Page 106 - Advanced Design Examples of Seismic Retrofit of Structures

98 Advanced Design Examples of Seismic Retrofit of Structures

TABLE 2.13 Comparison of Various Retrofit Methods for URM
Buildings—cont’d
Retrofit
Method Pros Cons
External l High increment in Fur l Corrosion
reinforcement l Prevent disintegration l Heavy mass
l Improves ductility and l Violation of performance
energy dissipation level
l Requires architectural
finishing
l Disturbance occupancy
Confinement l Prevent disintegration l Not easy to introduce
l Improve ductility and l Limited effect on ultimate
energy dissipation strength
l Requires architectural
finishing
l Disturbance occupancy
Posttension l No added mass l High losses
l No effect on building l Anchorage system
function l Corrosion potential
Center Core l No space reduction l Creation of zones with
l No architectural impact varying stiffness and strength
l No effect on building
function

results of the studies by Ghiassi et al. [50] are used here. They considered three
failure modes for shotcreted masonry walls: sliding, shear-tensile, and flexural.
They proposed relations for determination of the capacity for each failure mode.
The acceptance criteria similar to the corresponding reinforced masonry walls
in ASCE 41-06 [15] were assumed for the shotcreted masonry walls. The details
of their proposed relations are presented in the next parts of this chapter.

2.8.4.1 Selection of the Walls for Shotcreting
Generally, the vulnerable walls which were determined in the previous sections
of this chapter are considered for retrofit. This approach works well for URM
buildings without any ties which have flexible diaphragms. In these buildings,
each wall reacts independently to the seismic demands and its vulnerability is
independent of the vulnerabilities of other walls. However, this is not the case
for URM buildings having confined ties and/or with rigid diaphragms. In these
buildings, a group of parallel walls reacts to the seismic demand forces and each
wall in this group interacts with other walls. In this example, instead of