JP6089096B2 - Method for suppressing twist of precast girder and method for joining precast girder - Google Patents

Description

  The present invention relates to a method for suppressing twisting of a precast girder and a method for joining precast girders in a step of constructing a bridge girder formed of concrete and having a box-shaped cross section.

As a method of constructing a concrete box girder bridge, a support work is assembled from the ground between abutments or piers formed at a predetermined interval, and supported by this support work, forming a formwork, assembling reinforcing bars, and placing concrete. A so-called all-supporting construction method is widely used.
In the above all support construction methods, there is a problem that the amount of work to be done at the construction site of the bridge is large and the construction period is long, and a method using a precast segment made of precast concrete or a precast girder as a part of the concrete bridge girder is proposed Has been.

  For example, in the method described in Patent Document 1, precast girders made of precast concrete are produced in advance in a production yard or the like, and these precast girders are suspended between bridge piers and installed. The precast girder used in this method is composed of a lower floor slab part and two web part parts, and has a substantially U-shaped cross section. First, the bridge girder on the upper part of the pier is formed first, and the precast girder (girder without the upper floor slab) is lifted between the piers and joined with the bridge girder on the upper part of the pier, and tension is applied in the direction of the bridge axis Introduce. Such a construction is sequentially repeated for each span to construct a precast girder between all the spans, and an upper floor slab is constructed on the precast girder.

JP 2009-68249 A

  As described in the above-mentioned Patent Document 1, in the method in which the U-shaped precast girders are sequentially lifted and installed for each span, an upper floor slab must be formed on the precast girders, It is necessary to perform frame formation, reinforcement, concrete placement, demolding, etc. on site. On the other hand, if the upper floor slab is integrally formed as a precast girder, the weight increases significantly, and the girder for lifting, the lifting device for lifting, etc. become larger and the efficiency becomes worse. End up.

The present invention has been made in view of such circumstances, the purpose of which is to reduce the amount of work at the construction site of the bridge, shorten the construction period, and torsion of the precast girder of the shape obtained by dividing the bridge girder. It is possible to join in a suppressed state .

  In order to solve the above-mentioned problem, the invention according to claim 1 is provided when a precast girder formed of precast concrete is supported at both ends in a shape obtained by dividing a cross-section of a bridge girder having a box-shaped cross section. A method for suppressing twisting, wherein the precast girder has one web, an upper floor slab protruding from the upper part of the web to both sides, and a lower floor slab protruding from the lower part of the web to one side, A tension material is arranged in the axial direction of the precast girder near the side edge of the precast girder where both the upper floor slab and the lower floor slab project, and the tension material supports the precast girder at both ends. Introducing tension before lifting and fixing near the upper edge of the precast girder near both ends of the precast girder, and near the center in the axial direction of the precast girder, Near the lower edge of the precast girder bent axis of the tendons, upward force by tension introduced into the tension member to provide a precast girder method twist suppression arranged to act on the precast girder.

  In the invention according to claim 2, the first precast girder and the second precast girder, which are formed of precast concrete in a shape obtained by dividing the cross section of the bridge girder having a box-shaped part, are supported at both ends. A precast girder joining method for joining in a state, wherein the first precast girder is one web, an upper floor slab projecting from the upper part of the web to both sides, and projecting from the lower part of the web to one side. The second precast girder has one web, an upper floor slab protruding from the upper part of the web so as to face the upper floor slab, and a lower part. A lower floor slab projecting from the first precast girder and a lower floor slab projecting so as to face the first precast girder, and the first precast girder and the second precast girder A step of supporting the girder by supporting both ends in the axial direction, and supporting the girder in a predetermined position, and between and between the upper floor slabs protruding from both the first precast girder and the second precast girder Placing concrete between the overhanging lower floor slabs and integrally joining the first precast girder and the second precast girder, the first precast girder of the concrete A tension material is arranged in the axial direction of the first precast girder in the vicinity of a side edge to be joined to the second precast girder by placing, and the tension material supports the first precast girder at both ends. Then, tension is introduced before lifting and fixing near the upper edge of the first precast girder near both ends of the first precast girder, and in the axial direction of the first precast girder Near the center, the axis of the tendon is bent near the lower edge of the first precast girder, and an upward force is applied to the first precast girder by the tension introduced into the tendon. A precast girder joining method is provided.

  A precast girder with a box-shaped cross-section is split at approximately the center between the webs. The precast girder is suspended between the piers, so the weight of the precast girder is half the weight of the completed bridge girder. It can be as follows. Therefore, it is possible to reduce the size of a mechanism for lifting such as a girder or a hoisting machine. Precast girders can be made into box girders by joining the upper and lower floor slab parts, the amount of formwork assembled at the construction site of the bridge, the amount of reinforcing bars to be placed, and the amount of concrete cast Is reduced. Therefore, the amount of work performed at the construction site of the bridge is reduced, and the construction period can be shortened.

The precast girder is divided along the axis of the bridge girder at approximately the center between the webs of the box-shaped portion, and the cross-sectional shape of the divided precast girder is asymmetric and the portion constituting the box-shaped portion is the side. The shape is open to the direction. In the precast girder having such a cross-sectional shape, the position of the center of gravity of the cross-section and the position of the shear center are different. For this reason, if it is supported by suspension at both ends, torsional deformation occurs between the positions supported by its own weight. On the other hand, a tension material is arranged so that an upward reaction force component acts near the center in the axial direction, and a torsional deformation in the direction opposite to the torsional deformation due to its own weight is generated. Thereby, the deformation | transformation resulting from the twist when it lifts is reduced, and the two precast girders spanned can be joined to each other in a state where the twist is suppressed.

As described above, in the precast girder twist suppressing method and the precast girder joining method of the present invention, the weight of the box girder divided in the axial direction and suspended at one time is reduced, and the work amount at the construction site of the bridge is reduced. As a result, the construction period can be shortened and the bridge girder can be constructed, and the precast girder having a shape obtained by dividing the bridge girder can be joined in a state where twisting is suppressed .

It is the schematic sectional drawing and schematic side view which show an example of the box girder bridge which can be constructed | assembled by applying the method which concerns on this invention. It is the schematic side view and sectional drawing which show the position and shape which arrange | position the precast girder which comprises the box girder bridge shown in FIG. It is a schematic perspective view of the precast girder shown in FIG. FIG. 4 is a schematic side view, an end view, and a cross-sectional view showing a tendon disposed in the precast girder shown in FIGS. 2 and 3. It is a schematic sectional drawing which shows a deformation | transformation state when the precast girder shown in FIG.2, FIG3 and FIG.4 is supported by both ends. It is a schematic sectional drawing which shows the principal axis of the cross section of the precast girder shown in FIG.2, FIG3 and FIG.4. It is sectional drawing and a side view explaining the process of constructing the box girder bridge shown in FIG. It is sectional drawing and a side view explaining the process of constructing the box girder bridge shown in FIG. It is sectional drawing and a side view explaining the process of constructing the box girder bridge shown in FIG. 1 is a schematic cross-sectional view of a box girder bridge that can be constructed using the features of the present invention and a cross-sectional view of a precast girder that is formed to construct the box girder bridge.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic sectional view and a schematic side view showing an example of a box girder bridge that can be constructed by applying the method according to the present invention. 2 is a side view and a cross-sectional view showing the arrangement of precast girders used for constructing the box girder bridge shown in FIG. 1, and FIG. 3 is a schematic perspective view of the precast girders.
The box girder bridge 1 is a bridge having multi-girder continuous girders supported by piers 2 or abutments (not shown) constructed at predetermined intervals, and the bridge girder 3 is a box girder formed of precast concrete. It has become.

  As shown in FIG. 2 (b), the bridge girder 3 has a hollow box-shaped portion 4, which constitutes an upper portion of the box-shaped portion 4 and extends over both sides of the box-shaped portion 5a. The main part is comprised by the upper floor slab 5 which has this, the lower floor slab 7 which comprises the lower part of the said box-shaped part, and the two webs 6 which connect this lower floor slab 7 and the said upper floor slab 5 . As shown in FIG. 2 (a), the bridge girder 3 is divided into a bridge pier upper part 31 and a span part 32 spanned between the two piers and connected at both ends to the bridge pier upper part 31. It is what is done. The span portion 32 is formed in advance with a right precast girder 11 and a left precast girder 12 which are divided into left and right at substantially the center in the width direction of the box-shaped portion 4, and these are lifted and supported on the pier 2. It is formed by being joined to the upper pier upper portion 31.

Next, a precast girder twist suppressing method and a precast girder joining method, which are one embodiment of the present invention and can be applied to construct the above box girder bridge, will be described.
First, the pier 2 is constructed at a predetermined position on the site where the box girder bridge is constructed. At the same time, a precast girder production yard is provided near the construction site to form two precast girders 11 and 12.

  The two precast girders 11 and 12 constituting the span portion 32 are, as shown in FIGS. 2 (b), 3 and 4, substantially right half and almost left of a bridge girder having a box-shaped section. It constitutes half. And each is provided with the one web 6, and the overhanging part 5a of the upper floor slab and the part 5b which comprises a box-shaped part overhang on both sides from the upper part. Further, a lower floor slab 7a divided from the lower end portion of the web 6 is projected toward the other precast girder side to be joined. Therefore, the cross sections of the respective precast girders 11 and 12 have an asymmetric shape with the upper floor slab 5 projecting on both sides from the top of the web 6 and the lower floor slab 7a projecting on one side from the lower end.

  The two precast girders 11 and 12 are formed between the upper pier support portions 31 supported on the two adjacent piers 2 so as to be connected to the bridge piers of the upper pier portions 31. That is, it is set as the length which deducted the length of the pier upper part and the length of these junction parts 10 from the length between one diameter. Further, lateral girders 13a, 13b, and 13c are provided in the vicinity of the both ends in the axial direction of these precast girders 11 and 12 and in the central portion for suppressing deformation of the cross section of these precast girders 11 and 12. . That is, a wall body perpendicular to the axes of the precast girders 11 and 12 is formed so as to be continuous with the upper floor slab 5a, the lower floor slab 7a and the web 6 constituting the box-shaped portion. These cross beams 13a, 13b, 13c are also joined when the two precast beams 11, 12 are joined by placing concrete in the joint 9 between them, One continuous girder is formed in the box-shaped portion 4.

  The precast girders 11 and 12 can be formed in the production yard in the same manner as a normal concrete member. That is, a formwork is formed, and a reinforcing bar is assembled in this formwork. In addition, a sheath or the like is disposed to insert the necessary tendon or the tendon. Then, concrete is cast and demolded after the concrete is hardened.

In the precast girders 11 and 12, a tension material is arranged as follows.
4A is a side view from the side where the precast girders 11 and 12 are joined to each other, FIG. 4B is an end view of the precast girder, and FIG. 4C is a view in the vicinity of the central portion in the axial direction of the precast girders. It is sectional drawing.
As shown in these drawings, a tension member 14 is stretched around the side edges of the precast girders 11 and 12 that are joined to each other in the region inside the box-shaped portion 4. The tension member 14 is stretched outside the concrete member, and is fixed on the upper portions of the cross beams 13a and 13c near the ends in a state where the tension force is introduced. And it inserts in the through-hole provided in the lower part of the cross beam 13b of a center part, and makes the tension | tensile_strength material 14 into which tension | tensile_strength was introduced bend in this cross beam part. Thereby, the upward force by bending the tension material 14 introduced with the tension force is applied to the cross beam 13b.

  On the other hand, a sheath is embedded in the axial direction of the precast girders 11 and 12 in the concrete of the tip portion of the overhanging portion 5a of the upper floor slab and the connecting portion between the web 6 and the lower floor slab 7, and the tension members 15 and 16 is inserted and tension is introduced. As a result, prestress is introduced into the tip portion of the overhanging portion 5 a of the upper floor slab and the connecting portion between the web 6 and the lower floor slab 7.

FIG. 5 is a schematic diagram for explaining the effect of arranging the tension material 14 in the vicinity of the side edge 11a that joins the precast girder 11 to the other precast girder 12 and introducing a tension force. Shows the deflection of the central part due to its own weight when the precast girder is supported at both ends, comparing the position of the end part and the position of the cross section of the central part. FIG. 5 (b) is a diagram showing the deflection of the central part by introducing a tension force to the tension material, and FIG. 5 (c) is when the weight of the precast girder shown in FIG. 5 (a) is applied. It is a figure which shows the state which both the bending | flexion and the bending | flexion when the tension | tensile_strength of the tendon shown in FIG.5 (b) acted were acted.
In these drawings, the position of the cross section of the central portion of the precast beam 11 is indicated by a solid line, and the position of the end portion is indicated by an imaginary line.

  The cross-sectional shape of the precast girder 11 is a so-called open cross-section in which the upper floor slab 5b and the lower floor slab 7a protrude from one side surface but are opened between them. For this reason, as shown in FIG. 5A, the precast girder 11 is shifted in the horizontal direction from the position of the center of gravity and the position of the shear center, and when the self-weight distributed in the axial direction of the precast girder 11 acts, The torsional deformation occurs so that the side edge 11a joined to the precast girder 12 bends downward more largely than the other side edge 11b. On the other hand, when an upward force acts near the center of the precast girder 11 due to the tension of the tension member 14, as shown in FIG. 5 (b), the side edges 11a joined to each other are larger than the other side edge 11b. Torsional deformation occurs so that it can be lifted. When the precast girder 11 is suspended and supported at both ends, both of these act, and the deflection at the center is as shown in FIG. 5 (c), with the side edge 11a and the upper floor joining the two precast girders 11 and 12 together. There is no significant difference in the amount of downward deflection between the side edge 11b at the tip of the plate overhanging portion 5a. In this state, the two precast girders 11 and 12 arranged in parallel can be joined.

  On the other hand, as shown in FIG. 6, the cross section of the precast girder 11 is asymmetrical, so that the main axis of the cross section is inclined with respect to the horizontal direction or the vertical direction. That is, the direction in which the bending rigidity of the precast girder 11 becomes the smallest (the direction in which the bending moment acts around the X axis shown in FIG. 6) and the direction in which the bending rigidity becomes the largest (the direction in which the bending moment acts around the Y axis). ) And will be inclined. Thus, when the precast girder 11 is suspended and supported at both ends, the central portion is greatly bent in the direction in which bending deformation is most likely to occur, that is, in the direction in which bending rigidity is small. Tensile stress is likely to occur in the vicinity of the connecting portion with the lower floor slab 7. On the other hand, by prestressing these portions in advance, the deflection of the precast girder 11 is suppressed, and the generation of tensile force in the concrete of the precast girder 11 is suppressed.

Next, a method for installing the bridge girder 3 on the pier 2 using the precast girders 11 and 12 will be described.
First, as shown to Fig.7 (a), the pier upper part 31 of a bridge girder is formed in the upper part of the pier 2 raised from the foundation ground. The upper part 31 of the pier may be one that is pre-manufactured in a production yard or the like together with the two precast girders 11 and 12, and may be installed on the pier 2 or a support work is assembled on the pier 2; It is also possible to place concrete on the pier by installing the formwork and arranging the reinforcing bars.
The pier upper part 31 of the bridge girder is formed integrally with the entire cross section, and has a horizontal girder on the fulcrum at a position where the support is provided. Then, two precast girders 11 and 12 are connected to the end face in the axial direction of the pier upper portion 31.

  The upper part 31 of the pier is supported by the pier 2 via the support 18 and, when the bridge girder 3 is completed, allows rotational displacement around a horizontal axis perpendicular to the axis of the bridge girder 3, or together with this rotational displacement. The displacement of the bridge girder 3 in the axial direction is allowed. However, until the precast girders 11 and 12 are integrally joined, the pier upper part 31 is temporarily fixed so as to restrain displacement with respect to the pier 2. The temporary fixing method is, for example, by inserting a concrete block between the bridge pier 2 and the bridge pier upper portion 31 and introducing tension to the tension members arranged in the vertical direction so that the bridge pier upper portion 31 is connected to the pier 2. A tightening method can be employed.

  Next, the erection girder 22 is bridged over the pier upper part 31 of the bridge girder supported by the pier 2 through the support column 21. Then, as shown in FIG. 7 (b), the right precast girder 11 produced in advance is lifted between the piers 2 by a suspension member 23 suspended from the erection girder 22. At this time, the suspension members 23 are respectively engaged with both end portions of the precast girder 11 and are wound up in the vicinity of the columns 21 at both ends of the installation girder 22.

In this way, the right precast girder 11 is lifted to a predetermined position between the two pier upper portions 31 and temporarily supported by the pier upper portion 31 fixed to the pier 2 as shown in FIG. At this time, a space is provided between the upper pier portion 31 and a space for forming the gap, that is, the joint portion 10 for joining the upper pier portion 31 and the precast girder 11 by placing concrete at the construction site of the bridge girder. .
Various methods can be adopted as a method for temporarily supporting the precast girder 11 on the pier upper portion 31. However, the steel beam 24 for temporary fixing is fixed by projecting to the precast girder 11 side above the upper portion of the pier. In addition, the precast girder 11 can be temporarily supported via the steel beam 24.

  Subsequently, as shown in FIG. 8B, the erection girder 22 is moved in the lateral direction, and the other precast girder, that is, the left precast girder 12 is installed at a position to be lifted. Then, the left precast girder 12 is lifted in the same manner as the right precast girder 11, and the left precast girder 12 is temporarily fixed to the bridge pier upper portion 31 as shown in FIG. At this time, the upper floor slab 5b forming the box-shaped portion of the left precast girder 12 protrudes toward the side where the right precast girder 11 is supported, and similarly, both the upper floor slab 5b protruding from the right precast girder 11 Are opposed to each other at a predetermined interval. Similarly, the end surface of the portion 7a protruding from the web 6 also faces the lower floor slab 7 at a predetermined interval.

Each of the two precast girders 11 and 12 supported in this way has an open section between the upper floor slab 5b and the lower floor slab 7a protruding in a cross-sectionally asymmetric manner. For this reason, when supported at both ends as described above, torsional deformation occurs near the center in the axial direction due to its own weight, but the tension force introduced into the tension member 14 acts as an upward component near the center, and torsional deformation occurs. It can support in the state which suppressed.
Further, prestress is introduced in the vicinity of the front end portion of the overhang portion 5a and the joint portion between the web 6 and the lower floor slab 7, and the generation of tensile stress in these regions is suppressed.

Concrete is cast in the joint 9 between the right precast girder 11 and the left precast girder 12 and the joint 10 between the two precast girders 11 and 12 and the bridge pier upper part 31. These are joined together.
Prior to placing concrete, reinforcing bars protrude at predetermined intervals from the mutually facing end surfaces of the upper floor slab 5b provided in the right precast girder 11 and the left precast girder 12, or these rebars are overlapped, Alternatively, a new reinforcing bar is arranged so as to overlap with both of these reinforcing bars. In addition, reinforcing bars are similarly protruded from the end surface of the lower floor slab 7a protruding from both sides, the vicinity of both ends, and the opposite end surface of the cross beam 13 provided in the vicinity of the central portion in the axial direction so that they are connected. Place the rebar in And a formwork is provided on the lower side between the upper floor slab 5b and the lower floor slab 7a protruding so that the end faces face each other.

  On the other hand, in the space of the connecting portion 10 where the end face in the axial direction of the two precast girders 11 and 12 and the end face of the pier upper part 31 face each other, reinforcing bars may be protruded from both sides, but the end face is roughened. Alternatively, a convex portion or a concave portion acting as a shear key may be provided. And a rebar is arranged between these end faces, and a formwork is installed. Then, concrete is cast and hardened.

  After the concrete has hardened, a tension material (not shown) is inserted into a sheath embedded in the upper floor slab 5 in a direction perpendicular to the axis of the bridge girder 3 and is tensioned to introduce lateral prestress. Thereby, it shall resist the wheel load etc. with which the upper floor slab 5 is loaded. Further, in the axial direction of the bridge girder 3, a tension material (not shown) is additionally disposed outside the concrete member inside the box-shaped cross section, and the prestress is introduced into the concrete of the bridge girder 3 by tension. The tension members are arranged on both sides of the joint between the precast girders 11 and 12 and the pier upper part 31 and between the pier upper part 31 on which the large negative bending moment acts on the bridge girder 3 and the pier on which the positive bending moment acts. It is arranged so that a sufficient prestress is introduced near the center of the. At this time, the degree of compressive stress always acts between the end faces of the precast girders 11 and 12 and the concrete cast on the joint 10 and between the pier upper part 31 and the concrete cast on the joint 10. In addition, even when the reinforcing bars are not continuous at these boundary surfaces, a strong connection can be achieved.

When the precast girders 11 and 12 and the pier upper part 31 are integrally joined as described above, and the bridge girder 3 is bridged between the piers 2, as shown in FIG. The bridge girder between the next spans is constructed in the same way so as to be continuous with the bridge girder 3 that has already been bridged. Further, for the span where the bridge girder 3 has already been bridged, the temporary support of the precast girders 11 and 12 by the upper pier part 31 and the temporary fixing of the upper pier part 31 to the pier 2 can be released.
After the bridge girder 3 has been formed for all spans in this way, the construction of the box girder bridge is completed by applying ground cover, railing, pavement, etc. on the upper floor slab 5.

  Thus, by forming the bridge girder 3 having a box-shaped cross section, the two precast girders 11 and 12 having a shape obtained by dividing the box-shaped cross section into left and right are joined in a state in which almost no torsional deformation occurs. One bridge girder 3 having a box-shaped cross section can be obtained. That is, while avoiding the joining of the two precast girders 11 and 12 while the shearing force due to the torsion is applied, the vicinity of the side edges 11a and 12a where the two precast girders 11 and 12 are torsionally deformed and joined. It is possible to prevent the two precast girders 11 and 12 from being joined in a state of being greatly bent downward, and to form the bridge girder 3 in an accurate shape.

The present invention is not limited to the embodiment described above, and can be implemented in various forms within the scope of the present invention.
For example, in the present embodiment, the cross beams 13 are provided at the three positions of the both ends and the central portion in the axial direction of the precast beams 11 and 12, but can be provided at other positions in addition to these cross beams.
In the above-described embodiment, the precast girders 11 and 12 are lifted between the piers 2. However, the precast girders can be lifted in the same manner between the abutment and the pier or between the abutment and the abutment. . At this time, the end of the bridge girder is first formed as an end block on the abutment and temporarily fixed to the abutment. And a precast girder can be lifted between this end block and the pier upper part temporarily fixed on the pier, or between an end block and an end block.

The bridge girder 3 is supported on the pier 2 via the support 18 in the embodiment described above, but it may be a ramen structure in which the bridge girder is continuous with the pier. In this case, the upper part of the pier of the bridge girder can be formed integrally with the pier, and the process of temporarily fixing the pier upper part and the process of releasing the temporary fixation can be omitted.
Moreover, in the said embodiment, although the bridge girder 3 has one box-shaped part, as shown to Fig.10 (a), the bridge girder 40 in which the two box-shaped parts 41 and 42 have a continuous cross section. Can be formed in the same manner. The bridge girder 40 has three webs 43, 44, 45, and the upper and lower parts of these webs 43, 44, 45 are connected by an upper floor slab 46 and a lower floor slab 47, respectively. When constructing a box girder bridge having such a bridge girder 40, as shown in FIG. 10 (b), three precast girders 48, 49 in which the span portion of the bridge girder 40 is divided for each web by the dividing line in the axial direction. , 50. These are then sequentially lifted between the piers 51. At this time, the cross section of the precast girder 49 including the web 44 at the center of the cross section is substantially bilaterally symmetric, and almost no torsional deformation occurs. Therefore, the tension members 52 are arranged near the side edges to be joined to the other precast girders on the two precast girders 48 and 50 on both sides in the same manner as in the above-described embodiment, and they are lifted and joined while suppressing torsional deformation. can do.

1: box girder bridge, 2: bridge pier, 3: bridge girder, 4: box-shaped part, 5: upper floor slab, 5a: projecting part of upper floor slab, 5b: part constituting the box-shaped part of upper floor slab, 6: web, 7: Lower floor slab, 9: Joint between two precast girders, 10: Joint between the upper part of the pier and the precast girders, 11: Precast girders on the right side, 12: Precast girders on the left side, 13: Cross girders, 14: Tensile material, 15, 16: Tensile material arranged in concrete member, 18: Support, 21: Post, 22: Construction girder, 23: Suspension material, 24: Steel beam, 31: Upper part of bridge girder, 32: span part of bridge girder, 40: bridge girder, 41, 42: box-shaped part, 43, 44, 45: web, 46: upper floor slab, 47: lower floor slab, 48: left precast girder, 49: center Precast digits, 50: right precast digits, 51: Bridge pier

Claims (2)

A method for suppressing torsion when supporting a precast girder formed of precast concrete into a shape obtained by dividing a cross section of a bridge girder in which a part of the cross section is a box shape,
The precast girder has one web, an upper floor slab protruding from the upper part of the web to both sides, and a lower floor slab protruding from the lower part of the web to one side,
A tension material is arranged in the axial direction of the precast girder near the side edge of the precast girder where both the upper floor slab and the lower floor slab project.
The tension material introduces a tension force before supporting and lifting the precast girder at both ends, and is fixed near the upper edge of the precast girder near both ends of the precast girder, and in the axial direction of the precast girder Near the center, the axis of the tendon is bent near the lower edge of the precast girder, and an upward force is applied to the precast girder by the tension introduced into the tendon. Precast girder twist control method Joining of precast girders in which the first precast girders and the second precast girders made of precast concrete are joined to each other in a shape that divides the cross section of the bridge girder whose section is box-shaped. A method,
The first precast girder has one web, an upper floor slab protruding from the upper part of the web to both sides, and a lower floor slab protruding from the lower part of the web to one side,
The second precast girder has one web, an upper floor slab that projects from the upper part of the web so as to face the upper floor slab that projects from the first precast girder, and a projecting from the first precast girder from the lower part. A lower floor slab protruding so as to face the lower floor slab,
Supporting the first precast girder and the second precast girder by supporting both ends in the axial direction and supporting them at predetermined positions;
Concrete is laid between the upper floor slab projecting from both the first precast girder and the second precast girder and between the lower floor slab projecting from both, and the first precast girder and the second precast girder And a step of integrally joining the precast girder of
A tension material is arranged in the axial direction of the first precast girder in the vicinity of the side edge of the first precast girder joined to the second precast girder by placing the concrete.
The tension material introduces a tension force before lifting the first precast girder while supporting both ends, and is fixed near the upper edge of the first precast girder near both ends of the first precast girder. In addition, in the vicinity of the center in the axial direction of the first precast girder, the axis of the tendon is bent near the lower edge of the first precast girder, and an upward force is applied by the tension force introduced into the tendon. Is arranged so as to act on the first precast girder.

Images