KR20020031603A - Preflex Beam Bridge Structures Using Fiber Reinforced Concrete - Google Patents

Abstract

PURPOSE: Provided is a preflex beam bridge structure to prevent shrinkage and/or cracks caused by long behavior of concrete, to noticeably increase fatigue strength and durability of the structure by coating the structure with fiber reinforced concrete. CONSTITUTION: The preflex structure is prepared by a process comprising pre-bending I shape steel beam(2) into a desirable curvature of convex form; and covering lower flange(3) of the steel beam(2) with a lower concrete reinforcement layer(4) added with the fabric reinforced concrete. Alternatively, the structure is produced by installing the I shape beam(2); covering the lower flange(3) and middle portion(5) of the beam(2) with both of the lower reinforcing layer(4) and the middle layer(7). To a bottom slab(9) formed on outside of a top flange(8), the reinforcing bar(6) is arranged as added with the fabric reinforced concrete.

Description

Preflex Beam Bridge Structures Using Fiber Reinforced Concrete

The present invention relates to a preflex beam bridge structure using fiber-reinforced concrete, specifically, a fiber-reinforced concrete coated with fiber-reinforced concrete incorporating and reinforcing fiber, and optionally, an upper concrete floor plate as well. It relates to a preflex beam bridge structure composed of.

The simplest form of bridge is to form a bridge with simple straight lines. Fig. 3 schematically shows a bending moment generated by a load in a straight simple beam. As shown in Fig. 3, in the center of the beam, a bending moment in a forward direction due to dead and live loads (“static moment”) is shown. ) Will occur.

In order to reduce the tensile force acting on the lower portion of the beam by the constant moment, as shown in Figure 4a recently, after manufacturing the central portion of the beam 10 made of I-type steel to bend in advance in the upper direction As shown in Figure 4b by placing a concrete reinforcement layer on the bottom or the whole of the beam, when the beam is mounted, the compressive force is introduced in advance to the lower concrete reinforcement layer 11 of the beam to offset the tensile force acting on the lower concrete in use Increasingly, the use of preflex beams fabricated in bridges is increasing. The bridge is manufactured by integrally constructing a concrete floor plate on top of the preflex beam manufactured and installed as described above.

FIG. 5 schematically shows the shape of a two-span bridge. In constructing a long-length bridge of two or more spans as illustrated in FIG. 5, a simple bridge using a simple beam is generally used because of various advantages. Rather, it is a trend that each span is constructed as a continuous bridge.

6A to 6B, a construction method of a conventional preflex beam bridge structure will be described. FIG. 6a schematically shows a state in which two preplex beams 10 and 20 are mounted so as to face each other on a center point, ie, a center pier. The preplex beams 10 and 20 are bent upwards with a predetermined curvature before being mounted on the pier, and the lower flange is covered with the lower concrete reinforcement layer 11 on the outside of the I-type steel beam. In addition, the upper flange is covered with an upper concrete reinforcement layer 12, the abdomen of the steel beam is also covered with an abdominal concrete reinforcement layer (13).

A temporary support of a predetermined height is erected on a pier that is a central point, and as shown in FIG. 6A, the ends of the preplex beams 10 and 20 at both sides of the end of the preflex beam are positioned at a predetermined height than the point. Position them from above to face each other. In the connecting portion of the preflex beams 10 and 20 facing each other, as shown in FIG. 6B, the concrete is poured into the upper flange, the abdomen, and the lower flange of the preflex beams 10 and 20, respectively. 12), after forming the abdominal concrete reinforcement layer 13 and the lower concrete reinforcement layer 11, the temporary support is removed to permanently mount the preflex beams (10, 20) on the piers. The upper concrete reinforcement layer 11 will function substantially as an upper bottom plate.

In the conventional preflex beam bridge structure, the concrete reinforcing layer covering the outside of the steel beam is formed using ordinary ordinary concrete. However, such a preflex beam structure using the normal concrete is a tensile stress occurs when the action of the parent will cause cracks in the concrete slab slab of the continuous point portion, there was a problem that the durability is lowered accordingly.

The present invention was developed in order to overcome the above problems that the prior art had, specifically, by improving the durability and fatigue strength by forming a concrete reinforcement layer on the outside of the steel beam by using fiber reinforced concrete reinforced by mixing the fiber It is an object of the present invention to provide a high performance preflex beam bridge structure having shrinkage crack resistance and the like.

1 is a cross-sectional view of a preflex beam bridge structure according to the present invention used for the construction of a simple bridge.

2 is a cross-sectional view of a preflex beam bridge structure according to the present invention used for the construction of a continuous bridge.

3 is a bending moment diagram in a simple beam.

4A and 4B are schematic diagrams showing a form of applying a preflex beam structure to a simple bridge.

5 is a simplified side view of a continuous bridge.

6A and 6B are schematic diagrams for explaining a method of constructing a sequential preflex beam according to the prior art, and FIG. 6A shows a state in which two preflex beams face each other, and FIG. 6B is elevated after the sequencing operation is completed. It is a schematic side view which shows the state which put the prepreg beam on the pier.

* Explanation of symbols for the main parts of the drawings *

1 preflex beam bridge structure

2, 10, 20 preplex beams

3 Lower Flange 4 Lower Concrete Reinforcement Floor

5 Abdominal 6 Reinforcing Bars

7 Abdominal concrete reinforcement layer 8 Upper flange

9 Upper Concrete Slab Slab

In order to achieve the above object, in the present invention, as a preflex beam bridge structure used in the construction of a simple bridge, the lower concrete reinforcement layer covering the lower flange is composed of a fiber mixed concrete reinforced by mixing fibers. Beam bridge structures are provided.

In addition, in the present invention, as a preflex beam bridge structure used for the construction of continuous bridges, the lower concrete, the upper flange and the lower concrete reinforcing layer covering the abdomen, the upper bar concrete floor plate and the abdominal concrete reinforcing layer is a fiber reinforced by mixing the fibers A preflex beam bridge structure is provided which is composed of entrained concrete.

Hereinafter, with reference to the accompanying drawings will be described the configuration and effect of the present invention.

Figure 1 is a schematic cross-sectional view of the preflex beam bridge structure according to the present invention used for the construction of a simple bridge.

As described above, the preflex beam bridge structure used for the construction of the simple bridge is first bent in advance so that the center portion is convex upward so that the I-type steel beam 2 has a predetermined curvature.

The lower concrete reinforcing layer 4 is formed and coated to the outside of the lower flange 3 of the bent steel beam 2, in the present invention, the lower concrete reinforcing layer is made of fiber reinforced concrete mixed with fiber.

Steel fibers, synthetic fibers, etc. may be used as the fibers to be incorporated into the fiber reinforced concrete, and there is no particular limitation on the fibers used.

2 is a cross-sectional view of the preflex beam bridge structure according to the present invention used for the construction of a continuous bridge.

In the center, an I-beam 2 made of steel is installed, and a concrete reinforcement layer having a predetermined thickness is formed on the outside of the lower flange 3 and the abdomen 5. At this time, the reinforcing reinforcement 6 is placed in a predetermined position inside the concrete reinforcement layer. The amount and position of the reinforcing bar 6 is determined by calculating the appropriate structure.

In the present invention, the preflex beam bridge structure used for the construction of the continuous bridge, both the lower concrete reinforcing layer (4) and the abdominal concrete reinforcing layer (7) formed on the outside of the lower flange (3) and the abdomen 5 are mixed with fibers It is made of fiber reinforced concrete.

In other words, the outer flange of the I-beam 2 and the outside of the abdomen are covered by using fiber reinforced concrete in which fiber is mixed and reinforced with concrete.

In addition, the upper concrete slab slab (9) formed on the outside of the upper flange (8) is also made of fiber reinforced concrete reinforced by reinforcing reinforcement (6) and mixed with fibers. The upper surface of the upper flange 8 of the I-beam 2 is provided with a predetermined number of studs for integral coupling with the upper concrete slab slab 9.

In the case of using steel fiber as the fiber to be mixed, when the amount of steel fiber is 1.2 to 2.5% by weight, the breaking energy of concrete is increased by about 20 to 70 times or more than that of ordinary concrete without mixing the fiber. In addition, in the case of fiber reinforced concrete, the ultimate strength increases and the energy dissipation rate is reduced because the amount of energy dissipation is small even after reaching the ultimate strength. Therefore, in the case of the preflex beam bridge structure of the present invention in which the concrete reinforcement layer is formed using the fiber reinforced concrete, even if the concrete reaches the ultimate strength, the mixed fibers prevent the cracks from forming, so the ultimate strength of the structure increases and the cracks are increased. Even after this occurs, the mixed fibers inhibit the growth of the cracks, so the crack propagation rate is slow and the crack spacing is reduced.

Particularly, when the fiber is mixed with 2.0 wt%, the deflection of the structure decreases by about 20% with respect to the deflection of the structure over time such as creep and dry shrinkage, and the deflection occurs when the amount of fiber is 0.3 to 0.75%. About 10%. The fiber between the cracks does not creep under stress, thus preventing the deformation from increasing in the tensile region of the structure. Therefore, in the case of the preflex beam bridge structure of the present invention in which the concrete reinforcement layer is formed using fiber reinforced concrete, the deflection and curvature of the beam are reduced.

As described above, in the preflex beam bridge structure of the present invention, since the concrete reinforcing layer covering the outside of the steel beam is made of fiber reinforced concrete reinforced by incorporating fibers, the strength of the structure can be increased, such as drying shrinkage, and the like. Shrinkage cracks caused by concrete long-term behavior can also be effectively prevented to improve the durability of the bridge structure.

In particular, in the case of the preflex beam bridge structure used for the construction of the continuous bridge, as well as the lower flange and the abdomen, the upper concrete slab slab formed on the upper flange is also made of fiber reinforced concrete reinforced with fiber, Punching shear fatigue strength of slab can be increased significantly,

In the conventional composite bridge structures and preflex beam bridge structures, there is a problem that the amount of compression force introduced in advance is very large. However, as in the present invention, when fiber reinforced concrete is used for the preflex beam bridge structures, In addition, it is possible to significantly reduce the loss of precompression force introduced at the time of installation of the preflex beam bridge structure.

As a result of the improvement of durability, the improvement of strength and the loss of compressive force, it is possible to reduce the amount of steel used in the structure, thereby enabling more economical bridge construction.

Although the embodiments of the present invention have been described above, the present invention is not limited to the described embodiments, and free modifications and improvements can be made within the spirit and claims of the present invention.

Claims (2)

A preflex beam bridge structure used for the construction of a simple bridge, wherein the lower concrete reinforcement layer covering the lower flange is composed of fiber mixed concrete reinforced with fiber. A preflex beam bridge structure used for the construction of continuous bridges, wherein the lower concrete reinforcement layer, upper bar concrete deck and upper concrete reinforcement layer covering the lower flange, upper flange and abdomen are composed of fiber mixed concrete reinforced with fiber. Preflex beam bridge structure characterized in.