KR950001975B1 - Method for prestress compound beam - Google Patents

Abstract

The method is for curing concrete over a shaped beam and applying a prestress to the concrete-cured shaped beam, and specially prevents a local fracture in the cured concrete when applying the prestress to the shaped beam. The method comprises the steps of : inflicting a 1st pre-flection force while supporting both ends of a reinforcement member(5) in order to form spaces (7,7a,7b,7c, 7d,7e,7g) each to have a sheath pipe (8) at the bottom a pipe (8); curing a constant cross-sectioned concrete around a lower flange (6) while inflicting a 2nd pre-flection force; placing tendons (9) each through respectiue the spaces and pulling both ends of the tendon (9) fix to anchors (11) to both ends of the shaped beam (1), and inflicting a 3rd pre-flection force.

Description

Manufacturing method of composite prestressed composite beam

1A to 1H are front views of a shaped beam used in a composite beam according to the present invention.

2a to 2e is a manufacturing process diagram of the primary prestressed composite beam according to the first embodiment of the present invention.

3A to 3F are manufacturing process diagrams of a primary prestressed composite beam according to a second embodiment of the present invention.

4a to 4d are manufacturing process diagrams of the primary prestressed composite beam according to the third embodiment of the present invention.

5a to 5b are explanatory views of a method of applying a third prefraction load according to the present invention.

6A to 6G are sectional views taken along the line A-A in FIG. 5B.

7a to 7d are moment lines for determining the magnitude of the third order prefraction load according to the first, second and third embodiments of the present invention.

8A to 8C are stress-strain diagrams on the central portion of the beam beam according to the first, second and third embodiments of the present invention.

9 is a perspective view of a prestressed composite beam according to the prior art.

10a to 10f is a manufacturing process diagram of the prestressed composite beam according to the prior art.

11 is a bending moment diagram for a design maximum bending moment diagram of an I-beam for determining the magnitude of the primary pre-fraction load in the manufacturing process according to the prior art.

12 is a stress-strain plot at the center of a prestressed composite beam according to the prior art.

* Explanation of symbols for main parts of the drawings

1: beam beam 2: upper flange

3: concrete 4: web

5: reinforcing member 6: lower flange

7, 7a, 7b, 7c, 7d, 7e, 7f, 7g: accommodation space

8: sheathpipe 9: tandon

10: support plate 11: anchor

20, 20a, 20b: primary prestressed composite beam

The present invention relates to a method for manufacturing a prestressed composite beam that gives the prestress to the one-day flange of the steel beam after curing by pouring concrete into the steel beam, and in particular, the required amount of steel beam of the steel beam can be significantly reduced, and also the prestress. The present invention relates to a method for manufacturing a composite prestressed composite beam to prevent local breakage of concrete when imparted.

In general, pre-stressed composite beams, which are widely used in construction, mean that I-beams are good in terms of tensile strength, while concrete is superior in compressive strength, and as shown in FIG. It refers to a composite beam imparted with prestress by pouring and curing concrete 53 on one flange 52 in a state in which a load is applied to have elastic return stress within a predetermined elastic limit.

In order to manufacture such a composite beam, the manufacturing process is often performed as follows. First, as shown in FIG. 10A, the whole is bent to one side and manufactured by rolling or welding to have a predetermined capber (δ ₀ ). With both ends of the beam 51 simply supported, the first preflection within the elastic limit at two points approximately one quarter of the total length ι at both ends, as shown in FIG. 10B. When the load P ₁ is applied with a predetermined camber δ ₁ over about 60 minutes and then removed to give a bending moment slightly larger than the design maximum bending moment shown graphically in FIG. Reference numeral 51 denotes a permanent deformation due to internal residual force generated at the time of manufacture, and elastically returns with the camber δ ₂ somewhat smaller than the original camber δ ₀ as shown in FIG. 10C.

Subsequently, as shown in FIG. 10D, in the state in which the second pre-fraction load P ₂ having the same size as when the _first pre-fraction P ₁ is applied to the same position, the 10e As shown in FIG. 1, when the concrete 53 is poured into one flange 52 of the I-beams 51 to cure and then remove the _second pre-fraction load P ₂ , the I-beams 51 ) Is elastically returned, and prestress is applied to the steel concrete 53, thereby forming a prestressed composite beam having a predetermined camber δ _f as shown in FIG. 10f.

On the other hand, based on the stress (σ _s ) -strain (ε) diagram at the central portion of the I-shaped steel beam 51 in the manufacturing process as described above, as shown in FIG. 12, first I-shaped steel beam 51 The I-beam beam 51 to which the first pre-fraction load P ₁ is applied is subjected to the initial capber δ ₀ and the first pre-fraction load P while being subjected to stress σ _se from 0 to A point. ₁ ) 0-C (δ ₀ + δ ₁ ) corresponding to the camber δ ₁ by only a large deformation, and when the first pre-fraction load P ₁ is removed, the I-shaped steel beam 51 is internally Because of the residual stress of, it does not return from point A to point 0 but only returns to 0 ', accompanied by permanent deformation of δ ₀ -δ ₂ .

In the state in which the _second pre-fraction load P ₂ is applied again to the I-shaped steel beam 51 in which the permanent deformation has occurred, the concrete 53 is poured on one flange 52 and cured, and then the second pre-flag is formed. When the shunt load (P ₂ ) is removed, the I-beam steel 51 is elastically returned toward the starting point of 0 'point because the internal residual stress has already been induced to permanent deformation in the previous stage, while the concrete 53 is point D at point C. Compressed toward. In this process, the I-shaped steel beam 51 at points B and D in which the tensile force of the prestress tensile stress (σ _sp ) of the I-shaped beam 51 is equal to the compressive force of the prestress compressive stress (σ _cp ) of concrete. ), The elastic return movement is stopped, and the difference between the first camber (δ ₀ ) and the last camber (δ _f ), i.e., 0-H (δ), is given to the I-beam beam 51 with a prestressed tensile stress of σ _sp . _{While 0} -δ _f ) tensile strain occurs, the concrete 53 is subjected to compressive strain as much as CH while being given prestress compressive stress as much as σ _cp .

Therefore, since the prestressed composite beam manufactured through the above manufacturing process is given prestress therein, the prestressed composite beam has superior characteristics in terms of strength compared to the simple I-beam steel 51, and also the inside of the I-beam steel 51. As the concrete is cured in a state where residual stress is effectively induced to permanent deformation, cracking of the concrete 53 due to internal residual stress does not occur after construction.

However, the correlation between the bending moment (M), the internal maximum bending area (σ) and the cross-sectional coefficient (S) of the I-beam steel beam 51 by the first and second pre-fraction load (P ₁ , P ₂ ) The internal maximum bending stress σ of the I-beams 51 due to the bending moment M, whose relationship is sigma = M / S and is set slower than the design maximum bending moment, can be elastically recovered. Since the cross-sectional coefficient S of the I-beam steel 51 must be turned on because the elastic limit stress σ _P must be less than that, the flange 52 becomes large, so that the required amount of required steel material will eventually increase. Inevitably, there are disadvantages that are not economical.

Accordingly, the present invention has been made in view of the above circumstances, and in order to maintain the structural rigidity required for the prestressed composite beam, the steel is increased by increasing the cross-sectional area of the concrete while reducing the required amount of steel in the concrete pouring portion of the tension flange of the I-beam. The purpose of the present invention is to provide a method of manufacturing a composite prestressed composite beam having excellent mechanical properties as well as reducing manufacturing cost by reducing the discretion.

In order to achieve the above object, the present invention is provided with a reinforcing member installed in the longitudinal direction on the lower flange side so that both ends of the shaped beams shaped to have a minimum effective cross-sectional area are simply supported so that they are subjected to bending stress of less than the elastic limit stress. Induce residual residual stress to permanent deformation by applying the first prefraction load, and then apply concrete to the lower flange while applying the second preflection load of the same size at the same point as the first prefraction load. After pouring and curing, by putting a tendon (tendon) in the receiving space formed by the reinforcing member to pull in the opposite direction from both sides, the third pre-flection load is applied directly to the beam beam, the third The bending moment of the beam beam by the pre-fraction load and the second pre-fraction load is applied to be 10 to 20% larger than the design maximum bending moment to manufacture the composite beam. All.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1A to H are various cross-sectional views of the shaped steel beam 1 used in the method for manufacturing the composite beam of the present invention, which is generally used to directly apply the third prefraction load to the shaped steel beam 1. It is slightly deformed, that is, the lower flange 6 by installing a reinforcing member 5 having a hat-shaped cross section between one end portion of the web 4 and the lower flange 6 as shown in FIG. 1A. It has a structure in which the site is modified.

As another form of the beam beam 1, it is a matter of course that the cross section of the lower flange portion of the I beam can be modified as shown in Figs.

Here, the beam beam (1) is shaped to have a minimum effective cross-section with stability to the stress or leg buckling generated in the manufacturing process as possible to reduce the amount of steel required in the composite beam, this minimum effective cross-sectional area to have the production process according to the present invention the first embodiment for producing a composite prestressed composite beam with a shaped section steel beams (1) is entirely curved to the upper, as first illustrated in the 2a also predetermined camber (δ ₀₎ With both ends of the shaped steel beam 1 formed by rolling or welding to have a supported state, as shown in FIG. 2B, two points separated from each end by about 0.25L with respect to the total length L are shown. The first pre-fractional load P ₁ is applied for a predetermined time. In this case, the magnitude of the first pre-fractional load P ₁ is the elastic limit stress (σ) of the beam beam 1 at the point where the load is applied. _P ) less than It is determined to be elastically returned by bending stress. Here, the bending moment of the beam beam 1 by the first pre-fraction load P ₁ is designed to have the minimum effective cross-sectional area of the beam beam 1, so that the bending moment diagram is shown in FIG. 2b. Naturally smaller than the required design maximum bending moment as shown.

Thus, when the first pre-fraction load P ₁ is applied to the shaped beam 1 for a predetermined time, for example, for 60 minutes so as to receive a bending stress of less than or equal to the elastic limit stress σ _P , the shaped beam 1 ) Is a beam shaped elastically deformed with a camber (δ ₂ ) having a somewhat smaller than the original camber (δ ₀ ) as shown in FIG. 1) is obtained.

Next, the first car-free fraction load (P ₁₎ and the second pre-fraction loading (P ₂₎ a too slowly added state over a period of 60 minutes at the same point of the same size as shown in the 2d FIG. When the concrete 3 is poured around the lower flange 6 and cured, and then the second pre-fraction load P ₂ is removed, the beam beam 1 has a predetermined camber as shown in FIG. 2E. The concrete 3 is compressed to give a first prestressed composite beam 20 to which a prestressed compressive stress is applied while being tensioned with (δ ₃ ) to impart a prestress tensile stress.

On the other hand, as in the method of applying the first and second pre-fraction loads, as in the patent application No. 90-19911 previously proposed by the applicant, a different sized load is sequentially applied to predetermined portions or simultaneously, respectively, to form a beam beam ( The internal residual stress of 1) may be induced into permanent deformation.

That is, the method employed in the method of manufacturing the first prestressed composite beam in the second embodiment of the present invention is the first, second, and third preflags divided by three for convenience as shown in FIGS. Internal residual stress by applying shunt loads (P _1a , P _1b , P _1c ) sequentially at two points separated by 0.2L, 0.3L and 0.4L to 0.5L from the two ends with respect to the total length (L), respectively. In this case, the first, second and third order prefraction loads (P _1a , P _1b , P _1c ) are each load point (0.2L, 0.3L, 0.4L to 0.5L). The maximum internal bending stress of the beam (1) due to each of these loads should be determined to be equal to or less than the elastic limit stress (σ _P ).

Subsequently, the fourth order pre-fraction loads P _2a , P _2b , P _2c are simultaneously applied to the load points as shown in FIG. 3d, and the lower flange 6 is circumferentially shown in FIG. 3e. When the concrete 3 is poured and cured, the first prestressed composite beam 20a as shown in FIG. 3f is made, and the fourth prefraction loads P _2a , P _2b and P _2c . In addition, as in the first, second, and third pre-fraction loads P _1a , P _1b , P _1c , the maximum bending stress of the beam beam 1 at each load point is determined to be equal to or less than the elastic limit stress σ _P. Of course it should be added.

4 shows a third embodiment of the present invention, which is a method of simultaneously applying loads of different sizes to predetermined portions as shown in FIGS. 4A to 4D, for example, three first pre-flection loads. (P ' _1a , P' _1b , P ' _1c ) are symmetrical to each other at 6 points separated by 0.2L, 0.3L, 0.4L ~ 0.5L from both ends, and then gradually applied for a certain time, and then removed. It is intended to lead to permanent deformation. Wherein the first pre-fraction loading _{(P '1a, P' 1b} , P '1c) size, these loads (P' case _{1a, P '1b, P'} 1c) was added to at the same time, the section steel beams (1 The maximum bending stress at each load point of)) is set to be equal to or less than the elastic limit stress (σ _P ).

Subsequently, as shown in FIG. 4B, the concrete around the lower flange 6 is applied with the first pre-fraction loads P _2a , P _2b and P _2c applied in the same manner as in the second embodiment described above. By pouring (3) and curing, the first prestressed composite beam 20b shown in Fig. 4d is made.

As described above, the first prestressed composite beams 20, 20a, and 20b manufactured according to any one of the three methods are cured by the concrete 3 in a state in which a bending moment relatively smaller than the design maximum bending moment is applied. Is given so that it does not have sufficient structural rigidity.

FIG. 5 is a view for explaining a method of applying the second pre-fraction load P ₃ to the first pre-stressed composite beams 20, 20a, and 20b made as described above. As shown in FIG. 5A, the third pre-fraction load P ₃ is applied to both ends of the first pre-stressed composite beams 20, 20a, and 20b manufactured to have the predetermined camber δ ₃ to form the shaped beam 1 Decreases the prestress tensile stress while increasing the prestress compressive stress of the concrete 3, i.e. both ends of the primary prestressed composite beams 20, 20a, 20b as shown in FIG. Attach the support plate 10 to the lower end to install the anchor 11 so as to fix the tendon, and then install the tendon 9 inside the beam beam 1 by placing the tendon 9 on both sides by P ₃ If pulled by force and fixed at anchors installed at both ends, this tendon (9) To be applied directly to the composite beam is the third pre-fraction loading (P _3), the section steel beam (1) at each end of the (20,20a, 20b).

In this case, the tendon 9 is placed in a sheath pipe 8 fitted in the receiving spaces 7 and 7a formed by the reinforcing member 5 and the lower flange 6 as shown in FIGS. 6A and 6B. When inserted, the third pre-fractional load P ₃ is applied directly to the shaped steel beam 1 by the tendon 9 to be pulled, so that there is no breakage due to local stress caused by stress concentration directly acting on the concrete 3. do.

On the other hand, in the case where the beam beam 1 is as shown in FIG. 1c, the sheath pipe 8 into which the tendon 9 is fitted into the receiving space 7b in the reinforcing member 5 as shown in FIG. 6c. And the tendon 9 is pulled out, and in the cases shown in Figs. 1d to e and g, the 6d to e degrees are provided in the receiving spaces 7c, 7d, and 7f formed by the reinforcing member 5. As shown in FIG. g, the tendon 9 is tilted to insert the sheath pipe 8 to pour the concrete 3, and in the case as shown in FIG. 1f, the web (side) as shown in FIG. The sheath pipe 8 and the tendon 9 are respectively provided in the receiving space 7e in the pipe-shaped reinforcing member 5 welded to 4), while the reinforcing member 5 is shown in FIG. ) And the sheath pipe 8 and the tendon 9 may be provided in the receiving space 7g formed by the bottom flange 6.

On the other hand, the size of the third pre-fraction load P ₃ is slightly different depending on the method of manufacturing the first pre-stressed composite beam, that is, as shown in FIG. 7A in the first embodiment, the second car-free fraction by the load bending moment _{(P 2) (0.25P 2 L} ) and the third pre-fraction load bending moment due to the (P _3), (P e _3: e is the center line of the section steel beams (1) ( The total moment of C) to the point of eccentricity) is set to be 10 to 20% more than the required maximum bending moment.

In the second and third embodiments, as shown in FIG. 7B, the bending moment and the third prefraction load P are obtained by the second and second prefraction loads P _2a , P _2b , and P _2c . _{The third} pre-fractional load P ₃ is set such that the sum of the bending moment P ₃ e according to ₃ e) is 10 to 20% or more than the required design maximum bending moment.

On the other hand, the shape beam 1 is shown in the first g and h degree is that the reinforcing member is installed inward only by a predetermined length at both ends outside the lower flange 6, in this case as shown in 6g and h degree The sheath pipe 8 and the tendon 9 are inserted into the receiving space 7f of the concrete 3 and the reinforcing member 5 or the receiving space 7g of the reinforcing member 5 and the lower flange 6. When stretched to both sides, in both support points of the beams in the beam (1) it is not given a bending moment (P ₃ e) by the third pre-fraction (P _3), the second 7c and bending, such as the one shown in d Fig. The moment is imparted to the shaped beams 2. In this case as well, the bending moment due to the secondary preflection loads P ₂ ; P _2a , P _2b and P _2c , and the bending moment due to the third preflection load P ₃ (P ₃ e). The third pre-fraction load (P ₃ ) is set such that the sum of moments of N) is 10 to 20% or more than the required maximum bending moment.

Herein, the composite beam manufactured by the above method will be described based on the gamut (δ _s ) -strain (ε) diagram at the center of the shaped beam shown in FIG. 8A.

First, when the first pre-fraction load (P ₁ ) is applied to the beam (1) to be subjected to bending stress of less than the elastic limit stress (σ _p ), the beam (1) receives stress of σ _se from 0 to A point. When the first pre-fraction load (P ₁ ) is deformed, the internal residual stress is induced to permanent deformation, and it returns only to 0 'point without returning elastically from point A to 0 point. This will happen.

The ear around Applying a second pre-fraction loading (P ₂₎ of the same size at the same load point, the beams in the beam (1) is 0, the bar is again elastically deformed up to a point A on the point, the lower flange 6 in the state When the concrete 3 is poured and cured, and then the second pre-fraction load P ₂ is removed, the beam beam 1 is elastically returned toward the point 0 'from the point A and the concrete 3 is It is compressed from point C toward point D.

In this case, elastic recovery of the beam (1) at points B and D where the tensile force due to the prestress tensile stress (σ _SP ) of the beam (1) and the compressive force (σ _CP ) due to the prestress compression stress of the concrete (3) coincide. Is stopped, and the beam beam 1 is given a prestressed tensile stress as much as σ _SP and the difference between the first camber δ ₀ and the final camber δ ₃ , that is, 0-H (δ ₀ -δ ₃ ). While tensile strain is accompanied by, the concrete 3 is subjected to compressive strain as much as CH while being given prestress compressive stress as much as σ _CP .

On the other hand, according to the second embodiment, as shown in FIG. 8B, when the first pre-fraction load P ₁ is applied to the beam 1, the beam 1 has a value of σ _SP1 from 0 to A ₁ . When the first pre-fractional load (P ₁ ) is removed under stress under stress, only the 0 'point is returned, resulting in permanent deformation of 0-0', followed by the second pre-fractional load (P _2). ) for Applying a section steel beams (1) it is zero when the via a ₁ points in the point receiving the stress by σ _SP2 was transformed to a ₂ that removes the second prepregs load illustration (P ₂₎ 0 "point The permanent deformation of 0'-0 ＂occurs, while the third pre-fraction load (P ₃ ) is applied and then removed, it returns to 0 거쳐 through 0＂ A ₂ A, and finally 0- As the permanent deformation of 0 ＂(δ ₀ -δ ₂ ) is accompanied, the internal residual stress of the beam steel 1 is induced to the permanent deformation.

When the fourth prefraction loads P _2a , P _2b and P _2c are simultaneously applied, the beam beam 1 is elastically deformed from point 0 'to point A. In this state, the lower flange 6 When the concrete (3) is poured around and cured, and the fourth pre-fraction load is removed, the beam (1) is given a tensile stress as much as σ _SP and a tensile strength of 0-H (δ ₀ -δ ₃ ). While the deformation is accompanied, the concrete 3 is subjected to compressive deformation as much as CH while being given prestressed compressive stress by σ _CP .

In addition, according to the third embodiment, as shown in FIG. 8C, when the first pre-fractional loads P ' _1a , P' _1b , P ' _1c are simultaneously applied to the shaped beam 1 and then removed, The beam 1 is elastically deformed by 0-C under stress of σ _SPi from point 0 to point A and then returned to point 0 'to cause permanent deformation of 0-0', followed by the second When the pre-flection loads (P _2a , P _2b , P _2c ) are applied simultaneously and the concrete (3) is poured around the lower flange (6) and cured, σ _SP size is applied to the beam (1) and the concrete (3), respectively. Tensile stress and compressive stress as much as σ _CP are given, and tensile strain as much as 0-H and compressive strain as CH occur.

Subsequently, when the third pre-fraction load P ₃ is applied through the tendon 9 installed in the tension flange portion, the beam beam 1 is directed from the point B to the point B ＂as shown in FIG. 8A. In addition to the return of the prestressed tensile stress, the concrete 3 is further compressed in the direction of increasing the prestressed compressive stress from the point D to the point D ＂. For example, the tensile stress of the tensile flange portion is as much as D _SP '. If it decreases, the compressive stress of D _CP 'increases in the concrete (3).

If the third pre-fraction load P3 is continuously applied, the beam beam 1 is completely elastically returned at 0 'so that the tensile stress becomes zero (0), while the concrete 3 has a D ＂point. Until the prestressed compressive stress is applied and the third prefraction load P ₃ is continuously applied, the beam beam 1 is subjected to a compressive stress from this time. ) If the strain (ε) of) is 0.003 or more, the composite beam is broken. Therefore, the third pre-fractional load (P ₃ ) is applied until the strain (ε) is 0.003 or less, and it is 10 to 10 times the design maximum bending moment. Optionally apply about 20% greater bending moment.

However, in order to reduce the cross section of the tensile flange of the beam beam 1 and increase the bending rigidity of the composite beam cross section, the concrete cross section of the tensile flange should be increased, and the tensile force caused by the tensile stress generated in the tensile flange with the K elastic return ability. and a tensile flange the compression force due to the compression stress generated in the concrete cross-section casting equal there is on when applies a third pre-fraction loading (P ₃₎ in such a state of stress added by the P ₃ If to the same stress state If concrete area is called Act, Act = P ₃ / D _CP .

Therefore, the magnitude of the tertiary pre-fractional load (P ₃ ) applied by the tendon (9) is the secondary pre-fractional load at the concrete section of the tension-side flange of the total composite beam section obtained from the bending moment diagram considering the design maximum bending moment. It is an additional cross section limiting the concrete cross-sectional area obtained.

As described above, when the third pre-fraction load (P ₃ ) is applied to receive a bending moment about 10-20% larger than the design maximum bending moment, a synthetically stable composite beam having the required structural rigidity is manufactured. In addition to this, the composite beam manufactured as described above can be obtained with a beam having a minimum amount of steel, thereby obtaining a composite beam having excellent economic efficiency.

Claims (4)

In the method of manufacturing a prestressed composite beam by removing the internal residual stress of the I-beams curved upward to have a predetermined camber, and then curing by pouring concrete around the lower flange in a state in which the load is applied to the upper side, the I-beams Supported at both ends of the lower flange 6 of the various reinforcing members (5) are installed to accommodate the receiving space (7,7a, 7b, 7c, 7d, 7e, 7g) to be installed inside the sheath pipe (8) In this case, the first pre-fraction load (P ₁ ) with the maximum bending stress less than the elastic limit stress (σ _P ) at a symmetric position above the upper two points is applied for a period of time and then removed, leading to permanent deformation. The primary prestressed composite beam is removed by placing and curing concrete 3 of a predetermined cross-section around the lower flange 6 in the state of applying the secondary pre-fraction load P ₂ and then removing the load P ₂ . Produce Next, the sheath pipe 8 is installed in the accommodation spaces 7, 7a, 7b, 7c, 7d, 7e, and 7g, and the tendon 9 is penetrated through the sheath pipe 8 so that the tendon 9 is provided. The both sides of the beam are fixed to the anchors 11 fixed to both ends of the beams 1, and are combined with the secondary prefraction P ₂ so that the bending moment of the beams 1 is greater than the design maximum bending moment. A method for producing a composite prestressed composite beam, characterized in that a third order pre-fraction load (P ₃ ) is added to increase the ˜20%. The pre-fractionation load according to claim 1, wherein the first pre-fraction load (P ₁ ) is different from each other at load positions 0.2L, 0.3L, and 0.4L to 0.5L at both ends of the beam (1). Method for producing a composite prestressed composite beam, characterized in that to be applied sequentially with a predetermined time interval by the load (P _1a , P _1b , P _1c ). The method of claim 2, wherein the first pre-fraction load (P _1a , P _1b , P _1c ) is less than the elastic limit stress (σ _p ) to the load points (0.2L, 0.3L, 0.4L to 0.5L) Method for producing a composite prestressed composite beam, characterized in that at the same time to be subjected to the maximum bending stress of. The method of claim 1, wherein the second pre-fraction load (P ₂ ) is a different size of the pre-fraction load (P _2a , P) at each of the load points (0.2L, 0.3L, 0.4L to 0.5L) _2b , P _2c ) to be applied at the same time characterized in that the composite prestressed composite beam manufacturing method.