The term “retrofit” signifies the use of new innovations to a more seasoned system. Retrofitting is the process of adding some new elements to a structure that were not there previously. It is the method of changing or repairing something after it has been made. There are different retrofitting techniques for RCC buildings. The retrofitting techniques for RCC buildings are generally classified into two categories, such as, Global retrofitting techniques and Local retrofitting techniques.
Under this two categories of retrofitting techniques for RCC buildings, more techniques are added. Here it is discussed about what is retrofitting in construction, classification of retrofitting techniques, methods of retrofitting and need for retrofitting.
What is Retrofitting in Construction?
Retrofitting is the process of adding some new provisions that were not there previously. It is the method of changing or repairing and modifying something after it has been made. Retrofitting of buildings is needed for the houses that are influenced by disappointments and harmed by seismic forces. Retrofitting of structures implies making changes to an existing structure so as to protect it from flooding or different hazards like earthquakes, high winds, etc.
Retrofitting a building includes changing its structures or systems after its initial construction. This work can further develop conveniences for the building’s occupants and work on the performance of the building. As technology develops, the retrofitting of buildings can essentially decrease energy and water utilization.
There are a scope of technologies relevant to energy and water efficiency. Few out of every odd innovation will be fit to each building, so consistently get guidance from a certified building professional prior to undertaking any works. There are several retrofitting techniques for RCC buildings.
Classification of Retrofitting Techniques
The classification of retrofitting techniques for RCC buildings is mainly of two categories, such as,
- Global Retrofitting Techniques
- Local Retrofitting Techniques
Global Retrofitting Techniques
- Adding Shear Wall
- Adding Infill Wall
- Adding Steel Bracing
- Adding Wing Wall
- Wall Thickening Technique
- Mass Reduction Technique
- Base Isolation Technique
- Mass Dampers
Local Retrofitting Technique
- Jacketing of Beams
- Jacketing of Columns
- Jacketing of Beam-Column Joints
- Strengthening of Individual Footings
Methods of Retrofitting
Some of the commonly used methods of retrofitting of structure are:
- Adding Steel Bracing
- Jacketing Method
- External Plate Bonding
- Base Isolation Technique
- Mass Reduction Technique
- Wall Thickening Technique
- Fiber Reinforced Polymer (FRP)
- Adding Shear Wall
- Epoxy Injection Method
- Section Enlarging Reinforcing Method
Adding Steel Bracing
- Steel bracing is a successful arrangement in the retrofitting of building when enormous openings are required.
- Steel bracings are the most well-known and potentially powerful technical solutions for upgrading the seismic safety of previous standing RCC structures.
- The amount of work in this type of retrofitting techniques for RCC buildings are less which brings about less foundation cost, adding an extremely less weight to the existing structure.
Jacketing Method
- There are 3 types of jacketing, they are, Reinforced Concrete Jacket, Steel Jacket, Fiber Reinforced Polymer Composite Jacket (FRPC).
- Jacketing is the method for the structural retrofitting and structural strengthening.
- It is utilized for increasing bearing load capacity following an alteration of the structural design or to reestablish structural design integrity because of a disappointment in the structural member.
- This retrofitting techniques for RCC buildings is utilized on vertical surfaces like walls, columns and different combinations, for example, beam sides and bottoms.
- It comprises of added concrete with transverse and longitudinal reinforcement around existing column.
- In this process an existing structural member section is reestablished to the original dimensions or expanded in size by encasement utilizing reasonable materials.
- In this type of retrofitting techniques for RCC buildings, a cage like design made of steel reinforcement or a composite material wrapping is constructed around the deteriorated section onto which cast-in-place concrete or shotcrete is placed.
- Jacketing is especially utilized for the repair of crumbled columns, piers and piles and may effortlessly be utilized in underwater applications.
- This retrofitting techniques for RCC buildings is relevant for protecting concrete, steel, and timber sections against additional crumbling and for strengthening.
- Jacketing works on axial and shear strength of columns and a significant strengthening of the foundation might be stayed away from.
External Plate Bonding
- Strengthening of reinforced concrete beams with external plates or strips is a customary methods of retrofitting and has been used for a long time.
- The external plate bonding method can be utilized for expanding the shear strength of reinforced concrete beams by totally or somewhat wrapping steel plates at the joint of a column and beam.
- An external plate giving perpendicular to potential shear cracks is powerful to build the shear strength of the concrete reinforced member.
- The extra shear strength is accomplished in this type of retrofitting techniques for RCC buildings, however relying upon beam geometry, the existing concrete strength and the wrapping method is applied.
Base Isolation Technique
- When the superstructure is isolated from the foundation, then it is known as base isolation.
- It is the most remarkable method for passive structural vibrations control technique.
- When building isolates starting from the earliest stage causes lesser seismic loads, henceforth lesser harm to the structure and least repair of the superstructure.
- The disadvantage of this retrofitting techniques for RCC buildings is that it can’t be applied to structures like other retrofitting and costly in the spending plan.
- This methods of retrofitting is wasteful for high-rise buildings and not reasonable for buildings laid on soft soil.
Mass Reduction Technique
- In mass reduction technique of retrofitting, for instance, by evacuation of at least one storey.
- In this retrofitting techniques for RCC buildings, it is clear that the expulsion of the mass will prompt a reduction in the loading, which will prompt an increment in the necessary strength.
Wall Thickening Technique
- The existing walls of a building are added a specific thickness by adding concrete, bricks and steel adjusted at specific places as reinforcement.
- The wall weight increases and it can bear more horizontal and vertical loads in this type of retrofitting techniques for RCC buildings.
- It is designed under uncommon conditions that the transverse loads don’t cause abrupt disappointment of the wall.
- Rust can be created on reinforcement if not covered as expected by mortar.
Fiber Reinforced Polymer
- A fiber reinforced polymer is an axial strengthening system which used to improve or upgrade the capacity of reinforced concrete beams.
- It tends to be utilized for both circular just as a rectangular-shaped column yet it is more powerful fit.
- FRP builds the ultimate load carrying capacity of reinforced concrete members and further develops the shear capacity of the reinforced concrete element.
- In this type of retrofitting techniques for RCC buildings the ductility of a reinforced concrete column is expanded significantly.
- Composite should be dried before repair since all resins and some fiber ingest moisture.
Adding Shear Wall
- This is a regularly utilized retrofitting techniques for RCC buildings, of non-ductile reinforced concrete frame buildings.
- The elements can be either pre-cast concrete or cast-in-place concrete.
- New elements preferably are placed at the outside of the building.
- This methods of retrofitting isn’t preferred in the inside of the structure to stay away from inside moldings.
Epoxy Injection Method
- In the slabs, concrete walls, piers and columns an economical methods of retrofitting is used known as the epoxy injection for repairing of non-moving cracks.
- The epoxy injection is utilized in retrofitting of building to repair and fill the structural failure issue.
- This type of retrofitting techniques for RCC buildings are equipped for reestablishing the strength of concrete to its pre-cracked strength.
- The epoxy tensile bond to the concrete is more grounded than the tensile strength of concrete.
- Strengthening is given in this retrofitting techniques for RCC buildings by introducing extra reinforcement across the disappointment place in combination with the epoxy pitch injection.
Section Enlarging Reinforcing Method
- The developed cross section methods of retrofitting is utilized to build the components of the reinforcement region.
- It upgrades the bearing capacity and furthermore increment its cross section firmness and change the normal frequency of vibration.
- This retrofitting techniques for RCC buildings is broadly utilized in the reinforced concrete structure of the slab, beam column, etc.
- The amplified cross section method is reasonable for the reinforcement of the reinforced concrete bending and the compression member.
Need for Retrofitting
Some of the need for retrofitting are as mentioned below:
- Maintenance of structural cracks and structural members damages.
- Fundamental to diminish hazard and risk and losses from the non-structural elements.
- To correct the error in construction or design.
- To guarantee the safety and security of a building, structure functionality, employees, inventory and machinery.
- To reconstruct the structure for the advantages of excessive loading.
- Predominantly worried about structural improvement to decrease seismic hazard.
- To reconstruct the damages caused by the seismic hazard.
- Important buildings should be strengthened whose administrations are thought to be essential soon after a quake, like hospitals.
- Maintenance for the corrosion because of penetration in honeycomb pores.
So, here it is discussed about what is retrofitting in construction, classification of retrofitting techniques for RCC buildings, methods of retrofitting and need for retrofitting.
FAQ >
Q. When we do building retrofitting, how much does the life of the building increase?
Ans: There are many reasons for retrofitting of buildings, but primarily building retrofitting is done when there are structural cracks and damages of structural members due to earthquakes and other seismic hazards. After retrofitting of buildings, the life of the building increases up to 40% to 60% of the total life cycle given.
Q. Under which situation epoxy resin is used in retrofitting a building?
Ans: The epoxy injection method or the epoxy resin is used in retrofitting a building for repairing of non-moving cracks.
Q. State differences between retrofitting and safe construction practice.
Ans: The difference between retrofitting and safe construction practice is that, retrofitting is the method of changing or repairing and modifying something after it has been made or damaged by seismic hazards. But safe construction practice is the term that is taken care before or during the construction so that no workers gets harm while constructing a structure.
Q. Different methods for retrofitting beams in a residential building.
Ans: The different methods for retrofitting beams in a residential building are Jacketing Method, External Plate Bonding Method, Fiber Reinforced Polymer Method, Epoxy Injection Polymer Method and Section Enlarging Reinforcing Method.
Q. Can I retrofit the column of house if no lapping length provided in column for 1st floor construction above ground floor?
Ans: Yes, you can retrofit it with the direction given by the construction professional.
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