Retrofitting of buildings refers to the process of upgrading or modifying existing structures to enhance their performance, energy efficiency, safety, or functionality. This can be done for various reasons, including compliance with new building codes, improving sustainability, and adapting to changing needs. Retrofitting measures can be applied to different aspects of a building, including its structure, systems, and envelope.
What Is Retrofitting?
Retrofitting refers to the process of upgrading or modifying existing structures, systems, or equipment to improve their performance or make them more energy-efficient. This process is typically performed in older buildings or homes to bring them up to current standards and improve their energy efficiency.
Retrofitting of buildings can be an effective way to improve the energy efficiency and sustainability of existing buildings and homes. By reducing energy consumption and reducing waste, retrofitting can also help reduce environmental impact and save property owners money on utility bills.
Retrofitting of RCC structural members is carried out to regain the strength of deteriorated structural concrete elements. The main goal of retrofitting is to stabilize the current structure of buildings and make them earthquake-resistant.
Methods of Retrofitting of Building
The following are the most common methods of retrofitting of building
- Adding New Shear Wall
- Adding Steel Bracing
- Wall Thickening Technique
- Base Isolation Technique
- Mass Reduction Technique
- Jacketing Method
- Fiber Reinforced Polymer (FRP)
- Epoxy Injection Method
- External Plate Bonding
1. Adding New Shear Wall:
- This is a frequently used technique for retrofitting of a building of non-ductile reinforced concrete frame buildings.
- The elements can be either cast-in-place or pre-cast concrete elements.
- New elements preferably are placed at the exterior of the building.
- This method is not preferred in the interior of the structure to avoid interior moldings.
2. Adding Steel Bracing
- Steel bracing is an effective solution in the retrofitting of buildings when large openings are required.
- Potential advantages due to higher strength and stiffness and opening for natural light can be provided.
- The amount of work is also less so foundation cost may be minimized and adds much less weight to the existing structure.
3. Wall Thickening Technique
- The existing walls of a building are added a certain thickness by adding bricks, concrete, and steel aligned at certain places as reinforcement.
- The weight of the wall increases and it can bear more vertical and horizontal loads.
- Also, it is designed under special conditions so so that the transverse loads do not cause sudden failure of the wall.
- Rust can be developed on reinforcement if not covered properly by mortar.
4. Base Isolation Technique
Isolation of the superstructure from the foundation is known as base isolation. It is the most powerful method for passive structural vibration control techniques.
When a building is isolated from the ground it causes lesser seismic loads, hence lesser damage to the structure and minimum repair of the super-structure. The main demerit of this method is, it cannot be applied to structures like other retrofitting and is expensive in the budget.
This method is inefficient for high-rise buildings and not suitable for buildings resting on soft soils.
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5. Mass Reduction Technique
In mass reduction technique, for instance, by removal of one or more storeys as shown in the figure. In this method, it is evident that the removal of the mass will lead to a decrease in the loading, which will lead to an increase in the required strength.
6. Jacketing Method
It is the most used method of retrofitting of building. Jacketing is the most popularly used method for the strengthening of columns and beams of a building. Jacketing consists of added concrete with longitudinal and transverse reinforcement around the existing columns.
It improves the axial and shear strength of the column and major strengthening of the foundation may be avoided. The amount of work is less as foundation strengthening does not require and increases the shear strength of the column. It also increases the confinement of concrete in circular columns.
Steel jacketing does not increase the significant weight of the column and also saves construction time.
7. Fiber Reinforced Polymer (FRP)
A fiber-reinforced polymer is an axial strengthening system used to improve or enhance the capacity of reinforced concrete beams. It can be used for both circular as well as rectangular-shaped columns but it is more effective in the former shape.
FRP increases the ultimate load-carrying capacity of reinforced concrete members and improves the shear capacity of the reinforced concrete element. Also, the ductility of a reinforced concrete column is increased considerably. Composite must be dried before repair because all resins and some fiber absorb moisture.
8. Epoxy Injection Method
Epoxy injection is an economical method of repairing non-moving cracks in concrete walls, slabs, columns, and piers. In retrofitting buildings, epoxy injection is used to fill and repair the structural fault.
It is capable of restoring the strength of concrete to its pre-cracked strength. The epoxy tensile bond to the concrete is stronger than the tensile strength of concrete. Strengthening is provided by installing additional reinforcement across the failure plane in combination with the epoxy resin injection.Â
9. External Plate Bonding
Strengthening of reinforced concrete beams with external plates or strips is a conventional method and has been utilized for many decades. The external plate bonding method can be used for increasing the shear strength of reinforced concrete beams by completely or partially wrapping steel plates at the joint of a column and beam.
An external plate providing perpendicular to potential shear cracks is effective to increase the shear strength of the concrete reinforced member. The additional shear strength is achieved, but depending on beam geometry, existing concrete strength, and applied the wrapping method.
Read More: 8 Foundation Repair Techniques and Methods
10. Section-Enlarging Reinforcing Method
The enlarged cross-section method is used to increase the components of the reinforcement area, which enhance the bearing capacity and also increases its cross-section stiffness and changes the natural frequency of vibration. This method is widely used in the reinforced concrete structure of the beam, slabs, columns, etc.
The enlarged cross-section method is suitable for the reinforcement of reinforced concrete bending and compression member.
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