Page 307 - Advanced Design Examples of Seismic Retrofit of Structures

296 Advanced Design Examples of Seismic Retrofit of Structures

2
ð 2:31Þ
δ txðÞ ¼ 1:0 1:43 1:2 0:369 9:81 ¼ 84 cmÞ 1:5 ¼ 126 cmÞ
ð
ð
39:43
2
ð 0:31Þ
ð
ð
δ tyðÞ ¼ 1:0 1:43 1:2 0:825 9:81 ¼ 3:38 cmÞ 1:5 ¼ 5:07 cmÞ
39:43
For the sports building
5.5.4 Concurrent Seismic Effects
Based on ASCE 41, where concurrent multi-directional seismic effects must be
considered, horizontally oriented, orthogonal X- and Y-axes shall be estab-
lished. Components of the building shall be evaluated or retrofitted for combi-
nations of forces and deformations from separate analyses performed for ground
motions in X and Y directions as follows. For the example buildings, there is no
codified lateral load-bearing system for the main building. Also, no column is
subjected to concurrent seismic effects because the braces are along one direc-
tion of the building only. As a result, the buildings in this example are not sub-
jected to considering concurrent seismic effects.

5.5.5 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 [1]. 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); (2) force-controlled action: which cor-
responds to an action that is not allowed to exceed the nominal strength of the
element being evaluated. Based on these definitions, a typical structural com-
ponent 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.

5.5.5.1 Deformation-Controlled

Based on Code 360, deformation-controlled actions for LSP denoted by Q UD
shall be calculated in accordance with Eq. (5.14):
Q UD ¼ Q G + Q E (5.14)
where:
Q E ¼action caused by the response to the selected seismic hazard level cal-
culated using Section 5.6.1 of this example; and
Q G ¼action caused by gravity loads as determined according to either of
these methods: