After structural investigation and engineering evaluation, the Structural Engineer (SE) will have an idea of the present status of the structure. Then SE will evaluate and compare the status of the structure to the load it will carry. No retrofitting will be done if the present status of the structure can carry the load it will subject to, otherwise the SE will calculate and decide on the appropriate retrofitting technique applicable to the structure.
There are many method of retrofitting. The following are the most basic for local member:
Retrofitting by FRP materials. Both ACI and AASHTO provide code for this technique. ACI for concrete structure and AASHTO for Bridge structure. FRP is either made up of Carbon, Glass, Aramid, etc. FRP is very strong in tension and can be place on local member to reinforced its tension zone. But take note of its limitation.
Steel Jacketing. Steel is a good material both for compression and tension. SE can maximize this characteristic in strategic location within the local section to increase its strength. Steel is attached to concrete by means of post installed anchor bolt.
Concrete Jacketing. This is done by chipping the surface of the concrete then attaching additional reinforcing bar with lateral reinforcement. Rebar is attached to concrete with concrete epoxy. Additional strength to section is due to enlarged section and much farther d-distance of rebar.
Other methodology of retrofitting for the increase in structural stiffness of the whole structural system includes incorporating additional members to the structure such as Braces and Dampers. Base Isolator convert the energy coming from the earth movement into deflection so that structural member would absorb less energy.
As time goes by, new technology in retrofitting will be introduce since most of the structure in the future must be maintained.
