What Is Retrofitting & Methods of Retrofitting of Building

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 can involve a variety of different upgrades, including:

1. Insulation upgrades: Adding insulation to walls, attics, and floors to reduce energy loss and improve heating and cooling efficiency.
2. Lighting upgrades: Replacing traditional lighting fixtures with energy-efficient LED or CFL bulbs to reduce energy use and improve lighting quality.
3. HVAC upgrades: Replacing old or inefficient heating and cooling systems with more energy-efficient models to reduce energy consumption and improve indoor air quality.
4. Water conservation upgrades: Installing low-flow showerheads, toilets, and faucets to reduce water use and conserve resources.
5. Renewable energy systems: Installing solar panels, wind turbines, or other renewable energy systems to generate clean, renewable energy and reduce dependence on fossil fuels.

Retrofitting 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 strength deficiency of concrete structural members can be due to poor workmanship, design errors, and deterioration due to the aggression of harmful agents.

The main goal of retrofitting is to stabilize the current structure of buildings and make them earthquake resistant.

Read More: Concrete Crack Repair – Top 5 Best Methods of Concrete Repair

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What Is Need Retrofitting

There are several problems that structural members experience and needed to be tackled among them some common problems include:

• Structural cracks
• Damage to structural members
• Excessive loading
• Errors in design or construction
• Modification of the structural system
• Seismic damage
• Corrosion due to penetration- honeycombs

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Methods of Retrofitting of Building

The following are the most common method of retrofitting a building

1. Adding New Shear Wall
2. Adding Steel Bracing
3. Wall Thickening Technique
4. Base Isolation Technique
5. Mass Reduction Technique
6. Jacketing Method
7. Fiber Reinforced Polymer (FRP)
8. Epoxy Injection Method
9. 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.

Read More: Honey Combing of Concrete– Causes & Repair Methods

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. 

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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Factors Affecting in Selection of Retrofitting of Building Methods

The following factors should be kept in mind while selecting a method of retrofitting

There are several factors that can affect the selection and implementation of retrofitting in a building or home. These include:

1. Types of Building and its age: Older buildings may require more extensive retrofitting measures to bring them up to current energy efficiency standards.
2. Usage of Building: The type of building, such as a commercial office or a residential home, can affect the type and extent of retrofitting measures that are needed.
3. patterns of Energy Consumption: The amount and type of energy used in a building can affect the type and extent of retrofitting measures that are needed.
4. Budget constraints: The available budget for retrofitting can impact the type and extent of retrofitting measures that can be implemented.
5. Local building codes and regulations: Local building codes and regulations can affect the type and extent of retrofitting measures that are allowed.
6. Goals of Energy Efficiency: The desired energy efficiency goals for a building can impact the type and extent of retrofitting measures that are needed.
7. Availability of funding and incentives: Funding and incentives, such as tax credits or grants, can help offset the costs of retrofitting and make it more affordable.
8. Technical feasibility: The technical feasibility of retrofitting measures can impact the type and extent of retrofitting measures that can be implemented.
9. Building owner’s priorities: The priorities of the building owner, such as cost savings, environmental sustainability, or improved indoor air quality, can affect the type and extent of retrofitting measures that are implemented.

When selecting retrofitting measures, it is important to consider these and other factors to ensure that the best solution is selected for each individual building or home.

This may involve working with a professional contractor or energy consultant to identify the most cost-effective and energy-efficient retrofitting options.

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Identify the Structural Damages and Their Retrofitting Process

1. Retrofitting of Corroded Structural Member

If corrosion has started, the following process is adopted:

1. Remove weak concrete and expose reinforcement all around.
2. Clean the rust of steel with wire brushes or sandblasting.
3. Apply rust removers and rust preventers.
4. Reinforce to supplement rusted steel if required with anchorage i.e. shear connectors.
5. Apply tack coat or bonding coat (to provide a bond between the old concrete and new concrete) of polymer and epoxy resin-based bonding material.
6. Use one of the patching techniques to restore concrete to the original surface level. Polymer-defined mortars are very good. This can be used with or without gaining.
7. Injection of cement slurry or polymer-modified slurry or epoxy to fill up pores or internal cracks or honeycombing.
8. Apply a suitable protecting coating.

2. Retrofitting of Severely Damaged Concrete:

In case when the original concrete is in very bad condition and the injection of grouting is not able to rehabilitate the section to take the required loading, RCC Jacketing of the concrete section is to be provided.

1. Provide the essential supporting system to the structure.
2. Remove weak concrete.
3. Clean the surface and clean the corroded part of the steel.
4. Apply rust removers and rust preventers.
5. Provide additional steel all around the structure.
6. Provide required formwork.
7. Provide a polymer-based bonding coat between old and new concrete surfaces.
8. Place the concrete of the required thickness, grade, and workability admixed with different admixtures.

3. The benefit of Retrofitting of Building:

The followings are the benefits of the retrofitting of building technique:

• This technique is used to prevent displacement from the concrete foundation of the structure.
• It improves the stability and safety levels of the structure.
• Retrofitting buildings is more adaptable and suitable for existing activities or future activities and make a building more comfortable to resist loading.
• Helps to prevent damage to the structure and injury to the occupants.
• Retrofitted buildings are more energy-efficient and lower carbon emissions from building operations.
• The process helps to improve a resident’s ability to keep residents safe when there is an earthquake.
• Retrofitting also helps to make homes more habitable after any major earthquake.
• Also, when you get retrofitting done in your home, most insurance companies have increased their insurance benefits.
• Increasing the local capacity of the structural and non-structural components.

4. Demerits of Retrofitting of Building

Other than the advantages, retrofitting also has several disadvantages, such as:

• The skilled worker must be complying with the adopted retrofitting approaches
• Limited access to the construction site, since the building could be still in function.
• Difficult bonding mats arise between old masonry and the new concrete surface.
• Concrete has higher strength than old masonry structures, thus special care should be given to specify the strength of overlaid concrete.

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