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 according to the stiffness ratio of their respective sections.
