Question 17.8: Estimate the maximum sensitive response for the industrial b......

Damping = 5%

(i) NS direction, T = 0.567 s

From chart (see Fig. 17.23), spectra value S_d=6.35~ cm ; S_{p v}=71.12 ~cm / s; S_{p a}=784.35 ~cm / s ^2.

Maximum base shear = m S_{p a}

                                         = 131 697.2 × 7.843

                                        = 1032.9 kN

Column bending moment =\frac{3~ E I S_d}{h^2}

                                                  =\frac{3 ~\times ~200~ \times ~10^9~ \times~ 8.6997~ \times ~10^{-5} ~\times ~0.063}{4.2672^2}

                                                  = 181.9 Nm

(ii)     EW direction

          S_d=20~ mm

        S_{pv} = 393.7~ mm/s

        S_{pa} = 7.843~ mm/s²

         ω_{n} = 20~ rad/s

            T = 0.313

        Maximum base shear = m S_{p a}

                                                 = 1032.9 kN

        Axial force in rod = \frac{E A~ \cos \theta}{L} S d

                                       =\frac{506.7~ \times~ 10^{-6} ~\times~ 200~ \times~ 10^9 ~\times ~0.8712}{8.73} 0.02

                                       = 202.20 kN

    Comparison of the maximum response obtained from time history analysis response spectra and design spectrum analysis is presented in Table 17.4 for NS direction. There is a considerable discrepancy between the results of response spectrum and design spectrum. The former represents the response to a specific earthquake while the latter represents predicted response to any earthquake.