Page 81 - Advanced Design Examples of Seismic Retrofit of Structures

Example of a Two-Story Unreinforced Masonry Building Chapter 2 73

The participation factor of each wall in masonry buildings with flexible dia-
phragms from the shear force demand is calculated according to Eq. (2.26):

M i
PF ¼ (2.26)
M Story
The walls’ participation factors are presented in Table A-C-2-9.
As an example, the generated demand forces in Wall#1 are determined as
follows:
6858
PF ¼ ¼ 0:91%
756,179
f U i ¼ PF F U
f UD 1 ¼ 0:91% 2156 ¼ 19:6 Ton
f UF 1 ¼ 0:91% 766 ¼ 6:9 Ton

2.7.4 Actions Calculations

According to ASCE 41, action is referred to an internal moment, shear, torque,
axial force, deformation, displacement, or rotation corresponding to a displace-
ment caused by a structural degree of freedom; designated as force- or
deformation-controlled [2]. Generally speaking, there are two types of seismic
actions: (1) deformation-controlled action: which is an action that has an asso-
ciated deformation that is allowed to exceed the yield value of the element being
evaluated. The extent of permissible deformation beyond yield is based on com-
ponent modification factors (m-factors); and (2) force-controlled action: which
corresponds to an action that is not allowed to exceed the nominal strength of
the element being evaluated. Based on these definitions, a typical structural
component can be deformation-sensitive which is sensitive to deformation
imposed by the drift or deformation of the structure, including deflection or
deformation of diaphragms. Similarly, force-sensitive structural components
are defined.

2.7.4.1 Deformation-Controlled

Based on Code 360, deformation-controlled actions for LSP denoted by Q UD
shall be calculated in accordance with Eq. (2.27):
Q UD ¼ Q G + Q E (2.27)
where:
Q E ¼action caused by the response to the selected seismic hazard level cal-
culated using Section 2.7.1 of this example; and
Q G ¼action caused by gravity loads as determined according to either of
these methods: