Story drift determination The elastic response deflection δxe, corresponding to the design seismic lateral forces, applied to the steel special moment frame (SSMF), are shown in Figure 5.16. Risk Category II Ie = 1.0 SSMF (T 12.2-1) R = 8, Ω0 = 3, Cd = 5.5 Determine the maximum inelastic story

Question

Story drift determination
The elastic response deflection [latex]δ_{xe}[/latex], corresponding to the design seismic lateral forces, applied to the steel special moment frame (SSMF), are shown in Figure 5.16.
Risk Category II
[latex]I_e[/latex] = 1.0
SSMF (T 12.2-1)
R = 8, [latex]Ω_0 = 3, C_d = 5.5[/latex]
Determine the maximum inelastic story drift of the roof level and check the story-drift limit (Table 5.1).

Table 5.1 The elastic response deflection and maximum inelastic story drift at each level
Level	[latex]δ_{xe}[/latex] (in)	[latex]δ_x[/latex] (in)
Roof	1.41	7.75
4th	0.98	5.39
3rd	0.59	3.25
2nd	0.26	1.43

Accepted Answer

[latex]\delta_x=\frac{C_d \delta_{xe}}{I_e}[/latex] (ASCE 7 12.8-15)

[latex]=\frac{5.5δ_{xe}}{1.0}=5.5δ_{xe}[/latex]

Therefore,

[latex]∆ = δ_{x+1} − δ_x[/latex]

[latex]∆_{roof} = 7.75− 5.39 = 2.37[/latex] in.

From ASCE 7 T 12.12-1

Risk Category II

[latex]∆_a = 0.025h_{sx}[/latex]

When [latex]h_{sx}[/latex] = story height

then, [latex]∆_a = 0.025(10 imes 12)=3.0[/latex] in.

Therefore, [latex]∆_{roof} =2.37\lt 3.0[/latex] in OK.

The story drift is within the limit.

Question 5.2: Story drift determination The elastic response deflection δx...

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