SEISMIC REHABILITATION AND RETROFIT ~ ENGINEER'S LAB

With the enormous experience and available data on the earthquake performance
of RC frame structures, their deficiencies are well known and can be identified with
reasonable accuracy in some cases. Seismic assessment procedures are well established
at the present time. In many areas with high seismic risk, existing reinforced concrete
structures are being evaluated and retrofitted if found inadequate. A comprehensive
amount of research has been directed towards developing seismic retrofit techniques
applicable to RC frame structures.

Earthquake resistance in RC frame structures can be enhanced by either of the following
approaches:

• Strengthening the components, such as columns and beams, by jacketing with
concrete, steel, or fiber wrap overlays (see Figure 8)

• Increasing the overall capacity of the structural system by installing new concrete
infill walls or steel bracings.

The most common rehabilitation measure is installation of new reinforced concrete
infill walls (Figure 9) along with jacketing the columns to increase the strength of the
existing structure. These new walls are reinforced in such a way as to act in unison
with the existing structure.

However, careful detailing and material selection is required to ensure that bonding between
the new and the existing structure under earthquake loads is effective.

Figure 8: Jacketing of RC
frame members (WHE Report
11, Colombia)

Figure 9: Illustration of

seismic strengthening
with addition of RC
infill walls (WHE Report
62, Taiwan)

An alternative procedure which has been recently developed for RC frames with
unreinforced masonry infill walls proposes the use of carbon-fiber, reinforced polymers
(CFRP) applied on existing unreinforced masonry infill walls (Figure 10) to increase the
overall lateral load capacity. Although its cost is higher, this method is easy to apply and
much faster when compared to the installation of new concrete infill walls (Ozcebe et
al.2).