JP2584418B2 - Overhang construction method and stress improvement device for synthetic cable-stayed bridge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for erection of a cable stayed bridge and a device for improving stress.

[0002]

BACKGROUND OF THE INVENTION Generally, when a cable-stayed bridge is erected, a concrete casting supporter that can be moved in a horizontal direction with respect to a foundation below a tower column installed on land is constructed. The process of placing concrete on the support, stretching a cable having one end connected to the upper part of the tower column, and completing one block is repeated, and the beam is extended. (Sho 59
On the other hand, a composite cable-stayed bridge such as that seen in Hikihara No. 1 Bridge (Haga-cho, Anaguri-gun, Hyogo Prefecture / Steel Structure Series 5, "Steel Cable-Stayed Bridges-Technology and Changes") In the case of erection, a truss structure is constructed and extended in a horizontal direction with respect to the lower part of the tower pillar erected on land, a cable having one end connected to the upper part of the tower pillar is stretched, and this construction is extended. Precast slabs are laid on the structure and beams are extended. In this case, the stress of the composite structure of the completed cable-stayed bridge is composed of the pre-composite stress of the truss structure and the post-composite stress after the precast slab is laid. Therefore, if the construction method of extending the beam for each block is used for the construction of the composite cable stayed bridge, the pre-composite bending moment acts on the truss point, and this pre-composite bending moment is applied only to the steel section with a small section constant. Therefore, the degree of acting stress increases. Therefore, there is a possibility that stress may be applied to the portion where the cables are stretched and connected at the stage of constructing and extending the truss structure. Explaining the bending moment before synthesis of the upper chord material of the truss structure of FIG. 6, for example, the bending moment before synthesis of the steel section in the C section is -57.5 t · m, which is the completion after laying the precast floor slab. As shown in FIG. 7, the resultant bending moment is -50.7 t · m as shown in FIG. 7, but the bending moment before the synthesis is as large as -57.5 t · m. Therefore, it is desired to reduce the bending moment before the synthesis, reduce the stress used for the upper chord of the steel cross section after the bridge is completed, and obtain a steel chord having no stress over.

An object of the present invention is to provide a method and an apparatus for reducing and improving a negative pre-synthetic bending moment by applying a positive bending moment due to an external force to a negative pre-synthetic bending moment generated in an erection stage of a truss structure. To provide.

[0004]

SUMMARY OF THE INVENTION To solve the problems of the prior art, the construction of the present invention is to provide a truss structure which is horizontally extended with respect to a foundation on the lower part of a tower column constructed on land. In the method of overhanging a cable-stayed bridge, a cable having one end connected to the upper part of the tower pillar is stretched, and the process of laying a precast slab on the truss structure to be constructed and extended is repeated. With respect to the negative composite bending moment before laying of the precast floor slab generated at the upper chord material point of the truss structure to which the cable is stretched and connected, the negative composite bending moment is applied to the portion by applying a positive bending moment due to an external force. To reduce the pre-bending moment, improve the stress distribution after the bridge is completed and eliminate the stress over, and horizontally on the foundation at the bottom of the tower column built on land A cable having one end connected to the upper part of the tower pillar is stretched to the left and right of the upper chord material of the truss structure to be extended, and the process of laying a precast floor slab on the truss structure to be extended is repeated. At the time of the installation of the cable stayed bridge, the center part of the beam member is attached to and detached from the lower right and left lower chords directly below the left and right upper chords corresponding to the upper right and left chords constituting the truss structure where the cables are stretched and connected. A lifting means such as a jack for lifting the lower chord material and applying a positive bending moment to the upper chord material of the truss structure is provided at one upper end of the beam member. Provided with the same lifting means or spacers as described above.

[0005]

In a construction method of a cable-stayed bridge, a stress improvement device is provided for a negative combined bending moment (eg, -57.5 t · m) generated at the upper chord material point of a truss structure to which a cable is stretched and connected. By applying a positive bending moment generated by the lifting action of P applied between both ends of the beam member and the truss structure, the negative pre-synthetic bending moment of the upper chord material point of the truss structure is greatly reduced ( For example, -22.
8t · m), and the combined bending moment is, for example, −27.9 t · m, and −50.7 t · m is obtained as a total moment upon completion. The stress caused by the bending moment of the chord material on the steel section in the truss structure is obtained. Overover can be eliminated by a simple construction method and a stress improvement device, and a cable-stayed bridge with high durability can be easily obtained.

[0006]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a state in which the method of the present invention is carried out, FIG. 2 is a side view of a stress improvement device, FIG. 3 is a detailed view of a connecting portion between the stress improvement device and a truss structure, FIG. 4 is a sectional view of FIG.
FIG. 5 is a diagram showing the bending moment of the upper chord of the truss structure of the present invention before the composite, FIG. 6 is the diagram of the bending moment of the upper chord of the truss structure of the prior art before the composite, and FIG. 7 is the total bending of the present invention and the prior art when the bridge is completed. FIG.

The configuration of the embodiment of the present invention will be described with reference to the drawings. 1 is a truss structure which is a main member of the cable-stayed bridge A. The truss structure 1 includes a plurality of upper chords 2, lower chords 3, and upper and lower chords 2, 3 in a bridge axis direction. , A vertical member 4 connecting the upper and lower chord members 2 and 3
It is composed of diagonal members 5 and horizontal beams (not shown). One end of a cable 6 is connected to a portion where the upper chord 2, the vertical member 4, and the cross beam intersect, and the truss structure 1 is sequentially extended, and the truss structure 1 is stretched over the truss structure 1. The cable-stayed bridge A is completed by laying a precast floor slab 7 on 1.

Next, referring to the drawing, the stress improvement device B of the present invention will be described.
Will be described in detail. Reference numeral 8 denotes a beam member disposed along the left and right sides of the truss structure 1, that is, along the lower bridge axis direction of the lower chord member 3 on the upstream and downstream sides. Mounting side 1 that is axially attached to lower chord material 3 with pins 9
0 is provided upright, and a jack 11 is provided on the upper surface of one end of the beam member 8 and a spacer 12 is provided on the upper surface of the other end of the beam member 8. It is configured as described above.

[0009]

[Description of Construction Method] As shown in FIGS. 1 and 5, a truss structure 1 is constructed and extended for each section, and a cable 6 is attached to the center of the right and left chord members 2 constituting the truss structure 1 for each section. After the bridge, a plurality of precast floor slabs 7 carried by the carriage 13 equipped with a crane facility are laid on the truss structure 1, and mortar is injected and filled to form a bridge. Truss structure 1 is connected, and cables 6 are stretched on the left and right of the central portion of the truss structure 1. As described above, for example, a negative pre-combined bending moment of -57.5 t. Occurs. Next, the mounting piece 10 of the beam member 8 is pivotally supported by the pin 9 directly below the upper chord 2 part where the cable 6 of the section is stretched, and on the lower chord 3 part set via the vertical material 4.
The beam member 8 extends along the lower chord member 3, and the jack 11 and the spacer 12 provided at the end of the beam member 8 are interposed between the lower surface of the lower chord member 3 and the upper surface of the beam member 8. In this state, the lower surface of the lower chord material 3 is lifted by the action of the jack 11, and the force of P is applied by the jack 11 and the spacer 12, so that the pin connection portion of the beam member 8, that is, the portion where the cable 6 is connected The 2P reaction force acts on the upper chord material point of the truss structure 1 of the truss structure 1, and the bending moment before the synthesis of the upper chord material point of the truss structure 1 is reduced to, for example, -22.8 t · m. With the bending moment of the upper chord of the truss structure 1 greatly reduced in this way, the precast floor slab 7 is carried in, mortar is injected and filled, and the main erection step is completed. 8 is removed, a new truss structure 1 is constructed and extended, a beam member 8, ie, a stress improvement device B, is attached to the truss structure 1, and the above-described method is repeated to complete the cable-stayed bridge A. The bending moment before synthesis acting on the steel chord material before synthesis having a small section modulus is calculated as -57.7 t · m which is the bending moment before synthesis when the stress improvement device is not provided by providing the stress improvement device.
To -22.8 t · m. As a result, the pre-synthesis stress level generated in the steel cross-section before synthesis having a small section modulus can be suppressed to a low level. On the other hand, the post-composite bending moment acting on the composite section (composite section of the precast concrete slab and the steel chord) having the large section modulus is -50.7 t, which is the total bending moment at the time of completion.
-22.8 t · m which is the bending moment before synthesis from m
Minus 27.9 t · m. This is 6.8 t · m, which is a post-composite bending moment acting on a composite cross section when the stress improving device B is not used (50.7 t · m, which is the total bending moment at the time of completion, and is a pre-composite bending moment). 57.5 t · m). Therefore, by providing the stress improving device B, the post-combination stress degree generated in the combined cross section becomes larger than when the stress improving device B is not provided. However, since the combined section modulus is large, even if the combined bending moment increases, the increase in the combined stress degree is small. Therefore, by adopting the stress improving device B, the stress before synthesis is greatly reduced, and the increase in stress after synthesis is suppressed to a low value. The total stress degree can be kept low, and can be equal to or less than the allowable stress degree.

[0010]

According to the configuration of the present invention as described above, the following effects can be obtained. When a cable-stayed bridge is erected, a positive bending moment is forcibly applied to a large negative bending moment generated in the chord material of the steel section of the truss structure to be constructed and extended. By laying a precast slab in this state, the bending moment of the chord material on the steel section of the truss structure at the time of completion of the bridge is kept low as it is, eliminating stress over phenomenon and durability You can get a large cable-stayed bridge. On the other hand, the structure of the stress improvement device for implementing this method is simple, and its handling is also easy.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a state in which the method of the present invention is performed.

FIG. 2 is a side view of the stress improvement device.

FIG. 3 is a detailed view of a connecting portion between the stress improvement device and the truss structure.

FIG. 4 is a sectional view of FIG. 3;

FIG. 5 is a diagram showing a bending moment before synthesis of the upper chord of the truss structure of the present invention.

FIG. 6 is a diagram showing a bending moment before synthesis of the upper chord of the truss structure in the prior art.

FIG. 7 is a diagram showing the total bending moment of the upper chord member when the bridge is completed according to the present invention and the prior art.

[Explanation of symbols]

 A Cable stayed bridge B Stress improvement device 1 Truss structure 2 Upper chord material 3 Lower chord material 4 Vertical material 5 Diagonal material 6 Cable 7 Precast floor slab 8 Beam member 9 Pin 10 Mounting piece 11 Jack 12 Spacer 13 Carriage truck

Claims (2)

(57) [Claims] 1. A cable having one end connected to an upper portion of a tower column, which is connected to the left and right upper chords of a truss structure that is constructed and extended in a horizontal direction with respect to a foundation on a lower portion of a tower column built on land. In the method of overhanging a cable-stayed bridge in which the step of laying a precast slab on the truss structure to be constructed and extended is repeated, the precast generated at the upper chord material point of the truss structure to which the cable is stretched and connected. With respect to the negative bending moment before the slab laying, the positive bending moment due to external force is applied to the portion to reduce the negative bending moment before the composite, and before and after the composite after the bridge is completed. An overhanging method for a composite cable-stayed bridge characterized by improving stress distribution and eliminating stress over. 2. A cable having one end connected to the upper part of the tower column is stretched on the left and right of the upper chord member of the truss structure which is constructed and extended horizontally on the foundation of the lower part of the tower column built on land. When laying a cable-stayed bridge that repeats the step of laying a precast slab on the truss structure to be constructed and extended, the cable corresponds to the left and right upper chord members constituting the truss structure in which the cables are stretched and connected. At the lower part of the lower right and left lower chords, the center of the beam member is detachably supported on the axis of this lower chord, and the lower chord is lifted at one upper end of this beam and a positive bending moment is applied to the upper chord of the truss structure. A lifting device, such as a jack, acting on a member, and the same lifting device or spacer as above is provided on the other end of the beam member.