Page 503 - Advanced Design Examples of Seismic Retrofit of Structures

446 Advanced Design Examples of Seismic Retrofit of Structures

(A) (B)
FIG. 6.45 Cutting and folding the grid on each side of the opening [39]. (A) Both vertical sides.
(B) Below.

Some in-depth observations of damage of wall specimens after static cyclic
testing are presented in Fig. 6.46. In a specimen SMRA-WO (part A), there was
a sliding-rocking crack exactly at the level in which the steel mesh was cut. This
indicates the successful strategy of transferring the cracks from the more dan-
gerous upper parts of the wall to the more stable lower parts. As previously men-
tioned, the main weakness of this specimen was detachment the intersection of
perpendicular walls, which in some locations resulted in rupture of the steel
mesh (part B). Some local buckling of the steel mesh were observed in specimen
SMRA-LW (part C) mainly because of local instability around the opening;
however, because the mesh was not expected to carry compressive forces, this
behavior was considered as a weakness in the response of the specimen. More-
over, after removing the mesh from the specimen upon completion of the test,
the specimen collapsed (part D). As a result, it can be concluded that the steel
mesh not only improved the lateral response of the specimen to a large degree,
but also prevented the wall from collapse under vertical direction. The same
behavior was found in specimen SSRA-WO (parts E and F). In some cases,
excessive forces acted on the connections, which resulted in permanent defor-
mation of these parts (part G).
A comparison of response characteristics of walls models in static cyclic
testing is provided in Fig. 6.47. As can be seen, the openings have marginal
effect on the maximum strength of the adobe walls; however, retrofit measures
have led to considerable difference in the ductility of walls with different open-
ing configurations. In general, retrofit methods increased the ductility of the
walls from two to five times.

Shaking Table Tests The unretrofitted specimen was severely damaged and
collapsed during the 100% and 125% levels of excitation, respectively.
Although the walls experienced major shear cracking, the main cause of col-
lapse of the roof was in-balanced movement of the support walls which was
from out-of-phase motions of the parallel walls in out-of-plane direction.