Page 86 - Advanced Design Examples of Seismic Retrofit of Structures

78 Advanced Design Examples of Seismic Retrofit of Structures

0:93 4:63
V tc 1 ¼ 10883 + 0:5 2864Þ 1 ¼ 4961kg
ð
1:8 0:7 30
Lower-Bound In-Plane Diagonal Tension Strength of URM Walls
and Piers
Based on ACE41-13 [2], the lower-bound in-plane diagonal tension strength,
Q CL , of URM walls or pier components for the diagonal tension failure mode
shall be calculated in accordance with Eq. (2.36):

s ffiffiffiffiffiffiffiffiffiffiffiffi
Q CL ¼ V dt ¼ f A n β 1+ f a (2.36)

0
dt 0
f
dt
where:
A n ¼area of net mortared and/or grouted section of a wall or pier;
β ¼0.67 for L/h eff <0.67, L/h eff when 0.67 L/h eff 1.0, and 1.0 when
L/h eff >1.00;
h eff ¼height to resultant of seismic force;
L ¼length of wall or wall pier;
f a ¼axial compression stress caused by gravity loads specified in Eq. (2.28);
0
f dt ¼lower-bound masonry diagonal tension strength; and
V dt ¼lower-bound shear strength based on diagonal tension stress for wall
or pier.
Substitution of the lower-bound bed-joint shear strength, v mL , for the diag-
0
onal tension strength, f dt in Eq. (2.36) shall be permitted.
Similar to the previous version of ASCE 41, that is, ASCE 41-06 [15], Code
360 [2] considers no upper bound and lower bound for β and assumes β¼L/h eff
regardless of the value of L/h eff .
The values of V dt of the walls in the example building walls are presented in
Appendix Table A-C-2-10. As an example, the diagonal tension capacity of
Wall#1 on the first row of this table is determined as:
r ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
4:63
V dt 1 ¼ 2 3255 0:67ð Þ 1+ ¼ 7957kg
2

Lower-Bound In-Plane Vertical Compressive Strength of URM
Walls and Piers
Based on ACE41-13 [2], the lower-bound in-plane vertical compressive
strength, Q CL , of URM walls or pier components for the vertical compressive
failure mode shall be calculated in accordance with Eq. (2.36):

0
Q CL ¼ P CL ¼ 0:80 0:85f A n (2.37)
m