JP2004076457A - Method for building steel pc composite bridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a construction cost and improve the appearance of a bridge by inhibiting the partial increase of load at the intermediate stage of a construction and lowering the girder height of a bridge girder as much as possible in the building technique of the bridge by the steel PC composite bridge girder. <P>SOLUTION: A method for building a steel PC composite bridge comprises a process (a) in which a continuous steel girder 20, continueing extensively over the whole of a plurality of spans A-D, is constructed, the process (b), in which concrete girders 30, in which parts of the steel girder 20 are buried, are formed, prestress is introduced and the steel PC composite bridge girders are built at the places of piers 10 arranged in intermediate sections in the piers 10 of a plurality of the spans A-D, and the process (c) in which the steel PC composite bridge girders are constructed to the residual sections of the steel girder 20 and the continuous steel PC composite bridge girder is built extensively over a plurality of the spans A-D. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of erection of a steel-PC composite bridge, and more particularly, to a steel-PC composite bridge composed of a steel-PC composite bridge girder embedded with steel girder in a concrete girder and prestressed, and continuous over a plurality of spans. It is intended for the method of erection.
[0002]
[Prior art]
Steel PC composite bridges are known to provide lightweight, high-strength and durable bridges by using concrete girder embedded steel girder and prestressed steel girder, that is, steel PC composite bridge girder. I have.
In Japanese Patent Publication No. 36-23224, two bridge girders composed of pull-out steel trusses which are separately supported on left and right piers are erected so as to be in contact with each other at the center of the span. In the steel truss bridge girder, from the fulcrum of the pier, to both ends, concrete was poured into the formwork assembled with the steel truss as a framework, and prestress was introduced. The technology for constructing the entire bridge is disclosed.
[0003]
Further, Japanese Patent Application No. 2000-170881 (Japanese Patent Application Laid-Open No. 2001-348815), which was previously filed and filed by the present applicant, uses a hollow steel pipe in a cantilevered state at the end of a bridge girder that has already been installed. The bridge girder made of steel truss frame was connected, concrete was cast into the formwork installed and supported by the steel truss frame, concrete girder with steel girder embedded was formed, and hollow steel pipe was used. There is disclosed a technique of constructing a steel PC composite bridge girder by inserting a PC steel material into a concrete girder and introducing prestress. By constructing a new steel PC composite bridge girder sequentially in a cantilever state at the tip of the constructed steel PC composite bridge girder, the entire bridge is erected.
[0004]
[Problems to be solved by the invention]
In the conventional steel PC composite bridge construction technology as described above, a construction method is employed in which a bridge girder is sequentially extended in a cantilevered manner left and right around an intermediate pier. In this case, a load such as an extremely large bending moment is applied to the steel girder and the steel PC composite bridge girder under construction at the position of the supported intermediate pier during construction, and the intermediate pier is designed to withstand such a load. There is a problem that the bridge girder at the position must have a large girder height.
At the stage when the bridge is erected, the span girder will be supported by piers and abutments on both sides. Mechanically, it has a so-called both-ends support beam structure. When many bridge piers are connected by continuous bridge girders, a continuous beam structure in which each pier serves as a support point is used. At the design stage of the bridge, of course, in the completed state, it is necessary to have sufficient strength in consideration of the bridge girder, the structure such as the balustrade constructed on the bridge girder, and the heavy load including the traffic vehicle. In addition, the structural dimensions of the bridge girder and the pier are determined.
[0005]
However, if the erection of the bridge is not performed to reproduce the completed structural system but is performed in a structural system different from the completed state, the bridge may be subjected to loads such as bending moments generated during erection. Must also be designed to have sufficient strength.
For example, in the span spanning rivers, valleys, railways, roads, etc., when support work cannot be carried out along the way, the so-called cantilever type erection method is adopted, in which the bridge girder is sequentially erected from the middle pier position to the left and right in a cantilevered state. Often have been. In this case, in the middle of the erection work, a part of the bridge girder is not in the both-end support state in the completed state, but is in a cantilever support state protruding into the air from the pier position. The weight of the bridge girder in a cantilevered state applies a large bending moment to the bridge girder at the pier position serving as a fulcrum.
[0006]
This is exactly equivalent to the case where the support work cannot be constructed in the middle of the span in the construction of a normal PC bridge. In a steel PC composite bridge, such a state occurs in any of the prior arts of 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, it is necessary to increase the girder height or add a reinforcing structure such as introduction of prestress to the bridge girder at the pier position to withstand the load. Therefore, the weight of the entire bridge is increased, and the construction cost is increased. If the girder height of the bridge girder is partially different, the appearance of the entire bridge becomes worse and the scenery of the construction site is impaired.
[0007]
An object of the present invention is to provide a bridge construction technique using a steel PC composite bridge girder as described above, which reduces a local load at a specific pier position in the middle of construction, suppresses an increase in the girder height of the bridge girder, and reduces construction costs. The goal is to reduce and improve the bridge appearance.
[0008]
[Means for Solving the Problems]
The method of erection of a steel PC composite bridge according to the present invention is a method of continuously erection of a steel PC composite bridge girder in which a steel girder is embedded in a concrete girder and prestress is introduced, on a bridge pier of a plurality of diameters. A method for erection of a steel PC composite bridge comprising a continuous ramen bridge, comprising the steps of: (a) erection of a continuous steel girder continuous over the plurality of spans; and, after the step (a), A step (b) of forming a concrete girder for embedding a part of the continuous steel girder at an intermediate pier position of the pier and introducing a prestress to construct a steel PC composite bridge girder; Then, a step (c) of constructing the steel PC composite bridge girder in the remaining portion of the continuous steel girder and erection of a steel PC composite bridge girder continuous over a plurality of spans is included.
[0009]
[Steel PC composite bridge]
As long as the bridge uses a prestressed concrete bridge girder with embedded steel girder, that is, a steel PC composite bridge girder, it can be applied to bridges of various structures. Depending on the purpose of use, there are road bridges, railway bridges, road / railway bridges, and pedestrian bridges. Due to structural differences, there are continuous girder bridges and continuous ramen bridges.
Basically, a bridge is composed of piers arranged at regular intervals and bridge girders bridged between the piers. At both ends of the bridge, abutments that connect to the ground surface are installed instead of ordinary piers. In the present invention, a structure that supports or rigidly bridges the girder including the abutments is called a pier.
[0010]
The space between the pair of piers is called span. The present invention is applied to a bridge having two or more spans.
As the bridge girder, there are a case where an independent bridge girder is erected for each span, and a case where a continuous bridge girder is spanned for a plurality of spans. In the present invention, at least one portion of the bridge includes a continuous bridge girder continuously erected at pier positions of a plurality of spans. Such a continuous bridge girder and a single bridge girder independent of one span can be combined to form the entire bridge.
As a continuous bridge girder continuously constructed at a plurality of bridge pier positions, a steel PC composite bridge girder in which a steel girder is embedded in a concrete girder and prestress is introduced is adopted. A part of the bridge may be combined with a normal PC concrete bridge girder or concrete bridge girder other than the 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 horizontal movement and rotation are freely supported, or when only rotation is freely supported. There is.
(Steel girder)
Materials and structures similar to those of ordinary steel bridges can be adopted.
Basically, steel materials are combined and joined by bolts, rivets, welding, etc. to form the shape of the bridge girder. As the steel material, a shaped steel material such as a CT steel or an angle steel can be used. Hollow steel pipes, steel rods and steel plates can also be used. If a truss structure, a sheet girder, or a rigid frame structure is configured by combining steel materials, a steel girder excellent in strength can be obtained. The same technology as that used for ordinary truss bridges, sheet girder bridges, and ramen bridges can be applied to the arrangement structure of the steel members constituting the truss structure, sheet girder, and ramen structure.
[0012]
Steel girder can be constructed by assembling and joining steel materials at the bridge construction site, or a steel girder for a certain section is manufactured in advance at a factory etc., and this steel girder block is carried into the construction site. It is also possible to construct a bridge girder of a predetermined length by successively adding the bridge girder.
The steel girder can be provided with a sheath tube through which the PC steel material is inserted. A hollow steel pipe constituting a steel girder can also be used as a sheath pipe made of PC steel.
The steel girder may be rigidly connected to the pier or may be supported so as to be freely rotatable and movable in the horizontal direction. In some cases, horizontal movement is prevented due to free rotation. In the case of a bridge girder of a ramen bridge, the former is a rigid connection, and in the case of a bridge girder of a continuous bridge, the latter is in a freely rotatable state.
[0013]
[Concrete girder]
Basically, the same material and structure as that of a normal concrete girder can be adopted.
Concrete girders provide a structure for supporting road surfaces, balustrades, and other overhead loads, and are required for bridge girders by being integrated with steel girders, that is, constituting steel-concrete composite girders. Structural strength can be increased. Although the concrete girder may completely cover the outer periphery of the steel girder, a part of the steel girder may be exposed outside the concrete girder.
<Formation of concrete girder>
To form a concrete girder, first, a concrete casting formwork is placed around the steel girder. For the material and structure of the formwork, the same technology as that of a normal concrete girder can be applied. The steel girder supports the weight of construction materials such as formwork and scaffolding and concrete to be cast, so it is necessary to support the ground from above ground and install large-scale construction materials on the girder to support these weights. Disappears. If the form material is transferred from the outside of the side diameter connected to the ground surface to the position where the concrete girder is formed by using the erected steel girder, the material can be easily transferred. Large equipment for material transfer is not required.
[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 cast. When the concrete girder is simply supported on the pier, the concrete girder can be connected to the pier via a movable bearing or a fixed bearing.
The concrete girder can be provided with a sheath space for introducing prestress.
[Prestress]
Prestress is introduced into the concrete girder. The prestress is a restoring force of a PC steel material that is inserted into a concrete girder and subjected to a tensile force, and generates a compressive stress on the concrete girder. Usually, in the concrete girder, a prestress in the compression direction is introduced in advance to a place where a load in the tension direction is applied during the construction work of the bridge or when the bridge is used after the construction.
[0015]
The bending moment generated in the bridge acts in the span direction on the upper side and the lower side of the bridge girder in a direction opposite to the tensile direction and the compressive direction. In the concrete girder, a prestress in the compression direction may be introduced on the upper or lower side to which a tensile force is applied. In addition, a prestress can also be introduced in the width direction of the bridge girder or the girder height direction orthogonal to the span direction as necessary.
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 via the joint surface with the concrete girder. Prestress will also be introduced into the steel girder. Prestressing by PC steel can be simultaneously introduced into concrete girder and steel girder. Specifically, a pressure plate for transmitting the compressive restoring force of the PC steel to the concrete girder may be brought into contact with both the concrete girder and the steel girder. In this way, since the deformation behavior of the concrete girder and the steel girder match, peeling of the joint surface can be prevented, and the composite strength can be improved.
[0016]
<Introduction of prestress>
Basically, the technique of introducing prestress in a normal prestressed concrete bridge girder is applied.
A PC steel material is inserted and arranged inside a sheath tube or a space for a PC steel material provided on a concrete girder or a steel girder. As the PC steel material, the same material as that used in ordinary prestressed concrete production, such as a high-tensile steel rod or wire, is used.
The end of the PC steel is fixed to the end of the bridge girder while 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 into the bridge girder. The compressive force from the PC steel to the bridge girder may be applied to the concrete girder or to both the concrete girder and the steel girder.
[0017]
The prestress may be added to the overall length of the finally formed concrete girder, but usually, prestress is introduced for each block of concrete girder formed stepwise. In addition, since the direction and magnitude of the load differ depending on the location of the bridge girder, the position and intensity of the prestress are changed according to the load applied to that location. Therefore, it is desirable to perform prestressing work for each bridge girder in a certain section. When the concrete girder is formed by extending it stepwise, a new PC steel material penetrating the whole is inserted every time the concrete girder elongates, so that the prestressing operation can be performed.
[0018]
The bridge girder into which the prestress is introduced becomes a steel PC composite bridge girder, and the structural strength is greatly increased compared to before the prestress is introduced.
[Steel girder erection process]
In the construction of the bridge, a steel girder is erected on the upper part of the pier after the pier is constructed in accordance with the predetermined span arrangement.
In places where the span is long, a temporary pier can be installed between the piers. At the end of the bridge, a workbench or embankment surface can be constructed from the ground surface to the bridge girder erection position or abutment position. However, it is often not possible to install structures that support bridge girders, such as supports, in spans that span rivers.
[0019]
(Continuous steel girder)
It is a steel girder that is continuous over the entire span. In terms of structural mechanics, it is a structure called a continuous beam or a continuous ramen beam.
The continuous steel girder can be installed by bridging a steel girder previously manufactured in a factory or the like on a pier at a construction site. It is also possible to push the continuous steel girder into the air from the abutment leading to the ground surface, so that the continuous steel girder reaches the pier 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 may be manufactured by dividing it into a plurality of blocks, and before or after installation on the pier, the blocks may be connected and fixed to form a continuous steel girder. If a block having a length suitable for manufacturing and transportation is manufactured, it is easy to handle.
[0020]
On the pier, a steel girder or the like can be assembled to form a bridge girder block or a continuous steel girder. It is also possible to construct a continuous steel girder by extending the steel girder from a plurality of pier positions and connecting and fixing the ends of the elongated steel girder.
[First steel PC composite bridge girder construction]
After a continuous steel girder spanning a plurality of spans is erected, a procedure of forming a concrete girder around the continuous steel girder and introducing prestress into necessary places is sequentially performed, whereby a steel PC composite bridge girder can be constructed.
In the present invention, a steel PC composite girder is first constructed at a bridge pier located in the middle of a plurality of piers, similarly to a PC bridge by a normal cantilever type erection method. Subsequently, a steel PC composite bridge girder can be constructed at a predetermined portion adjacent thereto.
[0021]
Due to structural mechanics, a large load is applied to the intermediate pier portion as compared with other portions. First, a steel PC composite bridge girder is constructed at the middle pier portion where the large load is applied, and the structural strength of that portion is increased.
The load applied to the continuous steel girder is the weight of the continuous steel girder when the continuous steel girder is erected. Next, at the stage where the first steel PC composite bridge girder is constructed, the weight of the construction materials such as formwork and scaffolding and the weight of the concrete to be cast are loaded. All of these loads are carried only by continuous steel girders.
Also, at the stage where the steel PC composite bridge girder is constructed adjacent to the already constructed steel PC composite bridge girder, the load caused by the construction is that the part where the steel PC composite steel girder is already constructed is the steel PC composite bridge girder. The parts that have not yet been built are each 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, similarly to the ordinary composite girder.
Further, as the erection progresses, loads are added to the continuous steel girder and the steel PC composite bridge girder.
[Remaining steel PC composite bridge girder construction]
After the construction of the steel-PC composite bridge girder at the intermediate pier location is completed, the steel-PC composite bridge girder may be sequentially constructed on the remaining portion of the continuous steel girder in consideration of workability and the like.
[0023]
The manner in which the sequentially applied load is shared between the continuous steel girder and the steel PC composite bridge girder is the same as that described in the above [First Steel PC Composite Bridge Girder Construction].
Usually, the concrete girder is formed so as to extend from the pier position toward the center of the span, which facilitates construction and facilitates prestress introduction work.
When the construction of the steel PC composite bridge girder continuous over the entire steel girder is completed, the steel PC composite bridge girder is completed. The steel PC composite bridge girder has a structure of a continuous beam or a rigid frame that is continuous at least over a plurality of spans.
[Other work processes]
After the steel PC composite bridge girder is completed, if necessary, the same work steps as those for normal bridge construction can be performed.
[0024]
For example, a prestress can be introduced for a load applied thereafter. Paving work on roads and laying railways can be performed on the bridge girder. Installation of balustrades, lighting equipment, power lines, communication lines, etc. can also be performed. Corrosion protection and painting are also performed on the exposed parts of the steel girders. At both ends of the span, mounting roads can be constructed.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
The embodiment shown in FIGS. 1 to 5 shows stepwise the construction of a bridge consisting of a continuous girder bridge of three spans.
As shown in FIG. 1A, three spans are constituted by four piers 10 indicated by A to D.
The center span BC is between the pier 10B and the pier 10C, and the side span AB and the side span CD are between the pier 10A and the pier 10B and between the pier 10C and the pier 10D, respectively. It is. The center span BC is wider than the side spans AB and CD. For example, in FIG. 1A, the distance L _AB between the side spans _AB is set to the distance L _CD between the side spans _CD , and the distance L _BC between the center spans _BC is set to 60 m.
[0026]
The bridge has a symmetrical structure as a whole. In the following description, the left portion including the side spans AB is mainly described in FIG. 1A, but the same description applies to the right portion including the side spans CD.
[Erecting steel girder]
This step corresponds to the step (a).
As shown in FIG. 1A, a three-span continuous steel girder 20 is installed between the piers 10A and 10D.
FIG. 1B schematically shows the distribution of the bending moment due to the weight of the steel girder. This bending moment is an extremely small value compared to the bending moment generated in the subsequent steps.
[0027]
[Construction of steel PC synthetic steel girder]
The construction work of the steel PC composite bridge girder proceeds to FIGS.
<Formation of concrete girder>
This step corresponds to a part of the step (b).
As shown in FIG. 2A, construction of a concrete girder 30 to be a steel PC synthetic steel girder is started from the positions of the piers 10B and 10C. In terms of structural mechanics, the bridge girder of the piers 10B and 10C is a place where a load such as a bending moment is generally received, so that the concrete girder 30 is formed from this part. The hatched concrete girder 30 in the figure indicates the 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 devices for constructing the concrete girder 30 at the piers 10B and 10C may be lifted from the ground surface to the steel girder 20 on the piers 10B and 10C by a crane or the like, or the side spans AB and CD may be used. The steel girder 20 may be transferred from a communication path with the ground surface outside.
The construction of the concrete girder 30 can be carried out in the same manner as the conventional concrete girder. Specifically, although not shown, a formwork is installed around the piers 10B and 10C in the continuous steel girder 20. Cast concrete inside the formwork. When the concrete hardens, remove the formwork.
[0029]
FIG. 2B schematically shows the total bending moment generated in the three span continuous girder at this stage. As shown in this figure, the cumulative bending moment, piers 10B, takes a negative maximum value M ₂ at the position of 10C, the positive in the span.
For normal cantilevered construction, to act in the same load is cantilevered tip this stage, become larger than the M ₂ at the intermediate pier position, structural mechanics on, it is clear. Therefore, according to the present invention, it is possible to suppress an excessive generation of the bending moment at the intermediate pier position.
<Introduction of prestress>
This step corresponds to a 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 bridge 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.
The PC steel material 40 penetrating the concrete girder 30 is arranged near the upper side of the concrete girder 30. A sheath tube is embedded in the concrete girder 30 in advance, and a PC steel material 40 is passed through the sheath tube. A tensile force is applied to the PC steel material 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 40 is applied in the compression direction of the concrete girder 30. A prestress in the compression direction is introduced into the concrete girder 30.
[0031]
If the prestress in the compression direction is introduced on 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. When a prestress having a magnitude corresponding to the bending moment force applied to the continuous steel girder 20 is introduced, substantially no bending moment is applied to the continuous steel girder 20 at the pier position.
As a result, it is possible to reinforce the concrete girder 30 that is weak in tensile strength due to its material. Further, even when a bending moment similar to the above is added to the concrete girder 30 during the subsequent construction and after use of the bridge, excessive tensile stress is suppressed from being generated on the upper side of the concrete girder 30. . The magnitude of the prestress can be set in accordance with the bending moment or tensile force applied after the completion of the construction of the concrete girder 30 or after the completion of the bridge.
[0032]
The pre-stressed concrete girder 30 becomes a steel PC composite bridge girder.
<Extension of steel PC composite bridge girder>
This step corresponds to the step (c).
As shown in FIG. 3A, the formation of the concrete girder 30 is sequentially extended from the piers 10B and 10C to the entire side spans AB, BC and CD. The concrete girder 30 in the hatched portion in the figure indicates the block to be constructed at this stage.
FIG. 3B schematically shows the total bending moment generated in the three span continuous girder at this stage. As shown in this figure, the cumulative bending moment, piers 10B, takes a negative maximum value M ₃ at 10C position, the positive in the span.
[0033]
For normal cantilevered construction, to act in the same load is cantilevered tip this stage, the intermediate pier position, become larger than the M ₃ are, structural mechanics on, it is clear. Therefore, according to the present invention, it is possible to suppress an excessive generation of the bending moment at the intermediate pier position.
The bending moment shown in FIGS. 2 (b) and 3 (b) is the bending moment generated as the steel PC composite bridge girder is successively constructed. The sum of each step (c) is shown. This is because only the steel girder is borne in the part where the steel PC composite bridge girder is not constructed, and the steel PC composite bridge girder which is appropriately prestressed is loaded in the part where the steel PC composite bridge girder is constructed. Take charge of.
[0034]
Further, as described above, in the steel-PC composite bridge girder, the steel girder, concrete, and PC steel share the applied load according to their respective functional characteristics, similarly to the ordinary composite girder. Therefore, according to the present invention, a reasonable bridge girder can be created. As described above, according to the present invention, it is possible to suppress an increase in the girder height at the intermediate pier position and reduce the degree of necessity of structural reinforcement such as prestress. As a result, it is possible to construct an economical and rational bridge with excellent landscape.
[Example of cross-sectional structure of bridge]
FIG. 5 shows a more specific arrangement structure of the bridge structure.
[0035]
The left half of the figure, FIG. 5 (a), shows a bridge section of a portion arranged near the center of the span. The right half of the figure, FIG. 5 (b), shows a bridge cross section of a portion arranged near the pier 10B. Both have the same basic structure, but differ in the girder height and the state of introduction of prestress.
The steel girder 20 has a rectangular frame shape in cross section, and there is also a steel material arranged on a diagonal line of the rectangular frame. The steel girder 20 is formed by joining shaped steel materials such as angle steel and CT steel. The concrete girder 30 has a rectangular box frame shape covering the steel girder 20 having a rectangular cross section with a constant 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 protrudes in the width direction. Although not shown, a pavement structure, a drainage structure, a balustrade structure, and the like are provided on the upper surface.
In the bending moment distributions shown in FIGS. 2B and 3B, in the section of the bridge located near the pier 10B (FIG. 5B), a large tensile force is applied to the upper side due to the negative bending moment. It can be seen that it occurs. Therefore, near the upper side of the concrete girder 30, a large number of PC steel materials 40 are inserted to introduce prestress. Note that some of the PC steel materials 42 are not embedded in the concrete girder 30 but are arranged in the internal space of the box-shaped concrete girder 30. The PC steel material 42 in this portion is for coping with the load applied after the steel PC composite bridge girder is built over the entire span of three spans, that is, the bending moment due to the load of the pavement, the balustrade, and the load of the traffic vehicle.
[0037]
In the bending moment distributions shown in FIGS. 2 (b) and 3 (b), the bridge section [FIG. 5 (a)] of the portion arranged near the center between the side spans and the center span has a positive bending moment. It can be seen that a tensile force is generated on the lower side. Therefore, a number of PC steels 40 are inserted near the lower side of the concrete girder 30 to introduce prestress. A PC steel material 42 is also arranged 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 arranged near the pier 10B.
[Comparison of loads applied to 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 erection method will be compared taking a three-span continuous bridge as an example.
[0038]
The erection method according to the present invention, specifically, the erection method according to FIGS. 1 to 3 of the above-described embodiment, and the cantilever method which is often adopted when a support from the ground cannot be installed between the center diameters Consider the erection method. Here, the former is referred to as the erection method I, and the latter is referred to as the erection method II.
FIG. 6A shows the erection method II. This is a cantilever type erection method in which the steel girder 24 and the concrete girder 30 are sequentially stretched between the piers 10A, 10B, 10C, and 10D while maintaining the right and left weights from the pier 10B and the pier 10C. Since the load of the steel girder 24 and the concrete girder 30 to be erected is applied to the tip of the cantilever with the piers 10B and 10C as fulcrums, a negative moment is generated in the cantilever, which is the pier 10B and the pier 10B. It has a negative maximum value at 10C and is 0 at the end of the cantilever. As the erection progresses and the concrete girder 30 sequentially extends, this bending moment is added. In FIG. 6 (b), shows schematically the bending moment M ₄ The cumulative been.
[0039]
FIG. 7 shows the distribution of the cumulative bending moment in each of the erection method I and the erection method II. The maximum values of the bending moments at the positions of the piers 10B and 10C are shown by M _I [Erection Method I] and M _II [ Construction method II]. The magnitudes of these bending moments are shown in a schematic graph of the results obtained by engineering calculations. However, these graphs are intended to easily compare the tendency of the bending moment distribution and the relative difference, and do not quantitatively and strictly indicate exact numerical values at individual positions.
Since the total bending moment by the erection method II is the sum of the load applied to the tip of the cantilever, at the positions of the piers 10B and 10C, a very large negative maximum value M _II is taken, and at the center of the center span, It becomes 0. Further, between the side spans, a slight bending moment may occur due to the erection 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 Figure 7, piers 10B, with respect to the bending moment of 10C position, indicating that _{M I} is less than _{M II.}
Note that the cumulative bending moment distribution in the erection method I is calculated by calculating the total bending moment of the steps (a), (b), and (c), that is, the cumulative bending moments of FIGS. 1 (b), 2 (b), and 3 (b). the sum, _{M I is} a value obtained by adding the _{M 1, M 2, M 3} . For reference, FIG. 7 also shows M ₁ , M ₂ , and M ₃ at the positions of the piers 10B and 10C.
[0041]
[Evaluation]
In erection method I, all loads act on continuous girder. On the other hand, in the erection 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 added.
Focusing on the bending moments at the piers 10B and 10C, it is clear from structural mechanics that the bending moment M _I as a continuous girder in the erection method _I is smaller than the bending moment M _II as a cantilever in the erection method II. It is. That is, according to the present invention, it is possible to reduce the excessive bending moment at the intermediate pier position, which is easily generated conventionally.
[0042]
【The invention's effect】
The method of erection of a steel-PC composite bridge according to the present invention is to construct a steel-PC composite bridge girder at an intermediate pier portion after erection of a continuous steel girder continuous over a plurality of spans, and then, Build a PC composite bridge girder. As a result, in a specific pier portion to which an excessive load was conventionally easily applied, it is possible to suppress a large load from being applied locally in a construction step of a steel PC composite bridge girder including formation of a concrete girder. Therefore, the strength of the prestress to be introduced into the steel PC composite bridge girder can be reduced, and the work of introducing the prestress can be simplified. It is not necessary to increase the girder height to locally increase the structural strength of a specific pier or the like, and the difference in girder height in the entire bridge can be reduced, and the entire bridge can be made smart and has a good appearance. If the girder height can be reduced, the amount of materials such as steel and concrete to be used can be reduced, and the construction cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic structural view (a) and a load state diagram (b) showing a steel girder erection process according to an embodiment of the present invention.
FIG. 2 is a schematic structural diagram (a) and a load 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) showing a completed construction state of a steel PC composite bridge girder and a load diagram (b).
FIG. 4 is a schematic structural view showing a prestressed state at a pier location. FIG. 5 is a detailed sectional structural view of a bridge. FIG. 6 is a schematic structural view showing a construction state by a cantilever type erection method. And load state diagram (b)
FIG. 7 is a load state diagram showing a difference in load distribution according to different construction methods.
10 Pier 20 Continuous steel girder 24 Steel girder 30 in cantilever type erection method Concrete girder AD Bridge position

Claims (1)

A steel PC composite bridge consisting of a continuous girder bridge or a continuous ramen bridge, in which a steel girder embedded in a concrete girder and a prestress is introduced, is continuously erected on a pier of multiple spans. So,
(A) erecting a continuous steel girder continuous throughout the plurality of diameters;
After the step (a), a concrete girder that embeds a part of the continuous steel girder is formed at the middle pier position among the bridges of the plurality of spans, and prestress is introduced to construct a steel PC composite girder. (B)
Constructing the steel PC composite bridge girder in the remaining portion of the continuous steel girder after the step (b), and erection of a steel PC composite bridge girder continuous over a plurality of spans; Erection method.

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