CN108798054A - A kind of reinforcement means for the enhancing damaged frame column that ECC is combined with reinforced mesh - Google Patents

Abstract

The invention discloses a method for strengthening an earthquake-damaged frame column by combining ECC and steel mesh, and belongs to the field of strengthening the earthquake-damaged frame column in civil engineering. The invention adopts the steel mesh sheet to outsource the frame column, which can not only improve the vertical bearing capacity of the frame column, but also well limit the crack development of the frame column. The ECC used in the present invention is a randomly distributed short fiber reinforced cement-based composite material with super strength and toughness, which has remarkable effects in improving the ductility, energy dissipation capacity, erosion resistance, impact resistance and wear resistance of the structure.

Description

A strengthening method for strengthening earthquake-damaged frame columns by combining ECC and steel mesh

technical field

The invention relates to a strengthening method for strengthening earthquake-damaged frame columns by combining ECC (high-toughness cement-based composite material, Engineered Cementitious Composite, ECC for short) and steel mesh sheets, belonging to the field of strengthening earthquake-damaged frame columns in civil engineering.

Background technique

Columns are the most important load-bearing components of frame structures, even if individual columns fail, the structure will collapse. On the one hand, the frame column is a bias member, and its cross-sectional deformation bearing capacity is far inferior to that of a beam mainly subjected to bending. In order to make the frame column have better seismic capacity, it should be ensured that the frame column has sufficient bearing capacity and necessary deformation capacity. At present, the reinforcement of frame columns mainly includes outsourcing steel plate method, carbon fiber cloth reinforcement method, prestressed steel strand reinforcement method, etc. The outsourcing steel plate method mainly uses steel plate hoops, high-strength bolts and other components to form an outsourcing steel plate hoop to tightly surround the frame column, thereby strengthening the lateral restraint of the frame column; the carbon fiber reinforcement method is to paste carbon fiber cloth on the frame column, so as to give the frame The column increases the lateral restraint; the prestressed steel strand method uses galvanized steel strands, bolts and other accessories. The frame column is surrounded by steel strands, and the surrounding steel strands are stretched by tensioning method, and then the surface of the steel strands is coated with polymer mortar.

Contents of the invention

Aiming at the limitation of current reinforcement technology for frame columns, this paper proposes a method for strengthening frame columns by combining ECC and steel mesh.

The technical scheme adopted in the present invention is: a method for reinforcing frame columns combined with ECC and steel mesh, comprising the following steps:

Perform surface treatment on the earthquake-damaged frame column 1, chisel off the loose concrete layer, and clean the surface again after the coarse aggregate is exposed;

Steel mesh sheets 5 are installed around the processed frame column 1, and the protective cover composed of the steel mesh sheets 5 is attached to the surface of the frame column 1, wherein the steel mesh sheets 5 are vertically lapped by longitudinal bars and transverse bars, and the longitudinal bars and the diameter of the transverse reinforcement is not greater than the diameter of the inner stirrup of the frame column 1;

Brush the interface agent on the surface of the steel mesh sheet 5, and then apply ECC to form a reinforcement layer;

Carry out moisturizing maintenance to the ECC reinforcement layer 3 .

Preferably, the reinforcement mesh sheet 5 is installed in the following manner: the longitudinal bars are placed in the inner layer, the transverse bars are placed in the outer layer, the longitudinal bars are placed close to the surface of the processed frame column 1, and the longitudinal bars are connected by the transverse bars. Lap joints between transverse ribs on adjacent two sides, the position of the lap joints avoids the position of the column corner, and the adjacent lap joints are staggered from each other on each side; the intersection of longitudinal ribs and transverse ribs and the overlap of transverse ribs are connected by resistance welding.

Preferably, the interface agent is a cement expansion slurry interface agent, and the interface agent mixing ratio is cement: secondary fly ash: UEA expansion agent: water=1:0.1:0.1:0.4, when preparing, cement and secondary fly ash Perform dry mixing to form a dry powder and mix well; then mix the UEA expansion agent and water evenly to form a mixture; finally add the mixture to the dry powder and stir until viscous.

Preferably, the ECC is applied manually in two layers. The first layer is applied by rubbing vigorously to ensure the dense combination of the mortar, the interface and the steel mesh, and to avoid sealing the gap. The thickness of the first layer is controlled within 10mm; the first layer is applied After completion, apply the second layer immediately, and the thickness of the second layer should be controlled within 20mm. Among them, ECC is a polymer material mixed with cement, fly ash, sand, polyvinyl alcohol (PVA) fiber, water and admixtures. For the selection and preparation of ECC mix ratio, refer to the invention patent "a high Tough cement-based composite material" (Patent No. CN107382183) in the program. The specific components are cement, fly ash, sand, water, water reducing agent and PVA fiber, among which, in terms of mass ratio, cement: fly ash: sand: water: water reducing agent = 1: (1.0~1.2): (0.6~0.8): (0.42~0.57): (0.001~0.003); based on the total volume of cement, fly ash, sand and water reducer mixed uniformly, the dosage of PVA fiber is 13~20kg/m ³ . 7.

preferred, step In the middle, the ECC reinforcement layer should be moisturized and maintained for 28 days.

The working principle of the present invention: the reinforcement mesh provides lateral restraint for the frame column, thus constraining the lateral deformation of the concrete, improving the compressive strength and deformation capacity of the concrete, and providing lateral support for the reinforcement to prevent buckling of the longitudinal reinforcement. ECC not only has high toughness and high tensile strength, but also has good compactness. Using ECC to fill the reinforcement layer of frame columns can well meet the reinforcement requirements.

Beneficial effects of the present invention: adopting the method of the present invention to strengthen the concrete frame column can well improve the vertical bearing capacity of the frame column, can also improve the deformation capacity of the frame column, and can also improve the crack resistance of the frame column performance, corrosion resistance.

Description of drawings

Fig. 1 is the main schematic diagram of frame column reinforcement of the present invention;

Fig. 2 is the reinforced mesh schematic diagram of frame column reinforcement of the present invention;

Fig. 3 is a schematic cross-sectional view of the reinforced frame column of the present invention.

In the picture: 1 - frame column, 2 - reinforcement mesh sheet, 3 - ECC reinforcement layer.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments, but the invention is not limited to the following examples.

Embodiment 1: As shown in Figure 1-3, a method for strengthening a reinforced frame column combining ECC and steel mesh, including the following steps:

Carry out chiseling treatment on the damaged or loose concrete layer of the frame column 1, chisel off the loose layer on the concrete surface until the coarse aggregate is exposed, use tap water to wash the interface of the chiseled column body surface, and use a wire brush while flushing Clean up the loose powder layer;

Steel mesh 2 is installed around the processed frame column 1, and the protective cover composed of steel mesh 2 is attached to the surface of frame column 1, wherein the steel mesh 2 is formed by vertically lapping longitudinal bars and transverse bars, and the longitudinal bars and the diameter of the transverse reinforcement is not greater than the diameter of the inner stirrup of the frame column 1;

Brush the interface agent on the surface of the steel mesh 2, brush vigorously on the cleaned interface with a brush, and ensure that the interface agent is evenly applied, and then apply ECC to form a reinforcement layer;

Carry out moisturizing maintenance to the ECC reinforcement layer 3 .

Among them, ECC is a polymer material mixed with cement, fly ash, sand, polyvinyl alcohol (PVA) fiber, water and admixtures. For the selection and preparation of ECC mix ratio, refer to the invention patent "a high Tough cement-based composite material" (Patent No. CN107382183) in the program.

Embodiment 2: As shown in Figure 2, the installation method of the reinforcement mesh sheet 2 is: the longitudinal reinforcement is placed in the inner layer, the horizontal reinforcement is placed in the outer layer, the longitudinal reinforcement is placed close to the surface of the processed frame column 1, and the horizontal reinforcement is used Connect the longitudinal reinforcement, overlap the transverse reinforcement on the adjacent two sides, avoid the position of the lap joint, and stagger the adjacent lap joints on each side; the intersection of the longitudinal reinforcement and the transverse reinforcement and the overlap of the horizontal reinforcement The joints are connected by resistance welding.

ECC is applied manually in two layers. When the first layer is applied, rub it hard to ensure the dense combination of the mortar, the interface and the steel mesh, and avoid sealing the gap. The thickness of the first layer is controlled within 10mm; after the first layer is applied, tighten the Then apply the second layer, the thickness of the second layer is controlled within 20mm. Among them, ECC is a polymer material mixed with cement, fly ash, sand, polyvinyl alcohol (PVA) fiber, water and admixtures.

Embodiment 3: In this embodiment, the diameter of the longitudinal reinforcement is taken as 1/30 of the smaller side length of the frame column 1, and the grid size of the steel mesh sheet is taken as 1/20 of the smaller side length of the frame column 1. This time, according to The grid size is 15mm × 15mm for binding and positioning, and the overlapping length of the transverse reinforcement is 20mm.

Wherein the interface agent is a cement expansion slurry interface agent, and the interface agent mixing ratio is cement: secondary fly ash: UEA expansion agent: water = 1:0.1:0.1:0.4, and the cement and the secondary fly ash are dried first during preparation. Stir to form a dry powder and mix well; then mix the UEA expansion agent and water evenly to form a mixture; finally add the mixture to the dry powder and stir until viscous.

The filled ECC is carried out according to the mixing ratio and preparation method of Example 1 in the invention of "A High Toughness Cement-Based Composite Material" (Patent No. CN107382183), and the ECC reinforcement layer 3 is moisturized and maintained for 28 days.

In this test, the vertical bearing capacity, strength degradation and failure phenomena of the reinforced frame columns were explored. The test found that the effect of strengthening the earthquake-damaged frame column combined with ECC filling and high-strength steel mesh is better than that of increasing the cross-sectional size of the frame column, in which the bearing capacity is increased by about 25% and the degree of strength degradation is reduced. Especially when the bearing capacity of the component is high, the ECC filling layer only has cracks unfolding, and there is almost no ECC block peeling off, while the reinforced specimen using the enlarged section method has obvious polymer peeling off. To sum up, the combination of ECC filling and high-strength steel mesh to strengthen the earthquake-damaged frame column can get better results.

The specific implementation of the present invention has been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited thereto. Within the scope of knowledge possessed by those of ordinary skill in the art, various Variety.

Claims (7)

1. a kind of reinforcement means for the enhancing frame column that ECC is combined with reinforced mesh, which is characterized in that include the following steps：

To damaged frame column（1）It is surface-treated, cuts the concrete layer loosened, after exposing coarse aggregate again Secondary carry out removing surface；

Frame column after treatment（1）Surrounding install reinforced mesh（2）, reinforced mesh（2）The protective cover of composition is fitted in Frame column（1）Surface, wherein reinforced mesh（2）It is vertically overlapped by vertical muscle and transverse bar, the diameter for indulging muscle and transverse bar is little In frame column（1）The diameter of interior stirrup；

In reinforced mesh（2）External coating interfacial agents, then smear ECC formed reinforcing layer；

To ECC reinforcing layers（3）Carry out moisture-keeping maintaining.

2. the reinforcement means for the enhancing frame column that ECC according to claim 1 is combined with reinforced mesh, feature exist In the stepDetailed process be：To frame column（1）Outer layer breakage or the concrete layer loosened carry out at dabbing Reason, chisel remove the loosening layer of concrete surface, and until exposing coarse aggregate, interface is rinsed using tap water to the shaft surface of dabbing, The bisque that side trimming wire brushing loosens.

3. the reinforcement means for the enhancing frame column that ECC according to claim 1 is combined with reinforced mesh, feature exist In the reinforced mesh（2）Mounting means be：Vertical muscle is placed in internal layer, and transverse bar is placed in outer layer, and vertical muscle abuts against to treated Frame column（1）Surface, and vertical muscle is connected using transverse bar, is overlapped between the transverse bar of two adjacent surfaces, the position of lap joint Column Angle Position is avoided, adjacent lap joint is bounded on each side on face and offsets one from another；The infall of vertical muscle and transverse bar and and transverse bar take It meets place and uses resistance electric welding connection.

4. the reinforcement means for the enhancing frame column that ECC according to claim 1 is combined with reinforced mesh, feature exist In the interfacial agents are cement and expanded slurry interfacial agents, and interfacial agents match ratio is cement：Second class powered coal ash：UEA swelling agents：Water=1: 0.1:0.1:0.4, cement and second class powered coal ash are first carried out dry mixing formation dry powder when preparation, and be uniformly mixed；It is later that UEA is swollen Swollen dose and water are uniformly mixed and form intermixture；Finally intermixture is added in dry powder, and is stirred to viscous pasty state.

5. the reinforcement means for the enhancing frame column that ECC according to claim 1 is combined with reinforced mesh, feature exist In the smearing ECC is smeared using artificial, and point two layers of progress is firmly rubbed, it is ensured that mortar and interface and steel when first layer is smeared The closely knit combination of muscle net avoids enclosed gap, and first layer thickness control is in 10mm；And then first layer is smeared after the completion of smearing The second layer, second layer thickness control is in 20mm.

6. the reinforcement means for the enhancing frame column that ECC is combined with reinforced mesh according to claim 1 or 5, feature It is, the group of the ECC is divided into cement, flyash, sand, water, water-reducing agent and PVA fibers, wherein counts in mass ratio, cement：Powder Coal ash：Sand：Water：Water-reducing agent=1：（1.0~1.2）：（0.6~0.8）：（0.42~0.57）：（0.001~0.003）；With cement, fine coal Ash, the total volume of sand and water-reducing agent after mixing are radix, and the volume of PVA fibers is 13 ~ 20kg/m³。

7. the reinforcement means for the enhancing frame column that ECC according to claim 1 is combined with reinforced mesh, feature exist In the stepIn moisture-keeping maintaining is taken 28 days to ECC reinforcing layers.