Page 82 - Advanced Design Examples of Seismic Retrofit of Structures

74 Advanced Design Examples of Seismic Retrofit of Structures

(1) Where the effects or actions of gravity loads and seismic forces are addi-
tive, the action caused by gravity loads, Q G , shall be obtained in accordance
with Eq. (2.28):

Q G ¼ 1:1 Q D + Q L + Q s Þ (2.28)
ð
where:
Q D ¼action caused by dead loads;
Q L ¼action caused by live load, equal to 25% of the unreduced live load
obtained in accordance with ASCE 7 [14] but not less than the actual live
load; and
Q s ¼action caused by effective snow load which is assumed zero in this
example;
Q UD ¼deformation-controlled action caused by gravity loads and earth-
quake forces.
(2) Where the effects or actions of gravity loads and seismic forces are coun-
teracting, the action caused by gravity loads, Q G , shall be obtained in accor-
dance with Eq. (2.29):

Q G ¼ 0:9Q D (2.29)
The lateral shear forces for the displacement-sensitive components for each
story of the example building have been previously calculated in
Section 2.7.2.1.

2.7.4.2 Force-Controlled
According to Code 360, force-controlled actions for LSP denoted as Q UF shall
be calculated using one of the following methods [10]:
(1) Q UF shall be taken as the maximum action that can be developed in a
component based on a limit-state analysis considering the expected strength
of the components delivering force to the component under consideration, or
the maximum action developed in the component as limited by the nonlinear
response of the building.
(2) Alternatively, Q UF shall be calculated in accordance with Eq. (2.30):

Q E
Q UF ¼ Q G (2.30)
C 1 C 2 J
where Q UF ¼force-controlled action caused by gravity loads in combination
with earthquake forces and J ¼has been defined for Eq. (2.9).
The lateral shear forces for the force-sensitive components for each story of
the example building have been previously calculated in Section 2.7.2.2.