WO2018199528A1 - Prestressed concrete girder - Google Patents

Abstract

The present invention relates to a prestressed concrete girder widely used in a composite girder bridge method, and more specifically, to a prestressed concrete girder in which a girder shape and tendon arrangement and mounting method are optimized so as to minimize the weight of the girder by reducing the thickness of a girder web.

Description

Prestressed concrete girder

The present invention relates to prestressed concrete girders that are widely used in the composite girder bridge method (referred to as "PSC") girders, more specifically, the shape of the girders to minimize the weight of the girders by reducing the thickness of the girder The present invention relates to prestressed concrete girders, which have been optimized for the arrangement and settlement of tension members.

Precast prestressed concrete girders are constructed on the ground, and they are constructed on the substructures such as bridges and shifts, and the deck slabs are constructed on them. Among these composite girder bridge girders, the PSC type I girder (beam) composed of the upper flange, the lower flange and the abdomen is the most commonly used type, and there are pretension and posttension methods in the prestress introduction method. Since they are manufactured in the field, most of them use post-tension method. In the pre-tension method, the strands are individually arranged on the abdomen of the I-girder, but in the post-tension method, the thickness of the abdomen is greater than that of the pretension method because the sheath is arranged in the abdomen to form a duct in which the strand bundle is installed. Thickening Since the abdomen of Type I girders shares most of the shear force on the girders, the thickness should be determined by considering the shear force resistance as well as the placement of tension members.

1A and 1B are typical post-tension PSC type I girder shapes. FIG. 1A is a perspective view and FIG. 1B is a sectional view. PSC Type I girders consist of an I-shaped section consisting of an upper flange and a lower flange, and a thin abdomen connecting the two, except for both ends of the girder (see cross-section BB in FIG. 1 (b)). The cross section of an I-girder refers to this cross section. However, in the case of post-tensioned PSC girders, the cross section must be enlarged at the end of the girder because the anchorage must be installed at the end of the girder. Both ends of the PSC type I girder of FIG. 1 have different shapes, and the right end (section C-C) is a shape that is made of a nearly rectangular shape by increasing the thickness of the abdomen and is most commonly used. The section in which this cross-sectional shape persists is usually called an end block. The edge section is a section that gradually changes to an I-shaped cross section from the end block toward the center of the girder. The end block and edge section sections are generally designed so that the sum of the two sections has a predetermined length so as to alleviate the stress concentration caused by the settlement of tension members and to effectively resist the increasing shear force toward the end of the girder, but the length occupies the entire girder The ratio of is small. In the past, the end block section was long and the short edge section was used in many forms, but recently, the shape of shortening the end block section and lengthening the cross section is longer, as shown in the right side of FIG. This form change is intended to reduce the weight of the girders somewhat. The left end of FIG. 1 (a) (see section AA) is often used when the number of sheaths is increased, so that a large number of anchorages should be placed on the end surface. As the thickness of the abdomen increases gradually in the cross-sectional area, the thickness of the lower flange also becomes thicker. Figure 2 is a PSC type I girder cross section is one of the optimized cross-sectional shape has been used recently, the width of the flange is larger than the past and the thickness is thinner form. 2 shows the main reinforcing bars arranged in the cross-section together with the shear reinforcing bars (stirrup) and also shows how the sheath is arranged.

In the world, the abdominal thickness of PSC type I girder has been mainly used for pretensioning 180mm and 200mm for posttensioning. In Korea, the abdominal thickness of 200mm is used regardless of prestressing. In the case of PSC type I girder, the thinner the abdominal thickness, the better the structural efficiency. In foreign cases, the abdominal thickness was reduced to 150 mm in the pretension method, and the abdominal thickness was reduced to 180 mm in the post tension method. In post-tensioning, the size of the sheath through the abdomen must be reduced to minimize the thickness of the abdomen. As the size of the sheath decreases, the number of sheaths that can be accommodated increases, thereby increasing the number of sheaths. Increasing the number of sheaths increases the amount of material used, but at the same time increases the number of anchorages and tensions, which increases the manufacturing cost of the girder. For this reason, in the case of foreign countries, the method of reducing the abdominal thickness of type I girder is to reduce the thickness of the abdomen by easing the concrete covering regulations of the stirrups and tension materials (sheath) placed on the abdomen regardless of the prestressing method. The method has been mainly used.

The concrete bridge design standard of the road bridge design standard, which defines the domestic bridge design, was originally based on the American design standard, AASHTO. The recent road bridge design standard (2015) is based on the concrete bridge design standard in Europe. The concrete cladding regulations have been strengthened significantly by changing to. In particular, as the bridge's durable regulations increased to 100 years, the concrete cladding regulations for reinforcing bars and prestressing tension members were strengthened, but new post-tension duct attachment rules were added. As a result, the abdominal thickness of the type I girder was increased, and the abdominal thickness of the PSC type I girder, which was mainly 200 mm, was increased to 240 mm, seriously threatening the structural efficiency of the PSC type I girder. For this reason, measures to minimize the thickness of the abdomen of PSC type I girders have recently come to the fore.

Attempts have been made in Korea to reduce the weight of PSC type I girders by reducing abdominal thickness. Patent registration 10-1337330 shown in Figure 3 (PSC beam with optimized abdominal cross section, a method of manufacturing the same and the bridge construction method using the same) and the section (L1, L2) and the tension member (sheath) is arranged in the abdomen in the longitudinal direction of the girder and By dividing all the tension material into the section (L3) that is disposed only in the lower flange, and gradually reducing the thickness of the abdomen from the end to the center portion, while reducing the thickness of the girder by minimizing the thickness of the abdomen of the section (L3) where the tension material is disposed only in the lower flange The method is presented. That is, in the section I section of FIG. 1, a section in which all the tension members are disposed in the lower flange is separated, thereby reducing the abdominal thickness of the section I section. Figure 4 (a) is a conceptual diagram illustrating the limited range of the tension material downtown of the PSC girder limiting the tension material downtown (center of tension) where the concrete stress of the upper and lower girder does not exceed the allowable stress when the tension force is introduced and used in the simple beam structure The range is shown, and both upper and lower limits are parabolic convex down. Figure 4 (b) is a post tension tension tension (sheath) method of placing the tension material in a parabolic form so that the center of the tension material is located within the limits of the center of the tension material, all the tension material is similar to the form of the limited range of the tension material downtown It has a simple parabolic shape with a maximum altitude at the end and a minimum altitude at the center. In order to effectively reduce the weight of the girder in the same manner as in the invention of FIG. 3, the center of the tension member should be placed as close to the lower limit of the limit as possible to increase the length of the section through which the sheath passes only through the lower flange. However, the problem is that the length of the lower limit of the tension limit downtown is less than the lower flange height, the length of the section is not very long, and if the girder is long, the number of sheaths increases (usually 5-6), in which case all sheaths Is virtually impossible to place on the lower flange. In addition, in the invention of FIG. 3, there was no consideration of the minimum thickness (165mm) and the minimum reinforcement of the abdomen of the road bridge design criteria. Considering these points, the weight reduction effect is very limited.

In Patent Application Publication No. 10-1576501 shown in FIG. 5 (a), a tensioning sheath is placed only on the lower flange of which thickness is increased at the end of the girder, and an uncoated coated strand is used at the end of the upper flange. By arranging the strand assembly, it is possible to minimize the thickness of the abdomen by configuring the abdominal material not to pass through the abdomen, thereby reducing the girder weight. However, the cross section of the recently optimized PSC type I girder is much wider and the upper and lower widths of the upper and lower flanges are smaller than the cross section of the I type in the past as shown in FIG. In particular, because the thickness of the upper flange is very thin and difficult to install the strand assembly due to the concrete coating thickness specification, the method such as the invention of FIG. 5 (a) cannot use the latest optimized type I cross-sectional shape. In addition, since the strand assembly requires a certain amount of space not only for the tension end but also for fixing the fixed end, the number of the strand assembly can be installed in the upper flange, but the number of the strands arranged in the upper flange is arranged in the lower flange. Since the height is very small compared to the athletes, the height to raise the center of the entire tension member by using the strand placed on the upper flange is very limited. To satisfy the limit of the tension center, the center of the tension member disposed on the lower flange must be raised considerably. Therefore, the thickness of the lower flange has to be enlarged at a considerably long end section, and the width of the lower flange is large, thereby increasing the weight of the girder. In addition, the strand assembly is expensive because it is difficult to manufacture, and it controls the phase stress at the end of the girder and does not contribute to the introduction of prestress in the lower part of the girder which determines the structural efficiency of the PSC. . Therefore, this method is suitable for PSC type I girders of the pretension type as shown in Fig. 5 (b). In the pretensioning method, a portion of the strands arranged in the lower flange at the girder can be debonded to reduce the effective instructor, so that the center of the tension member can be considerably raised at the ends even with a small number of strand assembly placed at the top. Because it can. However, this method is based on the pretension method with debonding. The pretension method was originally developed based on factory manufacturing. Due to the strict restrictions on road vehicles in Korea (total weight less than 40 tons), it is not possible to manufacture PSC type I girders (typically 50 to 150 tons) that weigh more than 40 tons of girders themselves. Should be implemented in The pretensioning method should be able to supply high-strength crude steel concrete, require a huge reaction table, and have a crane to be stationed during the manufacturing process.In spite of many advantages, it is rarely used in the manufacture of PSC type I girder for bridges in Korea. That's the way it is.

In addition, the technology of materials related to PSC type I girder has been gradually developed in Korea. In the case of concrete, concrete with a compressive strength of 35MPa was used in the early stages of the introduction of PSC girders, but 40MPa was mainly used in recent years, but recently, 45MPa concrete can be supplied anywhere in the country. In addition, the tensile strength of 7 strands used as post tension PSC type I girder tension strength starts from 1,500 MPa class (SWPC7A), 1860 MPa class (SWPC7B), 2160 MPa class (SWPC7C), and recently 2,400 MPa class (SWPC7D) stranded wire. It is supplied. Therefore, the development of efficient PSC type I girder is required in spite of the strengthening regulations of road bridge design standards by taking full advantage of the development of this material technology.

The present invention has been made to solve the above-mentioned problems of the background art, and the present invention, despite the reinforced concrete coating regulations of the revised road bridge design standard (2015), utilizes the latest advanced material technology to post-tension (post- By minimizing the abdominal thickness of the tension type PSC type I girder, it reduces the weight of the girder and reduces the number of sheaths. To provide prestressed concrete girders.

As a first means of solving the above problems,

In prestressed concrete girder,

A central section having an I-shaped cross section including an upper flange, an abdomen, and a lower flange and being long in one direction;

A pair of edge face portions having an I-shaped cross section including an upper flange, an abdomen, and a lower flange, each extending from both ends of the central portion and increasing in thickness and extending in the extending direction of the lower flange;

A body made of reinforced concrete material comprising a pair of end blocks extending from each of the pair of edge faces;

It is disposed on the lower flange of the end block of the main body and the lower end portion and the central portion of the lower portion of the main body is disposed at the highest and the lowest in the middle, both ends of the lower end of the pair of end blocks, respectively, in the tension applied A first tension material to be fixed;

It is disposed on the upper flange of the end block of the main body and the upper end portion or the upper flange, the abdomen or the lower flange of the abdomen and the center portion, the height from the end of the main body to any point near the boundary between the edge and the central portion The second tension material is forged to increase and the height from the highest point to the center of the center portion is arranged to decrease the forging, both ends are fixed to the upper portion of the pair of end blocks, respectively, in the tension force is applied;

A first sheath pipe for accommodating the first tension material; And

It provides a prestressed concrete girder comprising a; a first fixing tool for fixing the first tension material and a second fixing tool for fixing the second tension material.

The present invention is in its second form,

In prestressed concrete girder,

A central section having a box-shaped cross section including an upper flange, a pair of abdomen and a lower flange, and being long in one direction;

A pair of edge portions having a box-shaped cross section including an upper flange, a pair of abdomen and a lower flange, each extending from both ends of the central portion and increasing in thickness in the direction of extension of the lower flange;

A body made of reinforced concrete material comprising a pair of end blocks extending from each of the pair of edge faces;

It is disposed on the lower flange of the end block of the main body and the lower end portion and the central portion of the lower portion of the main body is disposed at the highest and the lowest in the middle, both ends of the lower end of the pair of end blocks, respectively, in the tension applied A first tension material to be fixed;

It is disposed on the upper flange of the end block of the main body and the upper end portion or the upper flange, the abdomen or the lower flange of the abdomen and the center portion, the height from the end of the main body to any point near the boundary between the edge and the central portion The second tension material is forged to increase and the height from the highest point to the center of the center portion is arranged to decrease the forging, both ends are fixed to the upper portion of the pair of end blocks, respectively, in the tension force is applied;

A first sheath pipe for accommodating the first tension material; And

It provides a prestressed concrete girder comprising a; a first fixing tool for fixing the first tension material and a second fixing tool for fixing the second tension material.

The third aspect of the present invention is that

In prestressed concrete girder,

A central portion having a U-shaped cross section including a pair of upper flanges and an abdomen, and a lower flange connecting the pair of abdomens to each other;

It has a U-shaped cross section including a pair of upper flanges and the abdomen, and a lower flange connecting the pair of abdomen with each other extending from both ends of the central portion and the thickness of the lower flange and the thickness of the abdomen increases as the direction extends. And a pair of side faces

A body made of reinforced concrete material comprising a pair of end blocks extending from each of the pair of edge faces;

It is disposed on the lower flange of the end block of the main body and the lower end portion and the central portion of the lower portion of the main body is disposed at the highest and the lowest in the middle, both ends of the lower end of the pair of end blocks, respectively, in the tension applied A first tension material to be fixed;

It is disposed on the upper flange of the end block of the main body and the upper end portion or the upper flange, the abdomen or the lower flange of the abdomen and the center portion, the height from the end of the main body to any point near the boundary between the edge and the central portion The second tension material is forged to increase and the height from the highest point to the center of the center portion is arranged to decrease the forging, both ends are fixed to the upper portion of the pair of end blocks, respectively, in the tension force is applied;

A first sheath pipe for accommodating the first tension material; And

It provides a prestressed concrete girder comprising a; a first fixing tool for fixing the first tension material and a second fixing tool for fixing the second tension material.

In the three forms of invention,

It is preferable that the height change of the upper portion of the lower flange of the side of the cross section is convex downward.

More preferably, the downwardly convex curve has an arc shape with a constant radius of curvature.

The height change of the upper side of the lower flange of the edge portion may be configured in a straight shape.

It is preferable to further include a second sheath tube for accommodating the second tension material.

Part of the second tension member is a coated stranded wire, and more preferably further includes a second sheath tube for accommodating the stranded stranded wire.

According to the present invention, despite the strengthened concrete covering regulations of the recently revised Road Bridge Design Standard (2015), the shape of prestressed concrete girder and the arrangement and fixing method of tension members are improved, and the post-tension ( By minimizing the abdominal thickness of post-tension type PSC girders, it is possible to provide a PSC girder that maximizes structural efficiency and cost efficiency while reducing the weight of the girders and reducing the number of sheaths.

1A and 1B are respectively a perspective view and a cross-sectional view of a typical PSC type I girder of the prior art;

Figure 2 is a cross-sectional view and a back view of a typical PSC type I girder.

3 is a perspective view of a PSC type I girder for reducing abdominal thickness in a conventional multi-step manner.

Figure 4 (a) is a view for explaining the limitation range of the tension material downtown of the PSC girder having a simple beam structure (front view).

Figure 4 (b) is a view for explaining the arrangement method of the typical tension member in the post-tension method (front view).

Figure 5 (a) is a view of a conventional post-tension PSC type I girder to reduce the abdominal thickness.

Figure 5 (b) is a view of a conventional PSC type I girder reducing the abdominal thickness.

Figure 6 (a) is a perspective view of a prestressed concrete girder (L = 40m, type I) according to one embodiment of the first form of the present invention.

(B), (c), (d) is a front view, a plan view, and a sectional view for explaining the tension member arrangement of the prestressed concrete girder shown in FIG. 6 (a), respectively.

Figure 7 (a) and (b) is a view for explaining the spirit and principle of the tension member arrangement method of the present invention.

8 is a view for explaining a process of calculating the lower limit of the city limits of the tension material of the present invention.

9 is a view for explaining the stress distribution type of the lower edge of the PSC type I girder of the present invention.

10a to 10d are stress distribution diagrams of the lower edge of the girder immediately after the introduction of the tension force of the PSC type I girder, respectively designed L = 35m, 50m, 55m, 25m in accordance with the present invention.

Figure 11 (a) is a perspective view of a PSC type I girder designed L = 55m in accordance with the first aspect of the present invention.

(B), (c), (d) is a front view, a top view, and sectional drawing for demonstrating the tension material arrangement | positioning of the prestressed concrete girder shown in FIG. 11 (a), respectively.

Figure 12 (a) is a perspective view of a PSC type I girder designed L = 30m in accordance with the first aspect of the present invention.

(B), (c), (d) is a front view, a top view, and sectional drawing for demonstrating the tension material arrangement | positioning of the prestressed concrete girder shown in FIG. 12 (a), respectively.

FIG. 13A is a diagram for explaining the structure of a coated stranded wire; FIG.

Figure 13 (b) is a view for explaining a method of using a coated strand as a second tension member of the PSC type I girder of the first aspect of the present invention.

FIG. 14 is a front view for comparing a case where the thickness change of the lower flange is linear and a case where the thickness of the lower flange is in the cross-sectional area of the PSC type girder designed as L = 25m in the first form of the present invention.

Figure 15 is a perspective view for explaining an example of the various forms of the PSC type I girder end block and the anchorage installation method of the first aspect of the present invention.

Figure 16 is a perspective view for explaining the end-cutting form of the PSC type I girder and the anchorage installation method of the first form of the present invention.

Figure 17 (a) is a view for explaining a method for converting the cross section of the hollow box cross-section to the I-shaped cross-section of the same cross-sectional characteristics in the equations to define the limit of the center of the tension material through cutting and recombination.

Fig. 17 (b) is a view for explaining a method for converting a cross-sectional characteristic value into an I-shaped cross section in equations defining a restriction range of the tension center through cutting and recombination of the U-shaped cross section.

Figure 18 (a) is a perspective view of a prestressed concrete box girder according to one embodiment of the second aspect of the present invention.

(B), (c), (d) is a front view, a top view, and sectional drawing for demonstrating the tension material arrangement | positioning of the prestressed concrete girder shown in FIG. 18 (a), respectively.

Figure 19 (a) is a perspective view of a prestressed concrete U-shaped girder according to one embodiment of the third aspect of the present invention.

(B), (c), (d) is a front view, a top view, and sectional drawing for demonstrating the tension material arrangement | positioning of the prestressed concrete girder shown in FIG. 19 (a), respectively.

Figure 6 (a) is a perspective view of a prestressed concrete girder (L = 40m, type I) according to one embodiment of the first aspect of the present invention, Figure 6 (b), (c), (d) is A front view, a plan view, a cross-sectional view, and FIGS. 7A and 7B illustrate the tension member arrangement of the prestressed concrete girder shown in FIG. 6A, respectively. 8 is a view for explaining a lower limit calculation process of the tension material downtown limit range of the present invention, Figure 9 is a view for explaining the stress distribution type of the lower edge of the PSC type I girder of the present invention, Figure 10a to Figure 10d is a stress distribution diagram of the lower edge of the girder immediately after introduction of the tension force of the PSC type I girder designed as L = 35m, 50m, 55m, and 25m, respectively, according to the present invention, and FIG. 11 (a) shows L = according to the first aspect of the present invention. A perspective view of a PSC type I girder designed at 55 m, FIGS. 11B, 11C, and 11D, respectively, illustrate the frist shown in FIG. 12A is a front view, a plan view, a sectional view for explaining the tension member arrangement of the strut concrete girder, and FIG. 12A is a perspective view of a PSC type girder designed as L = 30m according to the first aspect of the present invention, and FIG. , (c), (d) is a front view, a plan view, a cross-sectional view for explaining the tension member arrangement of the prestressed concrete girder shown in Fig. 12 (a), respectively, and Fig. 13 (a) describes the structure of the coated steel wire 13 (b) is a view for explaining a method of using a coated strand as a second tension member of a PSC type I girder, which is the first form of the present invention, and FIG. 14 is an L as the first form of the present invention. Front view for comparing the case where the thickness of the lower flange is linear and curved in the cross-sectional area of the PSC type I girder designed to = 25m, Figure 15 is the first type of PSC type girder end block of the present invention To explain an example of the various forms and installation of the anchorage Try. Figure 16 is a perspective view for explaining the end-cutting form of the PSC type I girder and the fixing fixture installation method of the first embodiment of the present invention.

Prestressed concrete girder according to an embodiment of the first aspect of the present invention is a type I girder body 1, the first tensioning material 100, the second tensioning material 200, the first sheath pipe 150, the second sheath The pipe 250 is configured to include a first fixing unit 310 and a second fixing unit 320.

The main body 1 is made of a reinforced concrete material and comprises a central portion 10, a pair of end face portions 20, a pair of end blocks 30, shown in Figure 6 (a) As described above, the end block 30, the end face portion 20, the center portion 10, the end face portion 20, and the end block 30 are disposed in this order.

The central portion 10 has an I-type cross section including an upper flange 11, an abdomen 12, and a lower flange 13 as in the DD cross section shown in FIG. 6D and is formed to be long in one direction. It is arranged at the center side of the main body 1 as an example.

The edge end portion 20 extends from both ends of the central portion 10, and the upper flange 21, the abdomen 22, the lower flange 23, as shown in the cross-sectional view BB shown in Figure 6 (d). It has a form including a and the thickness of the abdomen 22 and the lower flange 23 increases in the direction extending from the center portion, that is to say toward the end of the body (1).

The thickness of the lower flange 23 may be formed in various ways. The lower flange 23 may be formed in a straight line, such as the lower flange 23a on the left end of FIG. 14. It may be configured in a curved shape like the lower lower flange (23b) (23a, 23b is a division for convenience of description), in this embodiment as shown in Figure 6 to the curved shape of the arc shape constant curvature radius To configure.

When the thickness of the lower flange 23 of the cross section changes in a curved shape, there is an advantage that it is easy to reduce the weight of the girder and the aesthetics are also beautiful. However, this is possible because the first tension member 100 is disposed in the shape of a curve (parabola) at the edge end portion 20. (Typically, the tension member is disposed in the form of a parabola.) Since the first tension member 100 is disposed in the form of a curve, the first tension member 100 may be changed even when the thickness of the lower flange 23 of the edge portion 20 changes in a curved shape. Since it is possible to secure the concrete coating thickness of), it can be manufactured in a curved form.

On the other hand, in order to manufacture the lower flange 23 of the cross-sectional surface portion may be accompanied by some difficulties in manufacturing the formwork. In general, the formwork of the girder is made of steel sheet, but in order to produce the lower flange 23 of the edge section 20 using a steel sheet pre-processed with a roller, the same curvature radius is produced when the arc shape is constant. In this embodiment, the upper flange of the lower flange 23 of the edge portion 20 may have an arc shape with a constant radius of curvature so that the manufacturing may be easily performed.

The end block 30 extends from the pair of end face portions 20 and is configured to have a pair, and may have various types of cross-sections. In this embodiment, the end face portion as shown in FIG. It is a shape in which the same cross section as the form of the end side of the main body 1 of the main body 20 is maintained.

The first tension member 100 is generally used as a configuration disposed in the lower portion of the end block 30, the end face portion 20 and the lower flanges 13 and 23 of the central portion 10 of the body (1). Strands can be used. At this time, in order to design the main body 1 efficiently by reducing the number of stranded wires, it is preferable to use a stranded wire with a tensile strength of 2400MPa (SWPC7D Φ15.2mm), and use a stranded wire with a tensile strength of 2400MPa (SWPC7D Φ15.2mm). The design method will be described later in the design example.

The vertical arrangement of the first tension member 100 is the highest at both ends of the main body 1 and the lowest in the center, as shown in FIGS. 6B and 6D, whichever of the main body 1 is disposed The altitude is gradually decreased in the end block and the end face section of the end portion of the end portion of the central portion 10, the altitude does not change, and is substantially symmetrically arranged with respect to the center of the body 1, and the tensile force is Both ends are fixed to the main body 1 by the first fixing holes 310 in the applied state. Since the first fixture 310 is generally used for prestressed concrete girder, further description thereof will be omitted.

The left and right direction arrangement of the first tension member 100 is spread from side to side in the end block 30 and the end surface portion 20 section as shown in (c) and (d) of FIG. In the form of maintaining a constant interval in the girder width direction is arranged substantially symmetrical with respect to the center of the main body (1).

The arrangement of the first tensioning material 100 is illustrated by a blue line in FIG. 6 (b), and the arrangement of the first tension material 100 can also be confirmed in the cross-sectional view of FIG. 6 (d). The first tension member 100 is installed in a state accommodated in the first sheath tube 150, and in the drawing, the first tension member 100 accommodated in the first sheath tube 150 and the first sheath tube 150. Is shown by one line, and is indicated by reference numeral 100 (150).

The second tension member 200 is the upper portion of the end block 30, the upper flange 21 or the abdomen 22 of the cross-sectional surface portion 20, the upper flange 11 of the central portion 10, the abdomen 12 or It is disposed over the lower flange 13 and is shown in red in the drawing for clear separation from the first tension member 100. The second tension member 200 is a structure in which both ends are fixed to the main body 1 by the second fixing holes 320 in a state where a tensile force is applied, and is accommodated in the second sheath tube 250.

In the present embodiment, the second tension member 200 uses a stranded wire having a tensile strength of 2400 MPa class (SWPC7D Φ15.2 mm), similar to the first tension member 100, and in some cases, an unattached strand may be used, which will be described later. do.

The arrangement of the second tension member 200 in the vertical direction is monotonically increased from the end of the main body 1 to the highest point P, which is one point near the boundary between the end face 20 and the center 10, and then the main body (from the highest point). In the present embodiment, the forging is reduced to the center of 1), and in the present embodiment, the height is reached from the middle of the cross section 20 to the highest point P near the boundary between the cross section 20 and the center 10. While maintaining the height is configured to continue to go down the highest point (P) to the central portion of the main body (1). Mathematically, if a value does not decrease in the defined interval, it is called monotone increasing, and if it does not increase, it is called monotone decreasing.

Since the thickness of the abdomen 12 of the central portion 10 may be reduced by vertically arranging the first tension member 100 and the second tension member 200, the technical spirit of the above-described arrangement and the effects thereof will be described below. It will be described in detail.

7 (a) and 7 (b) are views for explaining a method of arranging the first and second tension members 100 and 200, the shape of the main body 1 and the first tension member 100 and the second tension member. Since the arrangement form of 200 is symmetrical in the longitudinal direction with respect to the center of the main body 1, only half of the girder length is illustrated, and arbitrary ratios are used in the height and the longitudinal direction according to the position for convenience of illustration. The dotted lines in the figure indicate the upper ends of the lower flanges 13 and 23.

As described above, the first tension member 100 is arranged in a curved shape in which the altitude gradually decreases toward the center from the end of the girder in the section of the end block 30 and the edge section 20, and the lower flange 13 in the section of the central section 10. Are arranged in a straight line at a constant altitude.

When the first tension member 100 is disposed in this form, when the lower limit line of the tension member city center limit range as shown in FIG. 4 (a) is shown together, the lower limit of the tension center city limit line and the tension center city limit line of the first tension member The distance to the LL (lower limit line in the drawing), that is, the height (distance elevation difference) at which the center of the entire tension material (the center of the first tension material and the second tension material as a whole) should be lifted, can be known. A vertical line indicated by A in FIG. 7 (a) is a spaced altitude difference, which is the maximum value near the boundary between the edge end portion 20 and the center portion 10, and toward the end or the center of the main body 1 toward the center thereof. Its size gradually decreases.

In proportion to the vertical distance from the city center 101 of the first tension material to the city center 201 of the second tension material, the city center of the entire tension material rises up from the city center 101 of the first tension material, and the edge section 20 Since the separation altitude difference is the largest in the vicinity of the boundary of the central portion 10, the inner city 201 of the second tension member needs to be disposed highest in the vicinity of the boundary between the edge end portion 20 and the central portion 10. On the other hand, in order to fix the second tension member 200, a predetermined fixing area must be secured to the end surface of the main body 1, so that the fixing position of the second tension member 200 should be spaced apart from the upper end of the main body 1 by a predetermined distance. The requirements must also be met.

For this reason, the second tension member 200 increases forging up to the highest point P, which is a point near the boundary between the edge end portion 20 and the central portion 10, and forgings from the highest point P to the center of the main body 1. It is arranged to reduce the most ideal arrangement is the highest point (P) near the boundary between the edge section 20 and the center portion 10 after reaching the maximum height within the edge section as shown in Fig. 7 (a) While maintaining the same height up to), to the center of the body (1) continues to be arranged so that the altitude decreases.

In the case where the tension of the appropriate size optimally designed is applied to the PSC I-shaped section that is optimally designed by the conventional design method, the center of the first tension member 101 at the end and the center of the main body 1 is not lower than the lower limit (LL). Since it is disposed above or very close to the end of the main body 1, even if the altitude of the second tension member 200 is lowered, the entire tension center is not lower than the lower limit LL of the tension center.

In addition, since the separation altitude difference decreases toward the center of the main body 1, the second tension member 200 passes through the boundary between the edge end portion 20 and the center portion 10 so that the altitude decreases gradually to reach the lowest point from the center of the girder, thereby releasing the center. It is configured to have a parabolic shape that can contribute as much as possible to the introduction of compression prestress of lower smoke.

The arrangement method of the second tension member 200 is significantly different from that of the conventional tension member arrangement method having a simple parabolic form in which the altitude decreases gradually from the end to the center as shown in (b) of FIG. 4. In the case of the conventional simple beam structure PSC type I girder, all the tension members start at the end of the girder and the elevation change to the center of the girder is monotone decreasing, whereas the elevation change of the second tension member 200 of the present invention is the main body. (1) Begin at the end and monotonically increase to the boundary between the edge section 20 and the central section 10 and monotonically from the boundary between the edge section 20 and the center section 10 to the center of the body 1. As a decreasing form, it is a new idea that has not been found in the case of conventional PSC type I girder.

In FIG. 7 (a), the lower limit of the tension limit downtown range is a case where a constant cross-sectional shape is maintained over the entire length of the girder. By the way, the main body 1 of the present invention includes a cross-sectional surface portion 20 and the end block 30, so the cross-sectional shape is not constant, so it is necessary to examine this.

The following equations ⓐ to ⓓ are equations defining the limits of tension centers.

..................... ⓐ

...................... ⓑ

......................... ⓒ

....................... ⓓ

Where M _t is the acting bending moment during use, M _d1 is the bending moment due to the girder weight, Z _t and Z _b are the cross-sectional coefficients for the upper and lower girders, A _c is the cross-sectional area of the girder, and σ _ti and σ _ci are The allowable tensile stress and allowable compressive stress of concrete under stress, σ _ts and σ _cs , respectively, are the allowable tensile stress and allowable compressive stress of concrete during use, P _i is the introduction tension and R is the effective rate of tension. Equations ⓐ and ⓑ determine the lower limit of the tension eccentric distance using equations obtained from the allowable stress conditions immediately after the introduction of prestress. The limit of the eccentric distance of the tension member is determined by equations ⓑ and ⓓ.

Figure 4 (a) is a representation of the form of the typical tension range limits defined by equations (ⓑ) and (ⓓ) when the cross-sectional shape is constant over the entire length of the girder, the lower limit (LL) shown in (a) of FIG. Also shown based on this. In the case of the present invention, since the center of the entire tension member is located close to the lower limit of the tension center, the equations ⓐ and ⓑ that determine the lower limit are important, and the lower limit of the tension center is relatively higher among the curves obtained by equations ⓐ and ⓑ. Is located on the curve.

When calculating the lower limit of the limiting range of the tension material downtown to the shape of the main body 1 of the present embodiment shown in Figure 6 is the same as shown in Figure 8 but the thick solid line in Figure 8 is a graph in consideration of the cross-sectional change, The graph indicated by the dotted line is when the cross-sectional change is ignored. As can be seen in FIG. 8, the lower limit is determined by Equation ⓑ in the center 10 section, but the lower limit is determined by Equation ⓐ in most of the section 20 and the end block 30. As shown in FIG. 7B, the lower limit LL of the tension member city center and the city centers 101 and 201 of the tension member are redrawn in consideration of the cross-sectional change.

Considering the change in the cross section (Fig. 7 (b)) is spaced apart from the end block 30 section and the edge section 20 section compared to the case of not considering the change in the cross section (Fig. 7 (a)) Since there is only a difference in the altitude difference is small, even if the arrangement of the first tensioning material 100 and the second tensioning material 200 described above can be disposed above the lower limit (LL) of the downtown of the entire tension material.

The present invention is an invention for maximizing the structural efficiency of the girder by minimizing the abdominal thickness of the girder (in this embodiment, the thickness of the abdomen 12 of the central portion 10) within the range that satisfies the road bridge design criteria. Reducing the thickness of the abdomen requires minimizing the number of tensions placed on the abdomen. According to this request, in the present invention, the tension member is disposed separately from the first tension member 100 and the second tension member 200. The first tensioning member 100 is disposed in the lower portion of the end block 30, the end surface portion 20 and the lower flanges 13 and 23 of the central portion 10, it is not disposed in the abdomen. However, in the case of such an arrangement, in some sections, the center of the first tension member 100 may be disposed below the lower limit of the center of the tension member. (Refer to (a) or (b) of FIG. 7) In order to solve this problem, in the section in which the downtown 101 of the first tension material is below the lower limit of the tension material, the entire tension material is increased by increasing the city center 201 of the second tension material as much as possible. The center of gravity is to be placed above the lower limit of the tension center.

On the other hand, the second tension member 200 is inevitably disposed in the abdomen 12 of the central portion 10 in some sections, the number of the strands used as the second tension member 200 is very important variable. Since the thickness of the abdomen 12 of the center portion 10 can be reduced only by the diameter of the second sheath tube 250, the number of the strands used as the second tension member 200 is better. In order to arrange a large number of strands while using the second sheath pipe 250 having a small diameter, the number of second sheath pipes 250 may be increased, but this may lead to an increase in the related construction cost. Ideally, only one) is used. Reducing the number of strands used as the second tension member 200 inevitably reduces the tension applied to the main body 1. This problem is solved by increasing the number of the first tension members 100. In the present invention, the first tension member 100 is disposed only on the lower flanges 13 and 23 having a thickness greater than that of the abdomen, and the meaning that the first tension member 100 is disposed on a relatively thick member is advantageous to secure a concrete coating thickness, so that the second sheath pipe 250 Compared to), a sheath having a large diameter may be used as the first sheath tube 150. As the diameter of the sheath tube increases, the number of lecturers that can be accommodated increases in proportion to the square of the diameter, so that the first sheath tube 150 increases the number of strands that can be accommodated by using a product having the maximum diameter within the allowable range. desirable. Of course, at this time, it is also possible to expect the effect of reducing the construction cost by reducing the number of the first sheath tube 150 arranged by using a large diameter of the first sheath tube 150.

Hereinafter, the effects of the present invention will be described while comparing some examples of design of the girder according to the present invention and a comparative design example which is generally used.

Table 1 below summarizes the design results of the design example according to the present invention and the control design example according to the existing method in a table for easy comparison.

Principal (L) [m]	Design example according to the present invention				Contrast design example (existing modified PSC type I girder)
	Mold height [mm]	Abdominal thickness [mm]	Sheath number	Weight [ton]	Mold height [mm]	Abdominal thickness [mm]	Sheath number	Weight [ton]
25	1,000	180	3	35	1,100	240	5	46
30	1,200	180	3	46	1,200	240	5	57
35	1,500	180	3	62	1,500	240	5	73
40	1,800	180	3	78	1,800	240	5	92
45	2,200	180	3	98	2,200	240	5	116
50	2,500	180	3	121	2,500	240	5	136
55	2,700	180	4	138	2,700	240	6	156

[Table] Summary table of design examples according to the present invention and contrast design examples according to the existing method

First, the advantages of the present invention will be described by comparing two design examples after explaining the material properties of the design according to the present invention and the design of the existing method, the size of the sheath pipe, and the like. The design standard bridge summarized in the table is a four-week simple bridge with a width of 10.9m, the national standard bridge, and the design standard of 1st bridge was applied.

In the design example according to the present invention, a 60 mm sheath (based on the inner diameter) was used as the second sheath tube 250. Up to 10 15.2mm 7 stranded wires (SWPC7D Φ15.2mm) can be inserted into the 60mm sheath, and 9 stranded wires are designed for ease of operation. The abdominal thickness of at least 240 mm is required for 80 mm sheaths that are commonly used in PSC type I girders due to the thickness of the coating covering more than the duct diameter (sheath pipe inner diameter) required by the Road Design Standard (2015). It is possible to design the abdominal thickness to 180mm. (The concrete cover thickness of reinforcing steel 40mm (environmental condition ED1, compressive strength 45MPa concrete), the sum of the diameter of 13mm of shear reinforcement steel (D13) and sheath thickness 2mm is 55mm, so even if 60mm sheath is used, Dominates the abdominal thickness.)

In order to maximize the role of the second tension member 200, it is necessary to reduce the total number of strands using high-strength strands, if possible, and designed using a strand of tensile strength of 2400 MPa (SWPC7D Φ15.2 mm). ) As a sheath tube 150, a sheath tube of up to 100 mm diameter was used. The girder concrete uses 45MPa of compressive strength to increase the girder performance. The higher the compressive strength of the concrete used, the higher the structural efficiency of the girder. The reason for limiting the compressive strength to 45MPa is that 45MPa concrete is the largest concrete compressive strength that can be supplied anywhere in the country.

In relation to the number of arrangement of the first sheath pipe 150 and the second sheath pipe 250, from L = 25m to L = 50m, two sheath pipes are used to accommodate the first tension material 100 and the second tension material It is designed to use one sheath to accommodate (200). The PSC type I girder of the present invention was able to accommodate both the first tension member 100 using only two sheaths, but there was a reason to reduce the total lecturer by using a high-strength strand, but the first tension member 100 had a lower flange ( This is because it can be designed using a sheath having a large diameter because only 13, 23) passes.

On the other hand, the less the second tension material 200 disposed in the abdomen, the less the thickness of the abdomen, but the problem occurs when the second tension material 200 is less than a certain amount will be described. (This problem is different from the limits of the center of the entire tension material described above.) The compression prestress of the lower girder that occurs when the lecturer used as the second tension member 200 is fixed regardless of the total number of designed strands. Figure 9 shows the distribution of. 9 is a stress distribution of the lower edge of the girder immediately after the introduction of the prestress, and the bending stress distribution due to the girder self-weight, which can be divided into three types and is classified according to the ratio of the second tension member 200 among the total tension members. The curve labeled Type 1 is a flexural stress distribution when the ratio of the second tension member 200 to the total tension member is relatively large. The compressive stress at the center of the girder dominates the stress design, and the curve labeled Type 2 is relative to Type 1 As a result of the bending stress distribution when the ratio of the second tension member 200 is reduced, the compressive stress in the center portion 10 is substantially constant, and in this case, the stress at the center of the girder dominates the design. The curve shown as type 3 is a bending stress distribution diagram when the ratio of the second tension member 200 is smaller than that of type 2, and the compressive stress at the edge section point (the boundary between the edge section section and the center section) is the largest and the stress here is stressed. Dominate the design. It is structurally efficient when designed as Type 1 and Type 2, but in Type 3, it can be said that it does not utilize the maximum performance of concrete because the compressive stress at the center is smaller than the allowable stress, and the structural efficiency is not good. In general, if an appropriate type I cross-section is determined and a type height is selected for the girder length, the efficiency of the PSC type I girder depends on the size of the compression prestress that is introduced at the lower edge of the girder at tension. In the case of simple beam structure PSC girders, the amount of load that can be supported by the PSC girders because the tensile stress of parabolic shape (curve indicated by the dotted line in Fig. 9), which is maximized at the center of the girders, acts on the lower edge of the girders. Is proportional to the size of the compression prestress introduced at the center of the girder, so that after the introduction of the prestress, the girder weight must be the largest at the center of the girder and the PSC girder can support it when the stress is equal to the permissible stress (fca). The load that is present becomes the maximum. Therefore, when the compressive stress at the lower edge of the girder is designed as Type 1 and Type 2, which dominates the stress design, the PSC girder's performance is fully utilized because it can support the flexural tensile stress such as the curve indicated by the "parabolic parabola" in the median. In the case of the design of type 3, the performance of the PSC girder is not fully utilized because it can only support the flexural tensile stress such as the curve indicated by the "small parabola" as the median. Therefore, the ratio of the second tension member 200 among the total tension members should be maintained at least to the extent shown in Type 2, and thus the number of the strands used as the second tension members should also increase as the total number of the strands arranged.

The control design example is a new type PSC type I girder bridge construction method which is known to have the largest number of bridge applications in Korea. Compressive strength 40MPa concrete, 80mm sheath pipe, tensile strength 2160MPa class (SWPC7C Φ15.2mm) ) It is using stranded wire and uses two-stage tensioning method before and after girder mounting to increase structural efficiency. The comparative method uses a sheath of 80 mm, so the abdominal thickness is 240 mm. (In the control design example, the 80mm sheath tube is used in the abdomen because most of the sheath passes through the abdomen. When the 60mm sheath tube is placed to reduce the thickness of the abdomen, the number of sheaths increases exponentially and the sheath increases. This is because the number of fixing devices increases according to the number of pieces, and the amount of work increases with the increase in quantity, and it may become impossible to arrange the fixing devices in the present invention. Since the number of the second strands 200 is less, it is possible to design using a 60mm sheath pipe.)

As can be seen in Table 1, the girder designed according to the present invention is significantly reduced in weight (11% to 24%) compared to the girder designed according to the control design, it can be seen that the number of sheath pipes used is also reduced. In addition to the cost of materials, the reduction in the number of sheaths has the effect of reducing the cost due to the reduction of tension work as well as reducing the loss of tension due to elastic shortening during tension. Although the total number of strands used is not directly comparable due to different tensile strength grades of strands used, they are not shown in Table 1, but are estimated to decrease by the weight reduction of the girder at full load.

Hereinafter, the design method and results of the design example for each principal (girder length) will be briefly described.

First, in the design example of the present invention summarized in Table 1, except for L = 25m and L = 55m, the design of fixing the lecturer of the second tension member 200 to 9 and only changing the lecturer of the first tension member 100 Method was used. When the height of the bridge is determined, the tension to be introduced is determined and the number of strands to be used according to the tension is introduced. As described above, the number of strands is fixed to 9 and the number of strands to be used is adjusted by adjusting the number of strands 100 to be used according to the principal and sentence, L = 25m. In this case, the total number of lecturers is relatively small, and the number of second tension members 200 is designed to use eight. In the case of L = 55m, the number of total strands is large, so that the 16 second strands are used as the second tension members 200. Designed. In the design example except for L = 25m and L = 55m, even though the lecturer used as the second tension member 200 is fixed to nine, the design corresponds to the above-described type 1 or type 2, which will be described later.

6 is a diagram illustrating a method of disposing a main body 1, a first tension member 100, and a second tension member 200 when the principal is designed to have 35, 40, 45, and 50 m. Figure is shown.

Figures 10a and 10b shows the stress distribution of the lower edge of the girder immediately after the tension when the principal is 35m and 50m, respectively. In the case where the principal shown in FIG. 10A is 35m, the type 1 shown in FIG. 9 is close to the type 1 shown in FIG. 9, and the 50m shown in FIG. 10B shows a stress distribution similar to the boundary between the type 2 and the type 3 shown in FIG. This is because the number of strands used as the second tension member 200 is less than 50m as compared to the overall lecturer. (The difference between the stress at the edge of the cross section and the center and the stress magnitude at the center of the girder is important. The distribution can be adjusted by changing the placement profile of the second tension member between the two points if necessary.) In both cases, the compressive stress at the center of the body 1 dominates the stress design from a practical point of view. The compressive strength of the concrete used in the design example according to the present invention is 45MPa and the allowable stress is 27MPa. As can be seen in the drawing, there is a margin of stress (more than 10%), and the margin is a condition change during transportation or construction of the girder. Considering the lack of concrete curing, it is necessary.

11 is a view showing the shape of the main body 1 designed by the principal of 55 m and the arrangement of the first tension member 100 and the second tension member 200. In the case of L = 55m, since the number of tension members used increases, the number of second tension members 100 must be increased together to avoid the type 3 of FIG. 9. In order to increase the number of strands arranged in the second tension member 200, the diameter of the sheath tube should be increased or the number of sheath tubes arranged should be increased. In the case of L = 55m, the thickness of the abdomen 12 is not increased in order to increase the thickness of the abdomen 12. It was designed to accommodate a total of 16 strands as the second tension member 200, 8 per sheath, using two tubes. Since two first sheath pipes 150 and two second sheath pipes 250 are used, a total of four sheaths are used. The conventional L = 55m PSC type girder uses at least six sheaths. In light of this, the PSC girder of the present invention can still be said to have excellent economic efficiency. Even in the case of using two sheaths for the second tension member 200, the principle of placement is the same as using one sheath from the side of the city of the second tension member. The only difference is that the minimum spacing between sheaths and the minimum spacing between the sheaths should be taken into account in addition to the concrete covering conditions of the sheaths in consideration of the topmost or bottommost possible placement conditions.

FIG. 10C illustrates the stress distribution at the lower edge of the girder immediately after the tension when the principal illustrated in FIG. 11 is 55 m. It can be seen that a similar stress distribution is shown in Type 1 shown in FIG. 9, which shows that the compressive stress dominates the stress design at the center of the body 1. The allowable stress of the concrete used in the design example according to the present invention is 27MPa as described above, there is room for stress as can be seen in the figure.

FIG. 12 is a view showing the shape of the main body 1 in which the principal is designed to be 25 m or 30 m and the arrangement of the first tension material 100 and the second tension material 200. In the case of the design example shown in FIG. 12, since the mold height is low, it is difficult to arrange two first fixing holes 310 in one vertical column. When the first anchoring holes 310 are disposed from side to side, the number of strands that can be fixed in one anchorage is reduced because the anchoring area per anchorage is reduced. However, when the span length is shortened, the number of lecturers decreases, so the first tension member 100 is used. Since the number of lecturers to be used decreases and the area required for each anchorage becomes small, the anchorage may be designed to be horizontally arranged horizontally as shown in section AA of FIG. 12 (d). When the first fixing holes 310 are arranged horizontally, two first sheath pipes 150 can be arranged at regular intervals in the width direction as shown in FIG. 12C.

Figure 10d shows the stress distribution of the lower girder immediately after the tension when the principal is 25m. It can be seen that a similar stress distribution is shown in Type 1 shown in FIG. 9, which shows that the compressive stress dominates the stress design at the center of the body 1. The allowable stress of the concrete used in the design example according to the present invention is 27MPa as described above, there is room for stress as can be seen in the figure.

According to the present invention, the abdominal thickness of the PSC type I girder can be considerably reduced by arranging a small size sheath tube on the abdomen as described while comparing the design example according to the present invention with the control design example according to one of the conventional design methods. You can see that there are advantages.

The abdominal minimum thickness of the post-tension PSC girder specified in the Road Bridge Design Standard (2015) is 165 mm. As mentioned above, the total concrete cover thickness of rebar is 40mm (environmental condition ED1, compressive strength 45MPa concrete), the diameter of shear reinforcing bar (D13) is 13mm in diameter and 2mm sheath thickness is 55mm. Becomes the same as This means that when the second sheath pipe with an internal diameter of 55 mm is used, the thickness of the abdomen of the PSC type I abdomen can be reduced to 165 mm, which is the minimum thickness prescribed by the road design standard (∵165 mm = 55 mm + 55 mm + 55 mm).

However, if the environmental conditions change, the required concrete cover thickness of the rebar can be increased. In this case, a method of minimizing the abdominal thickness of the PSC type I girder is to use an unattached coated strand shown in FIG. 13A as the second tensioning material. The unattached strand shown in (a) of FIG. 13 is a nominal 15.2 mm strand and has a diameter of 18.2 mm including the covering. 13 (b) shows how the coated strands are arranged in two rows on the abdomen of the I-girder. When the coated strands are arranged in two rows, the minimum thickness of the abdomen is 142.4 mm (= 2 × 40 mm + 2 × 13 mm + 2 × 18.2 mm). The minimum inner diameter of the sheath supplied on the market is 45 mm, in which case the minimum thickness of the abdomen is 155 mm (= 55 mm + 45 mm + 55 mm). Therefore, the use of two rows of stranded stranded steel as the second tension member may be a useful way to make the abdominal thickness thin even when the environmental conditions change and the concrete covering conditions are reinforced. In addition, although not shown, there is also a method of using the coated strand together with the second sheath pipe 250. If the stranded wire that needs to be added is slightly insufficient to accommodate all of the second tension member 200 in one 60 mm sheath tube with the coated strand, the strand strand required for the second tension member 200 without increasing the size or number of sheath tubes. Quantity can be placed. As mentioned above, the method of arranging the coated strand may be designed in consideration of the city center of the second tension member 200.

On the other hand, in the design example described so far, the upper portion of the lower flange of the cross section was curved. Since the first tension member 100 is arranged in a convex parabola shape downward in the edge section, there is no problem in arranging the first tension member 100 even when manufactured in a curved form, and when the curved form is manufactured, the weight of the main body is reduced. This is because it is helpful and aesthetically superior. However, as shown in FIG. 14, when the main body is relatively short and can be designed with a low mold height, even when the upper portion of the lower flange of the cross section 20 is formed in a curved shape, the weight reduction effect of the main body is not large, but is manufactured in a curved shape. The aesthetic effect of doing so cannot be expected very much. The upper portion of the lower flange 23a shown on the left side of FIG. 14 is straight, and the upper portion of the lower flange 23b shown on the right is curved, but it can be seen that the difference is not so large for the naked eye. In this case, the upper portion of the lower flange 23 of the edge section 20 may be manufactured in a straight line in order to facilitate the formwork.

On the other hand, in the above-described design, the end block 30 cross-sectional shape was the same as the end cross-sectional shape of the edge section . The end block may be manufactured in various forms as long as there is no problem in the flow of the cross-sectional force transmitted through the end face portion 20 in structural dynamics as a form suitable for installing the anchorage. 15 is a form in which a part of the upper portion of the end block 30 is removed to favor the end crossbeam construction. The end robo is joined to the hatched portion on the drawing. Unlike the previous design examples, the end block illustrated in FIG. 15 uses four first sheath tubes (not shown in FIG. 15), and thus four first fixing holes 310 are installed. Since the use of four small anchorages requires a smaller fixing area than using two large anchorages, it may be designed to use four first anchorages 310 depending on the situation.

Figure 16 is a form that is sometimes required in connection with the coping of the pier or securing the flow area, in this case the lower part of the end block 30 is removed so that the end block has a rectangular cross-section in order to ensure the maximum cross-sectional area for cutting It is also designed to be somewhat longer. When the end is cut off, the end of the end becomes smaller, so that a part or all of the first fixing member must be installed on the vertical surface of the cutout, but it is not easy to secure the fixing area. It is designed to use 310. In FIG. 16, it is designed that two second fixing holes 320 are used, which is to illustrate various installation methods of the fixing device.

The I-type girder which was the first aspect of the present invention has been described above. As described above, the present invention is an invention characterized by the arrangement and profile of the first tension member 100 and the second tension member 200, so that the entire tension center is on the lower limit of the tension center, and the stress distribution of the lower edge of the girder after tension is also illustrated. By reducing the thickness of the abdomen 12 of the central portion 10 of the main body 1 while appropriately adjusting the number of each of the first tension member 100 and the second tension member 200 to correspond to the type 1 or type 2 of the main body ( It can be described as an invention capable of structurally efficient design by reducing the weight of 1).

The technical idea of the present invention is not only applied to the I-shaped cross section, but may be applied to the box beam shown in FIG. 17A or the U-girder shown in FIG. 17B, which will be described. FIG. 17 (a) is a view for explaining a method of converting a cross-sectional characteristic value into an I-shaped section having the same cross-sectional characteristic values through equations for defining the limitation range of the tension material center through cutting and recombination of the hollow box section, and FIG. 17 (b) Is a diagram for explaining a method of converting a U-shaped cross section into an I-shaped cross section with the same cross-sectional characteristic values in equations that define the limited range of tension centers through cutting and recombination. FIG. 17A shows a box-shaped beam cross section consisting of an upper flange 11 ', a pair of abdomen 12', and a lower flange 13 '. By disassembling according to the combination as shown on the right it can be seen that the shape of the I-girder. When disassembled and reassembled in a similar manner to the cross section of the U-girder shown in FIG. The left and right cross-sections shown in FIGS. 17A and 17B have the same cross-sectional area and cross-sectional secondary moments (or cross-sectional coefficients) in the vertical direction, respectively, so that they are sag or introduced due to tension or load to be introduced at design time. The cross-sectional characteristics for determining the rise due to the tension force and the like are the same. That is, the same cross-section is considered when applying the above equations ⓐ to ⓓ. Therefore, by applying the technical concept applied to the I-girder, the abdominal thickness of the box-beam or U-shaped girder can be reduced to reduce the weight of the body and the number of sheath tubes used. The box-beam or U-girder has two abdomen, so the weight reduction effect by reducing the thickness of the abdomen may be larger than the I-girder.

Hereinafter, one embodiment of a box girder which is a second aspect of the present invention will be described with reference to the drawings. The PSC girder according to the present embodiment includes a main body 1 ', a first tension member 100', a second tension member 200 ', a first sheath tube 150', a second sheath tube 250 ', and a first one. It comprises a fixing unit 310 ′, the second fixing unit 320 ′.

FIG. 18A is a perspective view of a prestressed concrete box girder according to one embodiment of the second aspect of the present invention, and FIGS. 18B, 18C and 18D are respectively FIGS. 18A The front view, top view, and sectional drawing for demonstrating the tension material arrangement of the prestressed concrete girder shown in FIG.

The main body 1 'is made of a reinforced concrete material and comprises a central portion 10', a pair of end face portions 20 ', and a pair of end blocks 30', which is shown in FIG. As shown in FIG. 6, the end block 30 ′, the end surface portion 20 ′, the center portion 10 ′, the end surface portion 20 ′, and the end block 30 ′ are disposed in this order.

The central portion 10 'has a box-shaped cross section including an upper flange 11', a pair of abdomen 12 ', and a lower flange 13' as in the DD cross section shown in FIG. 18 (d). As a structure formed long in one direction, it is arrange | positioned at the center side of the main body 1 '.

The edge end portion 20 ′ extends from both ends of the central portion 10 ′ and has an upper flange 21 ′ and a pair of abdomen 22 as in the cross-sectional view taken along line BB of FIG. 18 (d). The lower flange 23 'includes a shape and the thickness of the abdomen 22' and the lower flange 23 'increases in the direction extending from the center portion, that is, toward the end of the main body 1'.

Since the thickness of the lower flange 23 'becomes thicker than the corresponding configuration of the I-type girder described above, further description thereof will be omitted.

The end block 30 'is a configuration in which a pair is provided and extends from each of the pair of end surface portions 20' and may be configured in various shapes of cross-sections, and the shape of the cross-section is continuously changed. In this embodiment, as shown in FIG. 18, the same cross-section as that of the end portion of the main body 1 ′ of the edge section 20 ′ is maintained.

The first tension member 100 ′ is disposed at the lower portion of the end block 30 ′, the end surface portion 20 ′, and the lower flanges 13 ′, 23 ′ of the central portion 10 ′ of the main body 1 ′. The arrangement in the vertical direction is the highest at both ends of the main body 1 'and the lowest in the middle, as shown in FIGS. 18 (b) and (d), wherein any one of the main bodies 1' is disposed. The altitude is gradually lowered in the end block and the end face section of the end side, and from one point of the center portion 10 ', there is no change in altitude, and is disposed substantially symmetrically with respect to the center of the main body 1'. In this applied state, both ends are fixed to the main body 1 'by the first fixing holes 310'.

The left and right arrangement of the first tension member 100 is symmetrically with respect to the center of the main body 1 ′ as shown in FIGS. 18C and 18D to maintain a predetermined distance in the girder width direction. Is placed.

This arrangement of the first tensioning material 100 ′ is shown by blue lines in FIG. 18. The first tension member 100 ′ is installed in a state of being accommodated in the first sheath tube 150 ′, and the first sheath member 100 ′ is accommodated in the first sheath tube 150 ′ and the first sheath tube 150 ′. Tension material 100 is shown as a single line, also indicated by reference numeral 100 '(150').

The second tension member 200 ′ is an upper portion of the end block 30 ′, an upper flange 21 ′ or an abdomen 22 ′ of the edge end portion 20 ′, and an upper flange 11 ′ of the central portion 10 ′. ), The abdomen 12 ′ or the lower flange 13 ′, and are shown in red to clearly distinguish the first tension material 100 ′ from the drawing. The second tension member 200 ′ is a structure in which both ends thereof are fixed to the main body 1 ′ by the second fixing holes 320 ′ in a state where a tensile force is applied, and is accommodated in the second sheath tube 250 ′.

The vertical arrangement and related technical ideas of the second tension member 200 ′ are the same as the vertical alignment and related technical ideas of the second tension material 200 in the above-described I-type girder, and thus description thereof is omitted.

In relation to the horizontal arrangement of the second tension member 200 ', the box girders have two abdomens 12' and 22 ', so that the second sheath tube 250' accommodating the second tension member 200 'is also a drainage of 2 Place it to be symmetrical.

In the case of the box-type girders shown in FIG. 18, structural efficiency can be obtained by reducing the thickness of the body by reducing the thickness of the abdomen as in the type I girders described above, and by reducing the number of sheath pipes, it is expected to reduce the construction cost. The same is true.

Hereinafter, with reference to the drawings will be described an embodiment of a third type of U-girder of the present invention. The PSC girder according to the present embodiment includes a main body 1 ", a first tension member 100", a second tension member 200 ", a first sheath pipe 150", a second sheath pipe 250 "and a first And a fixing unit 310 " and a second fixing unit 320 ".

19A is a perspective view of a prestressed concrete U-shaped girder according to an embodiment of the third aspect of the present invention, and FIGS. 19B, 19C, 19D are 19A, respectively. The front view, top view, and sectional drawing for demonstrating the tension material arrangement of the prestressed concrete girder shown by).

The main body 1 "is made of a reinforced concrete material and includes a central portion 10", a pair of end face portions 20 ", and a pair of end blocks 30", and FIG. As shown in FIG. 6, the end block 30 ″, the end face portion 20 ″, the center portion 10 ″, the end face portion 20 ″, and the end block 30 ″ are disposed in this order.

The center portion 10 "has a pair of upper flanges 11", an abdomen 12 ", and a lower portion engaging the pair of abdomen 12" as in the DD section shown in FIG. 19 (d). It has a U-shaped cross section including a flange 13 "and is formed long in one direction, and is arrange | positioned at the center side of the main body 1".

The edge end portion 20 "extends at both ends of the center portion 10" and has a pair of upper flanges 21 "and an abdomen 22" as in the BB section shown in Fig. 19D. ), Having a U-shaped cross-sectional shape including a lower flange 23 "that engages the pair of abdomen 22", and the thickness of the abdomen 22 "and the lower flange 23" extends from the center portion again. That is, it increases toward the end of the body 1 ".

Since the thickness of the lower flange 23 ″ becomes thicker than the corresponding configuration of the I-type girder described above, further description thereof will be omitted.

The end block 30 ″ extends from the pair of end face portions 20 ″ and is provided with a pair, and may be configured in various shapes of cross sections, and may be configured in various shapes in which the cross sectional shape is continuously changed. In this embodiment, as shown in FIG. 19, the same cross-section as that of the end portion of the main body 1 ″ of the edge section 20 ″ is maintained.

The first tension member 100 "is disposed at the lower portion of the end block 30", the end face portion 20 "and the lower flanges 13" and 23 "of the central portion 10" of the main body 1 ". The arrangement in the vertical direction is the highest at both ends of the main body 1 "and the lowest in the middle, as shown in FIGS. 19B and 19D, whichever is one of the main bodies 1". The altitude is gradually decreased in the end block and the end face section of the end side, and is substantially symmetrical with respect to the center of the main body 1 "without any change in altitude from any point of the center portion 10". In this applied state, both ends are fixed to the main body 1 "by the first fixing holes 310".

The left-right arrangement of the first tension member 100 "is symmetrical with respect to the center of the main body 1" as shown in FIGS. Is placed.

The arrangement of the first tension member 100 "is shown by a blue line in Fig. 19. The first tension member 100" is installed in a state of being accommodated in the first sheath tube 150 ", and the first sheath is shown in the figure. The first tension member 100 "accommodated inside the tube 150" and the first sheath tube 150 "is shown by one line, and is indicated by reference numeral 100" (150 ").

The second tension member 200 " is the upper portion of the end block 30 ", the upper flange 21 " or the abdomen 22 " of the edge end portion 20 ", and the upper flange 11 " of the central portion 10 ". ), Abdomen 12 ″ or lower flange 13 ″, and are shown in red in the drawing for clear separation from the first tension member 100 ″. The second tension member 200 "is a structure in which both ends thereof are fixed to the main body 1" by the second fixing hole 320 "in a state where a tensile force is applied, and is accommodated in the second sheath tube 250".

The vertical arrangement and related technical ideas of the second tension material 200 ″ are the same as the vertical alignment and related technical ideas of the second tension material 200 in the above-described I-type girder, and thus description thereof is omitted.

In relation to the horizontal arrangement of the second tension member 200 ", the U-girder has two abdomens 12" and 22 ", so that the second sheath tube 250" receiving the second tension member 200 "is shown in FIG. Arrange in a multiple way to be symmetrical.

In the case of the U-type girder shown in FIG. 19, structural efficiency can be obtained by reducing the thickness of the body by reducing the thickness of the abdomen as in the aforementioned I-type girder, and by reducing the number of sheath pipes, the construction cost can be reduced. The same can be expected.

Claims (8)

1. In the prestressed concrete girder used in the composite girder bridge construction method for making precast prestressed concrete girders on the ground, placing them on the substructures of bridges, shifts, etc., and constructing slab slabs thereon,

   A central section having an I-shaped cross section including an upper flange, an abdomen, and a lower flange and being long in one direction;

   A pair of edge face portions having an I-shaped cross section including an upper flange, an abdomen, and a lower flange, each extending from both ends of the central portion and increasing in thickness and extending in the extending direction of the lower flange;

   A body made of reinforced concrete material comprising a pair of end blocks extending from each of the pair of edge faces;

   It is disposed on the lower flange of the end block of the main body and the lower end portion and the central portion of the lower portion of the main body is disposed at the highest and the lowest in the middle, both ends of the lower end of the pair of end blocks, respectively, in the tension applied A first tension material to be fixed;

   It is disposed on the upper flange of the end block of the main body and the upper end portion or the upper flange, the abdomen or the lower flange of the abdomen and the center portion, the height from the end of the main body to any point near the boundary between the edge and the central portion The second tension material is forged to increase and the height from the highest point to the center of the center portion is arranged to decrease the forging, both ends are fixed to the upper portion of the pair of end blocks, respectively, in the tension force is applied;

   A first sheath pipe for accommodating the first tension material; And

   Prestressed concrete girder comprising a; a first fixing tool for fixing the first tension material and a second fixing tool for fixing the second tension material.
2. In the prestressed concrete girder used in the composite girder bridge construction method for making precast prestressed concrete girders on the ground, placing them on the substructures of bridges, shifts, etc., and constructing slab slabs thereon,

   A central section having a box-shaped cross section including an upper flange, a pair of abdomen and a lower flange, and being long in one direction;

   A pair of edge portions having a box-shaped cross section including an upper flange, a pair of abdomen and a lower flange, each extending from both ends of the central portion and increasing in thickness in the direction of extension of the lower flange;

   A body made of reinforced concrete material comprising a pair of end blocks extending from each of the pair of edge faces;

   It is disposed on the lower flange of the end block of the main body and the lower end portion and the central portion of the lower portion of the main body is disposed at the highest and the lowest in the middle, both ends of the lower end of the pair of end blocks, respectively, in the tension applied A first tension material to be fixed;

   It is disposed on the upper flange of the end block of the main body and the upper end portion or the upper flange, the abdomen or the lower flange of the abdomen and the center portion, the height from the end of the main body to any point near the boundary between the edge and the central portion The second tension material is forged to increase and the height from the highest point to the center of the center portion is arranged to decrease the forging, both ends are fixed to the upper portion of the pair of end blocks, respectively, in the tension force is applied;

   A first sheath pipe for accommodating the first tension material; And

   Prestressed concrete girder comprising a; a first fixing tool for fixing the first tension material and a second fixing tool for fixing the second tension material.
3. In the prestressed concrete girder used in the composite girder bridge construction method for making precast prestressed concrete girders on the ground, placing them on the substructures of bridges, shifts, etc., and constructing slab slabs thereon,

   A central portion having a U-shaped cross section including a pair of upper flanges and an abdomen, and a lower flange connecting the pair of abdomens to each other;

   It has a U-shaped cross section including a pair of upper flanges and the abdomen, and a lower flange connecting the pair of abdomen with each other extending from both ends of the central portion and the thickness of the lower flange and the thickness of the abdomen increases as the direction extends. And a pair of side faces

   A body made of reinforced concrete material comprising a pair of end blocks extending from each of the pair of edge faces;

   It is disposed on the lower flange of the end block of the main body and the lower end portion and the central portion of the lower portion of the main body is disposed at the highest and the lowest in the middle, both ends of the lower end of the pair of end blocks, respectively, in the tension applied A first tension material to be fixed;

   It is disposed on the upper flange of the end block of the main body and the upper end portion or the upper flange, the abdomen or the lower flange of the abdomen and the center portion, the height from the end of the main body to any point near the boundary between the edge and the central portion The second tension material is forged to increase and the height from the highest point to the center of the center portion is arranged to decrease the forging, both ends are fixed to the upper portion of the pair of end blocks, respectively, in the tension force is applied;

   A first sheath pipe for accommodating the first tension material; And

   Prestressed concrete girder comprising a; a first fixing tool for fixing the first tension material and a second fixing tool for fixing the second tension material.
4. The method according to any one of claims 1 to 3,

   Prestressed concrete girder, characterized in that the change in the height of the upper side of the lower flange of the edge portion is curved convex down.
5. The method of claim 4, wherein

   The convex downward curved prestressed concrete girder, characterized in that the arc radius of curvature is constant.
6. The method according to any one of claims 1 to 3,

   Prestressed concrete girder, characterized in that the height change of the upper side of the lower flange of the edge portion.
7. The method according to any one of claims 1 to 3,

   Prestressed concrete girder further comprises a second sheath tube for accommodating the second tension material.
8. The method according to any one of claims 1 to 3,

   A portion of the second tension material is a coated stranded wire, the prestressed concrete girder further comprises a second sheath tube for receiving the unstretched stranded wire.

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