What are Structural Retrofittings?
Retrofittings are technical interventions in the structural system of a building that improve its resistance to earthquakes by optimizing the strength, ductility and earthquake loads. The strength of the building is generated from the structural dimensions, materials, shape, and number of structural elements, etc. Ductility of the building is generated from good detailing, materials used, degree of seismic resistance, etc. Earthquake load is generated from the site seismicity, mass of the structures, footprint of buildings, degree of seismic resistance, etc. While approaching the design of retrofitting, the engineer must comply with the local building codes. The results generated by the adopted retrofitting techniques must fulfill the minimum requirements on the building's codes, such as deformation, detailing, strength, etc.
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When is Retrofitting Needed?
Retrofitting is needed when the assessment of structural capacity shows insufficient capacity to resist the forces of expected intensity and acceptable limit of damages. It is not merely poor quality of materials and damage of structural elements that are considered when deciding whether or not to retrofit a building. Change of the building’s function, change of environmental conditions, and change of valid building codes could also be valid reasons for retrofitting.
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Retrofitting must be conducted by experts from each field. In most retrofitting processes, an engineer plays the main role. An engineer must assess and analyze the structural capacity and design the best retrofitting techniques to strengthen the structural deficiencies. The role of any non-engineer is restricted to identifying the possibility that a building's capacity may be insufficient.
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What are Advantages and Disadvantages of Retrofitting?
The advantages of adopting a retrofitting approach, despite reconstructing the building, are as follows:

• When a retrofitting approach is adopted, the retrofitted building can still be operated/inhabited during construction.
• Retrofitting will take relatively lower construction costs with similar structural performance achievements.
• Retrofitting will involve relatively fewer resources, either human resources or natural resources.
• Retrofitting will not significantly change the building's configuration and shape. It is preferable when the retrofitted building has historical values.
• Retrofitting the building will produce less debris than reconstructing the building.

However, retrofitting also has several disadvantages, such as:

• The skill of the worker must comply with the adopted retrofitting approaches.
• Limited access to the construction site, since the building could be still in use.