JP3739046B2 - Construction method of steel PC composite bridge - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for laying a steel PC composite bridge. Specifically, a steel PC composite bridge comprising a steel PC composite bridge girder in which a steel girder is embedded in a concrete girder and prestressed is introduced. It is intended for erection methods.
[0002]
[Prior art]
Steel PC composite bridges are known to provide lightweight, strong and durable bridges by using concrete girders with embedded steel girders and prestressed steel girders, that is, steel PC synthetic bridge girders. Yes.
In Japanese Patent Publication No. 36-23224, two bridge girders made of a steel truss supported separately on left and right piers are installed so as to be in contact with each other at the center of the span. In the steel truss bridge girder, the steel PC composite bridge girder was placed in the formwork assembled with the steel truss as a skeleton, and pre-stress was introduced sequentially from the fulcrum of the bridge pier to the both ends. The technology to construct all bridges is shown.
[0003]
Further, Japanese Patent Application No. 2000-170881 (Japanese Patent Application Laid-Open No. 2001-348815), which was previously filed by the applicant of the present patent application and published, uses a hollow steel pipe in a cantilevered state at the end of a bridge girder already installed. The bridge girder made of steel truss frames was connected, and the concrete was placed in the formwork that was supported by the steel truss frames to form a concrete girder embedded with the steel girder. A technique for constructing a steel PC composite bridge girder by inserting PC steel into a concrete girder and introducing prestress is shown. By constructing a new steel PC composite bridge girder in a cantilevered state sequentially at the tip of the constructed steel PC composite bridge girder, the entire bridge is installed.
[0004]
[Problems to be solved by the invention]
In the conventional steel PC composite bridge erection technique as described above, an erection method is adopted in which the bridge girder is sequentially extended in a cantilevered state from the middle pier to the left and right. In this case, the steel girder and the steel PC composite bridge girder under construction are subjected to loads such as extremely large bending moments during construction at the supported middle pier positions, so that the intermediate piers can withstand such loads. There is a problem that the bridge girder of the position has to be large.
At the stage where the bridge construction is completed, the bridge girder between the spans is supported by the piers and abutments on both sides. Dynamically, the structure is a so-called both-end support beam. When connecting many bridge piers with continuous bridge girders, each bridge pier has a continuous beam structure as a supporting point. Of course, at the bridge design stage, the bridge girder and the structure such as the balustrade constructed on the bridge girder, as well as the weight load including traffic vehicles, should be sufficient in such a completed state. The structural dimensions of the bridge girder and pier are determined.
[0005]
However, if bridge construction is not carried out to reproduce the structural system in the completed state, but is carried out in a structural system different from the completed state, it will not be subject to loads such as bending moments that occur during construction. Must also be designed to have sufficient strength.
For example, in spans spanning rivers, valleys, railways, roads, etc., when a support work cannot be performed on the way, a so-called cantilever construction method is adopted in which bridge girders are constructed in a cantilevered state sequentially from the position of the intermediate pier. It is often done. In this case, in the middle stage of the erection operation, a part of the bridge girder is not in the both-end support state in the completed state, but is in the cantilever support state protruding into the air from the pier position. The weight of the cantilever bridge girder will apply a large bending moment to the bridge girder at the pier position as a fulcrum.
[0006]
This is exactly the case when a normal PC bridge is installed and support work cannot be performed in the middle of the span. In the steel PC composite bridge, such a state occurs in any of the prior arts disclosed in Japanese Patent Application Laid-Open No. 2001-348815 and Japanese Patent Publication No. 36-23224.
When an excessive load is applied to a bridge girder at a specific pier position, the bridge girder at the pier position must be increased in height or added with a reinforcement structure such as prestressing to withstand the load. For this reason, the weight of the entire bridge is increased and the construction cost is increased. If the height of the bridge girder is partially different, the appearance of the entire bridge will be deteriorated and the scenery of the construction site will be damaged.
[0007]
The object of the present invention is to reduce the local load at a specific pier position in the middle stage of construction in the bridge construction technique using the steel PC composite bridge girder described above, suppress the increase in the bridge girder height, and reduce the construction cost. To reduce and improve the appearance of the bridge.
[0008]
[Means for Solving the Problems]
A steel PC composite bridge construction method according to the present invention is a continuous girder bridge in which a steel PC composite bridge girder in which a steel girder is embedded in a concrete girder and prestress is introduced is continuously constructed on a pier between a plurality of spans. A method for laying a steel PC composite bridge comprising a continuous rigid frame bridge, the step (a) of laying a continuous steel girder continuous across the plurality of diameters, and after the step (a), A step (b) of constructing a steel PC composite bridge girder by forming a concrete girder that embeds a part of a continuous steel girder at a pier position arranged in the middle of the piers and introducing prestress; and the step (b) And (c) including constructing the steel PC composite bridge girder in the remaining portion of the continuous steel girder and laying the steel PC composite bridge girder continuous across a plurality of diameters.
[0009]
[Steel PC composite bridge]
Any prestressed concrete bridge girder in which steel girders are embedded, that is, a bridge using steel PC composite girder can be applied to bridges of various structures. Depending on the purpose of use, there are road bridges, railway bridges, road railway combined bridges, and pedestrian bridges. Due to structural differences, there are continuous girder bridges and continuous ramen bridges.
Basically, the bridge is composed of bridge piers arranged at regular intervals and bridge girders spanned between the piers. At both ends of the bridge, an abutment connected to the ground surface is installed instead of a normal pier. In the present invention, a structure that supports or rigidly connects a bridge girder including the abutment is called a pier.
[0010]
The space between the pair of piers is called the span. The present invention is applied to a bridge having a plurality of spans of two or more spans.
As for the bridge girder, there are a case where an independent bridge girder is constructed for each span and a case where a continuous bridge girder is constructed between a plurality of spans. In the present invention, a continuous bridge girder that is continuously installed at a pier position between a plurality of diameters is included in at least one position of the bridge. The entire bridge can also be configured by combining such a continuous bridge girder and a single bridge girder having an independent span.
A steel PC composite bridge girder in which steel girders are embedded in concrete girders and pre-stress is introduced is adopted as a continuous bridge girder that is continuously installed at the pier positions between multiple spans. A part of the bridge can be combined with a normal PC concrete bridge girder or a concrete bridge girder that is not a steel PC composite bridge girder to constitute the entire bridge.
[0011]
The steel PC composite bridge girder is rigidly connected to the pier, that is, fixedly supported, when the horizontal movement and rotation are supported freely, or when only the rotation is supported freely There is.
[Steel Girder]
The same material and structure as a normal steel bridge can be adopted.
Basically, steel beams are combined and joined by bolts, rivets, welding, etc. to form a bridge girder shape. As the steel material, a shape steel material such as CT shape steel or angle steel can be used. Hollow steel pipes, steel bars, and steel plates can also be used. If a truss structure, a girder, and a ramen structure are constructed by combining steel materials, a steel girder excellent in strength can be obtained. The same arrangement as that of ordinary truss bridges, girder bridges, and ramen bridges can be applied to the steel structure that constitutes the truss structure, girder, and ramen structure.
[0012]
Steel girders can be constructed by assembling and joining steel materials at the construction site of the bridge, or steel girders of a certain section are manufactured in advance at a factory and the steel girder block is brought into the construction site. It is also possible to construct a bridge girder having a predetermined length by sequentially adding them.
The steel girder can be provided with a sheath tube through which the PC steel material is inserted. The hollow steel pipe which comprises a steel girder can also be utilized as a sheath pipe of PC steel material.
The steel girder may be rigidly connected to the pier, or may be supported to rotate freely and move in the horizontal direction. In some cases, the rotation is free and horizontal movement is prevented. In the case of the bridge girder of the ramen bridge, the former is rigidly connected, and in the case of the bridge girder of the continuous bridge, the latter is free to rotate.
[0013]
[Concrete girder]
Basically, materials and structures similar to ordinary concrete girders can be adopted.
Concrete girders are required for bridge girders by providing a structure to support road loads, balustrades and other overloads, and by forming a steel concrete composite girder by integrating with steel girders. The structural strength can be increased. The concrete girder may completely cover the outer periphery of the steel girder, but a part of the steel girder may be exposed outside the concrete girder.
<Formation of concrete girders>
In order to form a concrete girder, first, a concrete casting form is placed around the steel girder. For the material and structure of the formwork, the same technology as that of ordinary concrete girders can be applied. By supporting the weight of construction materials such as formwork and scaffolding and cast concrete to the steel girders, it is necessary to install support structures from the ground and large construction materials on the girders to support these weights. Disappears. If the formwork material is transferred from the outside between the side diameters connected to the ground surface to the formation position of the concrete girder using the installed steel girder, it is easy to transfer the material. Large-scale equipment for transferring materials is also unnecessary.
[0014]
The concrete girder can be rigidly connected to the pier. Specifically, a concrete structure that rigidly connects the concrete girder and the pier portion can be placed. When the concrete girder is simply supported on the pier, the concrete girder can be connected to the pier via a movable support or a fixed support.
The concrete girder can be provided with a sheath space for introducing prestress.
[Prestress]
Prestress is introduced into concrete girders. The pre-stress is a restoring force of the PC steel material inserted through the concrete girder and applied with a tensile force, and generates stress in the compression direction on the concrete girder. Usually, a prestress in the compression direction is introduced in advance to a portion of the concrete girder where a load in the tensile direction is applied during the construction of the bridge or when the bridge is used after the construction.
[0015]
The bending moment generated in the bridge causes a force in the opposite direction of the tension direction and the compression direction to act on the upper side and the lower side of the bridge girder in the span direction. The concrete girder may be prestressed in the compression direction on the side where the tensile force is applied on the upper side or the lower side. In addition, a prestress can be introduce | transduced as needed also in the width direction or the height direction of a bridge girder orthogonal to a span direction.
If prestress is introduced into a steel concrete composite bridge girder, a steel PC composite bridge girder can be obtained.
In the steel PC composite bridge girder, the prestress introduced into the concrete girder is transmitted to the steel girder through the joint surface with the concrete girder. Prestress will also be introduced to steel girders. Prestress due to PC steel can also be introduced simultaneously into concrete girders and steel girders. Specifically, a pressure plate that transmits the compression restoring force of the PC steel material to the concrete girder may be brought into contact with both the concrete girder and the steel girder. If it does in this way, since the deformation behavior of a concrete girder and a steel girder corresponds, peeling of a joint surface can be prevented and synthetic strength can be improved.
[0016]
<Introduction of prestress>
Basically, technology for introducing prestress in ordinary prestressed concrete bridge girders is applied.
PC steel material is inserted and arranged inside a sheath tube or PC steel material space provided in a concrete girder or steel girder. The PC steel is made of the same material as that used in normal prestressed concrete production, such as high-strength steel bars and wires.
The end of the PC steel is fixed to the end of the bridge girder in a state where a predetermined tensile force is applied to the PC steel. The restoring force of the PC steel in the compression direction is applied to the bridge girder, and prestress is introduced to the bridge girder. The compression force from the PC steel material to the bridge girder may be applied to the concrete girder, or may be applied to both the concrete girder and the steel girder.
[0017]
The prestress may be added to the total length of the concrete girder that is finally formed, but usually, prestress is introduced for each block of concrete girder that is formed in stages. Moreover, since the direction and magnitude of the load vary depending on the location of the bridge girder, the position and strength at which prestress is introduced are changed according to the load applied to the location. Therefore, it is desirable to perform prestress introduction work for each bridge girder in a certain section. When a concrete girder is extended and formed in stages, a new PC steel material penetrating through the entire PC girder can be inserted every time the concrete girder is extended.
[0018]
The bridge girder in which prestress is introduced becomes a steel PC composite girder, and the structural strength is significantly increased as compared with that before prestress is introduced.
[Steel girder erection process]
For the construction of the bridge, after the pier is constructed according to the predetermined span arrangement, a steel girder is installed on the upper part of the pier.
In places where the span is long, it is also possible to construct a support work to be a temporary pier between the piers. At the end of the bridge, a work table or embankment surface can be constructed from the ground surface to the bridge girder installation position or the abutment position. However, there are many cases where a structure that supports bridge girders such as support works cannot be installed in spans across rivers.
[0019]
[Continuous steel girder]
It is a steel girder that is continuous over a plurality of diameters. Structurally, it is a structure called a continuous beam or a continuous ramen beam.
A continuous steel girder can be installed by pre-fabricating a steel girder at a construction site. It is also possible to push the continuous steel girder from the abutment that leads to the ground surface into the air, and to reach the bridge piers installed at intervals. The method of manufacturing a continuous steel girder in advance is suitable when the total length of the bridge is short.
The continuous steel girder can be manufactured by dividing it into a plurality of blocks, and these blocks can be connected and fixed to form a continuous steel girder before or after installation on the pier. If a block having a length suitable for manufacturing and transportation is manufactured, it is easy to handle.
[0020]
On bridge piers, steel beams can be assembled to construct bridge girder blocks or continuous steel girders. It is also possible to construct a continuous steel girder by building steel girders from a plurality of pier positions and connecting and fixing the ends of the steel girders.
[First steel PC composite bridge girder construction]
A steel PC composite bridge girder can be constructed by sequentially implementing a procedure in which a concrete girder is formed around a continuous steel girder and a pre-stress is introduced at a necessary location after a continuous steel girder spanning multiple spans is installed.
In the present invention, a steel PC composite bridge girder is first constructed at a pier position arranged in the middle among a plurality of piers, similarly to a PC bridge by a normal cantilever construction method. Subsequently, a steel PC composite bridge girder can be constructed at a predetermined portion adjacent to the steel PC composite bridge girder.
[0021]
In terms of structural mechanics, a larger load is applied to the intermediate pier portion than to other portions. A steel PC composite bridge girder is first constructed at the middle pier where this large load is applied, and the structural strength of that part is increased.
The load applied to the continuous steel girder is the weight of the continuous steel girder when the continuous steel girder is installed. Next, at the stage where the first steel PC composite bridge girder is constructed, the construction materials such as molds and scaffolds and the weight of the concrete to be cast are loaded. All these loads are carried only by continuous steel girders.
In addition, at the stage where the steel PC composite bridge girder is constructed adjacent to the already constructed steel PC composite bridge girder, the load due to the construction is the steel PC composite bridge girder where the steel PC composite bridge girder has already been constructed. The parts that have not yet been constructed are shared by continuous steel girders.
[0022]
In the steel PC composite bridge girder, the steel girder, the concrete girder, and the PC steel material share the applied load according to their respective functions in the same manner as a normal synthetic girder.
Moreover, as construction progresses, loads are continuously applied to the continuous steel girders and the steel PC composite bridge girders.
[Construction of remaining steel PC composite bridge girder]
When the construction of the steel PC composite bridge girder at the intermediate pier portion is completed, the steel PC composite bridge girder may be constructed sequentially in the remaining portions of the continuous steel girder in consideration of workability and the like.
[0023]
The method of sharing the load applied sequentially between the continuous steel girder and the steel PC composite bridge girder is the same as that described in [First steel PC composite bridge girder construction].
Usually, it is easy to perform construction and to perform prestress introduction work so that the concrete girder is extended from the pier position toward the center of the span.
When construction of the continuous steel PC composite bridge girder is completed over the entire steel girder, the steel PC composite bridge girder is completed. The steel PC composite bridge girder has at least a continuous beam or rigid frame structure that is continuous between a plurality of diameters.
[Other work processes]
After the steel PC composite bridge girder is completed, if necessary, the same work process as ordinary bridge construction can be performed.
[0024]
For example, pre-stress can be introduced for a load applied thereafter. The road surface can be paved and railways can be laid on the bridge girder. Installation of balustrades, lighting equipment, power lines, communication lines, etc. is also possible. Anticorrosion treatment and painting are also applied to the exposed parts of steel girders. Installation roads can also be constructed at both ends between the side diameters.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
The embodiment shown in FIGS. 1 to 5 shows the erection of a bridge composed of continuous girder bridges with three diameters in stages.
As shown to Fig.1 (a), 3 spans are comprised by the four piers 10 shown by AD.
Between the pier 10B and the pier 10C is the center span BC, between the pier 10A and the pier 10B, and between the pier 10C and the pier 10D, respectively, between the side span AB and the side span CD. It is. The center span BC is wider than the side spans AB and CD. For example, in FIG. 1A, the distance L between the side spans AB. _AB = Side distance CD distance L _CD = 40m, distance L between central span BC _BC = 60 m.
[0026]
The bridge has a symmetrical structure as a whole. In the following description, in FIG. 1A, the left side portion including the side span A-B will be mainly described. However, the same description applies to the right side portion including the side span CD.
[Construction of steel girders]
This step corresponds to the step (a).
As shown to Fig.1 (a), the 3 span continuous steel girder 20 is constructed between bridge piers 10A and 10D.
FIG. 1B schematically shows the bending moment distribution due to the steel girder's own weight. This bending moment is an extremely small value compared to the bending moment generated in the subsequent steps.
[0027]
[Construction of steel PC composite steel girder]
2-3, the construction work of the steel PC composite bridge girder proceeds.
<Formation of concrete girders>
This stage corresponds to part of the step (b).
As shown to Fig.2 (a), construction of the concrete girder 30 used as the steel PC synthetic steel girder is started from the position of the piers 10B and 10C. In terms of structural mechanics, the bridge girder of the bridge piers 10B and 10C is generally a portion that receives a load such as the largest bending moment, and thus the concrete girder 30 is formed from this portion. In the figure, the hatched concrete girder 30 indicates a block to be constructed at this stage. The concrete girder 30 is connected to the pier 10 by a movable bearing or a fixed bearing. However, in the case of a ramen bridge, the concrete girder 30 can be rigidly connected to the concrete structure of the pier 10.
[0028]
Materials and equipment for constructing the concrete girder 30 at the positions of the piers 10B and 10C may be lifted from the ground surface to the steel girder 20 on the piers 10B and 10C with a crane or the like, or between the side spans AB and CD. The steel girder 20 may be transferred from a connection path with the outer surface of the ground.
The construction of the concrete girder 30 can be performed in the same manner as a conventional concrete girder. Specifically, although not shown, a formwork is installed around the bridge piers 10B and 10C in the continuous steel girder 20. Place concrete inside the formwork. Once the concrete has hardened, remove the formwork.
[0029]
FIG. 2B schematically shows the cumulative bending moment generated in the three-span continuous girder at this stage. As shown in this figure, the cumulative bending moment is a negative maximum value M at the positions of the piers 10B and 10C. ₂ Is positive in the span.
In the case of normal cantilever construction, the same load at this stage acts on the tip of the cantilever beam, so the above M ₂ It is clear from the structural mechanics that it becomes larger. Therefore, according to the present invention, it is possible to suppress an excessive generation of a bending moment at the intermediate pier position.
<Introduction of prestress>
This stage corresponds to part of the step (b).
[0030]
As shown in detail in FIG. 4, prestress is introduced into the concrete girder 30 at the pier position.
For example, in the concrete girder 30 at the position of the pier 10B, as shown by a dotted arrow in FIG. 4, a tensile force is applied to the upper side of the concrete girder 30 and a compressive force is applied to the lower side. Prestress is introduced to counteract such bending moments.
A PC steel material 40 penetrating the concrete girder 30 is disposed near the upper side of the concrete girder 30. A sheath pipe is embedded in the concrete girder 30 in advance, and the PC steel material 40 is passed through the sheath pipe. A tensile force is applied to the PC steel 40 using a jack device or the like. The PC steel material 40 with the tensile force applied is fixed to the end face of the concrete girder 30 using the fixing tool 44. The restoring force (solid arrow) of the PC steel material 40 is applied in the compression direction of the concrete girder 30. Prestress in the compression direction is introduced into the concrete girder 30.
[0031]
If the prestress of the compression direction is introduced into the upper side of the concrete girder 30 where the tensile force is applied by the load, the tensile force due to the load is canceled out. If a prestress having a magnitude corresponding to the bending moment force applied to the continuous steel girder 20 is introduced, the continuous steel girder 20 at the pier position is substantially free of bending moment.
As a result, it is possible to reinforce the concrete girder 30 that is weak in tensile strength in terms of material. Furthermore, even when a bending moment similar to that described above is added to the concrete girder 30 during use after construction and after completion of the bridge, it is possible to suppress the occurrence of excessive tensile stress on the upper side of the concrete girder 30. . The magnitude of the prestress can be set in accordance with the bending moment and the tensile force applied after the concrete girder 30 has been installed or after the bridge is completed.
[0032]
The concrete girder 30 in which the prestress is introduced becomes a steel PC composite bridge girder.
<Extension of steel PC composite bridge girder>
This step corresponds to the step (c).
As shown to Fig.3 (a), formation of the concrete girder 30 is extended to the whole side span AB, BC, and CD sequentially from bridge pier 10B, 10C. In the drawing, the hatched concrete girder 30 indicates a block to be constructed at this stage.
FIG. 3B schematically shows the cumulative bending moment generated in the three-span continuous girder at this stage. As shown in this figure, the cumulative bending moment is a negative maximum value M at the positions of the piers 10B and 10C. _Three Is positive in the span.
[0033]
In the case of normal cantilever construction, the same load as this stage acts on the tip of the cantilever beam. _Three It is clear from the structural mechanics that it becomes larger. Therefore, according to the present invention, it is possible to suppress an excessive generation of a bending moment at the intermediate pier position.
2 (b) and FIG. 3 (b), the bending moment generated as the steel PC composite bridge girder is sequentially constructed is determined for each erection stage, that is, the steps (b) and The cumulative total for each step of the step (c) is shown. This is because the steel PC composite bridge girder bears only the steel girder where the steel PC composite bridge girder is not constructed, and the steel PC composite bridge girder where the steel PC composite bridge girder is constructed properly. Take charge.
[0034]
Further, as described above, the steel PC composite bridge girder shares the load applied by the steel girder, concrete and PC steel material in accordance with the respective functional characteristics in the same manner as a normal composite girder. Therefore, according to the present invention, a rational bridge girder can be created. As described above, according to the present invention, it is possible to suppress the increase in the girder height at the intermediate pier position and reduce the degree of necessity for structural reinforcement such as prestress. As a result, it is possible to construct an economical and rational bridge with excellent landscape.
[Cross-section structure example of bridge]
FIG. 5 shows a more specific arrangement structure of the bridge structure.
[0035]
FIG. 5A on the left half of the figure shows a cross section of the bridge at a portion arranged near the center of the span. The right half of the figure, FIG. 5 (b), shows a cross section of the bridge at a portion arranged in the vicinity of the pier 10B. In both cases, the basic structure is common, but the carry height and the prestressing state are different.
The steel girder 20 has a rectangular frame shape in cross section, and there are also steel materials arranged on diagonal lines of the rectangular frame. The steel girder 20 is configured by joining shape steel materials such as angle steel and CT shape steel. The concrete girder 30 has a rectangular box frame shape covering the steel girder 20 having a rectangular cross section with a certain width. However, a part of the steel material constituting the steel girder 20 is exposed outside the concrete girder 30. In the figure, the steel material in the oblique direction is exposed in the internal space of the box structure of the concrete girder 30.
[0036]
On the upper surface of the concrete girder 30, a road surface is constructed and projects in the width direction. Although not shown, a pavement structure, a drainage structure, a balustrade structure, etc. are installed on the upper surface.
In the bending moment distribution shown in FIGS. 2 (b) and 3 (b), a large tensile force is exerted on the upper side due to the negative bending moment in the bridge cross-section [FIG. 5 (b)] located near the pier 10B. It can be seen that it occurs. Therefore, a number of PC steel members 40 are inserted near the upper side of the concrete girder 30 to introduce prestress. A part of the PC steel material 42 is not embedded in the concrete girder 30 but is arranged in the internal space of the box-shaped concrete girder 30. The PC steel material 42 in this portion copes with a load loaded after a steel PC composite bridge girder is constructed over the entire length of three spans, that is, a bending moment due to a load such as a pavement or a railing and a load of a traffic vehicle.
[0037]
In the bending moment distribution shown in FIGS. 2 (b) and 3 (b), the bridge cross section [FIG. 5 (a)] located near the center between the side diameters and the central diameter is caused by a positive bending moment. It can be seen that a tensile force is generated on the lower side. Therefore, a number of PC steel materials 40 are inserted near the lower side of the concrete girder 30 to introduce prestress. A PC steel material 42 is also disposed in the internal space of the concrete girder 30. The purpose of the arrangement of the PC steel material 42 is the same as that of the PC steel material 42 disposed in the vicinity of the pier 10B.
[Comparison of loads on bridges]
The distribution of the load (bending moment) applied to each part of the bridge when the same steel PC composite bridge is constructed with a different construction method will be compared using a three-span continuous bridge as an example.
[0038]
As the erection method, the method according to the present invention, specifically, the method of erection according to FIGS. 1 to 3 of the above embodiment, and the cantilever often employed when a support from the ground cannot be installed between the central diameters. Consider the formula erection method. Here, the former is called the construction method I and the latter is called the construction method II.
Fig. 6 (a) shows the construction method II. This is a cantilever erection method in which the steel girder 24 and the concrete girder 30 are sequentially extended between the piers 10A, 10B, 10C, and 10D while balancing the weight from the pier 10B and the pier 10C to the left and right. Since the load of the steel girder 24 and the concrete girder 30 to be installed is applied to the tip of the cantilever beam with the piers 10B and 10C as fulcrums, a negative moment is generated in the cantilever beam. It has a negative maximum at 10C, and is 0 at the tip of the cantilever. As the erection progresses and the concrete girder 30 extends sequentially, this bending moment is accumulated. FIG. 6B shows the accumulated bending moment M. _Four Is schematically shown.
[0039]
FIG. 7 shows the distribution of the cumulative bending moment in each of the erection method I and the erection method II, and shows the maximum value of the bending moment at the positions of the piers 10B and 10C. _I [Construction method I] and M _II It is shown in [Construction Method II]. The magnitude of these bending moments is a schematic graph showing the results obtained by engineering calculation. However, these graphs contrast the tendency of the bending moment distribution with the relative difference in an easily understandable manner, and do not quantitatively strictly indicate the exact numerical value at each position.
The cumulative bending moment according to the construction method II is the sum of the loads loaded at the end of the cantilever beam, so at the positions of the piers 10B and 10C, a very large negative maximum value M _II And 0 at the center of the center span. In addition, there may be a slight bending moment between the side diameters depending on the construction method.
[0040]
On the other hand, the cumulative bending moment by the erection method I has a negative maximum value at the positions of the piers 10B and 10C, and has a positive distribution between the center span and the side span.
In FIG. 7, regarding the bending moment at the positions of the piers 10B and 10C, M _I Is M _II Less than that.
It should be noted that the cumulative bending moment distribution in the erection method I is the step (a), (b), (c), that is, the cumulative bending moment of each of FIGS. 1 (b), 2 (b) and 3 (b). Total, M _I Is M ₁ , M ₂ , M _Three Is the sum of. For reference, FIG. 7 shows M at the positions of piers 10B and 10C. ₁ , M ₂ , M _Three It also shows.
[0041]
[Evaluation]
In the construction method I, all loads act on continuous girders. On the other hand, in the construction method II, the same load acts on the tip of the cantilever. In both the erection method I and the erection method II, as the erection progresses, bending moments due to these loads are accumulated.
Focusing on the bending moment at the piers 10B and 10C, the bending moment M as a continuous girder in the construction method I _I Is the bending moment M as a cantilever in construction method II _II It is clear from structural mechanics that it is smaller than. That is, according to the present invention, it is possible to reduce an excessive bending moment at the intermediate pier position, which has been easy to occur conventionally.
[0042]
【The invention's effect】
The steel PC composite bridge construction method according to the present invention is such that a steel PC composite bridge girder is constructed at an intermediate pier after a continuous steel girder continuous over a plurality of spans is constructed, and then the remaining portion is steel. Build a PC composite bridge girder. As a result, it is possible to suppress a large load from being locally applied in the construction process of the steel PC composite bridge girder including the formation of a concrete girder in a specific pier portion where it has been easy to apply an excessive load conventionally. Therefore, the strength of the prestress to be introduced into the steel PC composite bridge girder can be reduced, and the prestress introduction work can be simplified. It is not necessary to increase the girder height in order to increase the structural strength locally on a specific bridge pier, etc., and the difference in the girder height in the entire bridge can be reduced, and the entire bridge can be made smart and have a good appearance. If the girder height can be lowered, the amount of materials such as steel and concrete used can be reduced, and the construction cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic structural diagram (a) and a load state diagram (b) showing a construction process of a steel girder according to an embodiment of the present invention.
FIG. 2 is a schematic structural diagram (a) and a load state diagram (b) showing an initial stage of a construction process of a steel PC composite bridge girder.
FIG. 3 is a schematic structural diagram (a) and a load state diagram (b) showing a construction completion state of a steel PC composite bridge girder.
FIG. 4 is a schematic structural diagram showing the prestress introduction state at the pier location.
[Figure 5] Detailed cross-sectional structure of the bridge
FIG. 6 is a schematic structural diagram (a) and a load state diagram (b) showing a construction state by a cantilever construction method.
[Fig. 7] Load state diagram showing the difference in load distribution by different construction methods
[Explanation of symbols]
10 Pier
20 Continuous steel girders
24 Steel girders in cantilever construction
30 concrete girder
A to D Pier position

Claims (1)

A steel PC composite bridge girder in which steel girder is embedded in concrete girder and prestress is introduced, and is constructed by continuously installing steel PC composite bridge girder consisting of continuous girder bridge or continuous rigid frame bridge. There,
Step (a) of laying a continuous steel girder continuous across the whole of the plurality of diameters;
After the step (a), the concrete PC girder is constructed by forming a concrete girder that embeds a part of the continuous steel girder at the middle pier position among the plurality of span piers and introducing pre-stress. (B) performing
After the step (b), the steel PC composite bridge girder includes the step (c) of constructing the steel PC composite bridge girder in the remaining portion of the continuous steel girder and laying the steel PC composite bridge girder continuous across a plurality of diameters. Construction method.

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