KR101341830B1 - Psc girder making method using upper and lower psc tendon with straight tendon setting structure - Google Patents

Abstract

The present invention is to install the PSC tension material in both the upper and lower in the PSC girder, the lower portion of both ends to form a cross-sectional extension portion such as a sphere shape, the upper portion to form a pre-stress concentrated prevention end, bulb PSC girder It is a method of manufacturing a PSC girder that enables an efficient cross-sectional configuration as a tee, but solves the problems caused by the upper and lower tensile stress caused by the PSC tension material.

PSC girder, upper tensile stress

Description

PSC girder fabrication method using PCS bottom girder and PCS top tension member of straight arrangement type {PSC GIRDER MAKING METHOD USING UPPER AND LOWER PSC TENDON WITH STRAIGHT TENDON SETTING STRUCTURE}

The present invention relates to a PSC girder manufacturing method using a PSC lower tension member and a PSC upper tension member in a straight line configuration. More specifically, in the PSC girder fabricated in the form of a bulb tee, such as a PSC girder with an I-shaped cross section with an expanded upper flange, the arrangement of the PSC tension member disposed inside the PSC girder is changed from a conventional parabolic form to a straight line. It is about the manufacturing method of the PSC girder to manufacture, but to install the PSC tension material on both the upper and lower PSC girder to suit the long-term PSC girder.

Conventional PSC girder (10, Prestressed Concrete Girder), as shown in Figure 1a is installed in the sheath tube (post-tension method) inside the formwork using the formwork 40 or PSC tension material 20, pre-tensioned in the production table PSC (stranded wire) is placed and cured (pre-tension method) by pouring concrete (50),

In the case of the post-tension method, the pre-stress is introduced into the PSC girder by dismantling the formwork and inserting the PSC tension member 20 in the sheath tube and then fixing the end of the PSC tension member at the end of the PSC girder. do.

In the case of the pre-tension method, the required prestress is introduced into the PSC girder by dismantling the formwork and cutting the tensioned PSC tension member in the fabrication stage in advance.

Such PSC girders are generally formed in the I-shaped cross section in Korea, and in particular, the PSC girder of the I-shaped cross-section with the widened upper flange is particularly made in the form of a bulb bulge.

Accordingly, the PSC girder 10 having an I cross section is composed of an upper flange 14, an abdomen 15, and a lower flange 16 as an I cross section as shown in FIG. 1B, with a tension member 20 formed therein. It can be seen that produced.

FIG. 1C shows the arrangement of the PSC tension member 20 which is generally arranged in the PSC girder 10 of this type I cross section.

That is, the PSC tension member 20 is tensioned at both ends of the PSC girder 10, and then installed to be fixed by using fixing fixtures 30 (including fixing plates, wedges, etc.) at both end surfaces of the PSC girder 10. It can be seen that it is arranged in a parabolic shape as a whole over the entire extension length.

The reason for arranging PSC steel in the form of parabola is prestressing because the center part of the PSC girder has a large bending moment due to its own weight and working load, and a large downward deflection occurs. Or compressive force) also needs to be introduced at the central portion of the PSC girder 10, and both ends of the PSC girder 10 do not necessarily have to introduce the bending moment corresponding to the central portion because the bending moment is not largely generated.

Since the ends of the PSC girder are areas where the PSC steel is fixed after tension, prestress (tension or compressive force) can be locally concentrated, so that the prestress (tension or compressive force) is divided into horizontal and vertical components at both ends of the PSC girder. It is because it is necessary to form the introduction amount of prestress relatively small.

However, when placing the PSC tension material in the form of a parabola as described above, there was a problem that its installation is not easy.

In particular, when manufacturing PSC girders with long spans (approximately 40M or more), the PSC tension members are inevitably placed. However, when all of them are placed in a parabolic shape, the setting is not easy, which leads to poor workability. There was a problem that the insert operation is also not easy.

Therefore, when the PSC tension member is disposed in a straight line arrangement rather than a parabolic shape over the entire length of the PSC girder, the workability of the sheath tube and the PSC tension member may be improved,

Even if the same prestress is introduced by the arrangement of the straight PSC tension member, the prestress is not divided in the horizontal and vertical directions compared to the parabolic PSC tension member, so the loss of the prestress can be minimized. Done.

Nevertheless, the reason for not selecting the PSC tension members in a straight line was due to the problem of cracking at both ends of the PSC girder due to the concentration of prestress at both ends of the PSC girder.

In addition, the PSC girders, which are installed in the long span, were particularly problematic because they had to install more PSC tension members.

As such, PSC girders used in long spans (more than 40M) have limited cross-sectional sizes because of limitations in terms of height, etc., due to considerations such as limitations in transportation and transportation. The resulting prestress is introduced to the lower part of the PSC girder (below neutral axis),

This prestress acts as a compressive stress on the lower part of the PSC girder, while a tensile stress on the upper part (above the neutral axis).

In addition, compressive stresses occur across the shear surface of the PSC girder.

However, in the case of the upper part of the PSC girders between the long spans, the prestresses introduced are considerable, so that the tensile stress generated by this is larger than the compressive stress generated over the shear surface of the PSC girder, so that the tensile stress is dominant. Tensile cracks will occur.

Therefore, the tension cracks in the upper part of the PSC girder due to the installation of the PSC tension material in the long-term PSC girder must be controlled.

1D is a PSC girder introduced by a method called bicon, it can be seen that the steel rod 22 is installed on the upper portion of the PSC girder, and the PSC upper tension material 20 is installed in a parabolic form.

This steel bar is for resisting the compressive stress generated over the shear surface of the PSC girder as described above, the upper tension material PSC 20 is to introduce the required prestress to the PSC girder, so that the upper portion of the PSC girder is a tensile stress by the prestress Since it is not based on the prevailing state, it can be seen that there is a difference from the present invention.

In addition, there is a bi-pressing method introduced in Japan as a method for resisting the compressive stress generated across the shear surface of the PSC girder. Such a method has the disadvantage of restraining the state while compressing the steel bar and requiring additional equipment. In addition, since the upper part of the PSC girder is not premised on the condition governed by the tensile stress due to prestress, it can be seen that there is a difference from the present invention.

In the present invention, particularly, in the PSC girder between bulb-shaped long fingers, the tension of the upper and lower parts generated in the PSC girder is arranged by arranging the PSC tension member in the PSC girder in the straight upper and lower portions of the PSC girder over its entire length. The technical problem to be solved is to provide a method of manufacturing PS girder using the PS strain lower tension member and the PS strain upper tension member to effectively cope with stress.

According to an aspect of the present invention,

First, in the long span PSC girder, the upper part of the PSC girder goes beyond the dominant compressive stress and the tensile stress is dominant, so that the upper PSC girder is placed on the upper part of the PSC girder in order to resist the dominant tensile stress of the PSC girder. To be installed.

Furthermore, as the PSC upper tension material is installed, the prestress concentration preventing end is protruded upward over the entire length of the upper surface of the upper flange of the PSC girder.

In addition, the upper tension material of the PSC is to be installed in a straight line like the lower tension material of the lower PSC.

Second, both ends of the PSC girder in the state of maintaining the cross-sectional height (H, original height) in order to secure the cross-sectional force for introducing the required prestress according to the total length (L) in the I-shaped PSC girder. From the bottom surface to the section L1 spaced apart from the center by a predetermined distance, the cross-sectional heights H of both ends were made larger (H + ΔH, ΔH = increase height).

That is, by increasing the cross-sectional height of both ends of the PSC by the spaced increase height,

Even if the prestress caused by the upper tension material of the PSC is concentrated, it can be sufficiently resisted.

The central axis from the both ends of the PSC girder to the position (L1) spaced downward is to prevent the phenomenon that the prestress due to the PSC upper tension material is concentrated.

This cross-sectional height change is to be made of a cross-sectional extension portion formed to extend downward below both ends of the PSC girder.

In manufacturing the PSC girder according to the present invention, since the PSC upper and lower tension members can be arranged in a straight line with the sheath over the entire length of the PSC girder, the workability of the PSC upper and lower tension members is greatly improved. Not only enables efficient and economical production of PSC girders,

Since the concentration problem of prestress can be solved in both upper and lower ends of the PSC girder, so that the end crack problem of the PPS girder can be solved, the usability of the PSC girder can be improved.

By increasing the height of both ends up and down, the cross-sectional area for fixing the upper and lower tension members of the PSC can also be increased, so that the fixing portions of the upper and lower tension members of the PSC can be sufficiently secured. The upper and lower tension members can be effectively arranged and settled, and the cross-section stiffness of the PSC girder can be improved,

Since the upper part of the PSC girder is embedded in the slab and only the cross-sectional height of both ends is large, it has little influence on the mold height of the PSC girder, thus making it possible to manufacture the PSC girder by the optimized cross section.

In addition, even when manufacturing the PSC girders between the long and long segments, even when the segment is manufactured, the height of both ends is large and the cross-sectional height is not large therebetween, so there is no disadvantage in carrying and connecting the same.

Even when the PSC girders are constructed in a continuous bridge method, since the cross-sectional heights of both ends of the PSC girders located at the point where the bending moment is largely generated, it is possible to provide a PSC girders made of a very advantageous cross-sectional structure.

Particularly, when manufacturing the long span PSC girders, it is possible to solve some of the problems caused by the arrangement of PSC upper and lower tension members and the relaxation of prestress, which are structurally problematic.

In addition, after the slab construction, the tensile stress is generated in the lower slab due to the load in the shared state. In this case, when restraining the upper PSC steel of the present invention, it can be seen that a compressive stress capable of resisting the tensile stress is introduced to be more efficient in maintenance.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

First, the formwork for manufacturing the PSC girder 100 of the I-type cross section is prepared.

Although the formwork is not shown, the steel formwork is manufactured as shown in FIG. 1A so that the PSC girder 100 is divided into the upper flange 110, the abdomen 120, and the lower flange 130 to manufacture the PSC girder 100. .

In this case, as shown in FIG. 2, the width B1 of the upper flange 110 of the PSC girder 100 is a widened upper flange having a width larger than the width B2 of the lower flange 130. It is preferable to manufacture the formwork so that is formed.

As such, the PSC girder formed with the width B1 of the upper flange larger than the width B2 of the lower flange may be used as a formwork when the upper flange is later constructed with the slab, and the upper flange itself may be used as the slab. It has the advantage of being able to function.

The height H3 of the abdomen 120 of the PSC girder 100 is also determined so as to have a cross-sectional size by the required span in accordance with the width B2 of the upper slab. do.

PSC girder 100 according to the present invention is basically made of reinforced concrete (Reinforced Concrete) before placing concrete in the formwork PSC tension material, such as PSC strands, sheath pipe (Pension tension system) is inserted And a fixture for pre-tensioning the PSC tension member in advance in the formwork and its end face, and also setting the reinforcing bar assembly not shown in the formwork.

In this way, after the reinforcing assembly, PSC tension member, sheath, and anchorage are installed in the formwork and the end surface, the concrete not shown is cast into the formwork and cured.When the final concrete is poured, the PSC tension member is tensioned and fixed to fix the PSC girder. 100 is completed.

At this time, in the case of manufacturing the PSC girder in which the same prestress required is introduced in the case of the lower portion of the completed PSC girder as shown in FIG.

Unlike the original height H of the PSC girder with the required cross-sectional size, it can be seen that the cross-sectional height from both end faces to a predetermined spaced position L1 is formed with an additional increased height H + ΔH. And, it can be seen that both ends of the PSC girder protrude downward (site treated with hatching) so that the cross-sectional extension portion 140 is further formed.

Furthermore, it can be seen that the PSC lower tension member 200 in the PSC girder 100 has a straight arrangement.

Specifically, the initial height (H) of the PSC girder is when the PSC girder is designed to have a constant interval, for example, 40M interval, the required cross-sectional size is determined and the initial height (H) of the PSC girder according to this cross-sectional size Corresponds to).

As a result, it can be seen that the PSC girder according to the present invention has such an original height H over the entire length, and the height is increased at both ends thereof. In this case, the increased height will be referred to as an increasing height ΔH.

This difference in height ΔH eventually increases the height of both ends of the PSC girder 100 downward, thereby increasing the cross-sectional height of both ends (which increases in the vertical direction).

As such, the increase height ΔH may be formed over a section L1 having a predetermined distance from both end faces of the PSC girder, and the section L1 may be, for example, a parabolic shape of a conventional PSC upper tension member. When placed in, as shown in Figure 1 may be formed to a point bent upward in a straight section.

The section of L1 corresponds to about L / 10 to L / 5 based on the total length L of the PSC girder, which covers the section where prestress is concentrated.

Accordingly, as shown in FIG. 3A, the cross-sectional extension portions 140 formed at both ends of the PSC girder may have a rectangular sphere shape.

As shown in FIG. 3B, the cross-sectional extension portion 140 at both ends of the PSC girder is increased by the increased height ΔH of the PSC girder to the section L1 having a distance therefrom so that the cross-sectional height thereof is gradually reduced. It is possible to form a curved surface.

The shape of the cross-sectional extension 140 may be in another form, not shown.

Further, the width B of the cross-sectional extension portion 140 may be formed in an incremental downward extension type as shown in FIG.

In other words, it can be seen that the width B does not change according to the increase height ΔH of the cross-sectional extension portion 140, and according to FIG. 4, the width B increases in the downward direction.

In this way, when the width of the cross-sectional extension portion 140 is increased, the cross-sectional area of the cross-sectional extension portion is increased by the increase of the width, so that there is room for reducing the increase height (ΔH), thereby increasing the height (ΔH). This is because the adjustment is possible.

In addition, when the width of the cross-sectional extension portion 140 is increased downward, it is possible not only to enable stable end support for transporting or mounting the PSC girder 100, but also to support the bridge support. Because of this increase, safety construction is possible in the long-term PSC girder mounting.

Accordingly, it can be seen that the lower tension material 200 of the PSC based on the surface of the upper flange 110 of the PSC girder is arranged in the same horizontal straight line with the vertical distance d2 at both ends thereof.

That is, the upper PSC upper tension member 300 is disposed to have the same vertical separation distance d1 from the upper flange 110 surface of the PSC girder 100.

Accordingly, it can be seen that the PSC upper tension members 300 are arranged in the same horizontal straight line at both ends thereof on the basis of the upper flange 110 surface of the PSC girder.

Therefore, as shown in FIG. 5, the position of the central axis C2 of the central portion of the PSC girder is different from the center axis C1 and the L1 in the section from the two end faces of the PSC girder to the L1 spaced apart from the center portion. Can be.

That is, it can be seen that the central axis (C1) of both ends of the PSC girder is disposed more downward than the central axis (C2) of the central portion, thereby eccentric from the central axis of the both ends to the PSC lower tension material 200 It can be seen that the distance e1 is smaller than the eccentric distance e2 from the central axis of the central portion to the upper tension material PSC 300.

That is, both ends of the PSC girder having a small eccentric distance have a large amount of the lower PSC girder according to the production of the PSC girder between the long papers because the size of the prestress to be introduced is relatively smaller than the center portion even if the PSC lower tension member 200 is arranged in a straight line. It can be seen that the installation of 200 can prevent the effect of excessive prestress being concentrated at both ends of the PSC girder.

As a result, both ends of the PSC girder according to the present invention may increase the height in the cross-sectional size so that more anchorages 30 of the lower PSC lower tension member 200 can be installed, which is inevitably largely arranged when manufacturing the PSC girder between the papers. PSC lower tension member 200 can increase the installation area of the anchorage,

PSC girders with both ends of this height increase the cross-sectional size, even if the prestress caused by the lower tension material of the PSC is concentrated, thereby effectively coping with the end cracks.

Since the lower tension material of PSC is arranged in a straight line, the workability of the so-called PT WORK (PSC upper tension material construction work) is enhanced.

Since the central axis of both ends of the PSC girder is disposed below the central axis of the central part of the PSC girders, it can be seen that the phenomenon of prestress is concentrated on both ends of the PSC girder, as in the parabolic arrangement of the lower tension material of the conventional PSC. Can be.

In other words, it can be seen that by increasing the height of both ends of the PSC girder over a certain period (L1) to move the downtown axis downward to have a prestress dispersion effect as if the PSC lower tension material is installed in a parabolic form.

 As described above, the PSC girder 100 between the Jangji may be forced to increase the amount of the PSC lower tension member 200.

As such, when the amount of installation of the PSC lower tension member 200 increases, the compressive stress accumulates on the cross section of the PSC girder, and the upper part of the PSC girder is dominated by the tensile stress by the PSC lower tension member 200.

This tensile stress remains to offset the accumulated compressive stress, causing tension cracking problems on top of the PSC girder, which is fatal for the PSC girder.

In such a long span PSC girder, when the tensile stress is dominant on the upper portion of the PSC upper tension member 300 of the present invention.

Since the PSC upper tension member 300 is to resist tensile stress generated in the upper part of the PSC girder unlike the conventional bicon and bipressing methods, steel bars and compressive tension members are respectively installed to resist the compressive stress of the PSC girder. Can be compared.

The PSC upper tension member 300 is also installed over the entire length L in a straight shape inside the upper flange like the PSC lower tension member 200.

That is, it is to be arranged in a position spaced apart from the upper flange surface of the PSC girder by a certain distance.

As a result, the compressive stress is introduced into the upper portion (from the neutral shaft to the upper portion) of the PSC girder by the tension and fixation of the upper PSC upper tension member 300, which is sequentially performed after the tension and fixation of the lower tension component of the PSC.

As such, when the compressive stress by the PSC upper tension member 300 resists the dominant tensile stress of the upper portion of the PSC girder, the compressive stress may be concentrated on the upper part of the PSC girder. Because of their placement, this phenomenon occurs throughout the PSC girder.

Therefore, in the present invention, the prestressed concentration preventing end 150 is projected upward on the upper surface of the upper flange of the PSC girder, and the prestressed concentration preventing end 150 is formed over the entire length of the PSC girder.

However, the prestress concentration preventing end 150 is to be formed in a plurality or continuously spaced apart from each other over the entire length.

The formation height of the prestress concentration preventing end 150 may be at least enough to be embedded in the slab formed on the upper portion of the PSC girder, and the width thereof is preferably equal to the width B2 of the lower flange. .

The prestressed concentration preventing end 150 is embedded in the slab so as not to affect the mold height of the PSC girder, but the prestressed concentration preventing end 150 serves as a shear connector in the synthesis of the PSC girder and the slab.

This is possible because the prestress concentration preventing end 150 is formed over the entire length of the PSC girder.

In addition, when the pre-stress concentrated preventive end 150 is spaced apart from each other, the shape is also possible in the form of a square sphere, but may also be formed in the form of a horseshoe plate to promote the role of the shear connector.

In addition, the prestressed concentration preventing end 150 may be a structure that is very advantageous for the load resistance in the transverse direction because the upper portion of the PSC girder can be restrained in the transverse direction.

Furthermore, although the central axis C1 and C2 may be moved upward by the prestressed concentration preventing end 150, this may be different because it may be optimized by adjusting the height and width of the prestressed concentration preventing end 150. There is nothing to be done.

In addition, the PSC girder 100 of the present invention, so that the PSC upper tension member 300 is formed over the entire length of the PSC girder or at least over the L1 section of the PSC girder 100, the prestress concentration preventing end 150 It can also be adjusted accordingly.

1a, 1b, 1c and 1d is a perspective view of the manufacturing state of the PSC girder by the conventional formwork, the partial perspective view of the completed PSC girder, the PSC upper tension material arrangement perspective of the PSC girder, the Vicon PSC girder,

2 is a complete perspective view of the PSC girder according to the present invention,

Figure 3a, 3b and 4 is a perspective view of both ends of the PSC girder according to the present invention,

Figure 5 is a cross-sectional view of the installation of the upper and lower tension material of the PSC in the PSC girder according to the present invention.

<Brief description of the major reference numerals>

100: PSC girder 110: upper flange

120: abdomen 130: lower flange

140: cross-sectional extension

150: prestress concentration prevention

200: PSC lower tension member (PC steel)

300: PSC upper tension material (PC steel)

Claims (4)

In the long span PSC girder of the bulb type method (generally formed by the widened upper flange, the abdomen and the lower flange of the I-shaped cross section) manufactured by introducing a prestress using PSC steel to the reinforced concrete girder, A section of L / 10 to L / 5 positions based on the total length L of the PSC girder while maintaining the cross-sectional height H (original height) determined according to the interval of the PSC girder over the entire length L ( In L1), the cross section height (△ H, additional height) of the PSC girder is further increased. PSC lower tension member disposed on the PSC girder is to maintain the same distance from the upper flange surface over the entire length of the PSC girder to be arranged in a straight line on the bottom of the PSC girder, In order to prevent the prestress of the lower PSC girder is introduced so that the upper part of the PSC girder becomes dominant in tensile stress, the upper PSC girder is further disposed on the upper part of the PSC girder, so that the prestress is provided on the upper and lower parts of the PSC girder. Wherein each of the PSC upper tension members is arranged to be disposed in a straight line on the upper portion of the PSC girder by maintaining the same distance from the upper flange surface of the PSC girder; In order to resist local prestress caused by the upper tension material of the PSC, further forming a prestress concentration preventing end projecting upward on the upper surfaces of both ends of the PSC girder, the prestress concentration preventing end is a square sphere having a constant height PSC girder fabrication method using PSC lower tension member and PSC upper tension member in the form of a straight line arranged to be formed over the PSC girders, buried in the slab to be formed later to serve as a shear connector of the PSC girder. The method of claim 1, wherein in the section (L1) of the PSC girder, the shape of the lower end of both ends of the PSC girder having a larger cross-sectional height Method of producing a PSC girder between the PSC lower tension member and the PSC upper tension member in the form of a spherical shape formed so that its height gradually decreases from both end faces of the PSC girder or a straight rectangular shape whose height is formed in a constant rectangular sphere shape. . According to claim 2, wherein both ends of the PSC girder in the section (L1), the cross-sectional extension portion 140 is A method of manufacturing a PSC girder in which the PS strainer is disposed in a straight line so that the width thereof is gradually increased from both end faces of the PSC girder. delete

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