KR101576241B1

KR101576241B1 - Manufacturing Method of Prestressed Steel-Concrete Composite Beam

Info

Publication number: KR101576241B1
Application number: KR1020150144018A
Authority: KR
Inventors: 오두환
Original assignee: 오두환
Priority date: 2015-10-15
Filing date: 2015-10-15
Publication date: 2015-12-09

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a composite prestressed steel beam having a composite structure of a steel material and a prestressed concrete. More particularly, the present invention relates to a method of constructing a prestressed steel composite beam, To a method of constructing a composite beam.
The present invention relates to a method for producing a second beam of reinforced concrete material comprising a top flange and a belly portion and comprising a first beam of a long steel in one direction and a reinforcing concrete material which is arranged below the first beam and structurally synthesized with the first beam Beam forming step; In the beam forming step, a strand is formed inside the second beam in the form of a non-adherent strand at one end and the other is formed in the form of an adhered strand, a protrusion is formed on the surface of the adhered strand, And a linear fixed fixing unit for fixing the linearly fixed fixing unit to the second beam so that the linear fixed fixing unit can be fixed within the second beam without a separate internal fixed fixing unit, And a stranded wire in the form of a non-stiffened strand is disposed on one side of the second beam and an end of the non-stiffened strand is buried in such a manner as to be exposed to the outside of the second beam. Embedding step; And a prestressing step of applying a tensile force to the embedded strand assembly in the strand assembly embedding step after the concrete of the second beam is hardened to a predetermined strength to fix the strand assembly to the fixing device at the end so that the prestress acts on the beam The composite synthetic beam having a diameter greater than that of the prestressed steel composite beam.

Description

[0001] The present invention relates to a manufacturing method of a prestressed steel composite beam,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of constructing a composite prestressed steel beam having a composite structure of a steel material and a prestressed concrete. More particularly, the present invention relates to a method of constructing a prestressed steel composite beam, To a method of constructing a composite beam.

The prestressed steel composite girder which joins concrete to the lower part of the steel is constructed by combining the concrete under the steel girder to increase the stiffness in order to effectively solve the excessive sagging problem in the case of making the low grade girder only by the steel material As a girder type, compressive prestressing is introduced to offset the flexural tensile stress generated in the lower concrete by the working load.

The existing typical prestressed steel composite girder construction method is as follows. Fig. 1 is a view for explaining a method of manufacturing a preflex girder which can be called a low-strength composite girder. The left side of the drawing is a front view and the right side is a sectional view. First, as shown in Fig. 1 (a), a steel girder is manufactured by providing a camber, and a prestressing load Pf is applied in a state where both ends are supported as shown in Fig. 1 (b) . As shown in Fig. 1 (c), the lower concrete is laid under the condition that the prestressing load is applied. When the lower concrete reaches a predetermined strength, the prestressing load is removed as shown in FIG. 1 (d), and a compressive prestress is introduced into the lower concrete. FIG. 1 (e) is a final structural form of a composite steel girder constructed by carrying the preflex girder constructed as described above, placing it on the lower structure, and placing the abdomen and slab concrete simultaneously.

Fig. 2 is a cross-sectional view of an RPF (Represtressed PreFlex) girder. An unbonded strand is installed on the existing preflex girder at both ends of the lower concrete to introduce an additional prestress. This is because the prestress introduced into the lower concrete by the prefabrication of the original steel is not sufficient and the cracks are generated frequently in the lower concrete during the common use. However, the prestressing method using the post- It is very effective for the introduction of prestress.

The precom girder shown in Figs. 3A and 3B is a method of positively utilizing the fact that the method of torsion of the strand is more economical than the prefabrication of the steel in introducing the unit compressive prestress into the lower concrete of the steel composite girder to be. That is, the price is twice as high as that of the structural steel used as a tension member in a steel girder, but the strength is 5 times or more, so that the price per unit strength is much cheaper. Precom girders introduced most of the prestresses by the tension of the strand, and the amount of prestress introduced by the refraction of the steel girder was greatly reduced. Therefore, instead of the existing prismatic method which requires a large cost for installation and operation of the facility, as shown in FIG. 3A, when the steel composite girder is manufactured, the lower concrete form is hung from the steel girder to support both ends of the steel girder, The lower concrete and the form weight are applied to the prestressing load of the steel girder by pouring. The prestress introduced by this prefabrication method is relatively small, and most of the prestresses are introduced by the post tension method using a bundle of attached strands embedded in four ducts. As shown in FIG. 3B, when the tensile force is introduced into the tensile material, the tensile end is located at the end, but the fixed end is located at a certain distance from the end of the girder so as to solve the excessive compression prestress problem of the end, So that more prestress can be introduced into the center portion.

The MSP girder (Multi-Stages Prestressed Composite Girder) shown in FIG. 4 is a method for making full use of the fact that the method of using the torsion material is more economical than the prefacing of the steel in the introduction of the lower concrete. And the prestress is introduced into the lower concrete only by the tensile material. The MSP girder is made of precast concrete panel with four ducts with fixing device at the end. When the concrete reaches the predetermined strength, the primary tension is introduced and then the steel and precast panel After combining, a second strain is applied. By providing sufficient curing time before straining the precast panel, the shrinkage of the lower concrete and the long term loss of the tension due to creep are partially reduced. Since the prestress is introduced by the four strand bundles tensed and fixed at both ends of the lower concrete, the lower concrete is larger in size than the existing steel composite girder in order to solve the problem of easy installation of the fixing device and excessive compression prestress at the end , And the steel material is relatively small because it is not subjected to the relief.

The main difference between the existing methods of FIGS. 1 to 4 lies in the method of introducing the compressive prestress of the lower concrete and of the introduced prestress. Figures 5 (a) -5 (e) illustrate a prestress introduced into a lower concrete and a prestress that can be used by an applied load. Especially, since the stress of the lower concrete under the steel composite girder is the main factor that dominates the bending design, it is very helpful to understand the difference of each method. 5 (a) to 5 (e) show the stresses of the lower concrete underfloor of the simply supported prestressed steel composite girder along the girder longitudinal direction.

5 (a) shows the allowable compressive prestress which can be introduced into the lower concrete according to the position of the girder. The allowable compressive prestress at the center portion of the girder is larger than that at the end of the girder, It becomes a simple beam structure which is supported only at both ends, and a bending moment of a parabolic shape due to the weight of the girder acts. As a result, the parabolic shape of the lower concrete under- The bending tensile stress is generated and the compression prestress is exhausted, so that the compression prestress introduction capacity is increased correspondingly. However, the end point at the point is simply equal to the allowable compressive stress of the lower concrete because the bending moment due to the weight of the girder is zero. Permissible compressive prestress is equal to the allowable compressive stress of concrete indicated by dashed line plus the flexural tensile stress of parabolic shape due to the weight of the girder.

Fig. 5 (b) shows the maximum bending tensile stress due to an action load capable of resisting the maximum compressive prestress that can be introduced into the preflex girder of Fig. 1 and the thus introduced compressive prestress. Fig. 5 (c) Fig. 5 (d) shows the precom girder, and Fig. 5 (e) shows the maximum compressive prestress that can be introduced into the MSP girder, respectively, and the maximum bending tensile stress that can resist. 5 (b) to 5 (e) are the permissible compression prestresses shown in FIG. 5 (a) and the thick solid lines shown just below the outline are the maximum introduced compression prestresses that can be introduced, Is the maximum allowable bending tensile stress due to the action force (distribution load standard) that the maximum compression pre-stress can resist. The maximum available bending tensile stress is shown for the sake of convenience, not on the allowable bending tensile force but on the zero stress. In other words, it is shown that the lower concrete always maintains the compressed state during the joint use of the steel composite girder. The reason why the maximum allowable bending tensile stress that can be resisted by the distributed load criterion is as follows: girder bulk load which occupies more than 70% of the load acting on the girder, bottom plate slab load, This is because a dead load such as anchorage load is a distributed load and the maximum bending moment is a parabolic shape in the case of a simple beam due to the characteristics of the live load and the moving load such as the vehicle load.

In comparison with the type of prestress introduced, the preflex girder is a trapezoidal shape with a constant size at the center and a constant size at the end as shown in Fig. 5 (b) because of the refraction of the steel girder due to the concentrated load. In the case of the RPF girder shown in FIG. 5 (c), since the prestressing of the steel girder due to the tense and fixed tensions at the both ends of the girder and the concentrated load is used, the prestressing due to the tension material and the trapezoidal shape Prestress is the combined form. In the case of the precom girder shown in FIG. 5 (d), a parabolic prestress acts due to the preflection due to the distribution due to the distributed load, and two pairs of strands bundled inside the lower concrete and tense at the ends Because of the use of prestressed staircase, the stepped prism is used. Since the MSP girder of Fig. 6 (e) uses only the tension material which is tensioned and fixed at both ends, almost uniform prestress is applied over the entire length of the girder. However, in the lower concrete, the tensile material is placed lower at the center of the girder than at the end of the girder to slightly increase the eccentricity of the tensile material, thereby introducing a slightly larger prestress at the center.

5 (b) to 5 (e), the precom girder of FIG. 5 (d) most effectively utilizes the allowable compressive prestress of the lower concrete from the viewpoint of having the greatest maximum available flexural tensile stress . The efficiency of the RPF girder of Fig. 5 (c), the preflex girder of Fig. 5 (b), and the MSP girder of Fig. 5 (e) deteriorate. Although theoretically, RPF girder uses prefabrication by concentrated load, the efficiency is slightly lower than that of precom using prefabrication by distributed load, but considering the reality of designing with a certain safety factor, There is little difference in method, and the main difference is the ease of prefabrication work. In addition, as mentioned above, the method of tensioning of the tension member is more economical than the prestressing of the steel according to the introduction standard of unit compression prestress. This is why, in the recent RPF girder design, the steel girder is reduced in strength rather than in the initial stage of development, and the tension discretion is increased instead. However, in the case of the RPF girder, since the prestressing material is used for tensioning and fixing at the end of the girder, a certain amount of prestress is applied to the entire section by the prestressing material.

The equipment that acts on the steel girder is expensive to install and operate. The reason why the MSP girder has a certain competitiveness despite the least efficiency in terms of utilization of the permissible compression prestress is that it does not refine. However, since the MSP girder uses only the tensioned material to be tensioned and fixed at the end, it can not fully utilize the allowable compression prestress in the large central portion as compared with the girder end, and also introduces an unnecessarily large prestress to the end portion. The large prestress at the end is not a big problem when using a steel composite girder for a simple beam structure. However, when the steel composite girder is continuous or integrated into a substructure as in a ramen bridge, This can be a problem because of additional stress. Therefore, when introducing the prestress into the prestressing material, a method of reducing the prestress at the end of the girder and increasing the prestress at the center as much as possible is required. In the case of the precom girder, as shown in FIG. 3B, a method of reducing the prestress of the girder end portion by the tension member to half the center portion by fixing the tension member at a position slightly away from the end portion without fixing the end portion is used.

FIG. 6A shows a fixed fixing device for a bundle of twelve strands of a strand bundle embedded in a concrete structure. In the lower photograph of FIG. 3B, it can be seen that a concrete installation is actually installed before the concrete is installed. Although only four strands are installed However, the inside of the reinforcing steel surrounding it is very complicated. Therefore, it can be seen that it would not be easy to install a fixed fixing device for a bundle of stranded wires (usually 10 to 15 stranded wires) in a narrower lowered concrete. Also, as shown in FIG. 5 (d), the stress rapidly changes at the fixing position in the lower concrete. Such a sudden stress change raises the probability of causing a local problem. It is known that the problems related to the fixed fixing device in the lower concrete occasionally occur due to these causes. To solve this problem, a fixing device is provided on the lower concrete as shown in FIG. 6B. However, the method of installing a fixing device on the upper part of the lower concrete is not very good in terms of workability, and it is not very good in terms of aesthetics because it is disadvantageous in simplicity which is a merit of a steel composite girder. In particular, as the length of the composite girder increases, the number of stranded wires required increases proportionally.

FIG. 7 shows a method for fixing a tent in a concrete structure having a hybrid tendon structure and a method for manufacturing the same, which is a method of fixing a monotender composed of one strand of wire. As shown in FIG. 8, the monotender used herein is a coated strand with plastic sheath (HDPE sheath) attached to each strand. A grease is filled between the strand and the sheath for greasing and lubrication. It is an unbonded strand that is not needed. In order to fix the coated strand, the coated strand and the grease are removed from the one end of the coated strand and the strand is exposed and fixed, thereby fixing the inside of the concrete. The tensioning method of the coated strand is a post tension method and the fixing method using the exposed wire portion 210 is called a hybrid tendency in the sense that it is the same as the strand fixing method in the pretensioning method.

One of the advantages of the hybrid tendon is that it does not use the conventional internal fixed fixing device as shown in FIG. 6A in which a large volume of installation space is required. Generally, in the post tension method, a method of installing a tensile material is such that a sheath is embedded in a concrete to form a tensile duct, and when the concrete is hardened, a tensile material composed of a bundle of strands inserted into the duct is tensioned and fixed. When the tension fixture is completed, the duct is grouted and the tension member and the concrete are adhered to each other. FIG. 3B shows an example using the post tension method. It is not easy to install an internal fixed fixing device of a tension member composed of a stranded bundle, and it is difficult to increase the number of ducts. However, since the hybrid tendon can be applied even in a case where the installation clearance space is narrow in a plane direction perpendicular to the longitudinal direction, a plurality of stranded wires are densely arranged and distributed on a small cross section like the lower concrete of the prestressed steel composite girder The inner fixation position of each tendon can be freely adjusted. That is, even if the RPF girder of FIG. 2 uses the coated strand as shown in FIG. 8, if the above-described method of fixing the hybrid tendon is used, the introduction of the prestress of a certain size by the tension member, which is a problem of the RPF girder, .

However, the fixed fixing method of the tension member as shown in Fig. 7 is different from the fixing method of the stranded wire in the pretensioning method. 9 is a graph illustrating the introduction length ( _t ) and the fixing length ( _d ) of the strand in the pretension mode. Introduction length concrete from the free end of the stress of tendons effective tension stress in the stress of tendons zero beams (girder) to release (release) the strand is stress for the introduction of the curing after the prestress that has been buried (f _pe In this section, the tensile force of the tensile material is transferred to the compressive force of the concrete by the adhesive force between the tensile material and the concrete, and the prestress is gradually introduced. Development length is when additional load is applied to the concrete beam prestressed such attachment required for fixing the stress of such increased tendons (f _ps) for any increase in stress in the tendons attached to the behavior in bending stress and acts on the concrete length. Usually, f _{ps, which} is used when calculating the fixation length of the tensile material, is close to the tensile strength f _pu of the tensile material. The graph of FIG. 9 is composed of two straight lines with different slopes, which is due to the difference in the mechanism of adhesion between the tensions and the concrete. The adhesive force between the tension and the concrete is composed of the adhesion between the strand and the concrete, the friction, the twisted structure of the strand and the mechanical interlocking effect of the concrete. The tensile strength of the strand When released for the introduction of the prestress, the tensile force is reduced in the transmission length section, and the cross-sectional area of the tensioned material contracted due to tensile force during expansion increases, thereby improving the frictional force and mechanical engaging effect (Hoyer effect). However, in the section after the introduction length, the tensile stress of the tensile material is larger than that at the time of the introduction of the prestress due to the bending moment due to the additional load, so that the cross-sectional area of the tensile material is reduced and conversely the adhesive force, frictional force and mechanical engaging effect are reduced. This is why the slopes of the two straight lines in the fusing length of Fig. 9 are different.

However, in the post tension method, since the tension member installed in an untensioned state is tensed after the concrete is hardened, the graph of FIG. 9 has the same characteristics as the fixing period after the introduction length. In other words, when the tension is reduced, the cross-section of the tensions decreases, and the adhesion between the tensions and the concrete decreases. In Fig. 9, the difference between the slopes of the two straight lines is approximately three times. Considering these characteristics, the calculated length of the exposed strand of the coated strand as shown in FIG. 7 is about 5 m in the case of the 15.2 mm diameter strand (SWPC 7C). Since the fixing method as shown in FIG. 7 has not been used in the post tension method, the fixation length was calculated by using the pre-tension type fixing length designing method, and the fixing fixture of the hybrid tendon was performed. All of the strands were selected and failed to settle. It was assumed that the failure of the test was due to the fact that the grease was not completely removed during the removal of the coating of the coated strand and the removal of the grease. However, even if the experiment succeeded, the settlement length of about 5 m is too long to have applicability. Also, there is a problem that the complete removal of grease is virtually impossible to guarantee, but the biggest problem is that the entire beam must be disposed of if the fixation of the tension member fails in the concrete member. Therefore, it is necessary to appropriately reduce the fixing length in order to improve the safety of the fixing method of the tension member while improving the applicability.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a prestressed steel composite girder constructed by combining an upper steel material and a lower concrete, The present invention provides a method for manufacturing a prestressed steel composite girder which is capable of introducing a maximum of a large prestress into a lower concrete at a center portion of a girder having a prestress and alleviating a sudden stress change near an inner fixed fastening portion.

As a means for solving the above-mentioned problems,

A beam forming step of forming a first beam of a long steel material in one direction and a second beam of a reinforced concrete material structured below the first beam and structurally synthesized with the first beam, the upper beam including an upper flange and an abdomen;

In the beam forming step, a strand is formed inside the second beam in the form of a non-adherent strand at one end and the other is formed in the form of an adhered strand, a protrusion is formed on the surface of the adhered strand, And a reinforcing steel rod assembly made of a linear fixing fixture is buried in the longitudinal direction of the second beam,

Wherein the linear fixed fixing unit is arranged inside the intermediate beam and the one end of the second beam so that the linear fixed fixing unit is fixed inside the second beam without a separate internal fixed fixing device and a stranded wire in the form of a non- A stranded wire assembly embedding step of disposing the end of the unbonded stranded wire so as to be exposed to the outside of the second beam;

And a prestressing step of applying a tensile force to the embedded strand assembly in the strand assembly embedding step after the concrete of the second beam is hardened to a predetermined strength to fix the strand assembly to the fixing device at the end so that the prestress acts on the beam The composite synthetic beam having a diameter greater than that of the prestressed steel composite beam.

Further, according to the present invention,

In the beam forming step, a strand of a predetermined length of one end of the second beam is formed in the form of a non-bonded strand, the other is formed in the form of an attached strand, and a deformed sleeve in the form of a projection of a deformed reinforcing bar And a stranded wire assembly made of a linear fixed fixing unit is embedded in the longitudinal direction of the second beam,

Wherein the linear fixed fixing unit is disposed inside the intermediate beam and the one end of the second beam so that the linear fixed fixing unit is fixed inside the second beam without a separate internal fixed fixing device and the stranded wire in the form of a non- A stranded wire assembly embedding step of disposing the end of the unbonded stranded wire so as to be exposed to the outside of the second beam;

According to a third aspect of the present invention,

In the beam forming step, a strand having a predetermined length at one end inside the second beam in the form of unbonded strand, the remainder being made in the form of an attached strand, and a strand having a strength not lower than the concrete aggregate strength at the surface of the strand Wherein the strand assembly is formed by coating the particles with a linear fixing fixture in the longitudinal direction of the second beam,

Preferably, the strand assembly is disposed such that a tension force acts symmetrically on the basis of the length and width of the second beam.

It is preferable to control the size of the prestress acting on the beam and the section in which the prestress acts, by using different lengths of the non-adhered stranded portion of the strand assembly.

According to the present invention, it is possible to improve the tension and fixing method of the stranded wire in the prestressed steel composite girder, thereby minimizing the relief of the steel girder or maximizing the allowable compressive prestress of the lower concrete, The present invention also provides a method of manufacturing a prestressed steel composite girder which is economical and low in solidity, which can alleviate sudden stress change in an internal tension member fixing part and dramatically improve workability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a method of manufacturing a preflex steel composite girder. FIG.
2 is a cross-sectional view of a RPF (Represtressed PreFlex) girder.
3A and 3B are views for explaining the Precom girder construction method.
4 is a sectional view for explaining the MSP girder method.
5 (a) to 5 (e) are diagrams for explaining maximum allowable compression pre-stress and maximum allowable bending tensile stress of allowable compressive prestress of lower concrete underlayers and existing steel composite girders.
6A is a view for explaining an example of a fixed fixing device installed inside concrete.
FIG. 6B is a view for explaining an example of a fixing device installed on an upper portion of a lower concrete; FIG.
FIG. 7 is a view for explaining a conventional fixed fixing method of a hybrid tent. FIG.
8 is a view for explaining the structure of a coated strand.
9 is a view for explaining a transfer length and a development length of a strand in a pretension mode;
10 is a cross-sectional view illustrating a method of constructing a prestressed steel composite beam according to a first embodiment of the present invention.
11 is a view for explaining a planar arrangement method of a tension member for introducing a symmetric prestress and a compressive force introduced into a second beam by a deployed tension member.
12 is a view for explaining the allowable compression prestress and the maximum introduced compression prestress of the second beam lower edge according to the degree of change of the fixing position of the coated strand.
13 is a cross-sectional view showing an example of a method for installing a coated strand of the present invention for introducing a symmetric prestress.
14 is a view for explaining a method of joining a deformed bar having a larger cross-sectional area than a stranded wire to sleeve swaging.
15 is a view for explaining a strand assembly according to a second embodiment of the present invention.
16 is a view for explaining a strand assembly according to a third embodiment of the present invention.
FIG. 17A is a view for explaining an embodiment in which the second embodiment and the third embodiment of the present invention are used in combination; FIG.
17B is a view for explaining an embodiment in which the first embodiment and the third embodiment of the present invention are used in combination.

Hereinafter, a method of constructing a prestressed steel composite beam according to a preferred embodiment of the present invention will be described with reference to the drawings, thereby providing specific details for implementing the present invention.

First, a method of constructing a prestressed steel composite beam according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 10 is a sectional view for explaining a method of constructing a prestressed steel composite beam according to the first embodiment of the present invention, FIG. 11 is a schematic view showing a method of arranging a tension member for introducing a symmetric prestress, Fig. 12 is a view for explaining the allowable compressive prestress and the maximum introduced compressive prestress of the second beam lower edge according to the degree of change of the fixation position of the coated strand, Fig. 13 is a view for explaining the compressive force introduced, Fig. 14 is a view for explaining a method of joining a deformed bar having a larger cross-sectional area than a stranded wire to a sleeve swaging joining method.

The method of constructing a steel composite beam according to the present embodiment (first embodiment) includes a beam forming step, a strand wire assembly embedding step, and a prestressing step.

In the present invention, the beam is a structure including a long reinforcing concrete material which is resistant to a bending moment and is referred to as a beam but can also be used as a girder, and this embodiment is applicable to a case where a steel composite beam is used as a girder In the following, the steel composite beam and the steel composite girder are used as the same concept.

The beam forming step is a step of fabricating a beam composed of the first beam 10 and the second beam 20.

The first beam 10 is a beam of steel composed of an upper flange 11, a waist portion 12 and a lower flange 13 as shown in the sectional view of Fig. 10, and is long in one direction.

The second beam 20 is a beam of a reinforced concrete material structurally synthesized with the first beam 10 and is long in one direction like the first beam 10. Although the reinforcing bars are laid in the second beam 20, the reinforcing bars are omitted in the drawings for convenience of illustration.

This means that the lower flange 13 of the first beam 10 and a part of the abdomen 12 of the first beam 10 act as a second beam when the load is applied, 4, and only a part of the lower flange 13 may be embedded in the concrete of the second beam 20, or may be embedded in the concrete of the second beam 20. [ Or the like. For the synthesis of the first beam 10 and the second beam 20, various types of shear connectors may be used for the joint surfaces, but omitted for convenience of illustration.

The stranded wire embedding step is a step of embedding a stranded wire assembly in the second beam before placing the concrete in the beam forming step. The strand assembly is embedded in the longitudinal direction of the second beam 20 as shown in FIG.

The strand assembly 110 is composed of a linear fixed anchor and a non-attached strand 112 that are formed by combining an attached strand 111 and a deformed bar 113.

The non-adherent strand 112 has a coating on the outer periphery thereof, which means that the concrete and the strand are not in direct contact with each other and are not adhered to each other during curing of the concrete. In this embodiment, the unbonded strand 112 is a normal coated strand As shown in FIG. 8, a normal coated strand is a strand having a shape coated with HDPE coating on the outer circumferential surface of a strand, and a shape filled with grease for coating and lubrication between the coating and the strand.

The attached strand 111 refers to a strand which is attached to the interior of the concrete when curing the concrete. The strand 111 acts as an internal fixing device of the strand assembly 110 together with the deformed bar 113 and forms a thin and long fixing device. A configuration in which the releasing bar 113 and the attached strand 111 are combined will be referred to as a linear fixed fixing unit. The above-mentioned linear fixed fixing portion is a portion attached to the concrete except for the non-attached strand 112 portion of the strand assembly 110, and may have various deformed shapes.

The deformed bar 113 is a rod having a long length in one direction, and a protrusion like a rod is formed on the surface.

As the deformed bar steel, a threaded steel bar having a deformed reinforcing bar or a rolling screw can be used.

In order to withstand the maximum tensile strength of a steel strand having a small tensile strength due to its small tensile strength, it is necessary to use a reinforcing steel having a larger cross-sectional area than that of the steel strand. Recently, a tensile strength of 700 MPa Since the high strength steel (SD700) is produced and used domestically, it is possible to reduce the difference in cross sectional area between the steel wire and the deformed steel bar by using high strength steel bars. If the threaded bar is used as a deformed bar, the difference in cross-sectional area between the stranded bar and the deformed bar is further reduced since the tensile strength of the threaded bar is about 1000 MPa.

It is noted that bonding the deformed bar 113 with the exposed reinforcing wire 111 is intended to increase the bonding strength and there is a considerable difference in the bonding strength depending on the surface shape. In the bond strength test, a pull out test is used most commonly to pull out the tensions embedded in the concrete with a certain length until the bond is broken. In this experiment, an example of the bond strength test between the strand and the deformed bar The bond strength of the strand is about 3 MPa, and the bond strength of the deformed bar is about 26 MPa, which is 8 to 9 times different. The results of the full-out test show that the deviation is very large, but it is clear that the difference in bond strength between the strand-type stranded wire made of twisted wires and the deformed bar with protruding nodules is considerably large. The main reason for this difference is that the bearing effect by the nodule of the deformed bar is much more effective in improving the adhesion performance than the mechanical interlocking by the twisted structure of the stranded wire. In the tensile force (Fp) distribution graph of the tension member shown in the lower side of Fig. 10, the tensile force Fp is reduced at a different reduction rate (slope) in the linear fixed fixing portion, and the reduction rate is proportional to the adhesion strength. The fixation length becomes too long when the linear fixing fixture of the tensile material is constituted by only the exposed strand only because the adhesion strength of the strand is small and the reduction rate of the tensile force (Fp) is gradual. As shown in the figure, when the deformed bar is much larger than the strand, the slope can be increased and the fixing length can be reduced.

A variety of mechanical joining methods can be applied as a method of joining the bonded strand 111 and the deformed bar 113. In this embodiment, the joined portion of the bonded strand 111 and the deformed bar 113 is connected to a sleeve 115 A sleeve swaging joining method is used which is wrapped and compressed by applying a mechanical force. At this time, there may be a difference in cross-sectional area between the bonded strand 111 and the deformed bar 113. (The tensile strength of the strand is different from that of the deformed bar. As shown in the figure, a method may be used in which the step-adjustment sleeve 116 is inserted into the surface of a member having a small cross-sectional area, and then the sleeve 115 is connected to the sleeve. The sleeve swaging joint equipment is small in size and can be easily used in the field.

When the deformed bar 113 is bonded to the bonded strand 111, the disadvantage of the strand with small bonding strength can be compensated for as a deformed bar, thereby remarkably reducing the fixing length. As a result, the second beam 20 The length of the unbonded strand 112 for introducing the prestress can be increased and the safety factor of fixed fixing can be increased.

The method of placing the strand assembly 110 is shown in FIG. Is disposed between the middle and one end of the second beam (20) to be fixed to the second beam (20) without a separate internal fixed fixing device using a linear fixed fixing part including an attached stiffener (111) 112 are disposed on the remaining portion except for the linear fixed fixing portion and the end portion on the side of the unbonded strand 112 is exposed to the outside (end surface) of the second beam 20. This is for tensioning and fixing the external fixing device 30

10 is a view for explaining the fixation length of the linear fixed fixing unit in the strand assembly 110. As shown in FIG. The length of the linear fixed fixing part is longer than the designed fixing length. It is preferable to make the length of the exposed deformed steel bar longer than the assumed fixing length in the design calculation so as to reliably prevent the failure of the internal fixed fixing.

The prestress introduced into the beam by the strand assembly 110 is preferably arranged so that a symmetrical prestress can act in the longitudinal and width directions of the beam, and an example of such arrangement is shown in FIG.

Figure 11 (d) shows the distribution of the compressive forces introduced into the second beam 20 by the strand assembly 110 planarized in Figure 11 (a). For convenience of explanation, a tensile material having a linear fixed fixing portion on the right side of FIG. 11A is denoted by reference numeral 110A, and a tensile member having a linear fixed fixing portion on the left side of FIG. 11A is denoted by reference numeral 110B. 11 (b) shows the compressive force components introduced into the second beam 20 by a tensile member denoted 110A in a graphical form, and FIG. 11 (c) The compressive force components introduced into the beam 20 are shown in graphical form. FIG. 11 (d) shows the distribution of the sum of the two compression force components in a graph. Here, the sum of the compressive forces is symmetrical about the center in the longitudinal direction, and the tensile members 110A and 110B are symmetrical pairs in the width direction, respectively, so that only the longitudinal axial force is exerted without generating the wing force in the width direction.

When the PSC steel composite beam constructed according to the present invention is used in a simple beam structure, the compressive force acting on the second beam 20 and the compressive prestress due to this compressive force are in a simple proportional relationship according to the beam theory, The compressive stress (compressive prestress) acting on the lower edge of the beam 20 also has a distribution of the same type.

In this embodiment, various types of compressive forces (compressive prestress) can be introduced into the second beam 20 by adjusting the arrangement length of the unattached strand 112. Some examples are shown in Fig. 12 (a) shows a case in which a tensile stress is applied to the second beam 20 by using two types of tensile members 110a and 110b having different lengths of unbonded strand 112 disposed inside the second beam 20, 10b shows three types of tensile members 110a, 110b, and 110c having different lengths of unbonded strands 112 disposed inside the second beam 20, And a compressive prestress is introduced into the second beam 20 by using the same.

The tensions shown in Figs. 12 (a) and 10 (b) are arranged without consideration of the symmetrical arrangement described above, which is for convenience of illustration. 12 (c) shows a case in which a compression prestress is introduced into the second beam 20 by using four types of tension members having different lengths of the unattached strand 112 disposed inside the second beam 20 The placement of the tensions is omitted for convenience of illustration. The uppermost curve in each graph indicates the allowable compression prestress according to the interval. The parabolic curve indicated by the dotted line at the bottom of the graph of FIG. 12 (c) is the maximum allowable bending tensile stress due to the action force (distribution load reference) that the maximum introduced compression prestress can resist (see FIG. 5).

If the arrangement length of the unattached strand 112 is appropriately changed, it is possible to introduce a compressive prestress into the second beam 20 which can maximally utilize the allowable compression prestress of the lower beam of the second beam 20, There is an advantage that it can be designed efficiently.

In order to introduce a symmetrical prestress using the tensional force introduction system of the present invention, as shown in (a) of FIG. 11, four symmetrically arranged stranded wires must be used as one set, Since the number of stranded wires required for a prestressed steel composite girder is usually in the range of 50 to 80, the use of a quadruple number has little effect on the use efficiency of the stranded wire. Fig. 13 is a cross-sectional view near the end of the girder, showing a symmetrical arrangement of 72 strands of 36 stranded non-stuck stranded wires 112, . (In the present embodiment, the linear fixed fixing portion is composed of an attached strand 111 and a deformed bar 113, so the linear fixed fixing portion is denoted by reference numeral 113.) In a symmetrical position on the opposite side in the longitudinal direction of the girder, (Reference numeral 113 in FIG. 13) is reversed to the unattached strand 111, and the unattached strand 112 is reversed with a linear fixing fixture (reference numeral 113 in FIG. 13). In this case, since the four strands are arranged as one set, the length of the unattached strand 112 can be changed by a maximum of 18 times.

In the meantime, although the size of the compression prestress (or compression force) introduced into the second beam 20 in FIGS. 11 and 12 is shown in a stepwise manner, the compression prestress is gradually introduced in a curved shape gradually through the fixing length. Considering this point, the advantage of efficiently designing the beam as described above is further highlighted.

10, after the concrete of the beam is cured to a predetermined strength, the prestressing step fixes the strand assembly 110, which is embedded in the second beam 20, to the fixing device in a state of applying tensile force to the strand assembly 110, It is a step that allows the prestress to work.

The ends of the strand assembly 110 on the side of the unbonded strand 112 are exposed to the end face of the beam or the end side of the beam and are fixed to the external fixing device 30 after applying a tensile force thereto. In the case of using the coated strand by the unbonded strand 112, it is necessary to remove the covering of the coated strand of the exposed portion from the end of the beam in order to tense and fix the strand, The above description is omitted.

Hereinafter, a method of constructing a prestressed steel composite beam according to a second embodiment of the present invention will be described.

15 is a view for explaining a strand assembly according to a second embodiment of the present invention.

The method of constructing the beam according to the present embodiment includes a beam forming step, a strand wire assembly embedding step, and a prestressing step as in the first embodiment described above.

Since the configuration of the linear fixed fixing portion of the strand assembly that is embedded in the second beam 20 in the strand assembly embedding step is different from that of the above configuration and the rest are the same, a description of the beam forming step and one prestressing will be omitted, Will be described.

The strand assembly 210 used in this embodiment is formed by attaching a release strand 213 to the surface of an attached strand 211 and an attached strand as shown in Fig. 15 and a non-stick strand 212 ).

The release sleeve 213 may have a very short length of the sleeve to form one node for each one of the sleeves as shown in FIG. 15 (a), or a longer length of the sleeve as shown in FIG. 15 (b) It is preferable that the height of the knob of the release sleeve 213 is high so that a too great pressure is not applied to each knot.

The provision of the release sleeve 213 on the surface of the stiffened strand 211 is intended to increase the strength of adhesion to concrete as in the case of joining the deformed bar steel in the previous embodiment. As described above, attention is paid to the fact that the adhesive strength of the deformed reinforcing bar is larger than that of the strand, so that a sleeve similar to the protrusion of the deformed reinforcing bar is bonded to the surface of the strand.

The method of coupling the release sleeve 213 to the stiffening line 211 is similar to that of the sleeve 115 for coupling the stiffening stripe 111 to the release stiffener 113 in the previously described first embodiment, It is possible to use a swaging method in which a mechanical force is applied to press the surface of the bonded strand 211 while pressing it. On the other hand, in the case of FIG. 15 (b), a sleeve having a preformed portion may be used, or a die capable of forming a node may be used for swaging. 15 (c), it is also possible to sandwich the elongated sleeves, which have been preformed in advance, on the strands and grout the adhesive 214 between the strands and the sleeves.

The effect of reducing the fusing length using the release sleeve 213 has been described above and will be omitted here.

Hereinafter, a third embodiment of the present invention will be described.

16 is a view for explaining a strand assembly according to a third embodiment of the present invention.

The method of constructing the beam according to the present embodiment includes a beam forming step, a strand wire assembly embedding step, and a prestressing step as in the first and second embodiments described above.

Among these constructions, there is a difference in the configuration of the linear fixed fixing portion of the strand assembly that is embedded in the second beam 20 in the strand assembly embedding step, and the rest are the same, so that the explanation of the beam forming step and the prestressing step is omitted, Will be described.

The strand assembly of the present embodiment is constituted by a linear fixed fixing part and a non-attached strand 312 which are produced by coating the surface of an attached strand 311 and an attached strand with particles 313 as shown in Fig.

In order to improve the adhesion performance of a member adhering to concrete, a method of sticking hard silica particles to the surface of the member using a polymer (resin) is often used, and this method is used for the bonded strand 311. The hard particles (313) used in the particle coating means particles having strength equal to or higher than the concrete aggregate strength, and usually particles used as abrasives can be used.

When the particles 313 are coated on the stuck strand 311 using a polymer, the adhesion strength is increased. Particularly, when the sheath and grease of the coated strand are removed to form an attached strand, the grease on the surface of the strand is easy to remove, but since the grease remaining between the twisted strands is difficult to remove, such residual grease flows later, It is possible to reduce the frictional force. In the particle coating, the polymer used as the adhesive is applied to the surface of the strand, the particles 313 are evenly spread, and the polymer is applied on the particles again. So that it is possible to prevent the residual grease from leaking to the surface and reducing the frictional force.

Even when the coated particles 313 are used, the fixing length of the bonded strand 311 can be reduced, and the effect is as described above.

On the other hand, even when the above-described embodiments are used in combination, the effect of reducing the fixing length can be expected. As shown in Fig. 17A, the second embodiment and the third embodiment of the present invention are used in combination Alternatively, the first embodiment and the third embodiment of the present invention may be used in combination as shown in FIG. 17 (b). The deformed bar 113 shown in FIG. 17 (b) has a cross-sectional enlargement member 117 such as an enlarged head of a reinforcing bar at its end, so that the fixing length can be more effectively reduced.

In the above-described embodiments, the introduction of the prestress by the refraction of the first beam 10 is not described for the sake of convenience. However, in the present invention, as in the case of the existing prestressed steel composite girder methods, The first beam 10 is subjected to a prestressing load before the beam 10 and the second beam 20 are combined and the concrete of the second beam 20 is cured to form the first beam 10 and the second beam 20. [ 20) is synthesized, it is possible to use a method of introducing a prestress by removing the prillation load.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed exemplary embodiments, The present invention can be embodied as a method of constructing various types of prestressed steel composite beams.

111: Bonded strand 112: Unbonded strand

Claims

A beam forming step of forming a first beam of a long steel material in one direction and a second beam of a reinforced concrete material structured below the first beam and structurally synthesized with the first beam, the upper beam including an upper flange and an abdomen;
In the beam forming step, a strand is formed inside the second beam in the form of a non-adherent strand at one end and the other is formed in the form of an adhered strand, a protrusion is formed on the surface of the adhered strand, And a reinforcing steel rod assembly made of a linear fixing fixture is buried in the longitudinal direction of the second beam,
Wherein the linear fixed fixing unit is arranged inside the intermediate beam and the one end of the second beam so that the linear fixed fixing unit is fixed inside the second beam without a separate internal fixed fixing device and a stranded wire in the form of a non- A stranded wire assembly embedding step of disposing the end of the unbonded stranded wire so as to be exposed to the outside of the second beam;
And a prestressing step of applying a tensile force to the embedded strand assembly in the strand assembly embedding step after the concrete of the second beam is hardened to a predetermined strength to fix the strand assembly to the fixing device at the end so that the prestress acts on the beam Wherein the pre-stressed steel composite beam is applied to the pre-stressed steel composite beam.

A beam forming step of forming a first beam of a long steel material in one direction and a second beam of a reinforced concrete material structured below the first beam and structurally synthesized with the first beam, the upper beam including an upper flange and an abdomen;
In the beam forming step, a strand of a predetermined length of one end of the second beam is formed in the form of a non-bonded strand, the other is formed in the form of an attached strand, and a deformed sleeve in the form of a projection of a deformed reinforcing bar And a stranded wire assembly made of a linear fixed fixing unit is embedded in the longitudinal direction of the second beam,
Wherein the linear fixed fixing unit is disposed inside the intermediate beam and the one end of the second beam so that the linear fixed fixing unit is fixed inside the second beam without a separate internal fixed fixing device and the stranded wire in the form of a non- A stranded wire assembly embedding step of disposing the end of the unbonded stranded wire so as to be exposed to the outside of the second beam;
And a prestressing step of applying a tensile force to the embedded strand assembly in the strand assembly embedding step after the concrete of the second beam is hardened to a predetermined strength to fix the strand assembly to the fixing device at the end so that the prestress acts on the beam Wherein the pre-stressed steel composite beam is applied to the pre-stressed steel composite beam.

A beam forming step of forming a first beam of a long steel material in one direction and a second beam of a reinforced concrete material structured below the first beam and structurally synthesized with the first beam, the upper beam including an upper flange and an abdomen;
In the beam forming step, a strand having a predetermined length at one end inside the second beam in the form of unbonded strand, the remainder being made in the form of an attached strand, and a strand having a strength not lower than the concrete aggregate strength at the surface of the strand Wherein the strand assembly is formed by coating the particles with a linear fixing fixture in the longitudinal direction of the second beam,
Wherein the linear fixed fixing unit is disposed inside the intermediate beam and the one end of the second beam so that the linear fixed fixing unit is fixed inside the second beam without a separate internal fixed fixing device and the stranded wire in the form of a non- A stranded wire assembly embedding step of disposing the end of the unbonded stranded wire so as to be exposed to the outside of the second beam;
And a prestressing step of applying a tensile force to the embedded strand assembly in the strand assembly embedding step after the concrete of the second beam is hardened to a predetermined strength to fix the strand assembly to the fixing device at the end so that the prestress acts on the beam Wherein the pre-stressed steel composite beam is applied to the pre-stressed steel composite beam.

4. The method according to any one of claims 1 to 3,
Wherein the strand assembly is disposed such that a tension force acts symmetrically on the length and width of the second beam.

4. The method according to any one of claims 1 to 3,
Wherein the length of the unstretched stranded portion of the strand assembly is varied to control the size of the prestress acting on the beam and the section in which the prestress acts.