(1)The height of the foundation. The edge height of the tapered foundation is generally not less than 200mm, but not more than 500mm; Each side of the top extends 50mm along the edge of the column, and the cone slope is ≤1:3. The height of each step of the stepped foundation should be 300~500mm.

(2) Base cushion. There is usually a low-strength grade plain concrete cushion underneath the foundation, and the thickness of the cushion should not be less than 70mm. A 100mm thick C10 concrete cushion is often used, and each side of the cushion should be 100mm wider from the edge of the foundation. You can also use broken bricks, mixed soil, lime soil, etc. as a cushion.

(3) The strength grade of the foundation concrete should not be lower than C20. Pay attention to the requirements of the working environment on the strength grade of concrete.

(4) Steel bars. The minimum diameter of the stress-bearing steel bars of the extended foundation base plate should not be less than 10mm, and the spacing should not be greater than 200mm. The minimum reinforcement ratio should not be less than 0.15%. The diameter of the longitudinally distributed bars should not be less than 8mm, the spacing should not be greater than 300mm, and the area of ​​the distributed steel bars per linear meter should not be less than 15% of the area of ​​the stressed steel bars.

(1) For an independent foundation under a column, when the punching failure cone falls within the bottom surface of the foundation, the intersection between the column and the foundation should be checked. And the punching shear bearing capacity at the step change point of the foundation; (2) For independent foundations under columns where the short side dimension of the foundation bottom is less than or equal to the column width plus twice the effective height of the foundation, and For the strip foundation under the wall, the shear bearing capacity of the foundation at the intersection between the column (wall) and the foundation should be calculated; (3) The reinforcement of the foundation floor should be determined based on bending resistance calculation; (4) When the concrete strength grade of the foundation is less than the concrete strength grade of the column, the top surface of the foundation under the column should also be checked. Local compression bearing capacity.

Extended foundations refer to independent foundations under columns and strip foundations under walls equipped with reinforced concrete. The extended foundation has good tensile and bending properties. The foundation does not need to consider the rigid angle requirements, so the foundation height can be reduced.

Definition of punching failure

Causes of punching damage

Effect of punching damage

1. Shear crack: A type of crack formed on the surface or inside of a material due to shear stress on the material. Shear cracks affect the strength and toughness of the material.

2. Tensile cracks: A type of crack formed on the surface or inside of a material due to tensile stress on the material. Tensile cracks reduce the strength and toughness of the material.

3. Extrusion deformation: During the punching process, the material will be extruded and deformed, which is manifested as bulges or depressions on the surface or edges of the material. Extrusion deformation affects the appearance and accuracy of the material.

4. Rebound deformation: During the punching process, after the material is subjected to strong impact and deformation, there will be a rebound phenomenon, resulting in bulges or depressions on the surface of the material. Rebound deformation affects the surface quality and accuracy of the material.

5. Deformation hardening: During the punching process, after the material is deformed, the hardness will increase, which is called deformation hardening. Deformation hardening affects the material's processing properties and durability.

A deeper understanding of punching damage

Improved identification and assessment of punching shear damage

Mastered the repair and reinforcement methods of punching damage

Expands the research and application fields of punching shear damage

Inspiring innovation and development thinking on punching shear damage