by According to the latest national standard “General Code for Appraisal and Reinforcement of Existing Buildings” GB55021-2021, there are five methods for strengthening concrete components:.
When using the method of increasing cross-section to reinforce bending and compression components, the interface treatment and bonding quality of the reinforced components should meet the requirements calculated based on the overall cross-section.
The construction of reinforced concrete components with increased cross-section reinforcement should comply with the following regulations:.
1) The minimum thickness of the newly added concrete layer should not be less than 40mm for the slab; Beams and columns should not be less than 60mm.
3) The net distance between the newly added load-bearing steel bars and the original load-bearing steel bars should not be less than 25mm, and short bars or hoop bars should be welded to the original steel bars.
4) When reinforcing one side of the section under tension, U-shaped reinforcement should be set up and welded onto the original hoop reinforcement. The length of the weld seam welded on one side (both sides) should be 10 times (5 times) the diameter of the hoop reinforcement.
5) When reinforced with concrete casing, circular or anchored hoop reinforcement should be installed.
6) When U-shaped reinforcement is buried by planting due to structural limitations, anchoring type structural adhesive should be used for planting.
When using displacement method to locally reinforce concrete components with low strength or serious defects in the compression zone, the original components should be supported and topped when reinforcing beam type components; When reinforcing components such as columns and walls, the bearing state of the original structure and components should be verified, monitored, and controlled throughout the construction process; Measures should be taken to ensure the collaborative work of replacement concrete; The interface treatment and bonding quality of the replacement part of concrete structural components should meet the requirements calculated based on the overall cross-section.
1) The replacement depth of concrete and the minimum thickness of the newly added concrete layer should not be less than 40mm for the slab; Beams and columns should not be less than 60mm.
2) The replacement length should be determined based on the detection and calculation results of concrete strength and defects. However, for non full length replacement, the two ends should extend a length of no less than 100mm respectively.
When using the external steel reinforcement method to reinforce reinforced concrete solid web columns or beams, the following regulations should be met:.
1) The external forces borne by the steel frame and the original column after dry outsourcing steel reinforcement should be distributed among 5 concrete column reinforcement schemes according to their respective section stiffness ratios. Which method is better?.
The method of increasing column section reinforcement is a column reinforcement method that involves wrapping concrete on one side, both sides, or all sides of a concrete column based on its stress situation, increasing the structural cross-sectional area and reinforcement to improve the structural bearing capacity, increase the strength and stiffness of the column.
In concrete reinforcement, the method of increasing the cross-section is particularly suitable for situations where the bearing capacity is insufficient due to the small cross-section of the column.
In order to achieve the reinforcement effect of the enlarged cross-section method in concrete, it is necessary to ensure that the strength grade of the concrete substrate is not lower than C15, and the load-bearing steel bars used for reinforcement should not be less than 14mm. At the same time, different types, cross-sectional forms, and stress situations of concrete columns need to use different structural forms.
Advantages: Simple construction process, strong adaptability, and long-term usage experience;.
Disadvantages: The construction wet operation takes a long time, and the load needs to be limited during the concrete curing period. After reinforcement, the self weight of the structure increases, and the building’s usage space decreases.
Carbon fiber cloth reinforcement is suitable for strengthening concrete columns under axial compression, large eccentric compression, and insufficient ductility.
The insufficient bearing capacity and ductility of the normal section of concrete columns can be improved through circumferential confinement, which means continuous bonding without gaps in the circumferential direction; Carbon fiber cloth can also be pasted into circular hoops to improve the diagonal section bearing capacity of concrete columns.
The reinforcement of carbon fiber cloth should ensure that the strength of the substrate is not less than C15, and the positive tensile bonding strength is not less than 1.5MPa. At the same time, the lap length of carbon fiber cloth in the circumferential bundle should not be less than 50mm.
Advantages: Lightweight height, generally no need for overlap, can adapt to the bonding requirements of curved concrete, corrosion resistance, moisture resistance, and convenient construction;.
Disadvantage: There are temperature limitations on the usage environment and specialized protective measures are required.
In order to improve the ductility of concrete columns, wire winding method is often used to reinforce them.
The reinforcement principle of wire winding reinforcement method is to use annealed steel wire to constrain the concrete of the reinforced compression component, thereby improving the bearing capacity and ductility of the concrete component. This is a direct reinforcement method. There are five commonly used concrete column reinforcement schemes.
The method of increasing column section reinforcement is a column reinforcement method that involves wrapping concrete on one side, both sides, or all sides of a concrete column based on its stress situation, increasing the structural cross-sectional area and reinforcement to improve the structural bearing capacity, increase the strength and stiffness of the column.
In concrete reinforcement, the method of increasing the cross-section is particularly suitable for situations where the bearing capacity is insufficient due to the small cross-section of the column.
In order to achieve the reinforcement effect of the enlarged cross-section method in concrete, it is necessary to ensure that the strength grade of the concrete substrate is not lower than C15, and the load-bearing steel bars used for reinforcement should not be less than 14mm. At the same time, different types, cross-sectional forms, and stress situations of concrete columns need to use different structural forms.
Advantages: Simple construction process, strong adaptability, and long-term usage experience;.
Disadvantages: The construction wet operation takes a long time, and the load needs to be limited during the concrete curing period. After reinforcement, the self weight of the structure increases, and the building’s usage space decreases.
Carbon fiber cloth reinforcement is suitable for strengthening concrete columns under axial compression, large eccentric compression, and insufficient ductility.
The insufficient bearing capacity and ductility of the normal section of concrete columns can be improved through circumferential confinement, which means continuous bonding without gaps in the circumferential direction; Carbon fiber cloth can also be pasted into circular hoops to improve the diagonal section bearing capacity of concrete columns.
The reinforcement of carbon fiber cloth should ensure that the strength of the substrate is not less than C15, and the positive tensile bonding strength is not less than 1.5MPa. At the same time, the lap length of carbon fiber cloth in the circumferential bundle should not be less than 50mm.
Advantages: Lightweight height, generally no need for overlap, can adapt to the bonding requirements of curved concrete, corrosion resistance, moisture resistance, and convenient construction;.
Disadvantage: There are temperature limitations on the usage environment and specialized protective measures are required.
In order to improve the ductility of concrete columns, wire winding method is often used to reinforce them.
The reinforcement principle of wire winding reinforcement method is a direct reinforcement method that involves wrapping annealed steel wires to constrain the concrete of the reinforced compression component, thereby improving the bearing capacity and ductility of the concrete component.
