KR100912584B1 - Method for preventing lateral buckling of prestressed concrete beam in prestressing and apparatus thereof - Google Patents

Abstract

A prestressed concrete beam manufacturing method for preventing lateral buckling in prestressing and a lateral buckling prevention apparatus are provided to distribute the compressive force of the beam evenly through the entire cross-section and thereby prevent transverse displacement occurring after removing the traverse restraint. A prestressed concrete beam manufacturing method for preventing lateral buckling in prestressing is as follows. A plurality of concrete beams(10a) in which a plurality of tendons(31,32,33,34) are arranged is manufactured. The concrete beams are parallely arranged at regular intervals. The concrete beam to be prestressed is connected to the center of the span of a neighboring concrete beam(10b) and restricted in displacement of traverse direction. The tendons installed on the concrete beam to be prestressed are successively strained. The displacement restriction of the concrete beam is removed. Tension is successively applied to the manufactured concrete beams.

Description

Method for manufacturing lateral buckling to prevent lateral buckling and device for preventing lateral buckling {Method for Preventing Lateral buckling of Prestressed Concrete Beam in Prestressing and Apparatus}

The present invention relates to a method for manufacturing a PS beam, and more particularly, to a method for manufacturing a PS beam and a transverse buckling prevention device that can prevent buckling in the transverse direction when pre-stress is introduced into concrete. will be.

Prestressed Concrete Beam (hereinafter referred to as `` PS beam '') is a pre-stressed prestress (prestress) is introduced through the tension material disposed inside the cross section to offset the tensile stress occurring in the concrete by the self and external load Says one concrete beam.

Figure 7 shows the PS beam of the national standard cross-section used as the girder of the bridge, (a) is a cross-sectional view showing the longitudinal arrangement of the tension material, (b) is a cross-sectional view showing the tension material arrangement at the end, (c ) Is a cross-sectional view showing the tension material arrangement in the center part.

In general, the tension member is settled at the end of the beam and a large concentrated load is required, so a large area concrete section is required. Therefore, as shown in FIG. 7 (b), since a large acupressure stress is generated at the anchoring position, the anchorages are vertically aligned with the concrete beam cross-section in order to secure a large anchoring cross section capable of resisting and to cope with an external force generated in a parabolic form. Is placed. On the other hand, in the central portion of the PS beam as shown in Figure 7 (c) in order to maximize the eccentric effect, the tension member is disposed as far away from the horizontal axis (horizontal neutral axis, hna) passing through the city center of the concrete cross section as far as possible. Therefore, when each tension member is sequentially tensioned, the tension member disposed eccentrically on the longitudinal axis (vertical neutral axis, vna) has a structural defect that causes buckling because it generates an eccentric load.

That is, when the first tension member 111 and the second tension member 112 are tensioned, the transverse buckling rarely occurs because the tension member is positioned above the longitudinal neutral axis vna. However, in the case of tensioning the third tension member 113, since the tension member is disposed away from the longitudinal neutral axis (vna), transverse buckling is inevitably generated in proportion to the magnitude of the tension force and the eccentricity. And finally, when the fourth tension member 114 is tensioned, since the tension force corresponding to the third tension member 113 is introduced, the lateral buckling displacement generated by the third tension member 113 is recovered, so that the vertical neutral axis (vna) is restored. Returning to its original position is the fabrication principle of PS Beam.

Theoretically, however, one can expect to recover the buckling displacement by tensioning one tension member symmetrically disposed about the vertical neutral axis (vna) and tensioning the tension member symmetrically therewith. Even after tensioning the symmetrical tension member after directional buckling displacement, the vertical neutral axis does not return to its original position but remains permanently in buckling displacement.

In order to prevent such lateral buckling or fabricate PS beams within the permissible lateral displacement, the lateral stiffness of the concrete beam (the stiffness of the beam resisting the lateral buckling) must be increased, but the cross section can be increased to increase the lateral stiffness. Increasing the weight of the bridge increases its own weight, making it more uneconomical and unsuitable for the recent bridge technology.

In particular, in the case of the recently improved PS beam, the cross section is very small and the height is very low in lateral stiffness because the optimal cross section is selected to minimize the self weight and maximize the bending stiffness. Nevertheless, the lateral buckling frequently occurs when the tension is applied in the field because it is applied to the bridge between the long jigs and the design review is not made. Therefore, in reality, not only the risk of breakage and safety accidents during beam manufacturing but also the risk of lowering the load capacity and collapse of the bridge in the future is high.

The technical problem to be solved by the present invention is to provide a method for manufacturing a PS beam to effectively prevent the lateral buckling of the PS beam generated when the pre-stress is introduced without increasing the cross section of the beam.

According to a preferred embodiment of the present invention, (a) the production of concrete beams for producing a plurality of concrete beams, which are non-attached to concrete and arranged in a parabolic form over the center, with a plurality of tension members arranged in the center with an eccentricity about the vertical neutral axis step; (b) The transverse direction of the concrete beams to be introduced by arranging a plurality of concrete beams in parallel to each other at a predetermined interval and connecting the concrete beams to which tension is to be introduced from the center to the center of the neighboring concrete beams. A transverse constraining step for constraining the displacement to the conduit; (c) a tension step of sequentially tensioning the tension members installed in the concrete beam to introduce tension force; (d) a lateral restraining step of releasing the lateral restraint in step (b); And (e) repeating steps (b) to (d) to sequentially introduce tension force to the plurality of concrete beams manufactured by step (a). A method is provided.

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According to another suitable embodiment of the present invention, the transverse restraining step secures the first street material to the abdomen of the concrete beam to introduce the tension force, and the second street material having a hinge to the abdomen of the neighboring concrete beam. After fixing, the first and second street materials are connected to each other by a coupler, wherein the second street materials are divided into two and connect them to each other by pins.

According to another suitable embodiment of the present invention, the transverse restraining step secures the first cap member to the upper flange of the concrete beam to introduce tension and the second cap having a hinge to the upper flange of the neighboring concrete beam. After fixing the member, the first and second cap members are connected to each other by a coupler, wherein the first and second cap members are coupled to the channel-type member and the channel-type member to be covered by the upper flange of the concrete beam. It is composed of a member, the second cap member is a hinge is formed by joining the horizontal member and the vertical member forming the angle member with a pin.

According to another suitable embodiment of the present invention, the first street material is fixed to the abdomen of any one of the neighboring concrete beams; A second street material fixed to the abdomen of another concrete beam of neighboring concrete beams, divided into two and connected to each other by pins and having a hinge; It includes a coupler for connecting the first and second street materials to each other, the displacement of the concrete beam to introduce a tension force from the neighboring concrete beams in the height direction of the beam is allowed, but transverse displacement is constrained.

According to another suitable embodiment of the invention, the first cap member is fixed to the upper flange of any one of the neighboring concrete beams; A second cap member fixed to an upper flange of the other concrete beam among neighboring concrete beams and having a hinge; And a coupler connecting the first and second cap members to each other, wherein the first and second cap members are composed of a channel member coupled to the upper flange of the concrete beam and an angle member coupled to the channel member. The second cap member is connected to the horizontal member and the vertical member constituting the angle member by a pin so that the hinge is formed, the displacement of the concrete beam to introduce the tension force from the neighboring concrete beam in the height direction of the beam is allowed in the transverse direction The displacement of is characterized in that to restrain.

According to the present invention, by solving the problem that the interval could not be lengthened due to the lateral buckling generated when the tension is introduced, it becomes possible to manufacture the long-term PS beam. In addition, it is economical because it is possible to effectively prevent the lateral buckling with the addition of a simple manufacturing process and low cost. In addition, since the structure of the device that can prevent the lateral buckling is simple, it has an excellent advantage that can be applied to various types of PS beam.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same components or parts are denoted by the same reference numerals as much as possible, and detailed descriptions of related known functions or configurations are omitted.

Figure 1 shows the arrangement of the tension material disposed on a general PS beam, (a) is a side view representing the state before introducing the tension force in the state of manufacturing the PS beam and (b) is a PS beam It is a side view which expresses the state after introducing the tension force in the tension material arrange | positioned inside, (c) is a top view which represents the elongate material which is eccentrically arrange | positioned laterally based on a longitudinal neutral axis.

When the tension force is introduced into the PS beam, as shown in FIG. 1 (b), the upward rise occurs (represented by a dashed line), and both ends thereof become points to change the boundary condition of the hinge structure. In this state of boundary condition, the load of the tension member acts as the eccentricity, and the dynamic behavior of the buckling in the hinge state at both ends is achieved. Therefore, the tension member disposed eccentrically in the transverse direction causes the transverse buckling displacement according to the tension sequence.

Figure 2 is for showing the amount of lateral displacement caused by the eccentrically placed tension material, (a) shows the lateral displacement (δ1) generated when tensioning the eccentrically placed tension member in the general PS beam , (b) shows the lateral displacement δ2 which occurs when the transverse displacement is restrained by placing the boundary condition of the hinge structure at the center of the PS beam.

이다. 여기서, x는 지간의 임의 위치이다. 그러므로 지간 중앙에서 발생하는 횡방향 변위량(δ_L/2)은 긴장력과 편심에 의해 발생하는 모멘트를 적분한 값을 단면의 횡방향 강성(EI)로 나눈 값,

이 된다. (b)는 2경간 부정정 구조물에서 구하는 처짐량을 구하는 것처럼 (a)의 값을 통해 지간 중앙을 구속조건의 경계조건으로 가정하여 구하게 된다. 그러므로 지간 중앙에 경계조건을 두면 (a)에 비해 (b)의 최대 횡방향 변위량이 매우 작으며 지간 중앙에서의 변위량이 0이 된다.The amount of transverse displacement (δ _x ) generated by the eccentrically placed tension member (tension members 33 and 34 in FIG. 1) in the hinge structure at both ends of (a) is the moment (M _x = P xe _x ) generated by the tension force and the eccentricity. Integral divided by the transverse stiffness of the cross section

to be. Where x is any position between the branches. Therefore, the amount of transverse displacement (δ _{L / 2} ) that occurs at the center of the span is the value obtained by dividing the moment generated by tension and eccentricity by the transverse stiffness (EI) of the cross section.

Becomes (b) is calculated by assuming the center of the span as the boundary condition of the constraint through the value of (a). Therefore, when the boundary condition is placed in the middle of the interstitial zone, the maximum lateral displacement of (b) is very small compared to (a), and the displacement at the middle of the interstitial zone is zero.

As such, when prestress is introduced into the PS beam constrained by the transverse restraint device, the resistance to buckling load is improved, thereby effectively preventing the transverse buckling. Figure 3 schematically illustrates the principle of the buckling occurs when the pre-stress is introduced to the PS beam beam is installed transverse buckling restraint apparatus according to the present invention.

Referring to FIG. 3, when the pre-stress is introduced into the PS beam constrained by the transverse restraint device as the concept of the buckling load, the lateral buckling is prevented. Buckling load can be expressed by the following equation.

here,

P _cr : Buckling load (critical load)

k: effective length coefficient

l: length of the beam between supports

E: modulus of elasticity of beam

I: Cross-section secondary moment of beam

In the present invention, a method of reducing the effective length L of the PS beam is adopted so that the buckling does not occur even if the tension load is increased to increase the critical load. That is, if the transverse displacement can be constrained at the center of the beam at the time of prestress introduction, the lateral buckling occurring in the PS beam can be represented schematically as shown in FIG. 3 (a) (FIG. 3 when there is no lateral restraint device). Since L becomes 1 / 2L in the above equation, the resistance to buckling load is increased by 4 times (reducing the length L of the PS beam by 50% from the above equation results in the buckling load being It can be seen that it increases four times.) It is possible to prevent the transverse buckling caused when the tension members arranged symmetrically symmetrically about the vertical neutral axis (vna) are tensioned one by one.

Figure 4 is a front view showing a state in which the transverse restraint device is installed on the PS beam according to an embodiment of the present invention to create a boundary condition to control the buckling displacement occurring in the PS beam when the tension is introduced, Figure 5 Top view.

In the present invention, considering the principle of the buckling load to generate the buckling displacement (lateral buckling) as described above, the boundary condition was created to control the buckling displacement in the PS beam. In other words, the abdomen of the neighboring PS beams were connected to each other by a transverse restraint device to restrain the transverse displacement from occurring when a tension force was introduced.

Referring to FIG. 4, the lateral restraint device 20 may include a first horizontal member 21 having one end fixed to an abdomen of one of the neighboring PS beams 10a and 10b, and the other. One end is fixed to the abdomen of one PS beam (10b) and includes a coupler (23) for connecting the second and the second (22) member having a hinge (h) and the first and second (21, 22) do. The first and second street materials 21 and 22 may be formed of steel bars or steel pipes. In order to fix one end of the first and second street materials 21 and 22 to the PS beam, inserts 24 are embedded in the PS beams 10a and 10b in advance, and the first and second street materials 21 and 22 are used. At one end, the thread is machined to be screwed into the insert. Of course, it is also possible to combine the first and second street materials by processing the anchor hole without embedding the insert in the PS beam. In addition, the other end of the first and second street material (21, 22) is machined and the thread is processed on the inner peripheral surface of the coupler 23 to screw the first and second street material (21, 22) with the coupler (23). . Accordingly, the first and second horizontal materials 21 and 22 have a structure in which the length can be adjusted in correspondence to the interval between neighboring PS beams 10a and 10b using the coupler 23. On the other hand, the second street material 22 has a hinge h. To this end, the second horizontal member 22 is divided into two, and the pins are connected to each other. The reason why the hinge h is attached to the second street material 22 is not to restrain the rotational displacement in order to free up the CS beam when the tension force is introduced (that is, to free the displacement in the beam height direction). So that both ends have a point condition of the hinge structure). In addition, the first and second street materials 21 and 22 strain the tension members first to restrain the transverse displacements of the neighboring PS beams 10a and 10b. Therefore, the transverse restraint device according to the present invention creates a boundary condition that restrains the transverse displacement of the PS beam but does not restrain the height displacement when the tension force is introduced. That is, in the PS beam produced by connecting two neighboring beams to each other by the transverse restraint device, the transverse restraint device increases the buckling load by reducing the effective length of the PS beam. Since the lateral restraint device is intended to reduce the effective length of the PS beam, as shown in FIG. 4, only one may be installed in the center, but may be installed at one-third of each point. Reference numeral 30 indicates a tension member.

Figure 6 is a front view showing a state in which the transverse restraint device is installed on the PS beam according to another embodiment of the present invention to create a boundary condition to control the buckling displacement occurring in the PS beam when the tension is introduced.

As shown in Fig. 6, when the reinforcing bar protrudes in the abdomen or the transverse restraint cannot be installed in the abdomen for other reasons, the transverse restraint may be installed on the upper flange.

In the present embodiment, the lateral restraint device 20a includes the first cap member 25 fixed to the upper flange of one of the neighboring PS beams 10a and 10b, and the other PS. And a coupler 23 fixed to the upper flange of the seam beam 10b and connecting the second cap member 26 having the hinge h and the first and second cap members 25 and 26 to each other. The first and second cap members 25 and 26 include channel members 251 and 261 coupled to the upper flange of the PS beam and angle members 252 and 262 coupled to the channel members 251 and 261. In the case of the cap member 26, the horizontal member 262h and the vertical member 262v constituting the angle member 262 are joined by pins to have a hinge h. The coupler 23 screws the angle members 252 and 262 of the first and second cap members 25 and 26 to each other. The first and second cap members 25 and 26 are bolted to the upper flange of the PS beam and fix the separation distance between the upper flange of the beam and the channel member. The channel member and the angle member according to the present embodiment may be composed of any single steel rod or steel pipe known in the art and an assembled steel rod or steel pipe. The reason why the hinge h is attached to the second cap member 26 is to allow rotation in response to the rise of the PS beam when the tension force is introduced in the same manner as the hinge on the second street material in the above embodiment. . Therefore, when the tension is introduced, the boundary condition of the PS beam is constrained but not the height displacement.

The method of manufacturing the PS beam while preventing the lateral displacement during the introduction of the prestress using the transverse restraint device according to the present invention configured as described above will be described below with reference to FIGS. 4 and 5.

First, a concrete beam is manufactured so that a plurality of tension members 31, 32, 33, and 34 are installed in the concrete cross section. In the present specification, the concrete beam means a beam in which a tension member is disposed but is not strained, and thus prestress is not introduced into the concrete, and the PS beam refers to a beam in which prestress is introduced. The tension members 31, 32, 33, 34 are arranged parabolic over the entire length of the concrete through sheath pipes and eccentrically with respect to the vertical neutral axis, or at least at the center of the ground eccentrically with respect to the vertical neutral axis. There is no particular limitation on the cross-sectional shape of the concrete beam to which the present invention is applied. Preferably, the PS of the I-type or T-shaped cross-section which tends to cause lateral buckling when tension is introduced is less than the box-shaped cross-section having large lateral stiffness. It can be applied to the manufacture of beams.

Next, the concrete beams are spaced apart at regular intervals, and the concrete beams 10a for introducing the tension force are connected to the neighboring beams 10b so as to allow height displacement but restrain the lateral displacement, and the beam for introducing the tension force. Connect to one beam located on one side of the side or to both sides. The beams are connected to each other by a transverse restraint device 20 and are installed at a point half of the total length of the beam. However, the installation position of the transverse restraint device 20 is not limited to this, and may be installed at a point 1/3 or 1/4 respectively considering the length and the cross section of the beam.

Next, the tension members 31, 32, 33, 34 installed on the concrete beam are sequentially tensioned. That is, the present invention is applied to a method for manufacturing a PS beam manufactured by a post tension method. The tension members are symmetrically tensioned in order by the tension members arranged symmetrically with respect to the vertical neutral axis in a known method and order.

Finally, the PS beam is disconnected by removing the lateral restraint device 20. When the introduction of the prestress is completed, the beam is evenly distributed over the entire cross section so that the transverse displacement does not occur even if the transverse restraint device for buckling prevention is removed.

The PS beam manufactured in this way is installed by grouting between the tension member and the concrete member (between sheaths) to attach the tension member to the concrete, and when the bottom plate is placed, the bridge is completed. Previous PS beam beam bridges have been applied to spans less than 45m. The reason for this is that there are various problems of the PS beam to be applied to more spaces. A representative problem is the lateral buckling of the PS beam for the long span bridge. Therefore, if the stability of the buckling is secured by applying the above method, it is possible to eliminate the obstacles to fabricate the prestressed beam between the long span.

Although the present invention has been described above with reference to the drawings, the present invention is not limited to the embodiments and drawings disclosed herein, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. Can be done.

The following drawings, which are attached in this specification, illustrate the preferred embodiments of the present invention, and together with the detailed description thereof, serve to further understand the technical spirit of the present invention. It should not be construed as limited.

Figure 1 shows the arrangement of the tension material disposed on a general PS beam, (a) is a side view representing the state before introducing the tension force in the state of manufacturing the PS beam and (b) is a PS beam It is a side view which expresses the state after introducing the tension force in the tension material arrange | positioned inside, (c) is a top view which expresses the tension material arrange | positioned eccentrically in the horizontal direction with respect to a longitudinal neutral axis.

Figure 2 is for showing the amount of lateral displacement caused by the eccentrically placed tension material, (a) shows the lateral displacement (δ1) generated when tensioning the eccentrically placed tension member in the general PS beam , (b) shows the lateral displacement δ2 which occurs when the transverse displacement is restrained by placing the boundary condition of the hinge structure at the center of the PS beam.

Figure 3 schematically illustrates the principle of the buckling occurs when the pre-stress is introduced to the PS beam beam is installed transverse buckling restraint apparatus according to the present invention.

Figure 4 is a front view showing a state in which the transverse restraint device is installed on the PS beam according to an embodiment of the present invention to create a boundary condition to control the buckling displacement occurring in the PS beam when the tension is introduced, Figure 5 Top view.

Figure 6 is a front view showing a state in which the transverse restraint device is installed on the PS beam according to another embodiment of the present invention to create a boundary condition to control the buckling displacement occurring in the PS beam when the tension is introduced.

Figure 7 shows the PS beam of the national standard cross-section used as the girder of the bridge, (a) is a cross-sectional view showing the longitudinal arrangement of the tension material, (b) is a cross-sectional view showing the tension material arrangement at the end, (c ) Is a cross-sectional view showing the tension material arrangement in the center part.

Claims (6)

(a) a concrete beam manufacturing step of manufacturing a plurality of concrete beams, which are non-attached to concrete and disposed in a parabolic form over the center, and a plurality of tension members are disposed in the center to be eccentric with respect to the vertical neutral axis; (b) The transverse direction of the concrete beams to be introduced by arranging a plurality of concrete beams in parallel to each other at a predetermined interval and connecting the concrete beams to which tension is to be introduced from the center to the center of the neighboring concrete beams. A transverse constraining step for constraining the displacement to the conduit; (c) a tension step of sequentially tensioning the tension members installed in the concrete beam to introduce tension force; (d) a lateral restraining step of releasing the lateral restraint in step (b); And (e) Repeating the steps (b) to (d) repeats the step of sequentially introducing a plurality of concrete beams prepared by the step (a) of the PS beam preventing the lateral buckling, characterized in that . delete The method of claim 1, wherein the transverse restraint step, By fixing the first street material on the abdomen of the concrete beam to introduce the tension force, the second street material having a hinge on the abdomen of the neighboring concrete beam, and then connecting the first and second street material to the coupler with each other , At this time, the second horizontal material is divided into two and a method of manufacturing a PS beam to prevent lateral buckling, characterized in that they are connected to each other by a pin. The method of claim 1, wherein the transverse restraint step, The first cap member is fixed to the upper flange of the concrete beam to introduce the tension force, the second cap member having a hinge is fixed to the upper flange of the neighboring concrete beam, and then the first and second cap members are connected to each other by a coupler. Done, In this case, the first and second cap members are composed of a channel member coupled to the upper flange of the concrete beam and an angle member coupled to the channel member, and the second cap member includes a horizontal member and a vertical member forming the angle member. A method of manufacturing a PS beam to prevent lateral buckling, characterized in that the hinge is formed by bonding with a pin. A first street material fixed to the abdomen of any one of the neighboring concrete beams; A second street material fixed to the abdomen of another concrete beam of neighboring concrete beams, divided into two and connected to each other by pins and having a hinge; And a coupler for connecting the first and second street materials to each other, wherein the displacement of the concrete beam to introduce a tension force among neighboring concrete beams in the height direction of the beam is allowed but the displacement in the transverse direction is restricted. Device to prevent lateral buckling during seed beam manufacturing. A first cap member fixed to an upper flange of any one of the neighboring concrete beams; A second cap member fixed to an upper flange of the other concrete beam among neighboring concrete beams and having a hinge; It includes a coupler for connecting the first and second cap members to each other, In this case, the first and second cap members are composed of a channel member coupled to the upper flange of the concrete beam and an angle member coupled to the channel member, and the second cap member includes a horizontal member and a vertical member forming the angle member. Joining with a pin to form a hinge, An apparatus for preventing lateral buckling in manufacturing a PS beam, characterized in that the displacement of the concrete beam to introduce a tension force from the neighboring concrete beam is allowed in the height direction of the beam, but restrains in the transverse direction.

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