Last Updated on August 3, 2022 by Admin
Retrofitting is the technique by which we append new features to pre-existing buildings, bridges, historic monuments, etc. Retrofitting aids in lowering an existing structure’s susceptibility to damage in the event of a natural disaster or seismic activity. Retrofitting is a process used in the construction industry to restore and strengthen aging structures. Engineers employ the retrofit procedure to secure and seismically proof older buildings.
An alternative to reconstruction is retrofit. Instead of redeveloping, lengthening a structure’s lifespan is a more cost-effective strategy. Retrofitting is the process of giving anything a component or feature that was not included during manufacture or by adding something that was not present at the time of original construction. It frequently refers to the installation of new building systems, such heating systems, but it may also apply to the fabric of a building, like installing double glazing or retrofitting insulation.
A relatively ancient structure can now be adapted to survive seismic interactions thanks to modern technology, applications, and procedures. A system can be strengthened by the addition of new features. In order to strengthen the stability of existing structures and prevent their breakdown due to dangers, retrofitting is a relatively useful strategy. If the building has already been harmed, it also aids in recovering strength and stability.
Retrofitting requires careful balancing of several factors and their impacts on a building’s overall performance. A change in one area of a structure can have an impact on other areas, and sometimes this is only obvious after irreparable damage has been done. The primary objective of retrofitting is to make existing structures stronger, more stable, and secure against potential weaknesses.
What is Retrofitting in construction?
Retrofitting is the process of modifying existing structures, such as homes, bridges, and historic buildings, to make them resistant to seismic activity, such as earthquakes, volcanic eruptions, and other natural disasters, such as landslides, tsunamis, floods, and thunderstorms.
Retrofitting RCC structural members is done to restore the strength of the weakened concrete element structure. Additionally, it aids in halting additional damage to concrete components. Errors in the design or subpar construction could be to blame for the concrete element’s lack of strength. Another explanation for the decline can also exist, such as the aggressiveness of dangerous substances.
The extent of the damage caused determines how much capacity may be restored to the structure once the right retrofitting technique has been executed and specified. Numerous methods, including external plate bonding, grouting, external post-tensioning, section enlargement, and fiber reinforced polymer composites, are employed during the retrofitting process. When structures and engineering projects get damaged to the point that they cannot be used for general purposes, they may require strengthening and repair.
Such situations. The risk of lives being lost as well as any structural and content damage would be intolerable since the structure cannot sustain a subsequent sequence of the same action or other unintentional acts with acceptable reliability. Retrofitting is a strengthening modification that can restore a suitable level of safety and defense against such acts.
What is the purpose of Retrofitting?
As time goes on, the structure is impacted by a variety of environmental conditions. The most harmful of these is an earthquake, which disrupts the interior structure of the building and gradually causes that structure to lose its strength and stability. As a result, the building is rendered dangerous for usage in the future and could result in significant loss.
Throughout its lifetime, a structure is subjected to a variety of forces, including compression, shear, bending, and horizontal forces. Depending on the sort of building and how it is used, different forces will act on it. In addition to normal wear and tear, the building is severely harmed by a number of other natural factors, such as the climate, frequent use, and loading conditions.
However, seismic forces are the most harmful to any construction. Seismic forces can harm a structure, whether it be a building or a bridge, and cause it to lose its capacity to withstand and support loads for future usage. Buildings can develop fractures and structural problems as a result of many types of settlements.
There are a number of issues that structural members face that need to be resolved. Some of these issues include:
- Structural cracks
- Deterioration of structural members
- Extravagant loading
- Design or construction mistakes
- Changes to the structural system
- Seismic damage
- Honeycomb corrosion brought on by penetration
When dealing with damages, there are many different situations. If a building, whether it be in the public or private sector, such as an office or a home, suffers severe structural damage. Civil engineers prefer to tear down and rebuild the structure. However, dismantling significant or historically significant buildings is not an option. The retrofitting phenomenon is now upon us.
What are the Methods (or types) of Retrofitting?
The implementation of new technologies in an older system is referred to as “retrofitting.” Retrofitting is the process of incorporating new components into an existing structure that weren’t there before. It is a technique for modifying or fixing something after it has been created. For RCC buildings, various retrofitting methods exist. The retrofitting methods for RCC structures are often divided into two groups, such as Global and Local retrofit methods.
Among the often-employed techniques for retrofitting a structure are:
- Adding Steel Bracing
When huge openings need to be made in a building, steel bracing is a practical solution. The most well-known and potentially effective technical options for increasing the seismic safety of existing RCC structures are steel bracings. This type of retrofitting procedures for RCC structures require less effort, which results in lower foundation costs and significantly less weight added to the existing structure.
- Jacketing Method
There are three different types of jacketing: fiber-reinforced polymer composite, steel, and reinforced concrete (FRPC). The technique for reinforcing and retrofitting existing structures is called jacketing. It is used to increase bearing load capacity after a structural design change or to restore structural design integrity as a result of a structural member’s failure.
This RCC building retrofitting technology is applied to vertical surfaces like walls, columns, and various combinations, like the bottoms and sides of beams. Around the existing column, there is extra concrete with longitudinal and transverse reinforcement. By encasing it in suitable materials, an existing structural member section is restored to its original proportions or increased in size throughout this operation.
A cage-like structure made of steel reinforcement or a wrapping made of composite material is erected around the degraded part in this sort of retrofitting techniques for RCC buildings, and cast-in-place concrete or shotcrete is then poured on top of it. Jacketing may easily be used in underwater settings and is specifically used to repair crumbling columns, piers, and piles.
The strengthening and protection of concrete, steel, and timber sections are both possible with the use of retrofitting procedures for RCC buildings. By using jacketing, one can avoid significantly strengthening the foundation by focusing on the axial and shear strength of the columns.
- External Plate Bonding
Using external plates or strips to reinforce reinforced concrete beams is a traditional and long-used method of retrofitting. Using steel plates wrapped completely or partially at the intersection of a column and beam, the external plate bonding method can be used to increase the shear strength of reinforced concrete beams.
An external plate installed perpendicular to any potential shear cracks can significantly increase the concrete reinforced member’s shear strength. This sort of retrofitting procedures for RCC buildings achieve the additional shear strength, but they do so by relying on the geometry of the beams, the strength of the existing concrete, and the wrapping method.
- Base Isolation Technique
Base isolation refers to the separation of the superstructure from the foundation. It is the most impressive technology for controlling passive structural vibrations. Building isolating structures from the beginning results in lower seismic loads, which in turn results in less damage to the structure and less superstructure maintenance.
The fact that this retrofitting procedure for RCC buildings cannot be used on other structures and is expensive in terms of budget is a drawback. This approach of retrofitting high-rise structures is wasteful, and it is unreasonable for structures built on soft soil.
- Mass Reduction Technique
When using the retrofitting procedure for mass reduction, at least one story might be evacuated. It is obvious from these retrofitting methods for RCC buildings that the removal of the mass will result in a decrease in the loading, which will result in an increase in the required strength.
- Wall Thickening Technique
By adding concrete, bricks, and steel adjusted at specified locations as reinforcement, the existing walls of a building are increased to a specific thickness. In this type of retrofitting solutions for RCC buildings, the wall weight increases and it can support additional horizontal and vertical loads. Under unusual circumstances, it is planned that the transverse stresses won’t abruptly deform the wall. If the reinforcement is not properly covered by mortar, rust may develop on it.
- Fiber Reinforced Polymer (FRP)
An axial strengthening system called a fiber reinforced polymer is utilized to increase or upgrade the strength of reinforced concrete beams. It frequently serves as a round as well as a rectangular column, but it is a more forceful fit.
FRP improves the shear capacity of reinforced concrete elements and increases the ultimate load carrying capacity of reinforced concrete parts. The ductility of a reinforced concrete column is greatly increased in these types of retrofitting approaches for RCC buildings. Prior to repair, composite should be thoroughly dried because all resins and some fibers absorb moisture.
- Adding Shear Wall
This is a common retrofitting method for non-ductile reinforced concrete frame buildings made of RCC. Concrete can be cast in place or precast for the components. It is preferable to add new components to the building’s exterior. To avoid damaging inside moldings, these retrofitting techniques aren’t recommended for the interior of the building.
- Epoxy Injection Method
Epoxy injection is a cost-effective method of retrofitting used for the repair of non-moving fractures in slabs, concrete walls, piers, and columns. In order to retrofit a building and address the structural failure problem, epoxy injection is used. These types of retrofitting methods for RCC structures are capable of restoring the pre-cracked strength of the concrete.
Compared to the tensile strength of concrete, the epoxy tensile bond to the concrete is more stable. This retrofitting method for RCC buildings strengthens the structure by adding additional reinforcement throughout the problem area in conjunction with the injection of epoxy pitch.
- Section Enlarging Reinforcing Method
To construct the reinforcement region’s component parts, the established cross section retrofitting method is used. In addition to increasing cross-section stiffness and bearing capacity, it also modifies the natural vibration frequency. In the reinforced concrete structure of the slab, beam, column, etc., these retrofitting approaches for RCC structures are widely used. For both the reinforcing of the compression component and the bending of reinforced concrete, the amplified cross section technique makes sense.
Advantages of Retrofitting
The benefits of retrofitting a building technique include the following:
- This technique is used to prevent displacement from the concrete of the structure.
- To increase the structure’s level of protection.
- Retrofitting of the structure is crucial in current or upcoming actions to safely withstand load.
- The retrofitted buildings have reduced carbon emissions and are more energy efficient.
- It fortifies the structure and regulates
- It offers occupants safety and shields the building from earthquakes.
- Insurance companies support the growth of their insurance.
- Increasing the capacity of the structure and its constituent parts.
- Retrofitted structures produce a safe and comfortable environment for occupants by providing enough ventilation.
- The tenants of buildings are much more productive since the IAQ is improved and the environment is dynamic.
- Additionally, it has been noted that increased IAQ reduces office absenteeism, which benefits productivity.
- Globally, climate change is a big problem. Fossil fuel energy production results in increased pollution and hazardous gas emissions.
- Retrofitting will therefore be beneficial in this situation to combat climate change by minimizing the use of fossil fuels.
- Retrofitting will also improve the quality of our air, safeguard bio diversity and the environment, reduce water waste, and conserve natural resources.
- The relative advantages of energy efficiency will become more significant as long as energy prices keep rising.
- Modifications to lighting systems, water-saving fixtures, heating and ventilation system upgrades, and renewable energy installations are some examples of retrofit initiatives that can increase energy efficiency.
- Because sustainable materials need fewer replacement cycles and maintenance cycles over time, using them in a retrofit can also have long-term economic advantages.
- Several studies have supported the idea that giving workers a view that includes more natural landscape through retrofitting might boost wellbeing.
- When exposed to nature, employees show fewer indicators of stress, such as decreased irritability, enhanced patience, and higher levels of general satisfaction.
- The idea of biophilia, or the belief that people have a biological need for a connection to nature, is supported by the evidence.
- Maintaining a connection to nature while at work can improve our connections with others and our own sense of wellbeing.
- By implementing retrofits, your company will be able to reduce capital expenditures and operating expenses while also saving money on gasoline.
- Making little adjustments to the office’s design, such as installing better-fitting doors and windows, adding insulation, or upgrading the building’s central heating and air conditioning systems, will reduce the long-term operating costs of the structure.
- Recent developments in technology that improves sustainability have also created a lot of opportunities to seize.
- You may do this by installing water-saving flush toilets at work, LED lighting, motion sensors, and timers, all of which can significantly increase your energy efficiency ratings and lower your energy bills.
- By retrofitting your building, you can advance toward near-zero energy buildings, zero energy buildings, and energy positive buildings, which are the goals of the Energy Performance of Buildings Directive.
Disadvantages of Retrofitting
In addition to its benefits, retrofitting includes a number of drawbacks, including:
- The worker’s abilities must adhere to the retrofitting strategies that have been adopted.
- Limited access to the construction site due to the possibility that the building is still in use.
- There is a bonding issue between the new concrete surface and the old masonry.
- Old masonry structures are less strong than concrete, so extra attention should be taken when defining the strength of concrete that has been covered.
- The gifted employee gives up using the adopted retrofitting techniques.
- Since the building is undergoing the procedure, approval is required for the construction site.
- Between the new concrete surface and the ancient brickwork, there are noticeable hard bonding mats.
- Compared to older masonry constructions, concrete is stronger.
Challenges of Retrofitting
The following are the challenges with retrofitting.
- For contractors working on retrofit projects, a comprehensive understanding of the scope of the retrofitting tasks is essential.
- Because there are many unknowns in the buildings and their environs when they are opened up for renovation activities, scope creep is particularly prevalent in such contracts.
- During implementation, one must budget and plan for these known and unknown risks.
- Managing a retrofit job in a real setting has a number of special concerns, including occupant and worker safety, partial load shutdowns, construction waste disposal and hygiene maintenance, access issues for the other tenants, noise, etc.
- In order to ensure minimal disruption to a client’s company and on-time task completion, the project management staff should be skilled and prepared to manage complex refurbishment work schedules and location.
- If the task span is horizontal, it can be completed in sections; however, if it’s vertical, we must complete it floor-by-floor and in accordance with the client’s specifications.
- Effective signage and full application of HSE measures aid in preventing incidents and accidents on the job site. The management of the programs is typically aided by the cooperation of the building’s residents through awareness initiatives.
- To sum up, a safe renovation or retrofitting is one that increases durability, has no negative effects on occupant health, and optimizes resource consumption to levels that are long-term sustainable.
- Improving a building’s energy efficiency and lowering the amount of greenhouse gases released into the atmosphere through retrofitting is one of the most environmentally beneficial methods available.
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For the purpose of finding more effective sustainable retrofitting approaches, new techniques are being developed. The retrofitting of a structure affects how that structure responds to risks other than those related to flooding, such as wind hazards, and the architect, engineer, and code official must be aware of this.
When it is possible, dangers should be approached holistically. The retrofitting process should take into account both flood-related and non-flood-related risks, such as earthquake and wind forces, as well as water-borne ice and debris impact forces, erosion forces, and mudslide impacts.
A structure’s ability to endure the several risks outlined above may be harmed by retrofitting it to simply withstand floodwater-generated stresses. As a result, it’s crucial to use a multi-hazard strategy while choosing a retrofitting method and designing the project.