Seismic Design Example Static Procedure IBC 2003 ASCE 702 NFPA 5000

Given. A 12-story building located in downtown, Los Angeles, California. The building properties summarized in Fig. 2.46 are the same as those used in the 1997 UBC example, Section 2.13.19.1.

Occupancy group = II (Table 2.13 ASCE Table 1.1)

SDC = D (Tables 2.17 and 2.18; ASCE Tables 9.4.2.1a and b)

Site class as determined by project geotechnical engineer = D

Figure 2.46. Design example; ASCE 7-02 (IBC-03), static force procedure.

Building's lateral load system = SMRF with EBF

(Table 2.21 ASCE Table 9.5.2.2) Elastic fundamental period, TB from computer analysis = 2 secs Total seismic weight, W = 22,680 kips Building height hn, above shear base = 160 ft Mapped MCE, 5% damped, Spectral acceleration at short periods, SS = 1.5 Mapped MCE, 5% damped,

Spectral response acceleration at a period of 1 second, S1 = 0.6.

Required. Using the equivalent lateral force procedure of ASCE 7-02 determines the following:

Seismic base shear, V Vertical distribution of base shear V Seismic story shear Overturning moment Diaphragm design forces Allowable story drifts

Solution. Seismic design coefficients

Acceleration-based site coefficient (at 0.2 sec period), Fa = 1

Velocity-based site coefficient (at 1.0 sec period), Fv = 1.5

MCE spectral response acceleration at short periods for site class effects, SMS = Fa Ss = 1 x 1.5 = 1.5 ASCE Eq. (9.4.1.2.4.1)

MCE spectral response acceleration at a 1-sec period adjusted for site class effects, SM1 = Fv x S1 = 1.5 x 0.6 = 0.9 ASCE Eq. (9.4.1.2.4)

Design, 5% damped, spectral response acceleration at short periods, SDS = 2/3Sms = 2/3 x 1.5 = 1.0 ASCE Eq. (9.4.1.2.5.2)

Design, 5% damped, spectral response acceleration at a 1-sec period, SD1 = 2/3Sms = 2/3 x 0.9 = 0.6 ASCE Eq. (9.4.1.2.5.2)

Occupancy importance factor, I = 1 (Table 2.13; ASCE Table 9.1.4)

Response modification coefficient, R = 8.0 (Table 2.21; ASCE Table 9.5.2.2)

System overstrength factor, Qo = 2.5 (Table 2.21; ASCE Table 9.5.2.2)

Coefficient for upper limit on calculated period, Cu = 1.4

TABLE 2.23 Coefficient for Upper Limit on Calculated Period

Design spectral response acceleration at 1 Second, SD1 Coefficient Cu

TABLE 2.23 Coefficient for Upper Limit on Calculated Period

> 0.4

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