Page 152 - Advanced Design Examples of Seismic Retrofit of Structures

144 Advanced Design Examples of Seismic Retrofit of Structures

– By increasing stiffness, the demands in the existing RC shear walls and
columns are reduced. This can be done by adding extra shear walls to the
building in proper locations.
– The retrofitted elements or the added structural members are better
located on the corners of the building in order to minimize the conflict
with the operation related to architectural, electrical, and mechanical
equipment during the retrofit project.
– The demolition tasks should be limited to local scale with the aim of con-
necting the added members to the existing ones. Environmental consid-
erations also pose limits to the extent of demolition.
– The method should preferably minimize the required costs additional to
the cost related to the “basic” performance objective.
l The results of the study are as follows:
– No modification to the load-bearing system for the gravitational loads is
necessary.
– The extent of demolition is minimal.
– The columns do not need to be retrofitted (this is very important consid-
ering the huge number of columns and the geometry of the columns’
ends).
– The existing RC shear walls do not need to be retrofitted for flexural
actions.
– Some of the RC shear walls need to be retrofitted for shear actions.
– The southern building part requires retrofitting by adding RC shear walls
at the South-East and South-West corners. However, by properly con-
necting the two building parts together, there is no need for adding RC
shear walls at the South-East corner of the northern building.
– The total cost of retrofitting according to this strategy is estimated to be
$300,000. The general schematic view of the first retrofit strategy is
shown in Fig. 3.17.

3.4.2 Isolation the Two Building Parts From Each Other
and Increasing Stiffness of Each Part

l The main strategies are as follows:
– Providing the freedom for each building part to experience the necessary
displacements.
– Increasing stiffness of each building part to ensure a more optimum dis-
tribution of stiffness and to reduce the seismic demands in the existing
shear walls and columns.
l The results of the study are as follows:
– The columns do not need to be retrofitted.
– The existing RC shear walls do not need to be retrofitted for flexural
actions.
– Some of the RC shear walls need to be retrofitted for shear actions.