Page 80 - Advanced Design Examples of Seismic Retrofit of Structures
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72 Advanced Design Examples of Seismic Retrofit of Structures
Q UD 1 ¼ Max 8462, 8462 342 902 ¼ 8462kg
½
Q UF 1 ¼ Max 3005, 3005 121 320½ ¼ 3005kg
2.7.3.2 Flexible Diaphragms With Horizontal Ties
As mentioned before, demand force distribution between the walls in buildings
with flexible diaphragms with horizontal ties is first according to the seismic
mass of each walls axis. Then, this axis force is distributed between the walls
located in that particular axis based on their stiffness because of the rigidity
provided by the horizontal ties. Note that the modifications of piers stiffness
based on their location should be according to “Modification of the Stiff-
ness Relations for Piers in Single-Story Buildings” and “Modification of the
Stiffness Relations for Piers in Multistory Buildings” sections.
The generated demand force in each wall depends on the relative stiffness of
the walls to that of the integrated stiffness of the walls in the axis on which the
wall is located. Also, it depends on the relative contribution of that particular
axis in tolerating the seismic mass compared to other parallel axes. The partic-
ipation factor of each wall in masonry buildings with flexible diaphragms
with horizontal ties from the shear force demand is calculated according to
Eq. (2.25).
K i M Line i
(2.25)
PF ¼ X
L i
M Story
K i
i¼1
and M Story are the seismic mass of the ith axis and the story, respec-
where M Line i
tively. The walls’ participation factors and also demand forces are presented in
Tables A-C-2-7 and A-C-2-8, respectively.
As an example, the demand of Wall#1 is determined as:
2,986,473 82,698
PF ¼ ¼ 0:45%
71,781,210 756,179
f U i ¼ PF F U
f UD 1 ¼ 0:45% 2156 ¼ 9:8 Ton
f UF 1 ¼ 0:91% 766 ¼ 3:5 Ton
2.7.3.3 Flexible Diaphragms Without Horizontal Ties
As previously mentioned, the demand force distribution between the walls in
buildings with flexible diaphragms without horizontal ties is according to their
seismic mass. The modifications of piers stiffness based on their location are
based on the equations in “Modification of the Stiffness Relations for Piers
in Single-Story Buildings” and “Modification of the Stiffness Relations for
Piers in Multistory Buildings” sections.
