JP2008308935A - Construction method of truss structure - Google Patents

Abstract

An object of the present invention is to provide a construction method for a truss structure that can apply tension to a tension member inserted through a diagonal member without causing a large bending moment in the string member.
SOLUTION: Two floor slabs 10 and 20 (string members) arranged at a predetermined interval, and both ends are joined to the respective floor slabs 10 and 20, respectively, and a PC steel wire 40 (stretch material) in the axial direction. ) Is inserted into the diagonal structure 30, and includes a step of joining the upper end of the diagonal material 30 to the upper floor slab 10 and applying tension to the PC steel wire 40, and the diagonal material Joining the lower end of 30 to the lower floor slab 20 and imparting tension to the PC steel wire 40.
[Selection] Figure 6

Description

  The present invention relates to a construction method for a truss structure mainly used for a bridge.

  As a bridge using a truss structure, there is a bridge having a composite truss structure including a concrete upper floor slab and a lower floor slab, and diagonal members each having both ends joined to each floor slab. Some bridges reduce the tensile stress of diagonal materials by applying tensile force to the PC steel wires inserted through diagonal materials and applying axial compressive force to the diagonal materials. (For example, refer to Patent Document 1).

JP 2002-213017 (paragraphs 0033 to 0034, FIG. 1)

In the construction method of the conventional truss structure described above, the upper end portion of the PC steel wire is fixed in the upper floor slab, and both ends of the diagonal member through which the PC steel wire is inserted are joined to the upper floor slab and the lower floor slab, respectively. Thus, tension is applied to the PC steel wire from the lower surface side of the lower floor slab.
Here, when a tension force is applied to the PC steel wire inserted through the diagonal member, the diagonal member contracts in the axial direction by the compressive force applied to the diagonal member. In the conventional truss construction method, tension is applied to the PC steel wire with both ends of the diagonal member joined to each floor slab. Pulled in the axial direction of the material. Therefore, the conventional truss structure construction method has a problem that when a tension force is applied to the PC steel wire, a large bending moment is generated in each floor slab, and thus the floor slab is cracked.

  Accordingly, the present invention provides a construction method for a truss structure that solves the above-described problems and can apply tension to the tension material inserted into the diagonal material without causing a large bending moment in the string material. This is the issue.

  In order to solve the above-mentioned problems, the present invention includes two chord members arranged at a predetermined interval, diagonal members in which both ends are joined to each chord member, and a tension member is inserted in the axial direction, A construction method of a truss structure comprising: one end of an oblique member joined to one string member, a step of applying tension to the tension member, and the other end of the oblique member joined to the other string member, And a step of imparting tension to the tendon material. The chord material may be a rod shape or a beam shape, or may be a plate shape (slab shape).

In this configuration, one end of the diagonal member is joined to the chord member, and after applying tension (tensile force) to the tendon member with the other end being free, both ends of the oblique member are joined to each chord member. Furthermore, tension is given to the tendon. That is, the tension | tensile_strength finally provided to a tendon material is provided in 2 steps. When tension is first applied to the tension member, the other end of the diagonal member is a free end, and even if the diagonal member contracts, the string member is not drawn in the axial direction of the diagonal member. There is no moment. In addition, when the second tension is applied to the tension material in a state where both ends of the diagonal material are joined to each string material, a smaller tension force is applied compared to the case where the tension force is applied once. Therefore, the bending moment generated in each chord material can be reduced.
The ratio of tension applied to the tension material in two steps is not limited. However, the smaller the tension applied to the second time, the smaller the bending moment generated in each string material. It is desirable to apply 50 to 90% of the tension force to be applied first, and then apply the remaining tension force for the second time.

  In order to solve the above-mentioned problem, as another configuration of the present invention, two chord members arranged at a predetermined interval and both ends of each chord member are joined, and a tension member is inserted in the axial direction. A method of constructing a truss structure comprising a diagonal member, a step of joining one end of the diagonal member to one chord member in a state in which tension is applied to the tensile member, and the other end of the diagonal member to the other Joining the string material and applying tension to the tendon material.

In this configuration, after one end of the diagonal member is joined to the chord member in a state where a tension force (tensile force) is applied to the tendon member, the two end portions of the oblique member are further joined to each chord member. Giving tension. That is, the tension | tensile_strength finally provided to a tendon material is provided in 2 steps. When one end of the diagonal member is joined to the chord material, tension is already applied to the tension material at the factory, and the tension force of the tension material does not act on the chord material, so there is no bending moment in the chord material. . In addition, when the second tension is applied to the tension material in a state where both ends of the diagonal material are joined to each string material, a smaller tension force is applied compared to the case where the tension force is applied once. Therefore, the bending moment generated in each chord material can be reduced.
The ratio of tension applied to the tension material in two steps is not limited, but the smaller the tension applied to the second time, the smaller the bending moment generated in each chord material. It is desirable to apply 50 to 90% of the final tension to be applied first and then apply the remaining tension for the second time.

  According to the construction method of the truss structure of the present invention, the tension force to be finally applied to the tension material is divided into two times and the bending moment generated in the string material can be reduced. Cracks can be prevented.

Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
In the present embodiment, a case where a truss structure constituting an upper structure is constructed in a bridge of a composite truss structure will be described as an example.

In the superstructure of the bridge 1, as shown in FIG. 1, the truss is formed by a concrete upper floor slab 10 and a lower floor slab 20, and a plurality of diagonal members 30 arranged between the floor slabs 10, 20. A structure is formed. In the present embodiment, the diagonal members 30 are arranged at both ends in the width direction of the superstructure (the direction orthogonal to the bridge axis direction), as in a normal bridge. It is joined to the plates 10 and 20.
In the bridge 1, as shown in FIG. 7, tension is applied to the PC steel wire 40 inserted through the diagonal member 30, and an axial compressive force is applied to the diagonal member 30, thereby pulling the diagonal member 30. Stress is reduced.
The upper floor slab 10 and the lower floor slab 20 correspond to “string material” in the claims, and the PC steel wire 40 corresponds to “tension material” in the claims.

  As shown in FIG. 1, the upper floor slab 10 and the lower floor slab 20 are flat concrete members and are formed of cast-in-place reinforced concrete.

  As shown in FIG. 7, the diagonal member 30 has a steel pipe 31 having an upper end joined to the lower surface of the upper floor slab 10 and a lower end joined to the upper surface of the lower floor slab 20, and a plurality of pipes inserted into the steel pipe 31. PC steel wire 40. In the bridge 1, as shown in FIG. 1, a plurality of diagonal members 30... The diagonal members 30 are inclined in the bridge axis direction, and the adjacent diagonal members 30, 30 are inclined in the opposite direction.

As shown in FIG. 7, the steel pipe 31 is a cylindrical member filled with a concrete material, and disc-shaped end plates 32 and 32 are attached to both ends.
As shown in FIG. 8, the outer peripheral edge of the end plate 32 protrudes from the outer peripheral surface of the steel pipe 31, and a plurality of attachment holes (not shown) for attaching the anchor bolts 32a penetrate through the outer peripheral edge. ing. Further, an insertion hole 32 b for inserting each PC steel wire 40... Penetrates through the steel pipe 31 in the center portion of the end plate 32. In addition, between the upper surface of the end plate 32 attached to the upper end part of the steel pipe 31, and the lower surface of the upper floor slab 10, the filler 33, such as a non-shrink mortar and an epoxy resin, is provided in plate shape.

  In the steel pipe 31, a plurality of PC steel wires 40 are inserted in the axial direction, and a cylindrical inner pipe 34 in which each PC steel wire 40 is inserted is provided. Both ends of each PC steel wire 40... Protrude from both ends of the steel pipe 31 through the insertion holes 32 b of the end plates 32, 32, and both ends of each PC steel wire 40. 60 and 70 are fixed in the floor slabs 10 and 20, respectively.

  Further, the outer diameter of the inner tube 34 is smaller than the inner diameter of the insertion hole 32 b of the end plate 32, and the inner tube 34 can be inserted into the insertion hole 32 b of the end plate 32. In addition, the inner pipe 34 should just be provided with the intensity | strength of the grade which does not deform | transform with the pressure of a concrete material, when a concrete material is filled between the inner peripheral surface of the steel pipe 31, and the outer peripheral surface of the inner pipe 34. It is not limited to a product or a resin.

The upper fixing member 60 is a member for fixing the upper end portion of each PC steel wire 40... In the upper floor slab 10, and includes a bearing plate 61 and a helical reinforcing bar 62 attached to the lower surface of the bearing plate 61. And an anchor head 63 attached to the upper surface of the bearing plate 61.
The bearing plate 61 is a steel plate disposed above the end plate 32 attached to the upper end portion of the steel pipe 31 in the axial direction of the diagonal member 30. An insertion hole 61 a through which each PC steel wire 40... Is inserted passes through the center portion of the bearing plate 61.
The anchor head 63 is a steel block, and a plurality of mounting holes 63a through which one PC steel wire 40 is inserted pass therethrough.

Each of the PC steel wires 40 projecting from the upper surface of the end plate 32 passes through the helical rebar 62 and is inserted into the insertion hole 61a of the bearing plate 61 and the mounting holes 63a of the anchor head 63. Yes. In the helical rebar 62, each of the PC steel wires 40 is inserted into the sheath tube 64 to prevent the concrete material from adhering to the PC steel wire 40 in the fixing member 60.
Further, crimp grips 65 are attached to upper ends of the respective PC steel wires 40 projecting from the upper surface of the anchor head 63, and the crimp grips 65 are locked to the upper surface of the anchor head 63. Thus, the PC steel wires 40 and the upper fixing member 60 are connected to each other. Each crimping grip 65 is protected by being covered with a retainer cover 66.

  The lower fixing member 70 has substantially the same configuration as the upper fixing member 60 described above, and is attached to the bearing plate 71, the helical rebar 72 attached to the upper surface of the bearing plate 71, and the lower surface of the bearing plate 71. Anchor head 73. In the lower fixing member 70, wedges 75... Are attached to lower ends of the PC steel wires 40... Protruding from the lower surface of the anchor head 73, and the wedges 75 are attached to the anchor head 73. Each PC steel wire 40... And the lower fixing member 70 are connected by being locked in the hole 73a. In addition, in the helical rebar 72, each PC steel wire 40 ... is inserted in the sheath pipe 74. Further, the lower fixing member 70 has an anchor head 77 attached to the lower surface of the end plate 32 attached to the lower end portion of the steel pipe 31.

Next, the construction method of the truss structure in the bridge 1 is demonstrated.
In this embodiment, every time the diagonal member 30 is added, the upper floor slab 10 and the lower floor slab 20 are extended in the direction of the bridge axis. In the present embodiment, the process of adding one diagonal member 30 is performed. explain.

  First, as shown in FIG. 2, a formwork (not shown) is provided in a region where the upper floor slab 10 is extended, and the fixing member 60 and the anchor bolt 32a to which the upper ends of the respective PC steel wires 40 are fixed. Is placed in a mold, a concrete material is placed in the mold, and the fixing member 60 and the anchor bolt 32a are embedded in the upper floor slab 10. As a result, the upper fixing member 60 and the anchor bolts 32a are fixed in the upper floor slab 10, and the PC steel wires 40 are suspended from the lower surface of the upper floor slab 10. In addition, the lower end part of the sheath pipe | tube 64 and the lower end part of each anchor bolt 32a ... are made to protrude from the lower surface of the upper floor slab 10. As shown in FIG. Moreover, since each PC steel wire 40 ... is inserted in the sheath pipe | tube 64 in the upper floor slab 10, a concrete material does not adhere to each PC steel wire 40 ....

  Subsequently, as shown in FIG. 3, the inner pipe 34 is disposed in the steel pipe 31, and the insertion holes 32 b and 32 b of the end plates 32 and 32 of the steel pipe 31 are communicated with the openings at both ends of the inner pipe 34. Let The steel pipe 31 is disposed below the fixing member 60, and the PC steel wires 40 are inserted into the inner pipe 34, whereby the PC steel wires 40 are inserted into the steel pipe 31. At this time, the bundle of PC steel wires 40... Passes through the insertion holes 32 b of the end plate 32 attached to the lower end portion of the steel pipe 31 while being inserted into the inner pipe 34. It does not get caught on the upper surface (inner surface).

Moreover, the lower end part of each anchor bolt 32a ... is inserted in each attachment hole (not shown) of the end plate 32 attached to the upper end part of the steel pipe 31, respectively, and the upper surface of the end plate 32 and the upper floor slab 10 The steel pipe 31 is temporarily fixed to the lower surface of the upper floor slab 10 with a gap formed between the lower surface and the lower surface. Then, the filler 33 is placed in the gap between the upper surface of the end plate 32 and the lower surface of the upper floor slab 10.
After the filling material 33 is hardened, the upper end portion of the diagonal member 30 is placed on the upper floor by tightening the fastening nut 32d to each anchor bolt 32a... On the lower surface side of the end plate 32 attached to the upper end portion of the steel pipe 31. It will be in the state joined to the plate 10. And when filling a concrete material in the steel pipe 31 like this embodiment, a concrete material is filled between the inner peripheral surface of the steel pipe 31 and the outer peripheral surface of the inner pipe 34.

  Subsequently, as shown in FIG. 4, the anchor head 77 is brought into contact with the lower surface of the end plate 32 attached to the lower end portion of the diagonal member 30, and each attachment hole 77a of the anchor head 77 (see FIG. 8). Each PC steel wire 40 ... is made to pass through. Then, a hydraulic center hole jack (hereinafter simply referred to as “hydraulic jack”) 80 is attached to the lower surface of the anchor head 77, and the PC steel wire 40 is pulled to the lower end side by the hydraulic jack 80, so that the PC steel A tension (tensile force) is applied to the wire 40. The tension applied first to the PC steel wire 40 is referred to as primary tension. In the present embodiment, the primary tension is 50 to 90% of the tension finally applied to the PC steel wire 40.

  A wedge (not shown) is attached to the PC steel wire 40 on the lower surface side of the anchor head 77 while applying primary tension to the PC steel wire 40. By locking the wedge to the upper surface of the anchor head 77, the primary tension is applied to the PC steel wire 40 even after the hydraulic jack 80 is removed from the PC steel wire 40. Similarly, primary tension is applied to each PC steel wire 40... Using a hydraulic jack 80.

  Subsequently, as shown in FIG. 5, a mold (not shown) is provided in a region where the lower floor slab 20 is extended, and the fixing member 70 and the anchor bolt 32 a are disposed in the mold, and the fixing member 70 and The anchor bolt 32a is positioned below the end plate 32 attached to the lower end of the steel pipe 31. And the anchor bolt 32a was inserted in each attachment hole (not shown) of the end plate 32 attached to the lower end part of the steel pipe 31, and the upper end part of each anchor bolt 32a ... protruded from the upper surface of the end plate 32. Put it in a state. Further, the fixing member 70 in the mold is inserted into the insertion holes 72a (see FIG. 8) of the support plate 71 through the PC steel wires 40.

A concrete material is placed in the formwork, and the fixing member 70 and the anchor bolt 32a are embedded in the lower floor slab 20, so that the lower fixing member 70 and each anchor bolt 32a. Let it settle inside. At this time, the lower end of the lower fixing member 70 is exposed on the lower surface of the lower floor slab 20, and the PC steel wires 40... Are suspended from the lower surface of the lower floor slab 20. A recess 21 is formed on the lower surface of the floor slab 20.
After the placed concrete material is hardened, the lower end portion of the diagonal member 30 is joined to the lower floor slab 20 by tightening the fastening nut 32d to the upper end portion of each anchor bolt 32a ... on the upper surface side of the end plate 32. It will be in the state.

  In this embodiment, when the lower floor slab 20 is extended in the bridge axis direction and the lower fixing member 70 is fixed, the upper floor slab 10 is also extended in the bridge axis direction. Therefore, when the fixing member 70 is attached to the lower end portion of the steel pipe 31 or the anchor bolt 32a is disposed, the upper floor slab 10 is not constructed above the lower fixing member 70, and the upper space is widely used. Workability is improved.

  Subsequently, as shown in FIG. 6, the anchor head 73 is brought into contact with the lower surface of the pressure bearing plate 71 of the lower fixing member 70, and each PC is placed in each mounting hole 73 a (see FIG. 8) of the anchor head 73. Insert steel wires 40... Then, a hydraulic jack 80 is attached to the lower surface of the anchor head 73, and a tension force is applied to the PC steel wire 40 by pulling one PC steel wire 40 to the lower end side by the hydraulic jack 80. The tension applied to the PC steel wire 40 for the second time is referred to as secondary tension. In this embodiment, the secondary tension is a magnitude obtained by subtracting the primary tension from the tension finally applied to the PC steel wire 40, that is, 10 to 50 of the tension finally applied to the PC steel wire 40. % Tension. Thereby, tension is given to PC steel wire 40 in two parts.

Here, the ratio of the tension applied to the PC steel wire 40 in two steps will be described.
When tension is applied to the PC steel wire 40 inserted through the diagonal member 30, the diagonal member 30 contracts in the axial direction by the compressive force applied to the diagonal member 30. Therefore, when tension is applied to the PC steel wire 40 in a state in which both ends of the diagonal member 30 are joined to the upper floor slab 10 and the lower floor slab 20, the upper floor slab 10 The lower surface and the upper surface of the lower floor slab 20 are drawn in the axial direction of the diagonal member 30, and tensile stress acts on the upper floor slab 10 and the lower floor slab 20.
For example, for a 5-span continuous PC truss road bridge with a span of 155m, when tension is applied to the diagonal member 30 once with both ends of the diagonal member 30 joined to the floor slabs 10 and 20, respectively. Is calculated, the tensile stress generated in the floor slabs 10 and 20 is 2.5 to 6.5 N / mm ² . According to the road bridge specification, the limit value of the tensile stress of the concrete material at the time of tension of the PC steel wire is 1.5 N / mm ^{2. In} this embodiment, when the secondary tension is applied, the upper floor In order to keep the tensile stress generated in the plate 10 and the lower floor plate 20 within the limit value, as shown in the following formulas (1) and (2), a tension force of 40 to 40 to finally apply the primary tension force is applied. 77% is required. In the present embodiment, the calculated numerical value is provided with a margin, and is set to 50 to 90% of the tension that finally gives the tension during the primary tension.
In the case of 2.5 N / mm ² 1-1.5 / 2.5 = 0.40 (1)
In the case of 6.5 N / mm ² 1-1.5 / 6.5 = 0.77 (2)

  Then, a wedge 75 (see FIG. 8) is attached to the PC steel wire 40 on the lower surface side of the anchor head 73 while applying secondary tension to the PC steel wire 40. By locking the wedge 75 in the attachment hole 73a on the lower surface side of the anchor head 77, the tension force is applied to the PC steel wire 40 even after the hydraulic jack 80 is removed from the PC steel wire 40. It is. Similarly, after applying a secondary tension force to each PC steel wire 40... Using a hydraulic jack 80, a concrete material is placed in the recess 21 so that the construction of the truss structure shown in FIG. Complete.

  In the construction method of the truss structure as described above, the upper end portion of the diagonal member 30 is joined to the upper floor slab 10, and the lower end portion is free and the primary tension is applied to the PC steel wire 40, and then both ends of the diagonal member 30. The secondary tension is applied to the PC steel wire 40 in a state where the portion is bonded to the floor slabs 10 and 20. That is, the tension | tensile_strength finally provided to PC steel wire 40 is divided | segmented into 2 times and provided. When the primary tension is applied to the PC steel wire 40, the lower end portion of the diagonal member 30 is a free end, and the upper floor slab 10 is not drawn in the axial direction of the diagonal member 30 even when the diagonal member 30 contracts. No bending moment is generated in the upper floor slab 10. Further, when the secondary tension is applied to the PC steel wire 40 in a state where both ends of the diagonal member 30 are joined to the floor slabs 10 and 20, the tension is small as compared with the case where the tension is applied once. Therefore, the bending moment generated in the floor slabs 10 and 20 can be reduced, and the cracks of the floor slabs 10 and 20 can be prevented.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the spirit of the present invention. For example, in this embodiment, 50 to 90% of the tension force to be finally applied is applied to the PC steel wire 40 shown in FIG. 7 by the primary tension force, and the remaining tension force is applied as the secondary tension force. However, the ratio of the tension applied to the PC steel wire 40 is not limited. However, the bending moment generated in the upper floor slab 10 and the lower floor slab 20 can be reduced as the secondary tension applied to the PC steel wire 40 is smaller.

  Further, in the present embodiment, as shown in FIG. 4, the primary tension is applied to the PC steel wire 40 in a state where the upper end portion of the diagonal member 30 is joined to the upper floor slab 10, and then both end portions of the diagonal member 30 are respectively attached. The secondary tension is applied to the PC steel wire 40 in a state where it is joined to the floor slabs 10 and 20, but the upper floor slab is made of a precast concrete member in which the primary tension is applied to the PC steel wire in advance at a factory or the like. After joining both ends of the diagonal member to each floor slab, secondary tension may be applied to the PC steel wire 40. In this configuration, it is not necessary to insert a PC steel wire into the steel pipe at a high place or to apply a primary tension to the PC steel wire, so that workability can be improved.

Moreover, in this embodiment, as shown in FIG. 7, although the upper floor slab 10 and the lower floor slab 20 are flat concrete members, you may comprise with steel materials, and also the both ends of the diagonal material 30 may be comprised. The string material to be joined may be a beam-shaped member.
In the present embodiment, the PC steel wire 40 is inserted into the diagonal member 30 as a tension material, but various tension materials such as a PC steel rod can be used.
Further, the fixing members 60 and 70 and the anchor bolt 32a are not limited as long as they are fixed in the upper floor slab 10 or the lower floor slab 20.
Moreover, although the concrete material is filled in the steel pipe 31, the structure which is not filled with the concrete material in the steel pipe 31 can also be used.

It is the side view which showed the bridge using the truss structure of this embodiment. In the construction method of the truss structure of this embodiment, it is a sectional side view in the state where the fixing member and the PC steel wire were fixed to the upper floor slab. In the construction method of the truss structure of this embodiment, it is a sectional side view of the state which joined the steel pipe to the upper floor slab. In the construction method of the truss structure of this embodiment, it is the sectional side view which showed the aspect which provides primary tension | tensile_strength to PC steel wire. In the construction method of the truss structure of this embodiment, it is a sectional side view of the state where the fixing member is fixed to the lower floor slab. In the construction method of the truss structure of this embodiment, it is the sectional side view which showed the aspect which provides a secondary tension force to PC steel wire. It is the sectional side view which showed the truss structure of this embodiment. In the truss structure of this embodiment, it is the sectional side view which showed the junction part of each floor slab and diagonal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bridge 10 Upper floor slab 20 Lower floor slab 30 Diagonal material 31 Steel pipe 32 End plate 32a Anchor bolt 33 Filler 34 Inner pipe 40 PC steel wire 60 Fixing member 61 Bearing plate 63 Anchor head 64 Sheath pipe 65 Crimp grip 70 Fixing member 71 Support Pressure plate 73 Anchor head 74 Sheath tube 75 Wedge 77 Anchor head 80 Hydraulic jack

Claims (2)

Two strings arranged at a predetermined interval;
A construction method of a truss structure provided with a diagonal material in which both ends are joined to each chord material and a tension material is inserted in the axial direction,
Joining one end of the diagonal material to one of the string materials, and applying a tension to the tension material;
Joining the other end of the diagonal to the other chord, and applying tension to the tendon;
A method for constructing a truss structure characterized by comprising: Two strings arranged at a predetermined interval;
A construction method of a truss structure comprising a diagonal material in which both ends are joined to each chord material and a tension material is inserted in the axial direction,
In a state where tension is applied to the tension material, joining one end of the diagonal material to one of the string materials;
Joining the other end of the diagonal to the other chord, and applying tension to the tendon;
A method for constructing a truss structure characterized by comprising:

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