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 uses annealed steel wire to constrain the concrete of the reinforced compression component, thereby improving the bearing capacity and ductility of the concrete component. 【 Little Knowledge 】 The application scope and precautions of the external prestressed reinforcement method for concrete beams (1) When using unbonded steel strands as prestressed down bracing rods, it is suitable for the reinforcement of continuous beams and large-span simply supported beams;.
(2) When using ordinary steel bars as pre-stressed down bracing rods, it is suitable for the reinforcement of general simply supported beams.
(1) Including components with a reinforcement ratio of less than 0.2% on one side of the longitudinal load-bearing steel bars.
A. When using external prestressing method to reinforce reinforced concrete structures and components, the concrete strength grade of the original components should not be lower than C20..
B. When using this method to reinforce concrete structures, the newly added pre-stressed tension rod anchors, cushion plates, support rod battens, and various fasteners should all undergo reliable anti rust treatment..
C. For more matters, you can join the National Association of Reinforcement and Renovation Industry Societies to obtain more knowledge on seismic reinforcement plans for building structures – component reinforcement and reinforcement.
Earthquakes are the most destructive type of natural disasters, usually caused by crustal movements, which can directly damage or even collapse buildings, posing a huge threat to people’s lives and property safety.
According to the “Seismic Evaluation Standards for Buildings” and “Technical Regulations for Seismic Reinforcement of Buildings” of the Institute of Engineering Seismic Design of the Chinese Academy of Building Sciences, Xingtai, Hebei Province experienced earthquakes of 6.5 and 7.2 magnitudes on March 8 and March 22, 1966, respectively.
After the earthquake on March 8th, some villagers used iron wires to tie up the front and rear walls that flashed outside. However, when a stronger earthquake occurred again on March 22nd, none of these temporarily reinforced houses collapsed.
The results of multiple earthquake disaster investigations have shown that the effect of pre earthquake reinforcement is very effective. Therefore, seismic reinforcement of building structures is one of the effective means to reduce earthquake disasters.
At 7:58 on April 3, 2024, a magnitude 7.3 earthquake occurred in the sea area of Hualien County, Taiwan, with a focal depth of 12 kilometers.
The average elevation within a 5-kilometer radius of the epicenter is about -3560 meters, making it the largest earthquake in Taiwan 25 years after the 1999 921 earthquake.
As of April 8th, this earthquake has caused 13 deaths, 1145 injuries, and 6 people are still missing.
On May 12, 2008, at 14:28:04, a 8.0 magnitude earthquake occurred in Wenchuan, Sichuan, with a depth of 14 kilometers, making it the largest earthquake since the founding of New China. 500000 square kilometers of the ground were severely damaged, and as of June 3, a total of 10037 aftershocks occurred.
As of April 25, 2009, a total of 69227 people were killed, 374643 were injured, and 17923 were missing.
On July 28, 1976, at 3:42:53.8, a 7.8 magnitude earthquake occurred in Tangshan, Hebei Province, with a depth of 12 kilometers and a duration of about 23 seconds. The entire city of Tangshan was instantly flattened, and transportation, communication, water supply, and power supply were completely paralyzed. How can concrete prefabricated component factories reduce costs? Reducing the production costs of prefabricated concrete component factories is the key to improving competitiveness and profitability. Propose specific strategies in the following seven areas:.
By purchasing raw materials in large quantities, comparing goods with three suppliers, improving bargaining power, and obtaining more favorable prices. Regularly negotiate with suppliers to negotiate for lower prices or better payment terms. Research and test alternative materials with lower costs, as long as product quality is not sacrificed. Optimize the supply chain and reduce logistics costs..
02 Common mode cost reduction.
Design standardized molds that are suitable for multiple products and reduce the total number of molds. Share molds between different production lines or factories to improve mold utilization..
Optimize component design to reduce complexity and material waste in the production process. Adopting modular design to improve production efficiency and mold reuse..
04 Process cost reduction.
Continuously improve production processes, reduce unnecessary processes and time waste. Strengthen quality control, reduce scrap rates, and reduce rework and material waste..
The component factory has a breakeven point, which is to achieve a certain production volume at a reasonable price. By expanding production scale, sharing fixed costs, and reducing unit product costs. Explore new markets, increase order volume, and improve production efficiency..
6、 Intelligent cost reduction.
Invest in automated intelligent production lines to reduce labor costs and improve production efficiency. Utilize information technology to achieve intelligent management of the production process and reduce waste..
Regularly conduct energy surveys to identify areas of energy waste. Adopting energy-saving technologies and equipment, such as LED lighting, high-efficiency motors, etc. Recycling and utilizing waste heat and wastewater from the production process to reduce energy consumption..
Through the implementation of these strategies, prefabricated concrete component factories can effectively reduce production costs and improve market competitiveness. Abstract: A study on the bending performance of a new type of stainless steel pipe solid waste concrete component was conducted. Pure bending tests were conducted on six stainless steel pipe concrete specimens, and the influence of concrete type and section shape on the failure mode, load deformation relationship, bending stiffness, and bearing capacity of the new S35657 austenitic stainless steel pipe concrete component under bending load was analyzed. The experimental results show that solid waste concrete has little effect on the overall failure mode of the new stainless steel tube concrete pure bending component, but solid waste concrete is beneficial for improving the bending bearing capacity and stiffness of the component. Subsequently, a finite element model of stainless steel pipe solid waste concrete pure bending components was established and the applicability of existing material models was verified. Finally, the applicability and prediction accuracy of various code bending bearing capacity calculation methods were analyzed..
Keywords: S35657 austenitic stainless steel; Solid waste concrete; Steel tube concrete; Pure bending; finite element analysis.
Progress in Building Steel Structures Continues to be Compiled into Chinese Core Journals.
