JP2796943B2 - Construction method of multi-span continuous steel girder with reinforced concrete slab - 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 constructing a multi-span continuous steel girder such as a bridge in which a reinforced concrete slab is mounted on a steel girder.

[0002]

2. Description of the Related Art In a bridge in which a cast-in-place reinforced concrete slab (hereinafter abbreviated as RC slab) is provided on a steel girder composed of an I-girder or a box girder, a bridge or a slab is fixed between the RC slab and the steel girder. Are interposed, and restrain the free displacement of both. A long RC slab, such as a bridge, is divided into appropriate sections and sequentially constructed, but a corresponding stress is generated in the RC slab due to deformation of a steel girder during construction of the slab. Tensile stress is generated in the floor slab due to casting concrete in other sections, and cracks may occur due to this tensile force.Thus, deformation of steel girders due to concrete casting in each divided section must be thoroughly examined in advance. Must.

[0003] In the conventional method of constructing a multi-span continuous steel girder, in order to suppress such tensile stress, the center of the span is constructed in advance, and the intermediate fulcrum where a negative moment is generated is cast last. Was. In this case, a thorough study on the construction management such as the number of section divisions, the concrete placement amount in the section, the placement order, and the placement interval was indispensable.

[0004]

However, in such a conventional method of constructing a multi-span continuous steel girder, since concrete casting cannot be carried out by one-sided pressing, the location, order, spacing, etc. of the concrete placing are extremely limited. Therefore, it was not efficient in terms of materials and processes.

[0005] The present invention solves the above-mentioned problems, and provides a method of constructing a multi-span continuous steel girder having an RC slab that enables construction of an RC slab from one direction and that can improve the efficiency of materials and processes. It is intended to be.

[0006]

In order to solve the above problems, a method for constructing a multi-span continuous steel girder having an RC floor slab according to the present invention comprises a cast-in-place reinforced concrete floor on a steel girder supported by an intermediate fulcrum. In the method of constructing a multi-span continuous steel girder for constructing a slab, the slab is sequentially constructed by split construction from one end of the steel girder, and the steel of the uncast concrete span adjacent to the slab construction span is provided. The girder is provided with a tension member capable of adjusting the deflection, and after the tension is adjusted by adjusting the tension member, concrete placement of the floor slab is started. The tension member is attached to a temporary column supporting the steel girder of the span, and after tensioning the tension member to support the steel girder at a completed height, concrete casting of the floor slab is started. In addition, the slabs are sequentially constructed while the deflection of the steel girder in the span portion accompanying the slab construction substantially matches the deflection at the time of completion.

The tension member may be a PC steel material that connects the steel girder of the span and the bridge substructure or the temporary strut and is provided with an expansion / contraction adjusting device, or a steel girder of the span. PC steel material to which an expansion and contraction amount adjustment device is attached by anchoring to the directly below support ground, and after the PC steel material is tensioned to maintain the steel girder at the height at the time of completion, concrete casting of the floor slab is started, The present invention is characterized in that the slabs are sequentially constructed by using an expansion / contraction amount adjusting device while substantially matching the deflection of the steel girder of the span portion accompanying the slab with the deflection at the time of completion.

[0008]

According to the construction method of the present invention, after the steel girder of the continuous girder is set on each fulcrum, a predetermined span is pulled down by a tension member to adjust the deflection of the span. The steel girder has an overhang of a predetermined height formed by the production camber, but in the state where concrete is not cast, the steel girder part between the struts adjacent to the strut to construct the floor slab is pulled down with a tension member Under this load, the deflection between the floor slab construction supports is further amplified. In this state, concrete is placed on the floor slab sequentially from one end of the steel girder by split construction. Further, when the floor slab concrete in the lowering section is cast over the intermediate fulcrum, the floor slab load reduces the tension of the tension member. During this time, since the sectional force at the time of completion is always acting on the floor slab between the already-placed supports, no tensile stress causing cracks is generated.

In the construction method according to the second aspect, the tension member is tensioned, and the steel beam is supported by the temporary support at the height at the time of completion, and then the floor slab concrete is poured. Due to the sectional force caused by the construction of the floor slab, the deflection of the section where concrete is not cast tends to change sequentially, but the steel girder supported by the temporary rigid support column maintains the almost completed height during this time. When the entire floor slab is completed, the height at the time of completion is realized only by the dead load, so that the load acting on the tension member and the temporary support is dissipated.

According to a third aspect of the present invention, the steel girder is maintained at a completed height by tensioning a PC steel material as a tensile member. P
The lower end of the C steel material is anchored to a bridge substructure such as a bridge pier or a temporary support, and the length of the PC steel material is kept constant by using an expansion and contraction amount adjusting device such as a hydraulic jack with a sensor attached thereto. Deflection of the lowered section tends to change sequentially with the construction of the floor slab, but the steel girder of the section is always maintained at the completed height by appropriately changing the tensile load of the PC steel material. In the construction method according to the fourth aspect, the PC steel material is anchored to the supporting ground immediately below the steel girder.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a side view of a bridge constructed by the construction method of the present invention. Steel girder 1 has abutments 2a and 2b at both ends.
, And the middle part of the piers 3a, 3b, 3c, 3d,
3e,... Supported by 3 (n-1), 3n (n +
1) RC slab 4 that is a continuous girder span and is cast in place on the top
Is placed. The RC slab 4 is connected to the steel girder 1 via a slab stopper (not shown) fixed to the upper flange upper surface of the steel girder 1, and mutual free displacement is restricted by the adhesive force between the steel girder 1 and concrete. . Therefore, even if it is a non-composite girder, a horizontal shearing force in the bridge axis direction is transmitted, so that a stress is generated in the RC slab 4 with the deformation of the steel girder 1.

The steel girder 1 is manufactured by dividing a deflection caused by a dead load with a predetermined height raised by a manufacturing camber and making a single continuous girder using a temporary support provided between an abutment and a pier. At this time, fastening members 6a, 6b connected to the steel girder 1 are provided at the upper ends of the temporary supporting columns 5a, 5b, and supporting piles 7a, 7b are provided at the lower end thereof. The fastening member, the temporary support column, and the support pile constitute a tensile member integrally.

When the RC slab 4 is constructed from the abutment 2a side, the fastening members 6a and 6b are connected to the steel girder 1 in advance, lowered to the height at the time of completion, and then slab concrete is poured. Due to the sectional force caused by the construction of the floor slab, the deflection of the section where concrete is not cast tends to change sequentially. However, the steel girder 1 restrained by the tensile members such as the temporary rigid supporting columns 5a and 5b also has a substantially high height during this period. To maintain. When the slab concrete in the lowering section is cast over the pier 3a, the slab load decreases the load acting on the tension member. During this time, since the sectional force at the time of completion always acts on the RC floor slab 4 between the already installed supports, no tensile stress causing cracks is generated.

When the temporary support is not used as a tension member, a PC steel bar or a PC steel material such as a PC cable is connected to the steel girder 1 and an expansion / contraction adjusting device such as a hydraulic jack with a sensor is interposed between the steel girder 1 and the PC. By keeping the length of the steel material constant, the steel girder 1 is always maintained at the completed height. Since the lower end of the PC steel material must be a fixed point, for example, as shown in FIG. 1, the PC steel materials 8a and 8b are anchored to the piers 3b and 3c, or the PC steel materials 8c and 8d are supported on the supporting ground immediately below the steel girder 1. Earth anchor. Hydraulic jacks 9 with sensors are provided at both ends of each PC steel material, and the tensile load is appropriately changed so as to maintain a predetermined length.

Using the tension members as described above, the RC slabs 4 are sequentially constructed while always keeping the steel girder 1 at the span where the concrete is not cast and adjacent to the slab construction spans at the completed height. When the entire floor slab construction is completed, the height at the time of completion is realized only by the dead load, so that the load acting on each tension member is dissipated.

Next, an example of the procedure for erection of the steel girder and the change in the deflection of the steel girder will be described in detail with reference to FIGS. FIG.
Fig. 3 is a side view of a two-span continuous steel girder bridge constructed by the construction method of the present invention, Fig. 3 is an explanatory view of the construction procedure, Fig. 4 is a diagram showing a change in bending of the steel girder during construction, and Fig. It is a tension load change figure of a member. The steel girder 11 supports both ends and an intermediate portion thereof with abutments 12a and 12b and a pier 13, respectively. A fastening member 16a, a fastening member 16a is provided at an upper end portion of the temporary supporting columns 15a, 15b constructed at a predetermined position between the pier 13 and the abutment 12a.
16b and support piles 17a and 17b are provided at the lower end. When building RC floor slab 14 from abutment 12b side,
The fastening members 16a and 16b are connected to the steel girder 11 in advance, lowered to the height at the time of completion, and then the slab concrete is poured.

As shown in FIG. 3, the steel girder 11 in the lowered section is shown.
When "a" is lowered to the height at the time of completion by the temporary columns 15a, 15b and the like, the warp of the steel girder 11b between the floor slabs is amplified further upward due to the tensile load (FIGS. 3B and 4). In this state, concrete is laid on the RC floor slab 14 sequentially from one block on the side of the abutment 12b by divisional construction (FIG.
(C)-(e)). Due to the sequentially increasing RC slab load,
The deflection of the steel girder 11 changes sequentially as shown in FIG. At this time, due to the cross-sectional force caused by the construction of the floor slab, the deflection of the section where the concrete is not cast tends to change sequentially, but the steel girder 1 restrained by the tensile members such as the temporary supporting columns 15a and 15b having high rigidity.
1a maintains a substantially completed height during this time.

On the other hand, the tensile load introduced before the concrete is cast changes as shown in FIG. 5 because of the cross-sectional force accompanying the construction of the floor slab. At the time of completion of the five blocks shown in FIG. 3 (e), a load equivalent to the dead load at the time of completion is applied due to the tensile loads F1, F2 and the RC slab load. Realize.

When the slab concrete in the lowering section is cast over the bridge pier 13, the slab load gradually reduces the load acting on the tension member (FIG. 5). During this time, since the sectional force at the time of completion always acts on the RC floor slab 14 between the already-placed supports, no tensile stress causing cracks is generated. When the entire RC floor slab 14 is completed, the load acting on the temporary supporting columns 15a and 15b, which are tension members, is dissipated.

In the construction method described with reference to FIGS. 2 to 5, the temporary strut is used as a tension member in order to hold the steel girder at the height at the time of completion, but the construction method using PC steel is carried out in the same procedure. can do. However, in that case P
It is necessary to positively change the tension of the C steel material to the state shown in FIG. 5 to absorb the change in the deflection of the steel girder accompanying the construction of the floor slab. The construction method of the present invention can be applied to a multi-span continuous steel girder of a composite girder.

[0021]

As described above, the method for constructing a multi-span continuous girder having an RC slab according to the present invention tensions a tension member provided on a steel girder at a non-concrete cast-in support portion to adjust deflection. After the concrete laying of the slab is started, the RC slab to be built in advance is prevented from falling too much and tensile stress is generated in the already laid slab by receiving the load of the slab of the post-cast block. Can be prevented. For this reason,
It is not necessary to limit the order of construction of the RC slabs from the center of the span, and it is possible to perform single-push construction from the ends. Therefore, the efficiency of materials and processes can be improved.

In the construction method according to the second aspect, the steel girders are constrained by using the temporary columns, and the slabs are sequentially constructed while the deflection thereof substantially matches that at the time of completion.
The sectional force at the time of completion always acts on the C slab even when the adjacent section is constructed. Therefore, no tensile stress causing cracks is generated. Further, in the construction method according to the third and fourth aspects, since a PC steel material with an expansion and contraction amount adjusting device is used as the tension member, the deflection can be adjusted more accurately, and the height at the time of completion can be reliably maintained.

[Brief description of the drawings]

FIG. 1 is a side view of a bridge.

FIG. 2 is a side view of a two-span continuous steel girder bridge.

FIG. 3 is an explanatory view of an installation procedure.

FIG. 4 is a diagram showing a change in deflection of a steel girder during installation.

FIG. 5 is a diagram showing a change in tensile load of a tensile member during installation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel girder 2a Abutment 2b Abutment 3a Abutment 3b Abutment 4 RC slab 5a Temporary support 5b Temporary support 6a Fastening member 6b Fastening member 8a PC steel material 8b PC steel material 9 Hydraulic jack with sensor

Claims (4)

(57) [Claims] 1. A method of constructing a multi-span continuous steel girder for constructing a cast-in-place reinforced concrete floor slab on a steel girder supported by an intermediate fulcrum, wherein the floor slab is sequentially constructed by split construction from one end of the steel girder. At the same time, the steel girder of the non-concrete strut adjacent to the floor slab is provided with a tension member capable of adjusting the deflection, and after adjusting the deflection by tensioning the tension member, the floor slab is adjusted. A method for constructing a multi-span continuous steel girder having a reinforced concrete slab, characterized by starting concrete casting. 2. The tension member is attached to a temporary column supporting the steel girder of the span, and the tension member is tensioned to support the steel girder at a height at the time of completion, and then the concrete of the floor slab is formed. The reinforced concrete slab according to claim 1, wherein casting is started, and the slab is sequentially constructed while substantially matching the deflection of the steel girder of the span portion with the deflection at the time of completion with the construction of the slab. Construction method of multi-span continuous steel girder having. 3. The tension member is a PC steel member which connects a steel girder of the span portion and a bridge substructure or the temporary support column and is provided with an expansion / contraction amount adjusting device. After maintaining the girder at the height at the time of completion, start concrete casting of the floor slab, and use the expansion and contraction amount adjustment device to reduce the deflection of the steel girder of the span section accompanying the construction of the floor slab to the deflection at the time of completion. The method for constructing a multi-span continuous steel girder having a reinforced concrete floor slab according to claim 1, wherein the floor slabs are sequentially constructed while substantially matching them. 4. The apparatus according to claim 1, wherein the tension member is attached to a support ground immediately below the steel girder of the span section and a stretching amount adjusting device is attached.
After the PC steel is tensioned to maintain the steel girder at the height at the time of completion, the concrete casting of the floor slab is started, and the construction of the floor slab is performed using the expansion and contraction amount adjusting device. The method for constructing a multi-span continuous steel girder having a reinforced concrete floor slab according to claim 1, wherein the slab is sequentially constructed while making the deflection of the steel girder of the span substantially equal to the deflection at the time of completion.