Page 320 - Advanced Design Examples of Seismic Retrofit of Structures

Example of a Steel Frame Building Retrofitted Chapter 5 309

TABLE 5.11 Acceptance Criteria for Linear Procedures-Structural Steel
Components [3]
m-Factors for Linear Procedures W
Primary Secondary
Component/Action IO LS CP LS CP
Beams—flexure
a: b f ffiffiffiffiffip 52 and h ffiffiffiffiffip 418 2 6 8 10 12
2t f F ye t w F ye
640
b: b f ffiffiffiffiffip 65 or h ffiffiffiffiffip 1.25 2 3 3 4
2t f F ye t w F ye
c: Other Linear interpolation between the values on lines a and b
for both flange slenderness (first term) and web
slenderness (second term) shall be performed, and the
lowest resulting value shall be used.
Columns—flexure a,b
For P/P CL <0.2
a: b f ffiffiffiffiffip 52 and h ffiffiffiffiffip 300 2 6 8 10 12
2t f F ye t w F ye
b. b f ffiffiffiffiffip 65 or h ffiffiffiffiffip 460 1.25 1.25 2 2 3
2t f t w
F ye F ye
c: Other Linear interpolation between the values on lines a and b
for both flange slenderness (first term) and web
slenderness (second term) shall be performed, and the
lowest resulting value shall be used.
For 0.2 P/P CL 0.5
a: b f ffiffiffiffiffip 52 and h ffiffiffiffiffip 260 1.25 – c – d – e – f
2t f t w
F ye F ye
400
b: b f ffiffiffiffiffip 65 or h ffiffiffiffiffip 1.25 1.25 1.5 2 2
2t f t w
F ye F ye
c: Other Linear interpolation between the values on lines a and b
for both flange slenderness (first term) and web
slenderness (second term) shall be performed, and the
lowest resulting value shall be used.
a
Columns in moment or braced frames shall be permitted to be designed for the maximum force
delivered by connecting members. For rectangular or square columns, replace b t /2t f with b/t, replace
52 with 110, and replace 65 with 190.
b
Columns with P/P CL >0.5 shall be considered force controlled.
c
m ¼9(1 5/3 P/P CL ) in the plane of bending.
d
m ¼12(1 5/3 P/P CL ) in the plane of bending.
e
m ¼15(1 5/3 P/P CL ) in the plane of bending.
f
m ¼18(1 5/3 P/P CL ) in the plane of bending.
For P UF < 0:2
P CL
P UF M x M y
+ + 1:0 (5.29)
2P CL m x M CEx m y M CEy