Today, I would like to introduce the outsourcing angle steel reinforcement method:

Multi-storey reinforced concrete frame houses without seismic fortification often have weak links in seismic bearing capacity and deformation capacity. The main reasons are:

(1) The seismic bearing capacity of the column is insufficient.

(2) The stirrups of the column are thin in diameter and large in spacing, and the stirrups often use right-angle hooks. In addition, the axial compression ratio of some columns is too large, and brittle failures such as shear tension and shear compression are prone to occur in earthquakes, which makes the deformability of the column poor.

(3) Stirrups, etc. are not provided in the core area of the beam-column node.

In view of the fact that the existing reinforced concrete frame structure cannot be added with reinforced concrete seismic wall in the use function, the outsourcing angle steel reinforcement method can be adopted to enhance the bearing capacity and deformation capacity of the frame columns and nodes, so as to achieve the purpose of improving the overall seismic capacity of the frame structure

According to relevant experiments, the reinforced concrete column reinforced by the outer angle steel is a composite column composed of steel members and reinforced concrete. It not only maintains the properties of reinforced concrete, but also has certain characteristics of steel structure. Its main destructive characteristics are:

(1) Due to the tensile effect of the outer angle steel, the crack resistance of the reinforced column is greatly improved. Even in reinforced columns with large eccentric compression, the initial bending and tension cracks appear more obvious when the concrete in the tension zone is about 70% to 80% of the maximum load.

(2) Before reaching the ultimate bearing capacity, the angle steel and the column play an integral role, and there is no sign of sliding between the flat steel hoop and the column surface. When the ultimate bearing capacity is about to be reached, the cohesive force between the angle steel and the column surface gradually loses, resulting in relative sliding, but with the oblique dislocation of the flat steel hoop and the angle steel is tightened, the friction between the angle steel and the column also increases. Therefore, in the subsequent considerable loading process, the strain of the tension angle steel will not decrease rapidly, but the strain of the compression angle steel will continue to increase, so that the bearing capacity of the column will not drop rapidly. The angle steel gradually loses its ability to work with the column until the concrete is obviously crushed in the compression zone at the end of the column.

(3) Whether it is a large eccentric compression column or a small eccentric compression column, the rapid decrease in the bearing capacity of the reinforced column is due to the crushing of the concrete in the compression zone. However, a reinforced column wrapped with external steel members will not spall or collapse like a prototype column.

(4) After the test, the deformation of the prototype column is concentrated in the plastic hinge area at the end of the column, and the rest of the column remains almost straight. The deformation of the reinforced column is more evenly distributed along the height of the column, and the entire column is in an obvious bending state.

Experimental research also shows that after the use of outer-coated angle steel reinforcement, the column has a certain degree of homogeneity, presents a relatively symmetrical failure state, and the deformation capacity can be fully exerted. The displacement angle between layers is about twice as high as that of unreinforced columns. When the column is only reinforced with outsourcing flat steel hoops, it has a similar effect, but the effect is poor, and the spacing of the flat steel hoops must be small.

Outsourcing angle steel construction process