Page 474 - Advanced Design Examples of Seismic Retrofit of Structures

Examples of Nonengineered Buildings Chapter 6 417

demands. Compared to local ties, the addition of vertical straps better improved
the performance of the thin walls. The condition of the two in-plane walls shows
the difference between the use of local ties (Fig. 6.19A) and the use of vertical
straps (Fig. 6.19B). Good behavior was also observed in the moderate walls
with a bond beam and center cores during test level IX (Fig. 6.19C).
In addition to the partial diaphragms on each building, the minimum retrofits
for out-of-plane gable-end walls of the tapanco-style models were upper and
lower horizontal straps. The only gable-end wall that did not have lower hori-
zontal straps was the west wall of Model 8 (Fig. 6.20D), which had center-core
rods. In Model 7, the thick East wall (Fig. 6.20A) which remained stable had
only upper and lower straps. There was a large offset at the mid-height horizon-
tal crack, because there was little restraint across this crack plane. Vertical
straps provided additional restraint that minimized the extent of residual crack
offsets. In Model 7, the performance of the West wall (Fig. 6.20B) was better
than that of the East wall, because the vertical straps provided restraint for block
movements along horizontal and diagonal cracks.

(A) (B)

(C) (D)
FIG. 6.20 Comparison of the out-of-plane wall performance with differing retrofit systems after
test level X. (A) East wall of Model 7. (B) West wall of Model 7. (C) East wall of Model 8. (D) West
wall of Model 8. (Adapted from E.L. Tolles, E.E. Kimbro, F.A. Webster, W.S. Ginell, Seismic Sta-
bilization of Historic Adobe Structures, The Getty Conservation Institute, Los Angeles, 2000.)