KR101239179B1 - Construction method for prestressed concrete bulb-t girder bridge - Google Patents

Abstract

PURPOSE: A method for constructing a prestressed concrete bulb T-girder bridge is provided to solve the problems of chambers generated differently in girders and to easily apply it to a bridge of low height. CONSTITUTION: A method for constructing a prestressed concrete bulb T-girder bridge comprises; a step for manufacturing a girder(10) of a bulb T-shape having a wide upper flange(11) and a lower flange; a step for prestressing each girder; a step for installing the prestressed girders to a lower structure; a step for regulating the chambers generated in the each girder by prestressing; a step for placing a distribution bar between the upper flanges of the adjacent girders and placing concrete; a step for secondarily prestressing and installing a cross beam in the lower parts of the upper flanges; and a step for installing a barrier and paving materials.

Description

Construction Method for Prestressed Concrete Bulb-T Girder Bridge

The present invention relates to a construction method of a prestressed concrete bulb girder bridge, and more particularly, to a construction method of a prestressed concrete bulb girder bridge with simple structural construction while improving structural dynamic efficiency as compared with the related art.

Precast Prestressed Concrete (hereinafter referred to as 'PSC') Synthetic girder disturbances Prefabricated (precast) PSC girders on substructures such as shifts and piers, and deck slab formwork supported by girders PSC girder and concrete slab slab are synthesized by placing bottom slab concrete composited with the upper girder flange after installing the girder, and the secondary fixed load of pavement, protection wall, etc. acting on the upper slab by synthetic girder. It is a bridge of structural type supported by vehicle and vehicle load.

A typical PSC composite girder bridge is a type in which a concrete slab slab 3 is installed in a PSC-I type girder 1 as shown in FIG. 1. The initial PSC girders of type I cross section were almost the same size as the width of the upper flange and the lower flange. The width of the girder was much smaller than the height, so the shape of the cross section was similar to that of English I. After that, when the length of the girder is longer, the width of the upper flange is larger than the width of the lower flange, which is advantageous in manufacturing, transportation, and construction. In addition, the shape of the girder is also referred to as a bulb-T girder to distinguish it from the type I girder shown in FIG. 1.

The PSC-T type girder includes a wide upper flange as shown in FIG. 2, and the lower flange 1 ′ has no or very narrow shape. PSC-T type composite girder bridge as shown in Figure 2 is installed so close that the upper flange of the girder (1) is almost abut on the lower structure and then caulk a small gap between the upper flange of the girder without a formwork with an elastic material or the like. It was constructed by caulking, pouring concrete slab slab 3 and constructing a protective wall 4.

3A and 3B are cross-sectional views of the bottom plate integrated PSC bulb girder bridge, in which both the upper flange of the girder is used as the bottom plate of the bridge. There are two construction methods for connecting the girder and the girder in a transverse direction (orthogonal to the longitudinal direction of the bridge). There are two construction methods, as shown in FIG. 3A and a shear connecting member as shown in FIG. As you can see there is a way to use roof rebar. When rapid construction is important, as shown in FIG. 3A, the girder 1 is installed so that the upper flange is almost in contact with each other, and the shear connecting member 5 of the steel, which is installed at regular intervals along the longitudinal direction of the girder, is welded to each other. After connecting the girders to each other, the gap between the girders is using a shear connection method that is filled with mortar (6). In the case of the girder bridge shown in FIG. 3b, the reinforcing bars 7 are overlapped and the concrete 8 is poured. This construction method is also called a moment connection method. In the calculation of the design, the shear connection method is designed assuming that only the shear force is transmitted in the transverse direction, and the moment connection method is designed assuming that the bending moment is also transmitted. 3A and 3B, when the lateral connection of the upper flange is completed, the protective wall 4 and the pavement (not shown) are immediately constructed without a separate bottom plate pouring process. The girder 1 shown in Figs. 3a and 3b is usually bottomed because the width of the upper flange is much larger than that of the I-type girder 1 shown in Fig. 1 and the lower flange is larger than the conventional T-shaped cross section. It is called an integrated bulb tea girder (Decked Bulb-T or DBT).

The above-described type I girder, T type girder, and Bulb-T type girder tend to use the terms interchangeably because their distinction is somewhat ambiguous. However, despite some morphological differences, the confusion of terms does not matter much because the three cross sections have similar structural characteristics and the same design method.

Each of the three bridge types described above has its own advantages and disadvantages. First, the PSC-I type composite girder bridge shown in FIG. 1 is the most widely used bridge type in the world, and has the highest field applicability. Since PSC girder introduces prestress, it rises upward when it is hypothesized, and it is called camber. Even when the shape of girders and the prestress amount are designed equally, the variation of the constituents of the concrete, the variation of the curing environment, and the age variation In general, cambers of different sizes are generated for each girder due to tension, tendency of the tendons, positional error and frictional force variation. However, the type I girder type is made of wood slab formwork in the field, so as shown in Figure 1 by providing a haunch (2) on the upper flange of the girder to change the height of the haunch to correct the different camber between the girders. have. In addition, since the formwork can be manufactured in various shapes in the field even when skewed bridges, curved bridges, or deck slabs are expanded, they are applied to deck slabs of various shapes despite the use of straight girders. This is convenient. However, this type of bridge is vulnerable to safety accidents due to the need to install a wide bottom slab formwork supported by girders at high altitude, there is also a problem that the air is long due to the complicated formwork installation work.

PSC T-type composite girder bridge shown in Figure 2 does not need to install the bottom plate slab formwork is improved work safety, has the advantage of short air. However, because the upper flange of the girder is adjacent and does not use the formwork, the processing is not easy when the camber is different for each girder. Considering the method of placing the haunch shown in Figure 1, but the width of the haunch portion is too wide, there is a problem that the weight of the haunch portion is excessive if the camber difference between the girder becomes large. For this reason, PSC T-girder has been mainly used to reduce the camber difference between girders by increasing the height of the mold and reducing the amount of prestress to reduce the size of the camber. However, the biggest problem of these T-girders is that the distance between them is very short because the upper flanges of adjacent girders are almost in contact with each other, so the thickness of the bottom slab can be made very thin. There is no structural problem, but the slab thickness cannot be reduced below the limit. That is, the thickness of the upper flange in the up and down direction must be designed above the minimum slab design criteria regardless of the design site. In the case of the domestic road bridge design standards, the slab thickness is 220mm in the case of T-type composite girder because the minimum thickness of the concrete slab is 220mm. The slab thickness of the PSC-I type composite girder bridge of FIG. 1 is usually 240mm. This means that the wide top flange of the composite T-girder contributes little to reducing the thickness of the composite slab, which in turn is very inefficient in structure. Due to such structural inefficiency, T-type composite girder bridges have not been constructed recently.

3A and 3B show a bottom plate integrated PSC bulb tea (DBT) girder, which uses the upper flange 1a of the girder as the bottom plate, so that the structural efficiency is higher than that of the girders of the type described above. outstanding. Therefore, in general, the bottom plate integrated bulb tea girder is the lowest among the three girder types and the largest tension is introduced. The girder shown in Figure 3a has the advantage that rapid construction is possible because the weld connection of the shear connector (5) after the installation of the girder and filling the mortar (6) between the girders. Even in the case of the girder shown in Figure 3b, after installing the girders on the substructure, simply install the formwork and then cast the concrete (8) only need to connect the girder in the transverse direction, this type is also very fast construction advantages There is this. Designated by reference numeral 7 in FIG. 3B is a reinforcing bar in the form of a loop.

However, since the girder type shown in FIGS. 3A and 3B is integral with the bottom plate, the rigidity of the girder is large, and thus, if a camber having a different size is generated for each girder, its adjustment is difficult. Furthermore, in the case of gliding, the amount of rise of the upper flange end is equal to the amount of rise of the center of the girder section located at right angles in the longitudinal direction of the girder, and each girder cross section that determines the rise of the upper flange end in the transverse direction due to the square of the bridge. Since the centers of the girder have different relative positions in the longitudinal direction of the girder, even if the same camber is generated in each girder, the rises of the adjacent upper flange ends are not equal to each other. Even in this case, there is a difficulty in construction that requires adjustment or correction of the camber.

4A is a conceptual diagram illustrating one of methods of adjusting cambers between adjacent DBT girders. The adjustment of different cambers between girders is usually the method by which the camber picks up the small girder or the camber pushes down the large girder with the support of adjacent girders. The method shown in Fig. 4a is used to pull up a girder 1 "having a relatively small camber by using a hydraulic jack 9. The component indicated by 9 'in Fig. 4a pulls the girder 1". The rod is temporarily fixed to the girder (1 '') for lifting, and the component labeled 9 '' is the pedestal.

 4B is a photograph of fixing the leveling state after completing the camber adjustment work. The DBT girder shown in FIGS. 4A and 4B is a DBT girder of the shear connection method described above, and it is possible to check the shear connector (a) installed at regular intervals in FIG. 4B. The leveling work is called the leveling work, in which the upper surface of the girder upper flange is made into a plane of the designed shape by adjusting the camber of the girder. To fix the leveling state. Although the leveling of the DBT girder is somewhat cumbersome, the camber can be corrected by implementing the method illustrated in FIGS. 4A and 4B.

The biggest problem with the DBT girder is the problem of the bottom plate replacement. Bridge deck slabs are not only in direct contact with the vehicle but also susceptible to snow melts such as calcium chloride, which are very detrimental to the durability of reinforced concrete, and thus have a shorter endurance compared to girders. The bottom plate needs to be replaced.

However, in the case of the DBT girder, since the bottom plate slab is part of the girder, the bottom plate slab replacement is virtually impossible. In addition, since the lateral connection between the girder and the girder is a fundamentally weak structure, there is a problem that the breakage of the connection portion frequently occurs. Therefore, DBT girders are usually used for bridges with heavy traffic such as dump trucks, or for bridges that do not require much bottom plate replacement.

5 is a cross-sectional view of the composite PSC bulb girder bridge of the Republic of Korea Patent No. 10-571188 "wing girder bridge structure" (hereinafter 'wing girder'). Wing girder fabricates the girder by exposing the transverse rebar on the side of the upper flange in order to solve the structural inefficiency problem of the PSC T-type composite girder bridge of FIG. After mounting the fabricated wing girder to the undercarriage of the bridge, the exposed transverse reinforcement (R) is joined by the connector (C), and an additional bottom plate slab is cast, so that the moment-connected upper flange (or wing) Used as part of the slab of slab, as in the PSC T-type composite girder bridge of FIG. 2, structural efficiency is improved without the need for installing a slab slab formwork. However, when the structural efficiency of the girder is improved, the cross-sectional area of the girder is reduced and the height of the girder is reduced, but the self-weight of the girder is reduced, whereas the prestress introduction amount is relatively large, and accordingly, the camber is also large. However, the wing girder is an invention that overlooks the camber problem by the introduction of prestress. After the construction of the PSC girder, different cambers are generated in the adjacent girders, so that a step occurs between the upper surfaces of the adjacent upper flanges, thereby failing to form a plane. There is no countermeasure. In addition, the fact that the reinforcement of the rebar is not easy due to the position error due to the installation error in the girder and the different camber between the rebar girders exposed to the side of the upper flange also seems not to be considered. Moreover, when girders are laid on the undercarriage, they do not seem to consider the fact that the rebars overlap each other, making it very difficult to girder because of the interference of the rebars. In conclusion, winger is structurally efficient, but it seems to be an invention with many disadvantages in actual construction.

6 is a photograph showing a state in which the reinforcement of the reinforcement of the reinforced concrete intermediate cross beam after the conventional PSC bulb tea girder is mounted on the lower structure (picture taken from the bottom of the girder). After the reinforcement of the reinforcing bar (RB) is installed the formwork (not shown) and the concrete is poured through the through hole (H) formed in the upper flange of the girder. However, when performing such a work, the gap between the upper girder flanges is very narrow, so it is impossible to approach the lower side of the girder from the upper side of the girder, and thus there is a problem that the input of materials, equipment, and manpower should be made under the bridge. This is because when the girder is mounted at a very high position or when the lower part of the bridge is a river or sea, it is practically impossible to put equipment or manpower under the bridge. If steel beams are used for fast construction rather than reinforced concrete, the steel beams are so heavy that it can be very difficult to pull them from the bottom if the material cannot be put from the top to the bottom of the girder. This problem occurs in the girders shown in FIGS. 2, 3A, and 5, and the same problem may occur because the loop reinforcement 7 is densely installed in the case of the girders shown in FIG. 3B.

The present invention has been drawn to solve the problems of the prior art described above, the problem to be solved by the present invention is the existing precast prestressed concrete T-shaped formwork that does not need slab formwork of bridge or simple installation It is to provide a construction method of prestressed concrete bulb tea girder bridge that can improve the construction of composite girder bridge and bottom plate integrated girder bridge, and solve the rise problem that occurs differently for each girder according to the introduction of prestress. It is another object of the present invention to provide a construction method of a prestressed concrete bulb tea girder bridge, which can be easily applied even when the height of the mold is low and the structural efficiency of the composite PSC T-girder is low.

The present invention as a means for solving the above problems,

In the construction method of prestressed concrete bulb tee composite girder bridge,

Bulbs are formed on the side of the upper flange to protrude in the transverse direction of the girder along the longitudinal direction of the girder, so as not to interfere with the bars protruding on the side of the upper flange of the adjacent girder ( A girder manufacturing step of manufacturing a Bulb-T) girder;

A prestressing step of introducing prestress into each girder produced in the girder manufacturing step;

A girder hypothesis step of hypothesizing the girders into which the prestress is introduced;

A leveling step of adjusting a difference in the amount of rise formed in each girder by the prestress introduced in the prestressing step;

Installing a formwork on the bottom between the upper flanges of the adjacent girder and the moment connecting step to cure by placing concrete after placing the reinforcement on the formwork;

Includes; slab forming step of placing the reinforcing bar on the upper flange and placing concrete;

The reinforcing bar of the girder manufacturing step is installed in a place where people and materials need to be moved to the bottom of the upper flange, and is composed of a first reinforcing bar that can be attached and detached and a second reinforcing bar that is fixed to the upper flange side. At the bottom of the upper flange to move the person to do the necessary work, and provides a construction method of prestressed concrete bulb tea girder bridge, characterized in that the first reinforcing bar can be attached after the work of people and materials is completed.

The prestressing step includes a first prestressing step of applying only a part of the prestress to be introduced into each girder before the leveling step, and a second prestressing step to be introduced into each girder after the leveling step and the moment connecting step. It is preferred to consist of a prestressing step.

Further, according to the present invention,

In the construction method of the bottom plate integrated prestressed concrete bulb tea girder bridge,

Bulbs are formed on the side of the upper flange to protrude in the transverse direction of the girder along the longitudinal direction of the girder, so as not to interfere with the bars protruding on the side of the upper flange of the adjacent girder ( A girder manufacturing step of manufacturing a Bulb-T) girder;

A prestressing step of introducing prestress into each girder produced in the girder manufacturing step;

A girder hypothesis step of hypothesizing the girders into which the prestress is introduced;

A leveling step of adjusting a difference in the amount of rise formed in each girder by the prestress introduced in the prestressing step;

Installing a formwork on the bottom between the upper flanges of the adjacent girder and the moment connecting step of curing by placing concrete after placing the reinforcement on the formwork; Including,

The reinforcing bar of the girder manufacturing step is installed in a place where people and materials need to be moved to the bottom of the upper flange, and is composed of a first reinforcing bar that can be attached and detached and a second reinforcing bar that is fixed to the upper flange side. At the bottom of the upper flange to move the person to do the necessary work, and provides a construction method of prestressed concrete bulb tea girder bridge, characterized in that the first reinforcing bar can be attached after the work of people and materials is completed.

The prestressing step includes a first prestressing step of applying only a part of the prestress to be introduced into each girder before the leveling step, and a second prestressing step to be introduced into each girder after the leveling step and the moment connecting step. It is preferred to consist of a prestressing step.

In this case, the first prestressing may be performed by a pre-tensioning method, and the second prestressing may be performed by a post-tensioning method.

One end of the first reinforcing bar may be screwed with the upper flange of the girder and the other end may be a rod-shaped headed bar formed with an enlarged cross section, or one may be a hook-shaped reinforcing bar that is screwed with the upper flange of the girder. .

The tendons used for the first prestressing are settled at both ends of the girder, and the tendons used for the second prestressing are settled at the end sides of the girders.

In the present invention,

Further comprising a horizontal beam installation step for installing a horizontal beam on the girder,

In the girder manufacturing step, the cross beams are manufactured at the lower portion of the upper flange, and the cross beams of adjacent girders are connected to each other by moments in the field.

Removable reinforcing bar is preferably used for the moment connection of the cross beam, and the detachable reinforcing bar may be a reinforcing bar-shaped reinforcing bar, reinforcing bar or headed bar.

The cross beam may be disposed in the lateral direction of the girder and provided with a duct for inserting a steel rod or tendon.

According to the present invention, it is possible to improve the workability of the existing precast prestressed concrete T-type composite girder bridge and the bottom plate integrated girder bridge, which do not need the deck slab formwork of the bridge or use the simple formwork, and according to the introduction of the prestress. It is possible to provide a construction method of prestressed concrete bulb tea girder bridge that can solve the rise problem that otherwise occurs. In addition, the present invention can provide a method of constructing a prestressed concrete bulb tea girder bridge that can be easily applied even when the height of the structure is low and the height of the composite PSC T-girder.

1 is a cross-sectional view schematically showing a conventional PSC type I girder bridge.
2 is a cross-sectional view schematically showing a conventional PSC T-type composite girder bridge.
Figure 3a is a schematic cross-sectional view showing a conventional bottom plate integrated PSC bulb tea girder bridge (shear connection method).
Figure 3b is a schematic cross-sectional view showing a conventional bottom plate integrated PSC bulb tea girder bridge (moment connection method).
Figure 4a is a view for explaining an example of the leveling work method applied to the bottom plate integrated bulb tea girder bridge.
Figure 4b is a photograph for explaining an example of the leveling work method applied to the bottom plate integrated bulb tea girder bridge.
5 is a schematic cross-sectional view of a conventional synthetic PSC bulb tea girder; (Wing girder)
Figure 6 is a photograph of the reinforcing bar for the cross beam provided in the lower portion of the conventional PSC bulb tea girder.
7 is a cross-sectional view of the girder used in the construction method of the prestressed concrete bulb tee composite girder bridge according to an embodiment of the present invention.
8a to 8d is a view for explaining the procedure of the construction method of prestressed concrete bulb tee composite girder bridge according to an embodiment of the present invention.
9 is a cross-sectional view showing one example of formwork used in the construction method of the prestressed concrete bulb tea girder bridge shown in FIG.
10 is a diagram for explaining that a headed bar is used.
FIG. 11 is a cross-sectional view illustrating a method of installing the headed bar shown in FIG. 10. FIG.
12A and 12B are views for explaining an example of detaching reinforcing bars using a coupler.
FIG. 13 is a view for explaining arrangement of pretension and posttension tendons; FIG.
14 is a view for explaining the end anchoring and side anchoring for multi-stage tension.
15 is a view for explaining another example of the anchorage for multi-stage tension.
16a and 16b are views for explaining a conventional crossbeam installation method.
Figures 17a to 17c is a view for explaining a method of using a removable rebar in the crossbeam installation step.
18 is a plan view of the upper flange shape applicable to a curved bridge.
19 is a view for explaining a method of lifting a bulb tea girder of left and right asymmetrical shapes.
20a to 20c is a view for explaining the procedure of the construction method of the bottom plate integrated prestress bulb tea girder bridge according to another embodiment of the present invention.
21 is a view showing a headed bar used in the construction method of the prestress bulb girder bridge shown in FIGS. 20A to 20C.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings to provide specific contents for carrying out the present invention.

7 is a cross-sectional view of the girder used in the construction method of prestressed concrete bulb tee composite girder bridge according to an embodiment of the present invention, Figure 8a to 8d is a prestressed concrete bulb tee composite according to one embodiment of the present invention 9 is a cross-sectional view showing an example of formwork used in the construction method of the prestressed concrete bulb girder bridge shown in FIG. 8B, FIG. 10 is a headed bar used for explaining the procedure of the construction method of the girder bridge. FIG. 11 is a cross-sectional view illustrating a method of installing the headed bar shown in FIG. 10, FIGS. 12A and 12B are views for explaining an example of detaching reinforcing bars using a coupler, and FIG. Figure for explaining the arrangement of the pre-tension and post-tension tendon, Figure 14 is for explaining the end anchoring and side anchoring for multi-stage tension Figure, Figure 15 is a view for explaining another example of the anchorage for multi-stage tension, Figures 16a and 16b is a view for explaining a conventional crossbeam installation method, Figures 17a to 17c are removable rebar in the crossbeam installation step 18 is a plan view of an upper flange shape applicable to a curved bridge, and FIG. 19 is a view for explaining a method of lifting a bulb tea girder having left and right asymmetric shapes.

The construction method of the prestressed concrete bulb girder bridge according to the present embodiment relates to a method for constructing a composite girder, girder manufacturing step, prestressing step, girder construction step, leveling step, moment connection step, slab formation step and horizontal beam installation It consists of steps.

The girder manufacturing step is to produce a bulb-T shaped girder 10 having a lower flange and a wide upper flange as shown in FIG. 7, and a girder (side) of the upper flange 11. A plurality of reinforcing bar 20 is protruded along the longitudinal direction of 10) and the reinforcing bar 20 is disposed in the transverse direction when the girder 10 is installed. The state where several rebars are arranged can be seen in FIG. 10. At this time, the reinforcing bar 20 is disposed so as not to interfere with the reinforcing bars of the girders 10 are installed adjacent to, as shown in FIG. The upper side of the upper flange 11 is exposed to the shear reinforcing bars 12 for synthesis with the bottom plate slab concrete.

The reinforcing bar 20 may be divided into a first reinforcing bar 21 and a second rebar 22 fixed to the upper flange 11, wherein the first reinforcing bar 21 is as in the horizontal beam installation step. It is installed on the lower part of the upper flange 11 and the part that needs to be moved, so that when the first reinforcing bar 21 is detached so that the person can act as a manhole that can move to the lower side of the upper flange (11). So that people can do the work they need to do and attach it after the work is done.

As shown in FIG. 10, the first reinforcing bar 21 is a headed bar having a screw portion 211 formed at one end and a cross-sectional enlarged portion 212 formed at the other end thereof. The first reinforcing bar 21 is installed to be detachable and attached in a manner that is screwed to the female screw portion 213 embedded in the upper flange (11). As the first reinforcing bar 21, the headed bar is very effective even in the overlapping and can effectively avoid the mutual interference between the bars. 11 shows a method for installing a headed bar, in which an inner reinforcing bar 13 disposed in the transverse direction of the girder is installed on the upper flange, and couplers 213 are connected to both ends of the inner reinforcing bar 13. The first reinforcing bar 21 is connected to the internal reinforcing bar 13 by the coupler 213.

On the other hand, unlike the present embodiment, as shown in FIG. 12B, the same reinforcing bar 21 '' as in the second reinforcing bar 22 of FIG. 10 may be used and detachable using a coupler 211 ''. have.

As shown in FIG. 7, the second reinforcing bar 22 is exposed to the upper flange 11 in a fixed state, and is exposed to an upper side than the upper surface of the upper flange 11, and connects the upper flanges 11. It also serves as a shear reinforcing bar for synthesizing with slab concrete, as well as connecting to transfer moments.

The prestressing step is a step of introducing a prestress to each girder produced in the girder manufacturing step.

The girder hypothesis step is to construct the girder 10 into which the prestress is introduced, as shown in FIG. 8A, on a bridge structure (not shown). Although only girder is shown in FIG. 8A for convenience of illustration, it is actually hypothesized in the substructure.

The leveling step is a step of adjusting the difference in the amount of rise formed in each girder by the prestress introduced in the prestressing step. Since the leveling step may use the method described in the background art, further description will be omitted.

In the present embodiment, the prestressing step is divided into a first prestressing step and a second prestressing step.

The first prestressing step is a step of applying a part of prestress to be introduced into the manufactured girder, and the second prestressing step is a step of introducing prestress not introduced in the first prestressing step of the prestresses to be introduced after the leveling step. to be.

First, a first prestressing step of introducing a part of the prestress to be introduced is performed. In the present embodiment, the first prestressing step is to pre-tension to introduce prestress into the girder by releasing the tensile force when the concrete is placed to the girder by placing the concrete with the tensile force applied thereto and releasing the tensile force when the concrete reaches a predetermined strength. This is done by a pre-tensioning method. When the number of manufactured girders is large, the pretensioning method which does not require the tendon fixing device has an economical advantage. In the case of introducing prestress by the pretensioning method, it is advantageous to arrange the tendons in a straight line, so that tendons arranged in a straight line are used as indicated by 61 in FIG. 13. The size of the prestress introduced in the first prestressing step is ideally such that the camber does not occur because the sagging due to the girder weight and the rise due to the prestress introduction are the same.

When the first prestressing step is completed, the above-described leveling step is performed. The leveling step is a step of adjusting the difference in the amount of rise generated in each girder by the first prestressing.

When the leveling step is completed, the moment connecting step is performed. The moment connecting step is to step the reinforcing bar 31 in the longitudinal direction of the girder between the upper flanges 11 and cast concrete 30. The state in which the moment connecting step is completed is shown in FIG. 8B.

Since the distance between the upper flanges 11 is short and the amount of concrete to be poured is not large, a simple form can be used. An example of the form is shown in FIG. 9. Plate formwork 90 is fixed to the upper flange 11 is made by fastening the bolt 91 to the nut 92 embedded in the upper flange (11). At this time, the formwork 90 used may be dismantled after the moment connection step is completed, or may be permanently used when the demolition is cumbersome.

When the moment connecting step is completed, the second prestressing step is performed. As described above, the second prestressing step introduces the remaining prestresses other than the prestresses introduced in the first prestressing step out of the amount of prestresses to be introduced. In this embodiment, the second prestressing step is performed by a post-tensioning method. The tendons 60 for the second prestressing are arranged in a curved shape as shown in FIG. 13.

Recently, efforts have been made to reduce the height of the girder for securing the space of the mold and for aesthetic reasons, but the composite prestressed concrete bulb tea girder as the invention of the present embodiment has a good cross-section efficiency, which is suitable for reducing the height of the girder. to be. However, if the height of the girder is lowered, the amount of prestress introduced is increased in proportion to the height of the girder, so that the rise of the prestress is also increased. In general, the rise of the girder increases as the rise of the girder increases. However, it can be helpful to solve this problem by introducing prestress by dividing into several steps as in the present embodiment. If only a portion of the prestress is introduced in the first prestressing step, the rise is also reduced and the rise deviation can be reduced. As such, leveling is performed in a state where only a part of prestress is introduced, a moment connection step is performed to fix the leveling state, and a second prestressing step is performed to introduce the remaining prestress. This method has an advantage that the leveling operation can be made much easier because the leveling operation is not necessary or the level is not large.

On the other hand, the girder produced at the end of the air phase may not have sufficient curing period because the tension is completed before the girders are laid on the substructure. For that reason, it is common to consider about 80% of the design strength as the concrete strength when prestress is introduced. However, when the multi-stage tension as in the present embodiment, since the curing time of the sufficient girder before the second prestressing step can be secured, there is an advantage that 100% of the design strength can be utilized.

To achieve this multi-stage tension, the second prestressing step can be easily performed by using the anchorage exposed on the side of the girder end as shown in FIG. 14. The tendon 61 used in the first prestressing step is fixed using the fixing unit 611 exposed at the end of the girder, and the tendon 60 used in the second prestressing step uses the fixing unit 602 exposed at the side of the girder. Alternatively, the upper flange 11 may be partially cut off and then fixed using the fixing unit 601 installed at the cut portion. Of course, after the fixing is completed, the fixing unit 601 reinforces the slab reinforcement and pours / cures concrete. In this case, as shown in FIG. 15, the upper flange 11 may be partially cut without the fixing unit exposed to the side of the girder 10, and then the fixing unit 601 may be installed only at the cut portion to perform the necessary prestressing operation. In FIGS. 14 and 15, post-tensioning is used in the first prestressing step differently from the embodiment of FIG. 13.

The horizontal beam installation step is to install the horizontal beam 70 in the lower portion of the upper flange (11). Since the crossbeam is generally used in girders, a detailed description of the structural role of the crossbeam itself will be omitted.

The cross beam installation step is carried out before the moment connection step, and it is common to reinforce the reinforcing bar at the cross beam installation position between the girders installed on the lower structure, form the formwork, and then cast concrete. However, when rapid construction is required, a method of manufacturing a cross beam with a girder is often used as shown in FIG. 16A. After the girders fabricated in the form shown in FIG. 16a are hypothesized on the substructure, a steel rod or tendon is inserted into the duct 71 as shown in FIG. 16b, and fixed by applying a tensile force to bind the cross beams. However, this method is available for rapid construction, but there is an interference problem between the cross beams during the construction of girders, and construction is very difficult because it is difficult to correct the manufacturing and installation errors of the cross beams. Therefore, in the present embodiment, the horizontal beam is installed in the form shown in FIG. 17A, which will be described in more detail.

The horizontal beam 70 is manufactured in the girder manufacturing step as described above, and binds the horizontal beams 70 installed on the adjacent girders by a site casting method, and reinforcing bars for connecting moments (hereinafter, referred to as 'beam beams'). As shown in FIG. 17B, the horizontal beam 70 attached to the girder and the detachable head bar are used as the horizontal beam reinforcing bars 72, and the concrete 73 is cast / cured as shown in FIG. 17C. This completes the installation phase.

In this case, the headed bar has the same configuration as the headed bar used as the first reinforcing bar 21, but uses different reference numerals because its use and use are different. Meanwhile, the reinforcing bar reinforcement may be used instead of the headed bar shown in FIG. 12a or the hook-type reinforcement shown in FIG. 12b, and the detachment may appropriately use the coupler shown in FIGS. 12a and 12b.

In the cross beam installation step and the moment connection step, both the formwork installation work and the concrete placing work are generally performed at the same time.

When the prestressing step, leveling step, cross beam installation step, and moment connection step described above are completed, the slab forming step is performed.

The slab forming step is the step of placing the main reinforcing bar 42 and the reinforcing bar 41 on the upper flange 11 and pouring the concrete 40, as shown in Figure 8c. When the slab forming step is completed, as shown in FIG. 8D, the construction of the bridge is completed by installing the protective wall 51 and the pavement 50.

Hereinafter, a construction method of a bottom plate integrated prestressed concrete bulb girder bridge according to another embodiment of the present invention will be described with reference to FIGS. 20 and 21.

20A to 20C are views for explaining a procedure of a method of constructing a bottom plate integrated prestress bulb girder bridge according to another embodiment of the present invention, and FIG. 21 is a prestress shown in FIGS. 20A to 20C. It is a figure which shows the headed bar used for the construction method of a bulb tea girder bridge.

The construction method of the prestressed concrete bulb girder bridge according to the present embodiment relates to the construction of the bottom plate integrated girder is composed of girder manufacturing step, prestressing step, girder construction step, leveling step, moment connection step.

The girder manufacturing step is a step of manufacturing the girder 110 of the type shown in Figure 20a. There are some differences from the girder of the previous embodiment shown in FIG. 7, but since no slab is formed on the upper flange 111, there is no shear reinforcement 12 in the girder shown in FIG. The difference is that the position is lower than the upper surface of the upper flange 111. The side of the upper flange 111 of the girder 110 is provided with a removable first reinforcing bar 121 and the second reinforcing bar 122 is the same as the girder 10 of the previous embodiment.

In the present embodiment, the first reinforcing bar 121 has a threaded portion 1211 and a cross-sectional enlarged portion 1212 as headed bars, and is screwed to a coupler 1213 embedded in the upper flange 111.

The prestressing step is to introduce a prestress required for the girder 110.

The girder hypothesis step is to hypothesize the girder 110 into which prestress is introduced onto the lower structure of the bridge.

The leveling step is a step of correcting the different amount of rise of the girder 110 caused by the introduction of the prestress.

The moment connecting step is a step to reinforce the reinforced reinforcing bars 131 and pour / curing the concrete 130 as shown in Figure 20b.

The prestressing step, the girder hypothesis step, the leveling step, the moment connecting step is not a step that proceeds sequentially, in the case of pre-stressing multi-step as in the previous embodiment, the first pre-stressing step, girder hypothesis step, leveling step, moment connection step The construction may be performed in the order of the second prestressing step, and in the case of one prestressing, the construction may be performed in the order of the prestressing step, the girder hypothesis step, the leveling step, and the moment connecting step.

When the prestressing step, the girder hypothesis step, the leveling step, and the moment connection step is completed, as shown in FIG. 20C, the barrier wall 151 is installed and the pavement 150 is completed to finish the bridge construction.

Meanwhile, in the case of the curved bridge shown in FIG. 18, when the outer flange of the upper flange of the bulb girder on the outermost side is curved, construction of a curved bridge having a certain curvature is possible, and the width of the upper flange is girder. If the linear change in the longitudinal direction, it is possible to construct a widening bridge. At this time, when the girder is installed by the asymmetrical shape of the girder, the weight may be focused on one side, which may cause the girder to rotate. As illustrated in FIG. 19, the girder using the auxiliary crane string 82 in addition to the main crane string 81 may be used. Can prevent the rotation. The component indicated at 14 in FIG. 18 is the web of the bulb tea girder.

While providing a detailed description for carrying out the present invention by describing the construction method of the prestressed concrete bulb girder bridge according to the preferred embodiments of the present invention, the technical spirit of the present invention is limited to the described embodiment Or, it can be embodied by the construction method of the prestressed concrete bulb tea girder bridge of various forms within the scope not contrary to the technical idea of the present invention.

10: girder 20: rebar
30: cast-in-place concrete 40: slab concrete
50: packing

Claims (11)

In the construction method of prestressed concrete bulb tee composite girder bridge,
Bulbs are formed on the side of the upper flange to protrude in the transverse direction of the girder along the longitudinal direction of the girder, so as not to interfere with the bars protruding on the side of the upper flange of the adjacent girder ( A girder manufacturing step of manufacturing a Bulb-T) girder;
A prestressing step of introducing prestress into each girder produced in the girder manufacturing step;
A girder hypothesis step of hypothesizing the girders into which the prestress is introduced;
A leveling step of adjusting a difference in the amount of rise formed in each girder by the prestress introduced in the prestressing step;
Installing a formwork on the bottom between the upper flanges of the adjacent girder and the moment connecting step of curing by placing concrete after placing the reinforcement on the formwork;
A slab forming step of placing reinforcing steel on the upper flange and placing concrete; Including,
The reinforcing bar of the girder manufacturing step is installed in a place where people and materials need to be moved to the bottom of the upper flange, and is composed of a first reinforcing bar that can be attached and detached and a second reinforcing bar that is fixed to the upper flange side. The construction method of the prestressed concrete bulb tea girder bridge, characterized in that the person moves to the bottom of the upper flange to perform the necessary work, and the first reinforcing bar can be attached after the work of the person and the material is completed.
The method of claim 1,
The prestressing step includes a first prestressing step of applying only a part of the prestress to be introduced into each girder before the leveling step, and a second prestressing step to be introduced into each girder after the leveling step and the moment connecting step. Construction method of prestressed concrete bulb tea girder, characterized in that the pre-stressing step.
In the construction method of the bottom plate integrated prestressed concrete bulb tea girder bridge,
Bulbs are formed on the side of the upper flange to protrude in the transverse direction of the girder along the longitudinal direction of the girder, so as not to interfere with the bars protruding on the side of the upper flange of the adjacent girder ( A girder manufacturing step of manufacturing a Bulb-T) girder;
A prestressing step of introducing prestress into each girder produced in the girder manufacturing step;
A girder hypothesis step of hypothesizing the girders into which the prestress is introduced;
A leveling step of adjusting a difference in the amount of rise formed in each girder by the prestress introduced in the prestressing step;
Installing a formwork on the bottom between the upper flanges of the adjacent girder and the moment connecting step of curing by placing concrete after placing the reinforcement on the formwork; Including,
The reinforcing bar of the girder manufacturing step is installed in a place where people and materials need to be moved to the bottom of the upper flange, and is composed of a first reinforcing bar that can be attached and detached and a second reinforcing bar that is fixed to the upper flange side. The construction method of the prestressed concrete bulb tea girder bridge, characterized in that the person moves to the bottom of the upper flange to perform the necessary work, and the first reinforcing bar can be attached after the work of the person and the material is completed.
The method of claim 3,
The prestressing step includes a first prestressing step of applying only a part of the prestress to be introduced into each girder before the leveling step, and a second prestressing step to be introduced into each girder after the leveling step and the moment connecting step. Construction method of prestressed concrete bulb tea girder bridge, characterized in that consisting of a prestressing step.
The method according to claim 2 or 4,
The first prestressing is performed by a pre-tensioning method, and the second prestressing is performed by a post-tensioning method.
The method according to claim 1 or 3,
One end of the first reinforcing bar is screwed with the upper flange of the girder and the other end is a rod-shaped headed bar having a cross-sectional enlarged portion is the construction method of pre-stressed concrete bulb girder bridge.
The method according to claim 1 or 3,
The first reinforcing bar is a construction method of prestressed concrete bulb tea girder bridge, characterized in that the one end is a hook-shaped reinforcing bar threaded to the upper flange of the girder.
The method according to claim 2 or 4,
The tendon used for the first prestressing is fixed at both ends of the girder, and the tendon used for the second prestressing is fixed at the end side of the girder.
The method according to claim 1 or 3,
Further comprising a horizontal beam installation step for installing a horizontal beam on the girder,
In the girder manufacturing step, the cross beams are manufactured at the lower portion of the upper flange, and the cross beams of adjacent girders are connected to each other by moments in the field.
Construction method of the pre-stressed concrete bulb tea girder bridge, characterized in that for connecting the moment of the cross beam using a removable rebar.
10. The method of claim 9,
The detachable reinforcing bar is a prestressed concrete bulb girder bridge construction method, characterized in that the reinforcing bar reinforcement, loop-shaped reinforcement or headed bar.
10. The method of claim 9,
The crossbeam is disposed in the transverse direction of the girder construction method of prestressed concrete bulb tea girder bridge, characterized in that the duct is provided for inserting steel rods or tendons.

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