Benefits of retrofitting the building
Building retrofitting, a theoretical concept or a practical need?
The earthquakes of the past years showed that many buildings built in seismic areas are not able
to withstand the effects of earthquakes. Therefore, the implementation of the retrofitting plan
of a building is one of the main priorities of today’s Iranian society.
If your building also needs to be strengthened, I suggest you read this article before taking any action.
The main purpose of this article is to familiarize the reader with the concept of strengthening, methods and techniques of strengthening a building.
Why does a building need retrofitting?
Recent earthquakes have shown that a significant number of buildings did not have proper seismic performance. There are four main reasons for this, which are:
- Non-availability or lack of seismic design regulations during building construction
- Unfortunately, many of the existing structures were .built based on the regulations and standards
- that were compiled in the past. Many of these buildings are vulnerable to earthquakes due to
- weaknesses in the regulations.
- Weakness in the implementation and construction of the building structure is one of the reasons
- for its vulnerability to the earthquake phenomenon.
- The wear and tear of the building and the damage caused to its structure over time can make the
- building very vulnerable to earthquakes.
In planning a restoration or retrofitting project, the following should be considered:
A) Determining the condition of the structure
b) Determining the requirements of restoration or retrofitting operations
c) Preparing a work plan
d) monitoring the quality of work
Troubleshooting to retrofitting the building
The purpose of retrofitting a building is to improve its performance against earthquakes. This can be achieved with different strategies. Choosing the most optimal retrofitting strategy depends on a correct understanding of the building’s behavior against earthquakes. In fact, a retrofit solution with proper planning can make the performance of a building more stable and its performance more stable.
Initial review
In the early stages of a building’s retrofitting plan, it is important to carry out seismic troubleshooting in order to measure the performance of a building during an earthquake. Therefore, in the first step, the following must be controlled:
- Year of construction of the building
- Type of building structure
- Environmental conditions
- Availability of all maps
Knowing the weaknesses of the building
Recognizing the weaknesses of a building during an earthquake consists of three stages:
- first stage:
Early detection and troubleshooting of a building with a relatively large number of walls
- second stage:
Using basic diagnosis and troubleshooting methods that focus on structural components such as columns and walls.
- third level:
Accurate diagnosis and troubleshooting that examines beam strength compared to columns and walls.
Approaches used in building retrofitting
Seismic retrofitting is based on three main approaches:
- Building structure strengthening approach: It is the most popular method of retrofitting and
- improves the performance of a building.
- Seismic isolation approach: based on this approach, the amount of impact of the vibration
- produced by the earthquake on the building is reduced.
- Vibration and earthquake control approach: The vibration control of the building structure is the
- basis of the performance of this approach.
Methods of strengthening the building with steel bending frame
In the building with the structural system of the steel bending frame, the vertical loads are borne
by the building frames and the resistance against the lateral forces is provided by the bending frames.
Reinforcement of reinforced concrete columns
Use of concrete coating: It is not possible to compact concrete at that low level,
so it is possible to obtain the desired strength in poured concrete with self-compacting concrete.
This method can increase the weight of the structural system, when using reinforced concrete
cover, it is necessary to scratch the surface of the existing concrete before concreting the new
part for the cover
changes in the ratio of height to dimension, and as a result, the failure mode of the column will change from bending to shear.
Benefits of retrofitting the building
Use of steel sheets: The main problem of improving vulnerable reinforced concrete columns with
steel sheets is the lack of strain compatibility between the two materials (concrete and steel). It is necessary to
put a proper distance between the existing reinforced concrete sheet and column (at least 2.5 to 5 cm)
and inject the shrinking mortar and sometimes the expanding mortar in this distance to solve the problem
of non-coherence of these two materials to some extent.
one floor without increasing the bending capacity of the column. In this case, there should be a gap between the armor and the ceiling and the floor.
Using FRP coating: The best and easiest way to use FRP in strengthening concrete columns is to
screw the column. In this case, by enclosing concrete, not only the compressive strength of the member but also
the shear strength increases. Using this method is very effective in preventing the failure mechanism in