Steel-fiber composite material concrete combined column, and post-earthquake repair method thereof

Abstract

A steel-fiber reinforced polymer (FRP) composite material reinforced concrete column comprises an inner steel pipe arranged in the center, wherein the inner steel pipe is internally provided with an unbonded steel strand; the outside of the inner steel pipe is provided with an outer steel pipe, concrete is poured between the inner steel pipe and the outer steel pipe, a plurality of additional small steel pipes are evenly arranged outside the outer steel pipe, and each of the additional small steel pipes is internally provided with an additional unbonded steel strand. A composite bar cage coaxial with the outer steel pipe and arranged on the outside thereof is also provided, wherein both the outer steel pipe and the composite bar cage are covered by high-ductility concrete, and at a core area, the outside of the high-ductility concrete is wrapped with an anti-spalling layer.

Claims

1. A steel-fiber reinforced polymer (FRP) composite material reinforced concrete column, comprising an inner steel pipe arranged in the center, wherein the inner steel pipe is internally provided with an unbonded steel strand; outside of the inner steel pipe is provided with an outer steel pipe, concrete is poured between the inner steel pipe and the outer steel pipe, a plurality of additional small steel pipes are evenly arranged outside the outer steel pipe, and each of the additional small steel pipes is internally provided with an additional unbonded steel strand; a composite bar cage composed of a plurality of steel-fiber reinforced polymer composite bars (SFCBs) and steel wire-FRP spiral hoops coaxial with the outer steel pipe and arranged on the outside thereof is further comprised, both the outer steel pipe and the composite bar cage are covered by high-ductility concrete, and outside of the high-ductility concrete is wrapped with an anti-spalling layer; wherein each of the steel strands are stretched and pulled to recover a damaged section of concrete column; a steel plate is positioned to cover the outside of the outer steel pipe that contains damaged concrete; a respective steel-FRP composite bar or a stainless steel bar is inserted into a damaged section of the SFCB.

2. The steel-FRP composite material reinforced concrete column according to claim 1, wherein the plurality of the additional small steel pipes are arranged and are evenly disposed outside the outer steel pipe in a circular pattern.

3. The steel-FRP composite material reinforced concrete column according to claim 1, wherein the plurality of SFCBs located in the high-ductility concrete have unbonded length.

4. The steel-FRP composite material reinforced concrete column according to claim 1, wherein the high-ductility concrete is covered on core areas of the outer steel pipe and the composite bar cage.

5. The steel-FRP composite material reinforced concrete column according to claim 4, wherein the outer steel pipe in the area covered by the high-ductility concrete is formed by multiple steel pipes connected in sequence.

6. The steel-FRP composite material reinforced concrete column according to claim 4, wherein the anti-spalling layer is FRP.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of a steel-FRP composite material reinforced concrete column and a column platform according to the present invention;

(2) FIG. 2 is a schematic diagram of n A-A cross section in FIG. 1;

(3) FIG. 3 is a schematic diagram of a B-B cross section at a core area in FIG. 2;

(4) FIG. 4 is a schematic diagram of conducting post-earthquake repair to the combined column based on the configuration as shown in the figure;

(5) FIG. 5 is a schematic diagram of a C-C cross section in FIG. 4; and

(6) FIG. 6 is a post-earthquake repair process of the combined column.

DETAILED DESCRIPTION

(7) The present invention is further described hereinafter with reference to the drawings.

(8) As shown in FIG. 1 to FIG. 3, a steel-FRP composite material reinforced concrete column comprises an inner steel pipe 4 arranged in the center, and the inner steel pipe 4 is internally provided with an unbonded steel strand 2; the outside of the inner steel pipe 4 is provided with an outer steel pipe 5 coaxial with the inner steel pipe, concrete 6 is poured between the inner steel pipe 4 and the outer steel pipe 5, a plurality of additional small steel pipes 9 are evenly arranged outside the outer steel pipe 5, and each of the additional small steel pipes 9 is internally provided with an additional unbonded steel strand 11; a composite bar cage coaxial with the outer steel pipe 5 and arranged on the outside thereof is further comprised, both the outer steel pipe 5 and the composite bar cage are covered by high-ductility concrete 3, the outside of the high-ductility concrete 3 is wrapped with an anti-spalling layer 8, and the anti-spalling layer 8 is FRP. The high-ductility concrete 3 is only covered on the core areas of the outer steel pipe 5 and the composite bar cage, the core area is a plastic hinge area of the concrete combined column, the high-ductility concrete can be used in the whole concrete combined column, or used in the core area only. The outer steel pipe 5 in the covered area of the high-ductility concrete 3 is formed by multiple steel pipes connected in sequence, so that the outer steel pipe of the core area only plays a role of restraining the core concrete instead of making longitudinal bending resistance contributions. The composite bar cage is composed of a plurality of SFCBs 1 in the high-ductility concrete and steel wire-FRP spiral hoops 10. The plurality of SFCBs 1 located in the high-ductility concrete 3 have unbonded sections. An anti-buckling sleeve 7 is sleeved outside the SFCBs 1, and the SFCBs 1 located in the anti-buckling sleeve 7 are the unbonded sections, which are convenient for stretching and drawing in post-earthquake repair. Four additional small steel pipes 9 are arranged and are evenly disposed outside the steel pipe 5 in a circular pattern.

(9) The steel-FRP composite material reinforced concrete column according to the present invention is combined with the column platform into an integrity, the lower part thereof is the core area, the upper part of the core area is an elastic region, the core area is poured by the high-ductility concrete, the high-ductility concrete is not used in the elastic region, part of the combined column is fixed in the column platform, and each SFCB 1 stretches from the bottom part of the combined column and is provided with an anchor head 12. The post-yield stiffness of the SFCB 1 can control the earthquake displacement response of the combined column, the prestress unbonded steel strand 2 in the center can reduce the residual displacement during the earthquake, the high-ductility concrete 3 in the core area with large compressive strain and the unbonded sections of the SFCBs 1 can make the SFCBs 1 strained evenly to avoid tension rupture. The concrete 6 is restrained by the inner steel pipe 4 and the outer steel pipe 6, the outer steel pipe 5 is divided into multiple segments at the core area, so that the outer steel pipe 5 in the core area only plays a role of restraining the high-ductility concrete of the core area without making longitudinal anti-bending contributions. The core area is ensured to not have excessive plastic deformation in rare earthquakes by designing, so as to guarantee the axial bearing capacity and provide key supports to the quick post-earthquake restoration and maintenance of the plastic hinge area; and the outside of the high-ductility concrete in the core area is provided with a horizontal anti-spalling layer 8, which increases the ductility of the high-ductility concrete while avoiding the buckling of the unbonded regions of the SFCBs 1 due to the spalling of the concrete. For the SFCBs, avoiding the buckling can guarantee the tension/compression strength, and when the externally covered FRP is not used in the core area for restraining, the anti-buckling sleeve 7 is used to realize the unbonded SFCBs. The steel wire-FRP spiral hoops 10 are used as the hoops to completely realize that the combined column can be qualified to oceanographic engineering and other high corrosion environments.

(10) The present invention further provides a post-earthquake repair method for a steel-FRP composite material reinforced concrete column, which comprises the following steps of:

(11) S1: stretching and drawing the additional unbonded steel strands in each of the additional small steel pipes and the unbonded steel strand in the inner steel pipe to enable the combined column to recover to a displacement status before earthquake;

(12) S2: eliminating concrete damaged by various disasters until the outer steel pipe is exposed, connecting the section-type outer steel pipe into an integrity capable of stretching and restraining vertically, wherein the connecting method can be the use of a steel lathing, welding the upper end of the steel plate with the outer steel pipe, and putting the lower end deep into a column platform for anchorage;

(13) S3: implanting a new steel-FRP composite bar or a stainless steel bar in a damaged area if the FRP of the SFCB is damaged, connecting the upper end to the original SFCB by means of mechanical anchorage and bonded anchorage in a combined manner, implanting the lower end with a bonded sleeve into a column platform anchorage area, arranging a pier head anchor at the end part of the stainless steel bar if the stainless steel bar is planted, and grouting for anchorage;

(14) S4: confining the steel-FRP bar/stainless steel bar implanted in the core area by a steel wire rope (the steel wire rope is similar as stirrup);

(15) S5: pouring high-ductility concrete in the core area; and

(16) S6: wrapping FRP outside the high-ductility concrete poured in the core area in step S5, wherein, as shown in FIG. 6, the wrapping scope is larger than the scope of the high-ductility concrete poured to guarantee that the upper anchorage area of the newly implanted steel-FRP bar/stainless steel bar is in the confined scope, and then finishing the repair.

(17) The contents above are only preferred embodiments of the invention. It shall be pointed out that those skilled in the art can make a plurality of improvements and polishing without departing from the principle of the invention, which shall also fall within the protection scope of the invention.