Question 18.11: Determine the effective modal mass and the effective modal h......

The modal distribution of effective earthquake force is given in Fig. 18.30. Taking moment at base

                  h_1^*=\frac{(0.853 ~\times ~1~+~0.6035 ~\times ~2) ~h}{1.456}

                       =\frac{(0.853~+~1.2070)~ h}{1.456}

                       =\frac{(2.060) ~h}{1.456}

                       =1.414~ h \quad M_1^*=1.456~ m

                 h_2^*=\frac{(0.146~ \times~ 1~-~0.1035 ~\times~ 2) ~h}{0.0425 ~m }

                      =\frac{(0.146~-~0.2070)~ h}{0.0425}

                       (-1.435)~ h ; \quad M_2^*=0.0425~ m

The effective modal mass and modal height are indicated in Fig. 18.31.