Page 306 - Advanced Design Examples of Seismic Retrofit of Structures

Example of a Steel Frame Building Retrofitted Chapter 5 295

TABLE 5.6 Values for Modification Factors C 0 [1]

Other
Shear Buildings a Buildings
Number of Triangular Load Triangular Load Any Load
Stories Pattern Pattern Pattern
1 1.0 1.0 1.0
2 1.2 1.15 1.2
3 1.2 1.2 1.3
5 1.3 1.2 1.4
10+ 1.3 1.2 1.5

a
Buildings in which, for all stories, story drift decreases with increasing height.

2
T e
δ t ¼ C 0 C 1 C 2 S a g (5.13)
4π 2
where C 0 ¼modification factor to relate spectral displacement of an equivalent
single-degree-of-freedom (SDOF) system to the roof displacement of the build-
ing multi-degree-of-freedom (MDOF) system calculated using one of the fol-
lowing procedures: (1) the first mode mass participation factor multiplied by
the ordinate of the first mode shape at the control node; (2) the mass participa-
tion factor calculated using a shape vector corresponding to the deflected shape
of the building at the target displacement multiplied by ordinate of the shape
vector at the control node; or (3) the appropriate value from Table 5.6. In non-
linear static analysis, it is recommended to push the model to lateral displace-
ment larger than the target displacement; the applied displacement can be 1.5
times of the target displacement.
S a ¼according to the definition in Section 5.5.1;
g¼ acceleration of gravity;
C 0 ¼ according to the definition in Section 5.5.1;
C 1 ¼ according to the definition in Section 5.5.1;
C 2 ¼ according to the definition in Section 5.5.1
T e ¼ according to the definition in Section 5.5.1;
2
ð 0:49Þ
δ txðÞ ¼ 1:2 1:4 1:2 0:825 9:81 ¼ 9:93 cmÞ 1:5 ¼ 14:9cmÞ
ð
ð
39:43
2
ð 0:42Þ
ð
ð
δ txðÞ ¼ 1:2 1:4 1:2 0:825 9:81 ¼ 7:3cmÞ 1:5 ¼ 10:94 cmÞ
39:43
For the main building