JPH0571108A - Execution method for multi diameter continuous beam having rc floor plate - Google Patents

Abstract

PURPOSE:To freely set the order of placing concrete of a RC floor plate by controlling the tensile force generated in floor plate concrete in an intermediate supporting point of a multi-diameter continuous beam where a RC floor plate is formed in layer on a steel beam. CONSTITUTION:At the time of placing concrete of floor plate in a multidiameter continuous beam A where a RC floor plate 2 is formed in layer on a steel beam 1, in an intermediate supporting point of a continuous beam, compressive force is introduced as pre-stress in the upper portion of the steel beam 1 and concrete of the RC floor plate 2 through a pre-stress loading device 4 installed above a neutral axis of the steel beam 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for constructing a multi-span continuous girder in a bridge or the like in which RC slabs are layered on a steel girder.

[0002]

_2. Description of the Related Art A bridge having a conventional RC floor slab generally has a steel floor girder a ₁ or a steel girder a ₂ composed of a box girder a ₂ on which a RC floor slab b constituting a roadbed portion is formed. Layered and same R
A shift stopper c is installed between the C floor slab b and the steel girder a, and a stress is generated in the RC floor slab b portion as the steel girder a deforms. (See FIG. 8 and FIG. 9 as well as FIG.
Reference) d in the figure is a pier. In the case of the continuous girder as shown in FIG. 11, a negative moment is generated at the intermediate fulcrum by a vertical load such as a dead load, and a tensile force is generated at the RC floor slab b.

Therefore, at the time of concrete pouring of RC floor slabs, when the age of the cast concrete is low, sufficient strength of RC floor slabs cannot be obtained, and cracks or the like are caused by the tensile force generated at the intermediate fulcrum. The harmful damage of. For this reason, conventionally, the method of leaving the concrete of the RC floor slab at the intermediate fulcrum portion of the multi-span continuous girder and finally placing the concrete of the same portion was colored.

FIGS. 12 (a), 12 (b) and 12 (c) show the concrete pouring sequence of the RC floor slab, where p is a new concrete pouring portion and q is an existing concrete portion.

[0005]

In the above-mentioned prior art, it is necessary to consider the amount of concrete to be placed, the order of placing, etc., and the interval and the amount of concrete to be placed in the bridge erection process. May have serious effects. In spite of the examination of concrete pouring in this way, the degree of combined action of the steel girder and RC floor slab could not be fully grasped, and the tensile force more than estimated was generated and cracks were generated on the floor slab. It happened.

Further, the order of placing RC floor slabs is limited, and in particular, since the casting is carried out from the central portion of the span, RC floor slabs often hit a lower level than the planned cab value (planned height). It was almost impossible to modify after construction. The present invention has been proposed in view of the above circumstances, and the purpose thereof is to make it possible to freely set the concrete pouring order of RC floor slabs and the like, and to prevent structural damage that occurs in the concrete part. The point is to provide a construction method for a multi-span continuous girder having an RC floor slab capable of controlling various tensile forces.

[0007]

In order to achieve the above-mentioned object, according to the method for constructing a multi-span continuous girder according to the present invention, a multi-span continuous girder in which an RC floor slab is layered on a steel girder. Injecting compressive force as prestressing force into the steel girder upper part and floor slab concrete part through the prestress loading device installed in the steel girder part at the middle point store of the continuous girder at the time of placing the slab concrete in Is.

[0008]

According to the present invention, as described above, it is installed in the steel girder portion at the intermediate fulcrum where a negative bending moment is generated by the vertical load in the multi-span continuous girder in which the RC slab is layered on the steel girder. Since a compressive force is introduced as a prestressing force into the steel girder upper part and floor slab concrete via a prestressing load device, the tensile force is reduced or offset in the RC slab at the intermediate fulcrum caused by the negative bending moment. The generation of tensile force in the RC floor slab is suppressed.

[0009]

The present invention will be described below with reference to the illustrated embodiments. A indicates a multi-span continuous girder in which an RC floor slab 2 is layered on a steel girder 1, and 3 indicates its fulcrum. The prestress loading device 4 is mounted at an intermediate fulcrum in the continuous girder A. Figure 2
4 shows an embodiment of the prestress loading device 4, which is arranged in the web portion above the neutral axis of the steel girder 1 in consideration of the synthetic action of the RC floor slab 2, and the web of the steel girder 1 is provided. PC such as center hole jack 5 and PC cable 6
Anchors 7 constituting a steel fixing portion are provided opposite to each other and are attached to fixing girders 8, respectively.

When the RC floor slab 2 is cast into concrete, the PC cable 6 is tensioned by the center hole jack 5 and fixed to the anchor 7, so that the upper portion of the steel girder 1 and the RC floor slab 2 are compressed. Power is introduced as prestress. At this time, since the prestress loading device 4 is arranged above the neutral shaft of the web of the steel girder 1, the reaction force of the center hole jack 5 is reliably transmitted to the RC floor slab 2.

Thus, after the RC floor slab 2 exhibits sufficient strength, the prestress loading device 4 is removed. FIG. 5 shows a case where the rod 9 is used in place of the cable 6 in the prestress loading device 4, and the nut 10 is tightened to the screw portion 9a which is inserted into the fixing plate mounted on the fixing girder 8 to compress the prestress. It applies force and is applied when the range of influence of tensile force is short.

According to the above method, at the intermediate fulcrum of the multi-span continuous girder A having the RC slab 2, the compressive force is introduced as the prestressing force to the upper part of the steel girder 1 and the RC slab 2, so that the intermediate The tensile force generated in the RC floor slab 2 at the fulcrum portion is reduced, and the generation of cracks in the RC floor slab 2 is prevented. Further, as shown in FIG. 6, no tensile force is generated in the RC floor slab of the existing part p and the rigidity of the intermediate fulcrum is high, so that the chamber between the central supports can be improved. The prestress is introduced just before the existing floor slab p is solidified to some extent and new concrete is poured.

[0013]

According to the method of constructing a multi-span continuous girder having an RC floor slab according to the present invention, a compressive force is introduced as a prestressed force into the concrete part of the floor slab at the intermediate fulcrum of the continuous girder, and Tensile forces due to the negative bending moments that occur can be reduced or offset to eliminate cracking on the RC deck.

Further, the order of placing concrete and the period of placing concrete can be freely set, which is advantageous in the erection process, and can be used for correcting the amount of the chamber by setting the order of placing concrete and the amount of placing concrete.

[Brief description of drawings]

FIG. 1 is a front view schematically showing a multi-span continuous girder having an RC floor slab to which the method of the present invention is applied.

FIG. 2 is a front view showing an embodiment of a prestress loading device.

FIG. 3 is a side view of FIG.

FIG. 4 is a view taken along the line EE in FIG.

FIG. 5 is a front view showing another embodiment of the prestress loading device.

6 (a), (b) and (c) are process drawings showing a method for improving the amount of camber according to the method of the present invention.

7 (a), (b) and (c) are process diagrams showing a method for improving the amount of camber by a conventional method.

FIG. 8 is a front view of a multi-span continuous girder having an RC floor slab to which the method of the present invention is applied.

FIG. 9 is a vertical sectional side view of the multi-span continuous girder.

FIG. 10 is a vertical sectional side view showing another example of the multi-span continuous girder.

FIG. 11 is a bending moment distribution diagram of the multi-span continuous girder due to an evenly distributed load.

12 (a), (b) and (c) are process drawings showing the order of placing conventional RC slab concrete.

[Explanation of symbols]

 A Multi-span continuous girder 1 Steel girder 2 RC floor slab 3 Support point 4 Prestress loading device 5 Center hole jack 6 Cable 7 Anchor 8 Anchored girder

Claims (1)

[Claims] 1. When placing concrete on a floor slab in a multi-span continuous girder in which an RC slab is layered on a steel girder, through a prestress loading device installed in the steel girder part at an intermediate fulcrum of the continuous girder. RC characterized by introducing a compressive force as a prestressing force into the upper part of the steel girder part and the slab concrete part
Construction method for continuous span girders with floor slabs.