released at P3,
As described above, a negative bending moment occurs in that portion, and a positive bending moment occurs near the fulcrums B and C. Such a state is shown in FIG. 10(3). In addition, the stress distribution at the center of the span x 1 at this time is the 11th
The stress distribution at the fulcrums B and C is shown in FIG. 11 (4).

When the prestress is released in this way, the continuous composite girder bridge 1
A composite moment of the bending moment based on the prestress and the bending moment based on the load is generated, and this composite bending moment is indicated by the reference mark m3 in Fig. 10 (4).
It is indicated by. As is clear from Fig. 10 (4), the bending moment at the span center X1 is reduced by about 30% compared to the conventional one, and at the fulcrums B and C the bending moment is reduced by about 4% compared to the conventional one.
0% bending moment is reduced. Also, Figure 10 (
The stress distribution at the center of the span × 1 in the state of 4) is shown in Figure 11 (7), and the stress distribution at the fulcrums B and C is
This is shown in Figure 1 (8).

In this way, the sections PL, P2. By releasing the prestress at P3, it becomes possible to cancel out and reduce the bending moment due to the vertical load, which is considered in advance. Furthermore, as is clear from Fig. 11 (7) and (8), the stress generated in the upper seven flange 10 and the lower seven flange 11 of the steel girder can be reduced, and the compressive stress remains in the concrete slab 7. Since the concrete floor slab 7 can be left in place, cracking of the concrete slab 7 can be prevented. Therefore, the concrete cross section can be considered valid even for negative bending moments, making it more economical than conventional construction methods. In the above embodiment, the sections Pi, P2. Although the prestress is released for P3, it is also possible to select an arbitrary span and release the prestress by ν1 in an arbitrary section.

Further, although the concrete floor slab 7 was used as the auxiliary member in the above embodiment, a steel floor slab may also be used. When the deck is made of steel in this manner, the generation of the residual compressive stress makes it possible to use steel with lower strength than the steel girder 4, improving economic efficiency.

Effects As described above, according to the present invention, it is possible to reduce the negative bending moment at the intermediate support portion of the foundation member, and also to reduce the positive bending moment at the span portion. Furthermore, since compressive stress can remain in the auxiliary member, the cross sections of the auxiliary member and the base member can be made smaller, improving economical efficiency.

[Brief explanation of drawings]

FIG. 1 is a side view of a continuous composite girder bridge 1 in which the present invention is used;
Figure 2 is its plan view, and Figure 3 is the section line of Figure 2.
4 is a simplified perspective view showing the state in which the concrete slab 7 is attached to the steel girder 4, 5 is a side view as seen from the arrow H side, and 6 is a cross-sectional view as seen from ■. FIG. 7 is a sectional view taken from the cutting plane line ■-■ in FIG. 10 is a bending moment diagram of the continuous composite girder bridge 1, and FIG. 11 is a stress distribution diagram in FIG. 10. 1... Continuous composite girder bridge, 2, 3... Abutment, 4... Steel girder, 7.7a... Concrete deck slab, 8... PE steel wire, 12... Slip prevention member, 14... Long hole, 16
... Support plate, 17... Fixing member, 40... Seam, 50.51... Pier, Pi, P2. P3...Prestress release section, A. B, C, D...Fulcrum 1. /1. , /2. No. 3... Intermediate agent Patent attorney Number of strokes Keiichi Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 7a Fig. 9

Claims (1)

[Claims] Temporarily joining a plurality of auxiliary members to a base member supported by a plurality of fulcrums without gaps along the member axis direction of the base member,
Next, compressive stress is generated inside each auxiliary member by a compressive stress generating means, and then each auxiliary member is fixedly installed on the foundation member so that the acting direction of the compressive stress is parallel to the axial direction of the foundation member. Then, by releasing a predetermined amount of compressive stress in the auxiliary members that are present only between each span or selectively set spans, the negative bending moment at the span and the positive bending moment at the intermediate fulcrum are reduced. A synthetic structural member forming method that involves stress adjustment, which is characterized by generating only a predetermined amount.