JPH03212552A - End reinforcement structure of reinforced concrete coated steel pipe column - Google Patents

Abstract

PURPOSE:To improve the strength of a steel pipe pillar by making plural narrow stepped outside steel pipes in which moment acting on the pillar does not cause axial force adhere in layers to the outer periphery of an end part of a reinforced concrete coated steel pipe pillar along the pillar. CONSTITUTION:Plural narrow stepped outside steel pipes 6 in which bonding moment acting on a pillar A does not cause axial force are made to adhere in layers to the outer periphery of an end part of a reinforced concrete coated steel pipe pillar A along the pillar A. An inside steel pipe pillar 1 and the outside steel pipes 6 restrain a coated reinforced concrete 2 by utilizing the outward expansion caused by axial compressive force of the inside steel pipe pillar 1 to increase its strength. Thus concrete breakage at an end part of the pillar and the buckling of the steel pipe pillar A can be made difficult to occur.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an end reinforcement structure for a reinforced concrete-coated steel pipe column.

(Prior art) Reinforced concrete-coated steel pipe columns are made by covering a steel pipe (a) with a rectangular or circular cross section with reinforced concrete, and then horizontally binding the steel pipe with the reinforced concrete to maintain the integrity of the two.
Constructed to prevent buckling and resist external forces.

(See Figure 9) In the figure, (C) is the main reinforcement, and (d) is the tie reinforcement. Figure 10 shows a bridge using the reinforced concrete covered steel pipe columns (2), where (E9 is a beam and (0 is a slab).

(Problem to be solved by the invention) In a column where axial pressure is applied, a large compressive force acts on the column end along with a bending moment, which causes the concrete at the column end to break and the steel pipe end to buckle. This tends to lead to a decrease in proof strength.

Therefore, higher-strength concrete is required, and it is necessary to use a steel frame with a small (thick) width-to-thickness ratio.

The present invention has been proposed in view of the problems of the prior art, and its objectives are to reduce concrete failure at the end of the column, compared to conventional reinforced concrete coated steel pipe columns.
An object of the present invention is to provide an end-reinforcing structure for a reinforced concrete-coated steel pipe column in which buckling of the steel pipe is less likely to occur and structural performance is improved.

(Means for Solving the Problems) In order to achieve the above object, the end reinforcement structure of a reinforced concrete coated steel pipe column according to the present invention provides an axial reinforcement structure for the end of the reinforced concrete coated steel pipe column by bending moment applied to the column. It is constructed by wrapping multiple stages of small-width outer steel pipes, which do not generate any directional force, overlapping them in the height direction of the strut.

(Function) Since the present invention is configured as described above, the inner steel pipe column tends to expand outward due to the compressive force acting on the end of the reinforced concrete coated steel pipe column along with the bending moment, so that the outer circumference of the steel pipe column is The covered reinforced concrete part is subjected to lateral forces.

The reaction force of this lateral force is generated by multiple stages of narrow steel pipes wrapped around the outside of the concrete section, and thus the reinforced concrete section is tightened from the inside and outside.

At this time, if the width of the steel pipe wrapped around the outer side is large, when a bending moment is applied, an axial force will also be generated on the outer steel pipe, weakening the force restraining the covered reinforced concrete. According to the invention, since the outer steel pipe has a small width and does not undergo axial deformation of itself, it provides sufficient restraining force to the covered reinforced concrete and increases the compressive strength of the concrete.

(Example) The present invention will be described below with reference to the illustrated embodiments.

(1) is the inner steel pipe column in a reinforced concrete-coated steel pipe column, and its outer periphery is covered with reinforced concrete (2). be. Note that the stud bolt (5) is attached only to the hinge zone at the end of the column.

At the column head and column base of the reinforced concrete-coated steel pipe column, narrow outer steel pipes (6) that do not generate axial force due to the bending moment acting on both columns are wound in a heavy manner in the height direction of the column. It is worn. (See Figures 1 and 2) Figure 2 shows a frame using the reinforced concrete-coated steel pipe columns, where (marks indicate beams and Q indicates slabs).

The above embodiments show the case where the present invention is applied to a reinforced concrete coated steel pipe column with a square cross section, but Fig. 3 shows the case where the present invention is applied to a reinforced concrete coated steel pipe column with a circular cross section. The same reference numerals are given to parts equivalent to those of the above embodiment.

Since the illustrated embodiment is constructed as described above, an axial compressive force acting together with a bending moment on the end of the column retainer causes the inner steel pipe column (1) to move as shown in Due to compressive force, it contracts in the axial direction, expands in the transverse direction,
As a result, it tends to expand outward, and the reinforced concrete (2) at the outer periphery is thereby subjected to a lateral force as shown in y. In addition, no axial force acts on the outer steel pipe (6), the reaction force Z of the lateral force is generated by the outer steel pipe (6), and the reinforced concrete (2) part is connected to the inner steel pipe column (1) and the outer steel pipe (
6), the reinforced concrete part (2) receives lateral restraining force and its strength increases, and compared to conventional reinforced concrete coated steel pipe columns, the concrete at the end of the column is destroyed and the steel pipe is tightened. Buckling is less likely to occur.

FIG. 5 is a bending moment distribution diagram and a strain distribution diagram of the reinforced concrete coated steel pipe column constructed as described above.

At this time, if the width of the outer steel pipe (6) is large, as shown in FIG.
) shrinks in the direction of arrow U, and an axial force is also generated on the outer steel pipe (6), weakening the restraining force on the reinforced concrete (2). However, if an outer steel pipe (6) with a sufficiently small width is used, As shown in FIG. 7, since no deformation occurs in the axial direction of the concrete itself, it can sufficiently act as a restraining force on the reinforced concrete (2).

Figure 8 shows the case where the outer steel pipe (6) and the column surface are on the same plane, and in order to prevent the outer steel pipe (6) from acting on bending moment or axial force, the outer steel pipe (6) is wound on the outside of the design cross section. It will be worn.

Therefore, in order to make the outer steel pipe (6) the same as the column surface, the diameter of the column portion where the outer steel pipe (6) is not wound must be expanded. At this time, it is necessary to be careful not to apply direct axial pressure to the outer steel pipe (6), and to prevent the amount of deformation from occurring above or below the outer steel pipe (6) or between the steel pipes (6). An interval t is provided accordingly.

(Effects of the Invention) According to the present invention, as described above, multiple stages of outer steel pipes with a sufficiently small width are applied to the outer periphery of the end of a reinforced concrete coated steel pipe column so that no axial force is applied due to the bending moment applied to the studs. are wrapped in layers in the height direction of the column, and by utilizing the fact that the inner steel pipe column expands outward due to the compressive force in the axial direction, the covered reinforced concrete is restrained by the inner steel pipe column and the outer steel pipe, increasing its strength. This makes it more difficult for the concrete to break at the end of the column and for the steel tube to buckle, compared to conventional reinforced concrete-covered steel pipe columns, thereby improving structural performance.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional plan view showing one embodiment of a reinforced concrete-coated steel pipe column equipped with an end reinforcement structure according to the present invention;
1-1 in the figure, FIG. 2 is a front view showing a frame using the steel pipe columns, FIG. 3 is a cross-sectional plan view showing another embodiment of the present invention, and FIG. 4 is an operation of the present invention. 5 is a bending moment distribution diagram and a strain distribution diagram of the steel pipe column, FIGS. 6 and 7 are action explanatory diagrams of the outer steel pipe, and FIG. 8 is a longitudinal section showing another embodiment of the present invention. 9 is a cross-sectional plan view of a conventional reinforced concrete-coated steel pipe column taken in the direction of arrow X- in FIG. 10, and FIG. 10 is a front view of a frame using the same steel pipe column. Prisoner...Reinforced concrete coated steel pipe column, (1)...Inner steel pipe column, (2)-...Reinforced concrete, (6)
...outer steel pipe.

Claims (1)

[Claims] The outer periphery of a reinforced concrete-coated steel pipe column is made by wrapping multiple stages of small-width outer steel pipes, stacked in the height direction of the column, so that no axial force is generated due to the bending moment applied to the column. End-reinforcement structure for reinforced concrete-coated steel pipe columns.