KR100250937B1 - The manufacturing method of a simple beam type preflex composite beam by temporary hinge - Google Patents

Abstract

PURPOSE: A fabricating method of a simple beam type preflex composite beam is provided to prevent reduction of compressive stress due to creep and dry contraction by raising and dropping a branch point to obtain additional compressive stress. CONSTITUTION: Concrete is poured to a lower casing, cured and released when a preflex load is loaded. Then, a beam is mounted between piers to set an additional branch point in the center. Concrete is poured to an upper casing and cured. After that, the branch point falls down to apply additional compressive stress to the lower casing concrete. The branch point rises up or falls down to reduce final tensile stress by a dead load and a dynamic load with additional compressive stress. Thereby, a simple beam type preflex composite beam reduces the tensile stress of the lower casing concrete down to 30% and does not need a large amount of steel and concrete.

Description

Fabrication Method of Simple Beam Pre-Flex Composite Beam Using Branch Point

The existing simple beam preflex composite beam has a phenomenon in which the compressive stress introduced into the lower casing concrete decreases due to the initial creep and dry shrinkage, and thus the branch beam which is a manufacturing method of the simple beam preflex composite beam using the branch point according to the present invention. By using it, additional compressive stress can be introduced and the design can be made with smaller cross section than the existing cross section.

In the present invention, the conventional simple beam preflex composite beams are fabricated by dead and live loads by introducing additional compressive stresses by increasing and decreasing branch points installed in the middle of the reduction of compressive stress caused by creep and dry shrinkage. Tensile stress can be reduced.

1 is a manufacturing principle of a conventional simple beam preflex composite beam.

2 is a principle diagram for introducing an additional compressive stress by prestressing tension members to existing simple beam preflex composite beams.

3 is a manufacturing principle diagram of a simple beam-type preplex composite beam using a branch point according to the present invention.

Figure 4 (a) is a cross-sectional value in the case of pouring the lower casing concrete in the state of loading the preflection load in the simple beam preflex composite beam using the branch point according to the present invention.

4 (b) is a cross-sectional value when the upper casing concrete and the abdominal concrete is poured after the branch point is raised in the simple beam preflex composite beam using the branch point according to the present invention.

Figure 5 (a) is a cross-sectional specification and final stress of the simple beam-type preflex composite beam using the branch point according to the present invention.

Figure 5 (b) is a cross-sectional specification and final stress of the conventional simple beam preflex composite beam.

The conventional simple beam preflex composite beam has been widely constructed so far because of its advantages such as quickness of construction, high moldability, material reduction, and improvement of fatigue strength. The conventional simple beam preflex composite beam is made of steel I-shaped beam to be bent upward in the center, and then cast and cure casing concrete on the lower flange of the steel system while applying a preflection load downward within the elastic range of the material. Then, by removing the preflection load, the compressive stress is introduced to the lower casing concrete to reduce the tensile stress of the lower flange portion caused by dead and live loads. However, this manufacturing method primarily reduces the compressive stress due to creep and dry shrinkage during the casting and curing of the lower casing concrete under the preflection load. Therefore, in order to prevent the reduction of the compressive stress, an additional method of introducing a compressive stress using a tension material is used, but it is not only cumbersome in manufacturing but also additional costs such as tensioning the tension material. Therefore, in the present invention, a method for manufacturing a simple beam preflex composite beam using a branch point has been developed as a method for solving problems such as loss of compressive stress in the conventional simple beam preflex composite beam. Looking at the procedure of the manufacturing method of the simple beam preprex composite beam using the branch point according to the present invention.

FIG. 3 (a) is a state diagram in which a branch point is installed in the center of a bridge by placing the lower casing concrete in a state in which a preflex load is loaded and curing it, as in the conventional simple beam preflex composite beam. 3 (b) is a state diagram in which the upper casing concrete and the abdominal concrete are poured and cured in a state where the branch point according to the present invention is raised. 3 (c) is a state diagram in which additional compressive stress is introduced to the lower casing concrete by lowering the branch point after the upper casing concrete is cured. As the existing simple beam preflection composite beam is loaded under the prefraction load, the lower casing concrete is cured and the tensile stress generated in the concrete by creep and dry shrinkage decreases the compressive stress introduced into the lower casing concrete due to the preflection load. Let's go. Therefore, it is possible to compensate for the reduction of compressive stress due to creep and dry shrinkage by raising and lowering the branch point in the middle of the trunk.

FIG. 4 (a) is a cross-sectional value after placing and curing the lower casing concrete in the state which loaded the preflexion load using the branch point by this invention. FIG. 4 (b) is a cross-sectional value of the final section in the simple beam-type preflex composite beam using the branch point.

5 (a) is a cross-sectional view and final stress diagram for the 30m section of the simple beam-type preflex composite beam using the branch point according to the present invention. Figure 5 (b) is a cross-sectional view and the stress diagram for 30m section of the conventional simple beam preflex composite beam. In FIG. 5 (a), additional compressive stress can be introduced by the rise and fall of the branch point, so that it is possible to design a cross section smaller than in FIG. 5 (b) and to reduce the amount of steel and concrete in the upper and lower flanges. Can be. In addition, while the tensile stress at the lower end of the lower casing concrete is 61.43 kg / ㎠ of the conventional simple beam preflex composite beam, the simple beam preflex composite beam using the branch point according to the present invention reduces the stress to 20.97 kg / ㎠. Can be reduced to 30%. Comparing the steel amount and the concrete amount of the fifth (a), (b) is as follows. As shown in FIG. 5 (a), the amount of steel of the simple beam-type preflex composite beam using the branch point according to the present invention is 586cm2, and the amount of concrete is 9300cm2. Is 806cm2 and the amount of concrete is 10100cm2, which can greatly reduce the amount of steel and concrete.

The present invention loads and cures the lower casing concrete by loading the pre-fraction load, and then mounted between the shifts in the field and then set up branch points in the middle of the trunk to raise the branch points and then cast and cure the upper casing and the abdominal concrete. By lowering the branch point, it is a method that can additionally introduce compressive stress to the lower casing concrete.

Since the present invention can introduce additional compressive stress to the lower casing concrete using the branch point, the tensile stress at the lower end of the lower casing concrete generated by dead and live loads can be reduced to about 30% compared to the conventional one. It can greatly reduce the amount of steel and concrete in the quantity used.

An object of the present invention is to increase and decrease the creep and dry shrinkage by installing a branch point in the middle of the inter-center to prevent the reduction of the compressive stress due to creep and dry shrink in the conventional simple beam preflex composite beam It is to provide a manufacturing method of a simple beam preflex composite beam using a branch point that can prevent the reduction of the compressive stress due to and significantly reduce the amount of steel and concrete.

Claims (1)

In manufacturing the existing simple beam preflex composite beam, after reducing the initial stress due to creep and dry shrinkage, the branch point is set up in the middle of the bridge to raise and lower the branch after pouring and curing the upper casing concrete and abdominal concrete. By introducing additional compressive stress into the lower casing concrete, it is possible to significantly reduce the tensile stress occurring at the lower end of the lower casing concrete and to manufacture a simple beam preflex composite beam using branch points that can significantly reduce the amount of steel and concrete. Method.