KR100457961B1 - The construction and the method of continuous prestressed concrete composite structure connected span-division point - Google Patents

Abstract

In general, prestressed continuous composite beam construction is produced by dividing the prestressed composite beam for the convenience of construction and connecting the split prestressed composite beam to complete the prestressed continuous composite beam. In the present invention, the method of dividing the prestressed continuous composite beam is to find a sub-moment action point having the same maximum moment and absolute value in the same span, and select the span splitting point between the action point and the moment inflection point to form the prestressed continuous composite beam in the span section and the middle part. Split into branches. Span fabrication is made by the method of manufacturing simple beam prestressed composite beams by placing support points at one end of the span and moment inflection points. In the middle point fabrication, the composite section beams are processed according to the edges. It is a construction method to make a composite beam by forming the composite beams by connecting them and connecting them.

Description

Prestressed continuous composite beam structure connecting span segment and construction method {THE CONSTRUCTION AND THE METHOD OF CONTINUOUS PRESTRESSED CONCRETE COMPOSITE STRUCTURE CONNECTED SPAN-DIVISION POINT}

The present invention relates to a construction method of a prestressed continuous composite beam structure connecting the span point.

A method of connecting and constructing a conventionally prepared prestressed composite beam is cited in FIGS. 1 to 5.

FIG. 1 is a diagram showing a split position on a conventional equally distributed load prestressed continuous composite beam bending moment, and FIGS. 2A to 2D are flowcharts of manufacturing a span portion of a conventional prestressed continuous composite beam, and FIG. B) is a manufacturing flow chart of the intermediate point portion of a conventional prestress continuous composite beam, and FIGS. 4A to 4C are construction flowcharts of the prestress continuous composite beam separately manufactured in FIGS. 2 and 3. A continuous prestressed composite beam is completed by connecting the prestressed composite beam manufactured separately near the moment inflection point of FIG. 1 near the moment inflection point.

Specifically, the structure completed in FIG. 4 is divided into a span section and a mid-point section at a moment inflection point that changes from a positive moment to a sub-moment in the continuous bending moment diagram of FIG. 1, and a load P is applied as shown in FIG. 2. The prestressed composite beam of the span section is manufactured by the simple beam manufacturing method, and also the composite beam of FIG. 2 and FIG. After completing the construction of the upper slab, the continuous prestressed composite beam is completed.

The above structure coincides with the vicinity of the inflection point where the split point created by connecting and constructing the composite beam is changed soon. By the way, the moment inflection point or the vicinity of the moment is a part that is positively vulnerable to the fatigue load due to the interaction between the positive and negative moment due to the movement of the load applied to the structure. Accordingly, the moment inflection point is not preferable as the connecting portion of the continuous member, and cracks may occur in the connected lower casing concrete 10 due to the repeated repeated loads.

In addition, since the middle point portion must be reinforced in cross section to withstand the sub-moment, the middle point portion is made thicker in cross section. As a result, the connection process between the intermediate point steels of different thicknesses and the steel materials of the span portion is complicated and the processing result is rough.

Figure 5 (a) to (d) is a domestic existing invention to connect the prestressed composite beam manufactured by splitting in the point portion, and then the slab concrete in the sub-moment section in the state of raising the connection point, curing and point Construct the structure in a complex process of descending to withstand the moment and then cast and cure the slab concrete in the remaining sections to complete the prestressed composite beam.

In the structure of FIG. 5, the connection part is vulnerable because the divided prestressed composite beam is connected at the point where the sub-moment is greatest.

As described above, it is preferable that the connecting portion of the continuous member is installed to avoid the point having the greatest minor moment. In addition, it is pointed out that it is difficult to adjust the amount of rise and fall because the work cost is excessive due to the point rise and fall, and the dead weight of the structure is changed during the point rise and fall work.

The present invention has been made to solve the above problems. The present invention utilizes a prestressed composite beam that is separated from the adjacent part of the moment inflection point where the sub moment and the positive moment change, and the span split point where only the sub moment acts reliably even when a moving load is applied to avoid the point where the sub moment is greatest. Prestressed continuous composite beams are constructed and the shape of the intermediate point composite beams is made the same as the load type, so that the joints are smoothly processed and the point raising and lowering process is omitted, thereby reducing costs and ensuring the simplicity and reliability of construction. The purpose is to provide a new structure.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a split position on a conventional uniformly distributed load prestressed continuous composite beam bending moment;

Figure 2 (a) to (d) is a flow chart of the manufacturing section of the conventional prestress continuous composite beam.

Figure 3 (a) (b) is a manufacturing flow chart of the intermediate point portion of the conventional prestress continuous composite beam.

Figure 4 (a) to (c) is a construction flow chart of the conventional prestressed continuous composite beam manufactured separately.

5 (a) to (d) is a flow chart of a continuous prestress composite beam construction using the conventional point raising and lowering process.

6 is a moment diagram of the prestressed continuous composite beam showing the span split point on the present invention uniformly distributed load prestressed continuous composite beam bending moment.

Figure 7 (a) to (d) is a manufacturing process flow chart divided by the span split point of the prestress continuous composite beam of the present invention.

Figure 8 (a) (b) is a manufacturing flow chart of the intermediate point portion separated by the span split point of the prestress continuous composite beam of the present invention.

Figure 9 (a) to (c) is a construction flow chart of the prestressed continuous composite beam using the prestressed composite beam manufactured by separating the span point of the present invention. Figure 10 is the inflection point position and the connection position position for the fatigue load in the present invention The figure for demonstrating the relationship with and a crack generation.

In order to achieve the above object, in the prestress continuous composite beam structure connecting the span split point according to the present invention, in setting the span split point for introducing the prestressing by splitting the I-type steel during prestress continuous composite beam production, It is characterized in that the interval dividing point is defined as a point for dividing the bipartite between the point where the parent moment with the same positive moment and the absolute value acts, and the inflection point at which the positive moment changes. Is the point that divides the length from the inflection point where the positive and negative moments change and the parent moment where the maximum positive moment and the absolute value are equal to two times to the outermost point on the side where the maximum positive moment occurs is 0.825ℓ. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to solve the problems listed above, the construction method of prestressed continuous composite beam structure using separate prestressed composite beams is determined by setting rational span splitting points and connecting the prestressed composite beams separated by splitting points. And secure certainty.

First, a two-stage prestressed continuous composite beam will be described.

FIG. 6 is a bending moment diagram of uniformly distributed loads in two prestressed continuous composite beams. FIG. In FIG. 6, the maximum moment of a positive moment is made into MB and the sub moment of the point B is MB.

MC1 and MC2 indicate the moment where the absolute value is the same as MA in the section where the sub-moment acts. MC1 and MC2 are 0.1L from point B, and the moment inflection point is 0.25L from point B.

In addition, from the point A to the point MC1, the point C to the point MC2 means that it can withstand the load in the same section designed using the positive moment MA.

The span split point of the present invention lies between the MC1 action point or MC2 action point and the moment inflection point. Indeed, the span segment of the present invention should avoid inflection points and adjacent regions of inflection points. As an example, the position is preferably 0.175 L in the A direction from B, which is the middle of the moment inflection point and MC1 point between points AB, or 0.175 L in the C direction from B, which is the middle point of the inflection point and MC2 point between points BC. Location.

According to the above embodiment, the length of the beam to be manufactured separately from the prestressed composite beam is made of 0.825 L of the span portion, and 0.35 L of the intermediate point portion.

The span split point of the present invention selected as described above is a point where only the minor moment always acts, and the present invention uses the conventional moment inflection point as the span split point so that the positive and the negative moments intersect each other so that the connection part lower casing concrete 10 This is to prevent the end of cracks appearing in the.

In addition, in the present invention, the cross-sectional shape of the span split point may be the same cross section from both end points A and C to MC1 and MC2, so long as the cross section can withstand the maximum positive moment in the span.

7 is a manufacturing flowchart of span section prestressed composite beam divided into span split points.

(A) shows the I-shaped steel manufactured to have a predetermined rise in the form of a simple beam, and (B) is a state diagram in which a predetermined load P is applied to the I-shaped steel manufactured to have the rising. At this time, the B end of the support points A and B at both ends enters 0.075L from the end of the beam and is positioned at the moment inflection point so that bending deformation does not occur from the moment inflection point to the end of the protruding beam.

(C) is a state diagram in which the lower casing concrete 10 is poured and cured in the lower rigid flange 20 in a state where a predetermined load P is applied.

In (d), if the lower casing concrete 10 is cured and the load applied thereto is removed, a predetermined compressive force is introduced into the lower casing concrete 10 as a restoring force of the I-type steel to complete the prestressed composite beam. At this time, the introduced compressive force becomes a force that withstands the load on the floor.

On the other hand, the compressive force is not introduced into the lower casing concrete 10 from the point B to the protruding end. This is because the lower casing concrete 10 in the sub-moment section does not require a compressive force.

8 is a manufacturing flowchart of the intermediate point composite beam separated by a span split point.

(A) indicates the short side I-shaped steel manufactured to have a predetermined rise in the form of a simple beam, and the center section where the point is installed should have a sufficient height to withstand the maximum minor moment and the shape of the curved part is σ = M / The section modulus of the cross section of type I in Z is expressed as Z = BH3-bh3 / 6H. Therefore, the height change of type I steel according to the external force forms the secondary parabola, so maintain the secondary parabolic shape.

(B) pours and cures the lower casing concrete 10 surrounding the lower flange 20 of the I-type steel manufactured to have a predetermined rise. In order to be able to withstand the sub-moment at this time the compressive force is not introduced into the lower casing concrete (10).

9 is a construction flow chart for completing the prestressed continuous composite beam by connecting the prestressed composite beam manufactured by separating the span point.

(A) is a state diagram which connects the prestressed composite beam for span parts manufactured by FIG. 7 and the composite beam part of the intermediate point part manufactured by FIG.

(B) is a state diagram in which the casing concrete 10 of the connection part of the connected prestressed continuous composite beam is poured and cured.

(C) is a state diagram in which the upper slab concrete 30 is poured and the prestressed continuous composite beam is completed.

If the span splitting points of all prestressed continuous composite beams such as 3 spans and 4 spans are selected and constructed in the same span, the point where the maximum moment and the sub moment with the same absolute value are applied and the center of the moment inflection point are constructed. Then, in the present invention as described above, the relationship between the position of the inflection point with respect to the fatigue load, the relationship with the position of the connecting portion, and the relationship with the occurrence of cracks will be described here. In order to examine the fatigue loads of the 0.75ℓ and 0.825ℓ joints, a bridge of 50m prestressed composite beam is described as an example. On the bridge, a 3m long connection length is required for high tension bolts. Therefore, the length of the bridge at the inflection point of 0.75 l is 0.72 to 0.78 l at the left and right of the point of 0.75 l, and the length of the bridge at 0.825 l is 0.795 to 0.855 l at the left and right of the point of 0.825 l (See Fig. 10) 1) When a moving load is generated on the bridge (see Fig. 10), in the case of a bridge with a connection point of 0.75ℓ, it is 2 to 4% × 1 width (right and left around 0.75ℓ). The inflection point is moved within the dotted line in the range of 3%, so it is about 1.5% long, and the inflection point is always moved by one point. Therefore, when only the dead load acts on the bridge, tensile force is generated in the lower casing concrete in the section (0.72-0.75ℓ) around the joint point 0.75ℓ, and compressive force is generated in the section (0.75-0.78L). In addition, when the moving load acts on the bridge and moves from the 0.75ℓ point to the outer point direction, ① At the inflection point moved to a part of the section, the tensile force remains intact in the outer direction and the compressive force is temporarily generated in the inner direction. In case of moving in the direction, the tensile force is generated in the outer direction at the inflection point, and the inner direction is in the compressed state. ① In the section, the tensile force is always generated in the lower casing concrete when the dead load is applied. Tensile force is added at the boundary of ℓ, and compressive force is temporarily generated in some sections, but when the moving load is removed, only tensile force is generated again. ② In the section, the compressive force is always generated in the lower casing concrete during dead load action. This action causes some sections to generate tensile forces, but these sections typically have dead loads. As the size is about 2 to 4 times the size of the moving load (usually about 3 times), the small tensile force that can be generated in the lower casing concrete during the moving load is eliminated immediately when the moving load is removed and remains in a safe compression state. In case of bridge with 0.825ℓ connection, even though dead or moving load is applied, only the compressive force is generated in the lower casing concrete because it is located in the parent section where the width of the joint is 0.795 ~ 0.855ℓ around 0.825ℓ point. Therefore, ③ section (0.795 ~ 0.855ℓ) is a section where only the compressive force is always generated in the lower casing concrete. Note) Tolerances of compressive and tensile fatigue strengths for compressive and tensile design strengths are cited in Chapter 7, "Properties of Hard Concrete (P214)," in the New Concrete Engineering section. The allowable strength is only half of the compressive fatigue strength, so if the design is made within the design allowable load, it is not necessary to examine the fatigue failure. However, the tensile fatigue strength is smaller than the allowable strength of the tensile design, though Even if it is, the fatigue failure should be examined and the tensile fatigue resistance value (22 ~ 16.5 kgf / ㎠) is also insignificant compared to the compressive fatigue strength value (220kgf / ㎠). Therefore, when the contents of [Table 1], ① section, ② section, ③ section (refer to Fig. 1) are examined in relation to each other, ① section shows that the lower casing concrete is always in tension state. It is dominated by one tensile fatigue strength of 22 ~ 16.5 kgf / ㎠ and is always exposed to fatigue failure. ② In the section ②, a small amount of tensile stress is generated in the lower casing concrete when the moving load is applied, but only the compressive force is removed when removing the moving load The problem caused by the temporary tensile force acting immediately is eliminated and there is no problem in fatigue fracture under the control of compressive fatigue strength 220 kgf / ㎠. ③ In the section, the lower casing concrete is always in the compressed state, and the compressive fatigue strength is 220 kgf. 2) Fatigue fracture compared to 0.75ℓ and 0.825ℓ connection points.The left section of 0.75ℓ is exposed to fatigue fracture because the lower casing concrete is always in tension. In addition, once a crack is generated, the crack continues to crack due to the characteristics of concrete, which is weak to brittleness. The section on the right side of 0.75ℓ is in a compressed state, so it is safe for fatigue destruction.The section where the connection of 0.825ℓ is always in a compressed state because the lower casing concrete is always in a compressed state. If the connection part is placed in more than ℓ the steel cross section becomes large, the connection becomes difficult.

As described above, in the present invention, by constructing a reasonably selected spanning point as the connection point, the crack of the lower casing concrete due to the intersection of the moving loads generated when constructing the moment inflection point or the adjacent vicinity of the inflection point as the connection point, which is a conventional construction method. By preventing the phase and making the shape of the middle point beam in the form of secondary parabola, the thickness of the I-shaped steel flange of the span section and the flange thickness of the I-steel section of the middle section are matched to ensure the simplicity and certainty of connection construction. By eliminating the point raising and lowering process to reduce the construction cost, to ensure the stability of the construction, the connection of the member of the continuous beam is to avoid the point where the part moment is the greatest. As described above, the present invention is a patentable invention that ensures not only convenience of work but also stability, economical efficiency, and reliability of construction.

Claims (4)

The span splitting point for introducing prestressing in prestressed continuous composite beam is divided into two points between the point where the maximum moment and the parent moment with the same absolute value act, and the inflection point where the positive and minor moments change. A prestressed continuous composite beam structure that connects span spans. delete The method of claim 1, The span split point has a distance from the inflection point at which the positive and the parent moments change and the length from the point at which the maximum moment is equal to the maximum moment to the point where the maximum moment occurs and the outermost point on the side where the maximum positive moment occurs is 0.825. Prestressed continuous composite beam structure connecting L span segments. In the same span, divide the point between the moment where the maximum moment and the absolute value of the same moment are applied and the moment inflection point, and divide it into the span section and the middle point where the span division point is selected.The one-side load support point of the span section is the moment inflection point. The load supporting point of the other side is the span end point, and the span is characterized by the process of connecting the span part and intermediate point part produced by introducing the compressive force to the lower casing concrete only between the two support points and the span split point obtained by placing slab concrete. Construction method of prestressed continuous composite beam structures connecting split points.